Switching regulators of step-down type. And a transistor switching voltage regulator
Switching voltage regulators
DC-DC converters
DC-DC converters include switching voltage regulators and pulse-width converters.
Switching voltage regulators are used to regulate DC voltage. Compared to other control methods, they provide better energy characteristics and have less weight and dimensions.
The principle of pulse regulation is that a direct current source is periodically connected to the load at a certain frequency. Connection interval duration t u for one period T determines the voltage across the load. The load (if active) is made inductive using a choke L. The circuit parameters are selected in such a way that the time constant of the load circuit significantly exceeds the current switching period. At the same time, a continuous flow of current with permissible ripple is ensured in the load circuit.
The diagram of a step-down type pulse regulator is shown in Fig. 3.1 (a), timing diagrams of the operation of this circuit are in Fig. 3.1(b).
When the transistor is turned on VT the inductor current increases almost linearly from Imin before Imax. The voltage across the inductor is equal to:
and under load
provided that .
When the transistor is turned off, the inductor current decreases from Imax before Imin, while the voltage at the inductor provides the voltage value at the load:
().
.
Therefore, by changing the duty cycle of control pulses, it is possible to regulate the voltage on the load within 0…E P.
Taking into account the voltage drops across the transistor and diode, the actual maximum voltage is (0.9 … 0.95)E P.
If the load is inductive (for example, a DC motor), then the required value of current ripple is achieved by choosing the switching frequency of the transistor VT. The absolute value is:
,
and the maximum value is reached at KZ = 0.5. Taking this into account, the required switching frequency to ensure the required current ripple coefficient is:
.
When the load resistance is active, a choke with inductance is connected to the circuit L, which determines the current ripple in the load. To reduce the inductance of the inductor, a capacitor is connected in parallel with the load. To ensure the continuous nature of the inductor current, the value must satisfy the condition:
If there is a capacitor, the alternating component of the inductor current (triangular in shape) is closed through the capacitor. The voltage drop across the capacitor, caused by the first harmonic current, determines the voltage ripple across the load:
For a triangular current shape, the amplitude of the first harmonic is maximum at KZ = 0.5 and amounts to (according to the Fourier series expansion):
.
Hence,
;
When using powerful MOSFET and IGBT field-effect transistors as a switching element, the switching frequency can be tens to hundreds of kilohertz.
When using thyristors, the switching frequency does not exceed several kilohertz. The diagram of a pulse regulator based on an unlocked thyristor with forced switching is shown in Fig. 3.2.
To turn off the main thyristor VS1 auxiliary thyristor is used VS2 and switching capacitor WITH. Pre capacitor WITH charged via circuit VS2 – R – Lн up to supply voltage. After switching on VS1 the capacitor is recharged in the circuit VS1 – VD1 – Lк – С, and the transition process is oscillatory in nature. Presence of diode VD1 leads to the fact that only the first positive half-cycle of the capacitor current flows in the circuit, after which the voltage across the capacitor does not change. To turn off the thyristor VS1 thyristor turns on VS2 and capacitor C discharging through the circuit VS2, VS1 turns off, by applying voltage in the opposite direction, the thyristor VS1. In this case, the voltage at the load will increase abruptly to the value E+Uc. The load current remains unchanged during the switching interval, so the voltage on the capacitor changes according to a linear law. When the capacitor WITH will discharge to zero, at the anode of the thyristor VS1 the direct voltage increases again at a rate of . For reliable locking of the thyristor VS1 The discharge time of the capacitor must be greater than the turn-off time of the thyristor.
Then the load voltage continues to decrease linearly until the capacitor is completely recharged WITH via thyristor VS2. When the thyristor current VS2 decreases to zero, it turns off. The load current is closed through the diode circuit VD 0.
The presence of voltage “spikes” at the load requires choosing semiconductor devices with double supply voltage. In addition, the voltage regulation range is reduced, since at low duty cycles these “spikes” do not allow the voltage to be reduced below a certain level.
In the soft switching switching regulator circuit, the main thyristor VS1 shunted in the opposite direction by a diode VD2(Fig. 3.3).
Capacitor recharging process WITH happens in the same way as in the previous diagram. After turning on the thyristor VS2 in a chain C – Lк – VS2 – VS1 – C An oscillatory transient process of recharging the capacitor occurs. When the instantaneous value of the capacitor discharge current is equal to the instantaneous load current, the thyristor VS1 de-energizes and then the difference between the capacitor and load currents is closed through the diode VD2. To the main thyristor VS1 applied reverse voltage equal to the forward voltage drop across the diode VD2. Current through VD2 must flow for a time sufficient to turn off the main thyristor VS1. When the capacitor current becomes less than the load current, the capacitor is additionally charged by the load current, and the voltage across the load decreases according to a linear law; at this interval, the difference current of the load and capacitor is closed through the diode VD 0. The instantaneous voltage value at the load does not exceed the value E.
Connecting a reverse diode in parallel with the main thyristor allows you to transfer the load power to the power source. This mode is possible when the DC motor switches to generator mode (dynamic braking mode). At the same time, due to the low reverse voltage applied to the main thyristor, the turn-off time of the thyristor increases.
Circuit of a pulse regulator that allows you to regulate the voltage across the load from E P and above, shown in Fig. 3.4.
The voltage at the load increases due to the energy of the inductor connected in series to the load circuit. When the transistor is on VT the inductor is connected to a constant voltage source, the inductor current increases linearly from Imin before Imax. The voltage across the inductor is almost equal E P.
A closed diode will divide the circuit into two sections. Previously charged capacitor WITH discharges to the load, ensuring continuity of the load current.
When the transistor is closed, the inductor current is closed through the opened diode and decreases from Imax before Imin. The voltage at the inductor changes polarity and is connected in series with the load in accordance with the power source:
,
(),
Where 
.
From the equality to zero of the average voltage value at the inductor it follows:
The control characteristic (Fig. 3.5) of a boost pulse regulator is nonlinear, and its type depends on the ratio of the resistances of the circuit elements (transistor, diode, inductor) and the load resistance. As this ratio increases, the maximum voltage decreases and stable operation of the regulator is possible up to a certain value of the duty cycle of the control pulses.
The average value of the diode current is equal to the load current:
The average value of the inductor current, and, consequently, the constant voltage source is equal to:
.
The average value of the transistor current is:
.
All semiconductor devices must be selected for a voltage no less than the maximum load voltage.
Switching regulators for DC motors, in addition to regulating the voltage supplied to the motor, must also perform the functions of reversing (changing the polarity of the output voltage) and dynamic braking (returning energy to the DC voltage source when the motor switches to generator mode). These functions are performed using DC-DC converters with pulse-width control.
The converter is a bridge circuit with fully controlled switches, which are shunted with freewheeling diodes (Fig. 3.6).
Freewheeling diodes are used to return energy to the source, so if the DC voltage source does not conduct bi-directionally (for example, a rectifier), then the output of the source must be bypassed with a capacitor WITH corresponding container.
The main parameters of the converter are determined by the key management algorithm. There are three ways to manage keys:
Symmetric;
Asymmetrical;
Alternate.
With symmetrical control, the keys are switched in pairs in antiphase. When turning on the keys K1 And K4 the motor voltage is E P and has a positive polarity; when turned on K2 And K3 The voltage on the motor changes polarity, remaining the same in magnitude. The average voltage across the load is determined taking into account voltages of both polarities (Fig. 3.7 (a)).
The voltage value is determined by the duty cycle of control pulses: for one pair of keys ( K1 And K4) is equal K Z, and for the other ( K2 And K3) – 1-K Z:
.
Within the range of changes K Z from 0 to 0.5 the load voltage varies from - E P to 0, and in the range from 0.5 to 1 – from 0 to E P.
The shape of the load current has the same character as in pulse regulators: with the switches on K1 And K4 load current increases linearly from Imin before Imax, When K1 And K4 are closed, then the load current, determined by the load inductance, through the diodes VD2 And VD3 returns the energy stored in the inductance to the source and decreases from Imax before Imin.
When the load (DC motor) operates in generator mode, when the emf. anchors E I more E P, the load current changes its direction even when the keys are turned on K1 And K4 load current through diodes VD1 And VD4 returns energy to the source, while the current decreases from - Imax before - Imin, and with the keys turned on K2 And K3 load current increases from - Imin before - Imax, storing energy in the load inductance. When the duty cycle of the control pulses changes, the amount of energy returned to the source changes.
The symmetrical control method is characterized by increased load current ripples due to changes in load voltage from - E P to + E P, and a disproportionate dependence of the load voltage on the duty cycle.
With an asymmetrical control method for the positive polarity of the voltage at the load, the switches K1 And K2 controlled in antiphase, key K4 always open and K3- permanently closed. For negative voltage polarity, vice versa: K3 And K4 controlled in antiphase, K2– open, K1– closed. Next, we consider the operation of the converter with positive voltage polarity at the load (Figure 3.7 (b)).
When switch K1 is open, the load current increases from Imin before Imax, the load voltage is + E P. When K1 closes, the load current is closed through K4 And VD2, decreasing from Imax before Imin, while the voltage across the load is practically zero. The duty cycle of control pulses can vary from 0 to 1, while the load voltage changes from 0 to + E P:
When the load operates in generator mode with the K1 load current through diodes VD1 And VD4 returns energy to the source, and when open K2 load current is closed through K2 And VD4, storing energy in the load inductance.
If the limit switching frequency of the switches is not high enough, the alternating method of controlling the keys allows you to double the frequency of current ripples in the load. If there is no need to implement the energy return mode to the source, then the control voltage is applied only to the switches of one diagonal: for positive voltage on K1 And K4, for negative – by K2 And K3.
The shape of the control voltage is shown in Fig. 3.8(a).
The pulse duration varies from to , and the control voltage pauses are shifted by half a period. The voltage across the load is equal to the supply voltage when both switches are open, and equal to zero when one of the keys is closed. The load current is closed through another open switch and the corresponding reverse diode. This situation occurs twice during the period of the control voltage, so the frequency of voltage and current ripples in the load is twice as high. A change in the duration of control pulses from to corresponds to a change in the duty cycle of the voltage pulses at the load from 0 to 1.
If you control key K2 in antiphase with key K1, and key K3 in antiphase with key K4, then the converter can operate in the mode of returning energy to the source when the DC motor is operating in generator mode (Fig. 3.8 (b)).
Automatic impulse regulators
Automatic control is widely used in many technical and biotechnical systems to perform operations that cannot be carried out by humans due to the need to process a large amount of information in a limited time, to increase labor productivity, the quality and accuracy of regulation, and to free humans from controlling systems operating in conditions of relative inaccessibility or hazardous to health. The purpose of control is in one way or another associated with the change in time of the regulated (controlled) quantity - the output quantity of the controlled object. To achieve the control goal, taking into account the characteristics of controlled objects of various natures and the specifics of individual classes of systems, an influence on the control bodies of the object is organized - a control action. It is also intended to compensate for the effect of external disturbing influences that tend to disrupt the required behavior of the controlled variable. The control action is generated by the control device (CD).
The combination of interacting control device and controlled object forms an automatic control system.
In modern automatic control systems, automatic control systems are subsystems of automatic control systems and are used to regulate various parameters when controlling an object or process.
The principle of operation of any automatic control system (ACS) is to detect deviations of controlled quantities that characterize the operation of an object or the flow of a process from the required mode and at the same time influence the object or process in such a way as to eliminate these deviations.
To implement automatic regulation, an automatic regulator is connected to the regulated object, which generates a control effect on the regulatory body. This control action is generated by the controller depending on the difference between the current value of the controlled variable (temperature, pressure, liquid level, etc.) measured by the sensor and its desired value set by the controller.
The controlled object and the automatic controller together form an automatic control system.
The main feature of the ACS is the presence of a main feedback loop, through which the regulator controls the value of the controlled parameter.
Figure 1. - Functional diagram of the ACS:
Z - adjuster, to set the specified value of parameter X0;
D - sensor (thermocouple, thermistor, level sensor, speed sensor, etc. for different systems);
R - regulator;
IM - actuator (electric motor with gearbox, pneumatic cylinders, etc.);
RO - regulatory body (faucet, valve, damper, etc.);
O - object of regulation (furnace, electric motor, tank, etc.);
U - regulatory (control) influence;
Z - interference (disturbance);
X - adjustable parameter;
X1 - signal at the sensor output;
eX1X0 - error, occurs when a parameter deviates from the setting;
X0 - the set value of the adjustable (controlled) parameter can be constant X0 or variable (Ut).
The signal from the controller can be:
- - constant X0, const. to maintain a constant regulated parameter of temperature, pressure, liquid level, etc. (stabilization systems);
- - can change in time U(t) according to a specific program (program control);
- - can change in time U(t) in accordance with the measured external process (tracking control).
The industry produces a large number of different automatic regulators designed to regulate the operating mode of boiler plants (temperature, pressure, flow, level, composition of the substance, etc.).
The most widely used in industry are stabilizing automatic regulators of continuous action and relay ones, which respond to the deviation of the controlled variable and use electrical energy or compressed air energy to influence the actuator. In modern regulators, the regulation law is formed, as a rule, in the corresponding feedback devices, with the exception of the integral regulator, which does not have additional feedback.
A pulse regulator is an automatic intermittent regulator, the output signal (control action) of which has the character of a modulated sequence of pulses.
A necessary element of a pulse regulator is a pulse element (modulator), which modulates the output pulse sequence in accordance with the magnitude of the error signal. Depending on the type of pulse modulation, amplitude-, width-, and pulse-frequency regulators are distinguished.
The pulsed nature of control facilitates the solution of a number of technological problems that arise during the development of automatic regulators, and allows the creation of certain control devices that have significant design and operational advantages.
One of the main advantages of a pulse regulator is that with the help of simple and economical technical means it is possible to resolve the contradiction between the accuracy and power of control signals.
With the continuous nature of control, the primary measuring device (magnetoelectric galvanometer, ratiometer, gyroscope, etc.) is constantly connected to a transducer sensor, which converts the device readings into a powerful signal that controls the operation of the actuator.
The sensor is an additional load on the moving system of the device, reducing the accuracy of its readings. The pulse regulator has the ability to connect the sensor to the primary device only for the duration of the control pulse.
During this time, the moving system of the measuring device is fixed in the position in which it was before the pulse appeared, so that the accuracy of the device readings does not deteriorate.
A significant advantage of regulators with amplitude and pulse width modulation (APM, PWM) is the ability to carry out multi-channel regulation.
In this case, one pulse regulator controls the operation of several control objects OU1, OU2, OUN due to the time division of control channels carried out by pulse elements IE-1, IE-2,..., IE-N, operating with the same or multiple repetition periods T, but shifted in phase by the amount?T.
Figure 2. - Multichannel pulse ATS:
a - block diagram;
b - diagram of the operation of pulse elements;
xi - controlled quantities;
ei - error signals;
ui - control actions.
The main advantage of pulse regulators with frequency and pulse width modulation (PWM and PWM) is the combination of high quality control with the design simplicity and reliability characteristic of relay systems. High quality of regulation is ensured here by the linearizing effect of PFM or PWM, due to which the dynamic characteristics of a switching regulator approach those of linear regulators.
At the same time, the relay nature of the output signal of such regulators allows the use of simple and reliable actuators with relay control: squirrel-cage asynchronous motors, hydraulic or electro-pneumatic drives, solenoid valves, stepper motors, etc.
As an example, Figure 3 shows a block diagram of a simple pulse-frequency regulator. The error signal e(t), amplified by a voltage amplifier (VA), is fed to an integrating RC filter. The signal after the filter, amplified by a power amplifier (PA), is fed to the RU relay, which controls the operation of the actuator (AM) and time relay (RT). The RV, operating with a short time delay?t, discharges capacitor C.
This leads to the return of the RU and stopping the MI. As a result, rectangular pulses with a constant duration?t and with a frequency approximately proportional to the error signal e(t) appear at the output of the switchgear. In terms of dynamic properties, such a pulse regulator is close to the simplest linear astatic controller, and in terms of design simplicity and reliability - to a three-position relay controller.
Figure 3. - Block diagram of a pulse-frequency modulator:
The pulse method of information transmission has increased noise immunity. Therefore, pulse regulators are used in automatic control systems containing wired or radio communication channels. Examples of such systems are tracking radar stations, telecontrol systems for industrial facilities, etc.
In the electric power industry, voltage, frequency and active power regulators with PWM and PFM have become widespread. In the USSR, a large assortment of devices for single- and multi-channel pulse and digital control of the MIR-63 type, pneumatic running devices of the UMO-8 and UMO-16 types, designed for 8- and 16-channel pulse control and produced as part of the “START” system, were produced , machines for centralized control and multi-channel digital regulation of the types “ELRU”, “Zenit”, “Tsikl-2”, “AMUR”, “MARS-200R”, etc.
Pulse regulators, together with special logic-computing devices, make it possible to create extreme control systems designed to automatically maintain the maximum (minimum) value of the controlled variable. Examples of extreme pulse regulators are the pulse-frequency extreme regulator "ERA-1" and extreme pneumatic regulators of the APC series ("START" system).
Conclusion
Improving technology and increasing labor productivity in all sectors of the national economy are among the most important tasks of technical progress in our society. Solving these problems is possible only with the widespread introduction of automatic regulation and control systems for both individual objects and production, industry and the entire national economy as a whole.
The scientific and technological revolution caused by the creation of digital computers affected the development of many branches of science and technology. The theory and practice of automatic regulation and control of objects and sets of objects in both civilian and military technology have been particularly strongly influenced.
The use of digital computing technology opens up great opportunities in the control of such complex devices and systems as rolling mills, blast furnaces, paper-making machines, production lines, moving objects (airplanes, rockets, spaceships, etc.), automated production control systems, railway transport, air movement, etc.
List of sources used
- 1. Shandrov, B.V. Technical means of automation Text: textbook for students. higher textbook establishments / B.V. Shandrov, A.D. Chudakov. - M.: Publishing center "Academy", 2007. - 368 p. - ISBN: 978-5-7695-3624-3.
- 2. Tkachuk, Yu.N. Technical means of automation of printing production Text: textbook. allowance / Yu.N. Tkachuk, Yu.V. Shcherbina. - Moscow state University of Printing. - M.: MGUP - 2010. - 230 p. - ISBN 978-5-8122-1114-1.
- 3. Klyuev, A.S. Setting up automation equipment and automatic control systems: Reference manual / A.S. Klyuev, A.T. Lebedev, S.A. Klyuev, A.G. Commodity, ed. A.S. Klyueva. - 2nd ed., revised. and additional - M.: Alliance, 2009. - 368 p.: ill. - ISBN: 5-903034-84-5 978-5-903034-84-0.
- 4. Kaganov, V.I. Computer analysis of a pulsed automatic control system / V.I. Kaganov, S.V. Tereshchenko // Bulletin of the Voronezh Institute of the Ministry of Internal Affairs of Russia. - 2011. - No. 2. - P. 6-12. - ISSN 2071-3584. sensor pulse modulator
- 5. Purro V. Automation of processes.
This article compares three different approaches to creating a voltage regulator with an output voltage of 5 V and a maximum load current of 100 mA, fed from a 24 V bus. The synchronous buck converter is compared with an integral linear regulator and with a discrete linear regulator. Comparisons of size, efficiency, thermal performance, transient response, noise, circuit complexity, and cost will help designers select the option that best meets the requirements of a particular application.
Comparison conditions
5V is required in most industrial applications that use the 24V rail to power, for example, logic circuits and low-voltage microprocessors. A current of 100 mA was selected as sufficient for most of these loads. However, the decision to select a switching or linear regulator may be influenced by the level of power dissipation. The circuits shown in Figures 1, 2 and 3 are assembled on a common printed circuit board using absolutely identical capacitors with a capacity of 1 µF at the input and 4.7 µF at the output.
The circuit in Figure 1 uses a commercially available synchronous buck converter with integrated power MOSFETs. Note that this circuit does not require a clamping diode, but does require an inductance, five capacitors and four resistors, some of which are installed in the frequency compensation circuit of the feedback loop. The circuit is configured to use the same input and output capacitors as the linear circuits shown in Figures 2 and 3.
The design shown in Figure 2 is based on the popular, industry-standard linear regulator with a wide input voltage range and output current up to 1.5 A. The circuit uses two external resistors and two capacitors. The significant difference between the input and output voltages and, accordingly, high power dissipation require the use of a microcircuit in a low thermal resistance package (DDPak).
To implement the discrete circuit shown in Figure 3, a transistor, a zener diode, two external capacitors, and four resistors are required. A zener diode with a breakdown voltage of 5.6 V is connected to the base of the NPN transistor. The drop at the base-emitter junction reduces the output regulated voltage to approximately 5 V. External resistors absorb some of the excess power, easing the thermal behavior of the transistor.
Table 1 compares the three designs in terms of the number of components used and the required PCB area.
| Table 1. | Board area and number of components. |
Due to the need to provide proper thermal profile on the printed circuit board, linear regulators require a larger area. At maximum load, each linear regulator must dissipate about 2 V of power. As a rule of thumb, every watt of power dissipated across a 1 x 2 inch area of a PCB increases its temperature by 100 °C. Linear regulators are designed in such a way that their overheating does not exceed 40 °C. Of course, with a limited printed circuit board area, a synchronous step-down converter will be preferable, even despite the increased number of external components and the complexity of calculating the frequency compensation circuit of the feedback circuit and the inductance value.
Thermal characteristics
The thermogram in Figure 4 shows the temperature profile of each of the three circuits placed on the PCB. The board is designed in such a way that no circuit affects the thermal performance of the adjacent circuit. From Table 2 it can be seen that the switching regulator operates with the lowest overheating, equal to 11 °C. Due to the large difference between the input and output voltages, a switching regulator with synchronous rectification is superior in efficiency to any of the linear circuits (Table 3). Note that overheating an integrated linear regulator circuit is different from overheating a discrete linear regulator circuit. This is because the integrated regulator housing (DDPak) is larger and the heat it dissipates is distributed over a larger area. Used in discrete linear design, the SOT-23 and SOT223 packages are smaller than DDPak, making heat dissipation more difficult.
| Table 2. | Summary of thermal characteristics. | ||||||||||||||||
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Efficiency comparison
The thermal performance of each regulator is directly related to its efficiency. Figure 5 allows you to compare the efficiency of the three circuits. As you would expect, the switching regulator is unrivaled here - both at light loads and at maximum loads. At light loads, switching losses and self-current consumption dominate, which explains the decrease in efficiency at low output currents. For light loads, it is better to look at the power loss graphs (Figure 6) than the efficiency graphs, since a 2-fold difference in efficiency at 10 mA seems too large. At the same time, the amount of current consumed by the load is very small. With an input voltage of 24 V and an output current of 10 mA, the power loss in a switching regulator is 2.8 mW, and in an integral linear regulator it is 345 mW. At maximum load, the measured power losses are 0.093 W for a switching regulator and 2.06 W for a linear one.
Table 3 summarizes the efficiency and power loss measurements for all three designs. It can be noted that the intrinsic current consumption of a discrete linear regulator is less than that of its integral analogue. An integral linear regulator contains more energy-consuming internal circuits, but it also performs more functions than a discrete linear regulator.
| Table 3. | Efficiency and power loss. | |||||||||||||||||||
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Output characteristics
Analog circuits can be sensitive to power supply ripple, and digital processors can be sensitive to the accuracy of core supply voltage. Therefore, it is important to compare our circuits in terms of parameters such as output ripple, voltage stabilization accuracy, and response to sudden load changes. Linear regulators, by their very nature, are low ripple and are often used to remove noise from switching converters.
The voltage ripple of both linear regulator circuits at maximum load does not exceed 10 mV. As a fraction of the output voltage, this is better than 0.2%. On the other hand, the ripple of switching converters reaches 75 mV, or 1.5% of the output voltage. The low equivalent series resistance of the output ceramic capacitor allows you to reduce ripple in the switching regulator circuit.
When comparing the accuracy of output voltage stabilization over the entire load range, the switching regulator wins. From the reference data for the components used, it is clear that the reference voltage source (VS) of the pulse converter is characterized by the best accuracy. Switching regulators are relatively new integrated circuits, and their quality is constantly improving. A discrete linear circuit, which uses the simplest method of stabilizing the output voltage, has the worst characteristics. However, often high accuracy is not required from a 5 V source, especially if this voltage is the input to the next level of regulators.
Oscillograms of output voltages and currents in transient modes can be seen in Figures 7-9. Although the voltage accuracy of a switching regulator is high, its transient characteristics are much worse than those of linear circuits. The measured peak-to-peak response of a switching regulator to a load current step from 50 to 100 mA is 250 mV, or 5% of the output voltage, versus 40 mV for linear circuits. You can reduce voltage surges at the load of a switching regulator using an additional output capacitor, but this will lead to an increase in price and size. It should be noted that a discrete linear circuit is not designed to stabilize the output voltage during load transients. In addition, the simplicity of the circuit does not allow the implementation of current limiting functions or protective shutdown in case of overheating.
Table 4 summarizes the output voltage characteristics for the three regulator circuits.
| Table 4. | Summary of output voltage characteristics. | ||||||||||||||||
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Cost comparison
Most external components used in circuits are passive resistors and capacitors, costing well under $0.01. The most expensive in all three schemes are silicon devices. The component cost data shown in Table 5 for all circuit options is collected in the United States through distribution channels based on retail prices recommended for lots of 10,000 components. As you can see, both linear regulators are much cheaper than pulse ones. Unfortunately, the switching regulator requires an external inductance, which can cost about $0.10, but the additional cost may be justified by the improved efficiency and size characteristics. The difference in prices for linear circuits is only $0.06! When choosing between an integral and discrete linear regulator, the former may be preferable due to the presence of built-in protection circuits.
Conclusion
Power supply developers have a wide range of technical solutions at their disposal. Which one will be best depends on the requirements for a particular application. Power management systems that consume less power and take up less board space allow designers to make their products more customized and marketable. Synchronous buck converters are radically different from linear regulators in their efficiency and compactness. If cost is a primary consideration, a discrete linear regulator may be appropriate, but this will come at the cost of poorer performance, lack of safety features, and likely additional heat sink costs.
Linear discrete
The complete set of characteristics of all three regulators that a designer needs to select the option that best meets the requirements of the application he is creating is given in Table 6.
Linear stabilizers have a common disadvantage - low efficiency and high heat generation. Powerful devices that create load current over a wide range have significant dimensions and weight. To compensate for these shortcomings, pulse stabilizers have been developed and used.
A device that maintains a constant voltage at a current consumer by adjusting an electronic element operating in key mode. A switching voltage stabilizer, just like a linear one, exists in series and parallel types. The role of the key in such models is played by transistors.
Since the effective point of the stabilizing device is almost constantly located in the cutoff or saturation region, passing through the active region, a little heat is generated in the transistor, therefore, the pulse stabilizer has a high efficiency.
Stabilization is carried out by changing the duration of the pulses, as well as controlling their frequency. As a result, a distinction is made between pulse-frequency and, in other words, width-width regulation. Pulse stabilizers operate in a combined pulse mode.
In stabilization devices with pulse-width control, the pulse frequency has a constant value, and the duration of the pulses is a variable value. In devices with pulse-frequency control, the duration of the pulses does not change, only the frequency is changed.
At the output of the device, the voltage is presented in the form of ripples; accordingly, it is not suitable for powering the consumer. Before supplying power to the consumer load, it must be equalized. To do this, leveling capacitive filters are mounted at the output of pulse stabilizers. They come in multi-link, L-shaped and others.
The average voltage applied to the load is calculated by the formula:
- Ti is the duration of the period.
- ti – pulse duration.
- Rн – value of consumer resistance, Ohm.
- I(t) – value of the current passing through the load, amperes.
Current may stop flowing through the filter by the start of the next pulse, depending on the inductance. In this case we are talking about the operating mode with alternating current. The current can also continue to flow, which means operation with direct current.
With increased sensitivity of the load to power pulses, the DC mode is performed, despite significant losses in the inductor winding and wires. If the size of the pulses at the output of the device is insignificant, then operation with alternating current is recommended.
Principle of operation
In general, a pulse stabilizer includes a pulse converter with an adjustment device, a generator, an equalizing filter that reduces voltage pulses at the output, and a comparing device that supplies a signal of the difference between the input and output voltages.
A diagram of the main parts of the voltage stabilizer is shown in the figure.
The voltage at the output of the device is supplied to a comparing device with the base voltage. The result is a proportional signal. It is supplied to the generator, having previously amplified it.
When controlled in a generator, the difference analog signal is modified into a ripple with a constant frequency and variable duration. With pulse-frequency control, the duration of the pulses has a constant value. It changes the frequency of the generator pulses depending on the properties of the signal.
The control pulses generated by the generator pass to the elements of the converter. The control transistor operates in key mode. By changing the frequency or interval of the generator pulses, it is possible to change the load voltage. The converter modifies the output voltage value depending on the properties of the control pulses. According to theory, in devices with frequency and width adjustment, voltage pulses at the consumer may be absent.
With the relay principle of operation, the signal, which is controlled by the stabilizer, is generated using a trigger. When constant voltage enters the device, the transistor, which acts as a switch, is open and increases the output voltage. the comparing device determines the difference signal, which, having reached a certain upper limit, changes the state of the trigger, and the control transistor switches to cutoff.
The output voltage will begin to decrease. When the voltage drops to the lower limit, the comparing device determines the difference signal, switching the trigger again, and the transistor will again go into saturation. The potential difference across the device load will increase. Consequently, with a relay type of stabilization, the output voltage increases, thereby equalizing it. The trigger limit is adjusted by adjusting the amplitude of the voltage value on the comparing device.
Relay-type stabilizers have an increased response speed, in contrast to devices with frequency and width control. This is their advantage. In theory, with a relay type of stabilization, there will always be pulses at the output of the device. This is their disadvantage.
Boost stabilizer
Switching boost regulators are used with loads whose potential difference is higher than the voltage at the input of the devices. The stabilizer does not have galvanic isolation between the power supply and the load. Imported boost stabilizers are called boost converters. The main parts of such a device:
The transistor enters saturation, and current flows through the circuit from the positive pole through the storage inductor, the transistor. In this case, energy accumulates in the magnetic field of the inductor. The load current can only be created by a discharge of capacitance C1.
Let's turn off the switching voltage from the transistor. At the same time, it will enter the cut-off position, and therefore a self-induction EMF will appear on the throttle. It will be switched in series with the input voltage, and connected via a diode to the consumer. The current will flow through the circuit from the positive pole to the inductor, through the diode and the load.
At this moment, the magnetic field of the inductive choke supplies energy, and capacitance C1 reserves energy to maintain the voltage at the consumer after the transistor enters saturation mode. The choke is for energy reserve and does not work in the power filter. When voltage is applied again to the transistor, it will open and the whole process will begin again.
Stabilizers with Schmitt trigger
This type of pulse device has its own characteristics with the smallest set of components. The trigger plays a major role in the design. It includes a comparator. The main task of the comparator is to compare the value of the output potential difference with the highest permissible value.
The principle of operation of the device with a Schmitt trigger is that when the highest voltage increases, the trigger is switched to the zero position with the electronic key opening. At one time the throttle discharges. When the voltage reaches its lowest value, switching by one is performed. This ensures the switch closes and current flows to the integrator.
Such devices are distinguished by their simplified circuit, but they can be used in special cases, since pulse stabilizers are only step-up and step-down.
Buck stabilizer
Pulse-type stabilizers, operating with voltage reduction, are compact and powerful electric power supply devices. At the same time, they have low sensitivity to consumer interference with a constant voltage of the same value. There is no galvanic isolation of the output and input in step-down devices. Imported devices are called chopper. The output power in such devices is always less than the input voltage. The circuit of a buck-type pulse stabilizer is shown in the figure.
Let's connect the voltage to control the source and gate of the transistor, which will enter the saturation position. It will carry current through the circuit from the positive pole through the equalizing choke and the load. No current flows through the diode in the forward direction.
Let's turn off the control voltage, which turns off the key transistor. After this, it will be in the cut-off position. The inductive emf of the equalizing choke will block the path for changing the current, which will flow through the circuit through the load from the choke, along the common conductor, diode, and again come to the choke. Capacitance C1 will discharge and will maintain the voltage at the output.
When an unlocking potential difference is applied between the source and gate of the transistor, it will go into saturation mode and the entire chain will repeat again.
Inverting stabilizer
Inverting-type switching stabilizers are used to connect consumers with constant voltage, the polarity of which has the opposite polarity direction to the potential difference at the output of the device. Its value can be above the power supply network, and below the network, depending on the settings of the stabilizer. There is no galvanic isolation between the power supply and the load. Imported inverting type devices are called buck-boost converters. The output voltage of such devices is always lower.
Let's connect a control potential difference, which will open the transistor between the source and the gate. It will open, and the current will flow through the circuit from the plus through the transistor, the inductor, to the minus. In this process, the inductor reserves energy using its magnetic field. Let's turn off the control potential difference from the switch on the transistor, it will close. The current will flow from the inductor through the load, diode, and return to its original position. The reserve energy on the capacitor and magnetic field will be consumed by the load. Let's apply power to the transistor again to the source and gate. The transistor will again become saturated and the process will repeat.
Advantages and disadvantages
Like all devices, a modular switching stabilizer is not ideal. Therefore, it has its own pros and cons. Let's look at the main advantages:
- Easily achieve alignment.
- Smooth connection.
- Compact sizes.
- Output voltage stability.
- Wide stabilization interval.
- Increased efficiency.
Disadvantages of the device:
- Complex design.
- There are many specific components that reduce the reliability of the device.
- The need to use power compensating devices.
- Difficulty of repair work.
- Formation of a large amount of frequency interference.
Allowable frequency
The operation of a pulse stabilizer is possible at a significant conversion frequency. This is the main distinguishing feature from devices that have a network transformer. Increasing this parameter makes it possible to obtain the smallest dimensions.
For most devices, the frequency range will be 20-80 kilohertz. But when choosing PWM and key devices, it is necessary to take into account high current harmonics. The upper limit of the parameter is limited by certain requirements that apply to radio frequency devices.
Transcript
1 95 Lecture 0 PULSE VOLTAGE REGULATORS Plan. Introduction. Buck switching regulators 3. Boost switching regulators 4. Inverting switching regulator 5. Losses and efficiency of switching regulators 6. Conclusions. Introduction Secondary power supplies built according to a traditional scheme (transformer, rectifier, smoothing filter and stabilizer) are simple in design and have a low level of electromagnetic radiation. However, they dissipate significant power and have large mass and dimensions. The large dimensions of such sources are due to the fact that the supply voltage has a low frequency of 50 Hz. This leads to the need to use transformers with a large cross-section of the magnetic core and the use of large capacitors in smoothing filters. These disadvantages are also typical for linear stabilizers discussed in the previous lecture. In particular, the efficiency of such stabilizers often does not exceed 50%. The low efficiency values of linear stabilizers are due primarily to the fact that the power dissipated by the control transistor turns out to be quite large, especially when stabilizing low voltages. Significantly greater efficiency is provided by circuits in which the regulating element is a switch (switch), which, with a certain repetition period T, switches from a closed state to an open state and back. Bipolar or MOS transistors are used as switches. The ratio of the time of the open (closed) state of the key to the repetition period T can be adjusted. By changing this ratio, we can widely regulate the average voltage across the load. This control method is called pulse width modulation (PWM pulse width modulation). A low-pass filter is connected in series with the switch, smoothing out the output voltage ripple to an acceptable value. Such circuits are called switching regulators.
2 96 The main components of switching power supplies are chokes, capacitors, controlled switches and transformers. All of these components have low losses, ideally equal to zero. If the resistance of the switch in the closed state is low, then the efficiency of the pulsed source can reach 90% or more. Energy losses in a transistor used as a switch occur mainly during the switching interval and are determined by the duration of this interval. Therefore, the better the frequency properties of the transistor, the higher the efficiency of the switching regulator. Let us list the main advantages of pulsed PVEP. High efficiency. Small weight and dimensions. 3. The ability to obtain an output voltage higher than the input (step-up regulators). Pulse sources of secondary power supply made it possible to move from the conversion of electrical energy at low frequencies to operation at frequencies of tens and hundreds of kilohertz. This made it possible to significantly reduce the size and weight of transformers and smoothing filters. The advent of powerful high-voltage transistors and low-loss materials for magnetic cores of high-frequency transformers has made it possible to create pulsed sources with a transformerless input. With an output power of 00 W, such sources can have a specific power exceeding 00 W/dm, whereas for traditional PVES this figure does not exceed 0 W/dm. Let us indicate the main disadvantages of pulsed sources. Voltages and currents are pulsed in nature. This may result in high-frequency interference in the load and external network. To reduce the noise level, it is necessary to use anti-aliasing filters, careful shielding, etc. The switching regulator and the switch control circuit form a feedback system. Special measures are required to ensure the stability of the regulator. 3. Switching power supplies, including switching regulators, are more expensive and require more development time. Switching power supply circuits are distinguished by a wide variety of design principles. We will devote several lectures to the consideration of such sources. Let us first consider the basic circuits of switching regulators.
3 97. Buck Switching Regulator The circuit of the buck regulator is shown in Fig. 0.. Fig. 0. The regulating element is a switch, shown in the diagram as a key. The inductor and capacitor C form a smoothing filter. The switching frequency of the switch must be high in order to ensure low output voltage ripple. It can reach hundreds of kilohertz and units of megahertz. Increasing the switching frequency can significantly reduce the weight and dimensions of the anti-aliasing filter. Let's consider electromagnetic processes in the circuit in Fig. 0., which occur in the interval T. When the switch is closed, the inductor current increases and energy accumulates in the magnetic field of the inductor. When the switch is open, the inductor current is closed through the open diode VD. The energy accumulated in the magnetic field of the inductor is spent to maintain a constant output voltage. Let's consider how the inductor current changes during the switching interval of the commutator T. We will assume that the capacitance of the smoothing capacitor is very large, so that the output voltage is constant. The operating mode of the circuit depends on the state of the key. Let us denote t and the time during which the key is closed. Let's consider the following time intervals: Interval 0 t. The key is closed. A reverse voltage is applied to the diode and it is closed. Current increment at this interval in out = t and i.. Interval t and T. The key is open. The diode is open, and the inductor current is closed through the diode and load resistance Rn. Current increment (T t) out and i =. Timing diagrams of voltages and currents of the pulse regulator are shown in Fig. 0..
4 98 Fig. 0. Since switching occurs periodically, the total change in current over the time interval T is zero: i = i T in and out + i = = From this relationship it follows that the output voltage t 0.
5 99 t out = and in = D in. (0.) T t Here D = and pulse duty cycle. T Equality (0.) is called the control characteristic of a pulse regulator. Thus, the output voltage of the switching regulator is proportional to the duty cycle of the commutator pulses. Since D<, выходное напряжение всегда меньше входного. Поэтому такой регулятор называют понижающим. Величиной выходного напряжения можно управлять, изменяя коэффициент заполнения импульсов D. Такой процесс управления называется широтно-импульсной модуляцией (ШИМ). Она широко применяется не только в импульсных источниках питания, но и в других устройствах. Формула (0.) справедлива, если ток i (t) на интервале 0 T не обращается в нуль. Такой режим называют режимом непрерывного тока. Если ток дросселя в течение какого-либо промежутка времени на интервале 0 T обращается в нуль, то имеет место режим прерывистого тока. Поскольку емкость конденсатора конечна, выходное напряжение будет пульсирующим. Определим, как влияют на амплитуду пульсаций значения индуктивности и емкости сглаживающего фильтра. При оценке величины пульсаций выходного напряжения для упрощения анализа примем, что индуктивность дросселя; ток дросселя при этом имеет форму прямоугольных импульсов (рис. 0.3). Среднее значение тока () I ср = D I. Рис. 0.3 Если емкость конденсатора достаточно велика, его сопротивление на частоте первой и высших гармоник значительно меньше сопротивления нагрузки: ωc 6 00 In this case, we can assume that the alternating component of the current is closed through the capacitor. The approximate shapes of the voltage u C (t) and current i C (t) curves are shown in Fig. Voltage increment u C Fig. 0.4 DT DT () (D) DT u = I dt = D I dt = I. C C C av 0 0 From the resulting expression it follows that the amplitude of the output voltage ripple does not depend on its average value. To reduce the amplitude of the output voltage ripple, it is necessary that the condition C (D) DT I. u C be satisfied. Similarly, it can be shown that the amplitude of the current ripple decreases if the inductance of the inductor (D) DT N. i C 7 0 In steady state, the magnitude of current ripple does not depend on its average value. 3. Boost switching regulator The circuit of a boost switching regulator is shown in Fig. When the switch is closed, the diode is closed, and the input voltage is applied to the inductor. Using the assumptions adopted in the previous paragraph, we will determine the change in the inductor current over the interval 0 t and input i = t and. (0.) After opening the switch, the diode will open and a series circuit will be formed. The energy stored in the inductor is transferred to the output of the circuit. In this case, the inductor current decreases. Change in current over the interval t and T ()(T t) out input and i =. (0.3) Fig. 0.5 Since the average value of the current remains unchanged, the total change in current over the interval T is zero: i + i = 0. Substituting formulas (0.) and (0.3) into the last equality, we obtain the control characteristic of the circuit shown in Fig. 0.5: = D out in. 8 0 When D > 0.5 the output voltage exceeds the input. Therefore, the regulator in Fig. 0.5 is called increasing. The magnitude of the output voltage can be controlled by changing the duty cycle of the pulse D. As in the buck converter, the amplitude of the current ripple in the circuit in Fig. 0.3 does not depend on its average value. 4. Inverting pulse regulator The circuit of the inverting regulator is shown in Fig. Divide the conversion cycle into two cycles. During the first cycle, with the switch closed, the current circulates in the circuit formed by the input voltage source, the switch and the inductor. At the same time, energy is stored in the throttle. When the switch opens, the energy stored in the inductor is transferred to the capacitor and load resistance. Rice. 0.6 Let us determine the regulating characteristic of the circuit in Fig. We assume that during each cycle the voltage is constant, and the inductor current changes linearly. When the key is closed, i =. tand Here t is the interval during which the switch is closed, i is the current increment over this interval. When the key is open, output i =. T ti Here i is the change in current over the interval T ti. The average current value per conversion cycle should remain unchanged. Therefore, the total change in current over the interval T i + i = 0. The control characteristic of an inverting pulse regulator 9 03 D =. D out in 5. Losses and efficiency of switching regulators The switch is one of the main sources of losses in switching power supplies. Depending on the topology of the converter, the switch accounts for 40 to 50% of the total losses. The voltage and current curves in the switch of a step-down pulse converter are shown in Fig. A MOS transistor is used as a switch. Rice. 0.7 The Roman numeral I indicates the time intervals corresponding to the closing and opening of the key. Number II indicates the interval corresponding to the closed state of the key. As follows from Fig. 0.7, the main part of the losses in the switch consists of conduction losses and switching losses. To reduce conductivity losses, they try to minimize the voltage on the closed switch. Another element that makes a significant contribution to the total loss is the diode. The graph of the diode current over the commutation interval is shown in Fig. 0.8. 10 04 Fig. 0.8 The main share of losses in a diode consists of losses due to electrical conductivity and reverse recovery. Losses associated with the passage of reverse current through the diode during the reverse recovery interval can be significant. The reverse current of the diode can cause an inrush current in the switch, which will lead to additional losses. To reduce losses, Schottky diodes are used, which have a lower forward voltage. Another way to reduce losses is to replace the diode with a MOS transistor. The effect of the replacement is that the on-channel resistance of the MOSFET is very low. Control pulses are applied to the gates of the MOS transistors in such a way that the lower transistor opens only after the upper transistor is completely closed. This control of MOS switches imitates the operation of a diode and is called synchronous control. Let us approximately determine the losses in the step-down switching regulator shown in Fig. 0.. This will make it possible to evaluate the influence of the controller parameters on the amount of efficiency loss of the circuit under consideration. To simplify the calculations, we will accept the following assumptions. We will consider the current-voltage characteristic of the switch to be piecewise linear (Fig. 0.9). In the closed state, the key current is zero, and in the open state, the key has a resistance equal to R on. The resistance of the switch in the open state does not depend on the current through it. Rice. 0.9 Fig. 0.0 11 05. We will also consider the current-voltage characteristic of the diode to be piecewise linear (Fig. 0.0). The value 0 determines the threshold voltage at which noticeable diode current appears. The on-state resistance of the diode is R D. 3. Let us assume that the inductance of the inductor is infinite. This means that the current in the switch and diode when they are open is constant. Taking into account the accepted assumptions, we will determine the losses in the step-down switching regulator. They consist of conduction losses and switching losses. (D) + R I (D) R I P open = Rcl DI n + I n 0 D n + other n. In the last expression I n is the load current. Switching losses are equal to the average power dissipated in the switch during its switching on and off. Analytical assessment of switching losses is associated with great difficulties, since the curves of currents and voltages when closing and opening a switch have a complex shape. Let us assume that the current changes linearly when the switch is closed and opened. Under this assumption, switching losses equal to the average power dissipated in the switch, P per = T t t 4 i dt + () in n i dt = I t + t in n in on off. t T t 3 T The resulting expressions show that the losses of the step-down switching regulator are smaller if the pulse duty cycle is close to unity. In a similar way, you can estimate the losses in a boost switching regulator. 6. Conclusions. Secondary power supplies built according to the traditional scheme (transformer, rectifier, smoothing filter and stabilizer) dissipate significant power, have large mass and dimensions, and low efficiency. Significantly greater efficiency is provided by pulsed sources, in which the regulating element is a switch (switch), which switches with a certain repetition period T. 12 06 3. The main components of switching power supplies are elements with low losses: chokes, capacitors, controlled switches and transformers. 4. Pulse secondary power supplies operate at frequencies of tens and hundreds of kilohertz. This made it possible to significantly reduce the size and weight of transformers and smoothing filters. 105 Lecture 11 PULSE CONVERTERS WITH GALVANIC SEPARATION OF INPUT AND OUTPUT Plan 1. Introduction. Forward converters 3. Flyback converter 4. Synchronous rectification 5. Correctors 5 Lecture 2 INVERTERS Plan. Introduction 2. Push-pull inverter 3. Bridge inverter 4. Methods for generating sinusoidal voltage 5. Three-phase inverters 6. Conclusions. Introduction Inverter Devices, 75 Lecture 8 RECTIFIERS (CONTINUED) Plan 1. Introduction 2. Half-wave controlled rectifier 3. Full-wave controlled rectifiers 4. Smoothing filters 5. Losses and efficiency of rectifiers 6. Castro M.Yu., Lukin A.V., Malyshkov G.M. TRANSIT OF SWITCHING LOSS ENERGY TO THE LOAD Circuits consisting of passive and nonlinear elements (LD) and allowing to reduce switching losses are often called Lecture 7 RECTIFIERS Plan 1. Secondary power supplies 2. Half-wave rectifier 3. Full-wave rectifiers 4. Three-phase rectifiers 67 1. Secondary power supplies Sources 9. Switching power supplies. Pulse width modulation. In the modern world of technology, with its tendency towards miniaturization and efficiency, switching power supplies have become widespread Fundamentals of the functioning of converter electronics Rectifiers and inverters RECTIFIERS ON DIODES Indicators of rectified voltage are largely determined by both the rectification circuit and the used 84 Lecture 9 VOLTAGE STABILIZERS Plan 1. Introduction 2. Parametric stabilizers 3. Compensation stabilizers 4. Integral voltage stabilizers 5. Conclusions 1. Introduction For the operation of electronic 165 Lecture 17 SUPPRESSION OF ELECTROMAGNETIC INTERFERENCE Plan 1. Introduction 2. Sources of electromagnetic interference 3. Methods for suppressing electromagnetic interference 4. Conclusions 1. Introduction Switching secondary power supplies The invention relates to electrical engineering and is intended for the implementation of powerful, cheap and efficient adjustable transistor high-frequency resonant voltage converters for various applications, 63. Study of single-phase rectifiers Purpose of the work:. Study of the design and operating principle of single-phase rectifiers. 2. Determination of external characteristics of rectifiers. Required Equipment: Modular Laboratory work 5.3 RESEARCH OF FULL-WAVE RECTIFIER 5.3.1. Rectifiers Rectifiers are used to convert AC supply voltage into DC. Main purpose of the rectifier CALCULATION OF RECTIFIERS 1.1. Composition and main parameters of rectifiers Electric (EP) is designed to convert alternating current into direct current. In general, the VP circuit contains a transformer, valves, Topic: Anti-aliasing filters Plan 1. Passive anti-aliasing filters 2. Active anti-aliasing filter Passive anti-aliasing filters Active-inductive (R-L) anti-aliasing filter It is a coil Topic 16. Rectifiers 1. Purpose and design of rectifiers Rectifiers are devices used to convert alternating current into direct current. In Fig. 1 shows the block diagram of the rectifier, Soloviev I.N., Grankov I.E. LOAD INVARIANT INVERTER A pressing task today is to ensure the operation of the inverter with loads of various types. Operation of the inverter with linear loads is sufficient 15.4. SMOOTHING FILTERS Smoothing filters are designed to reduce rectified voltage ripple. Their main parameter is the smoothing coefficient equal to the ratio of the ripple coefficient What's the difference between apple and apple The article proposes new approaches to the construction of static converters, allowing to increase their Chapter 6. ENERGY INDICATORS OF CURRENT RECTIFIERS, QUALITY OF RECTIFIED VOLTAGE AND WAYS TO IMPROVE THEM Energy indicators of rectifiers are the coefficient of efficiency (efficiency), coefficient MUSKATINEV A. V., PRONIN P. I. INVERTER POWER SOURCE FOR WELDING Abstract. The article discusses the problems of choosing a power circuit for a welding source. A description of the electrical principle AC CIRCUITS LECTURE 4 Circuits with mutual induction. Let us consider two closely spaced circuits with the number of turns w and w. In the figure we will conventionally show these contours in the form of one turn. Current flowing in COLLECTION OF SCIENTIFIC WORKS OF NSTU. - 2005. - 1. - 1-6 UDC 62-50:519.216 ANALYSIS AND SELECTION OF DAMPING CIRCUITS FOR POWERFUL PULSE CONVERTERS V.S. DANILOV, K.S. LUKYANOV, E.A. MOSEEEV Currently widespread TOPIC 7 Temperature stabilization As the ambient temperature rises, the transistor current increases and its characteristics shift upward (Fig. 1). Fig. 1 Emitter stabilization. Is to use Chapter 10. DC VOLTAGE CONVERTERS 10.1. Classification of DC voltage converters DC voltage converters (DCC) are designed to convert DC voltage Lecture 3 “AC voltage rectifiers.” Circuits called “rectifiers” are used to convert AC mains voltage to DC. To implement the rectification function in such FEDERAL AGENCY FOR EDUCATION NOVOSIBIRSK STATE UNIVERSITY Faculty of Physics Department of Radiophysics Workshop on radio electronics Switching power supplies Guidelines 6 Lecture 6. TRANSIENT PROCESSES IN ELECTRICAL CIRCUITS. Introduction.. Inductive and capacitive elements. 3. Commutation laws and initial conditions. 4. Conclusion... Introduction So far we have considered circuits Laboratory work 1 Secondary power supplies The purpose of the work is to study the main parameters of the secondary power supply of electronic equipment based on a single-phase full-wave rectifier. Chapter 17. SOURCES OF TORIC POWER SUPPLY 17.1. General characteristics and classification of secondary power sources Secondary power sources (SPS) convert alternating or direct POWER SUPPLY BPS-3000-380/24V-100A-14 BPS-3000-380/48V-60A-14 BPS-3000-380/60V-50A-14 BPS-3000-380/110V-25A-14 BPS-3000- 380/220V-15A-14 instruction manual CONTENTS 1. Purpose... 3 2. Technical Transient processes “in the palm of your hand”. You already know methods for calculating a circuit in a steady state, that is, in a state where currents, as well as voltage drops across individual elements, are constant over time. CHAPTER 7 Combined switching voltage regulator with input voltage coupling. Functional and circuit diagram of the stabilizer In Chapter 7, a functional diagram of a combined Laboratory work 2 Study of converting devices: inverter, converter in the software environment for modeling electronic circuits Electronics Workbench 5.12. Purpose of work: To get acquainted with the work Constant Peak PWM Current Driver for Powering LEDs Suresh Hariharan Optimal performance of ultra-bright LEDs is ensured when powered from a current source 5 Lecture HARMONIC AND PULSE SIGNAL GENERATORS Plan Principle of operation of generators C-generators of harmonic oscillations Rectangular pulse generators 4 Rectangular pulse generators on specialized Lecture 7 Topic: Special amplifiers 1.1 Power amplifiers (output stages) Power amplification stages are usually output (final) stages to which an external load is connected, and are designed 114 power electronics Parallel operation of pulsed boost DC converters in the presence of inductive coupling of chokes Anatoly KORSHUNOV Parallel operation of pulsed boost converters 1 Lectures by Professor Polevsky V.I. Sinusoidal current rectifiers Volt-ampere characteristic of an electrical conversion diode In Fig. 1.1. presents the current-voltage characteristic (CVC) of the electrical converter 6. TRANSFORMERS A transformer is a static electromagnetic device that is used to convert alternating current electrical energy with one parameter into electrical energy with another COLLECTION OF SCIENTIFIC WORKS OF NSTU. 2006. 1(43). 147 152 UDC 62-50:519.216 CONSTRUCTION OF DAMPING CIRCUITS FOR POWERFUL PULSE CONVERTERS E.A. MOISEEV Provides practical recommendations on the selection of elements 11.5. GENERATORS OF LINEAR VARIABLE VOLTAGE Linearly varying or sawtooth voltage is called electrical oscillations (pulses) containing sections in which the voltage changes practically MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION Federal state budgetary educational institution of higher professional education "UFA STATE AVIATION TECHNICAL Introduction SECTION I General electrical engineering Chapter 1. DC electrical circuits 1.1. Basic concepts of electromagnetic field 1.2. Passive circuit elements and their characteristics 1.3. Active elements Lecture 5 PASSIVE COMPONENTS OF POWER ELECTRONICS DEVICES Outline 1. Introduction 2. General properties of magnetic materials 3. Magnetic materials used in converter devices 4. Transformers 97 Lecture 9. BASIC LOGIC ELEMENTS Plan. Elements of transistor-transistor logic (TTL).. Elements of CMOS logic. 3. Basic parameters of logical elements. 4. Conclusions.. Elements of transistor-transistor IPC H03F03/62 BIDIRECTIONAL VOICE FREQUENCY AMPLIFIER The invention relates to amplification devices and can be used in telephone communications. A known bidirectional amplifier containing inverting RESEARCH OF POWER FACTOR CORRECTORS Ignatenko V.V. PrE-1106. gr.361-3 Power factor correction problem Inefficient use of electricity, interference in the electrical network caused by connected UDC 621.314.5 Ph.D. Saratovsky R.N., Afanasyev A.M. (Donetsk State Technical University, Alchevsk, Ukraine) RESONANCE INVERTER WITH A COMBINED STRUCTURE We look at the circuit implementation of a resonant inverter with a combined structure New power modules with a wide (4:1) input voltage range One of the important problems of power electronics is the development of secondary power supplies (SPS) operating from the network 54 Lecture 5 FOURIER TRANSFORM AND SPECTRAL METHOD FOR ANALYSIS OF ELECTRICAL CIRCUITS Plan Spectra of aperiodic functions and the Fourier transform Some properties of the Fourier transform 3 Spectral method Installation and repair of power supplies for digital STV receivers Attention! Use this copy for informational purposes only (burn after reading) Rip by Vasya Pupkin The power source is one CONTENTS Introduction 3 Chapter 1. APPLICATION OF SEMICONDUCTOR CONVERTER ENGINEERING BASIC METHOD FOR CONVERTING ELECTRIC ENERGY PARAMETERS 1.1. Subject of conversion technology... 5 1.2. “Electronic choke” Evgeniy Karpov The article discusses the features of the operation of an electronic power filter and the possibility of its use in sound-reproducing equipment. The motivation for writing Integrated medium voltage AC drives Perfect Harmony: a new standard for energy conversion quality 1. Medium voltage AC drives This class 1 Laboratory work 17 Study of the operation of diode limiters A four-terminal device, at the output of which the voltage () remains practically unchanged and equal to U 0, while the input voltage () can Laboratory work 1.3 Study of the energy characteristics of rectifier devices for powering telecommunications equipment 1. Purpose of work 1.1 Determine the most efficient converter 1 S. CLEMENTE, B. PELLY, R. RUTTONSHA AN-939A UNIVERSAL 100 KHz POWER SUPPLY ON ONE MOSFET Abstract High-power MOSFETs are attractive candidates for use in pulsed DETERMINATION OF STATE VECTORS IN A QUASI-RESONANCE PULSE CONVERTER SWITCHED AT ZERO VOLTAGE VP Voitenko, YuA Denisov Chernigov State Technological University Ukraine, 68 Lecture 7 TRANSIENT PROCESSES IN FIRST ORDER CIRCUITS Plan 1 Transient processes in first order RC circuits 2 Transient processes in first order R circuits 3 Examples of calculating transient processes in circuits Karzov B.N., Kastrov M.Yu., Malyshkov G.M. PULSE PROPERTIES OF DIODE CONNECTION CIRCUITS OF MOS TRANSISTORS When choosing different methods of controlling the basic diode connection circuits of MOS transistors used LABORATORY WORK 5 STUDY OF PULSE DC VOLTAGE STABILIZER Objectives of the work: 1. Study of circuits and main characteristics of DC voltage regulators and stabilizers with pulse 10.2. ELECTRONIC KEYS General information. An electronic key is a device that can be in one of two stable states: closed or open. Transition from one state to another in STC SIT SCIENTIFIC AND TECHNICAL CENTER FOR CIRCUIT ENGINEERING AND INTEGRAL TECHNOLOGIES. RUSSIA, BRYANSK PWM CONTROLLERS WITH CURRENT REGULATION K1033EU15xx K1033EU16xx RECOMMENDATIONS FOR APPLICATION DESCRIPTION OF WORK Chip 1 Lecture SECONDARY POWER SUPPLY SOURCES 1 Introduction Rectifier devices 3 Linear parametric voltage regulators 4 Theoretical summary on the topic 1 Introduction All power supplies STABILIZED POWER SUPPLIES IPS-300-220/24V-10A IPS-300-220/48V-5A IPS-300-220/60V-5A DC/DC-220/24B-10A (IPS-300-220/24V-10A ( DC/AC)/DC)) DC/DC-220/48B-5A (IPS-300-220/48V-5A (DC/AC)/DC)) DC/DC-220/60B-5A Boost DC/DC converter chip (Functional analogue of LT1937 from Linear Technology Corporation) The IZ1937 chip is a boost DC/DC converter designed specifically for control Linevich E. I. [email protected] Primorsky Krai, Artyom Electromagnetic energy source (physical basis of the principle of operation) An electrical energy generator is proposed that can be used Nizhny Novgorod State University named after. N. I. Lobachevsky Faculty of Radiophysics Department of Radio Electronics Laboratory report: NONLINEAR SIGNAL CONVERSIONS Completed: Checked: Elena Morozova, Alexey Razin Laser power supplies Brief lecture notes on the discipline “Laser technology” Tomsk 202 Lecture Elementary base of power supplies and the simplest circuits based on them Any laser DYNAMIC UNINTERRUPTED POWER SUPPLY SYSTEM (UPS) NO-BREAK KS Main elements shown in the figure: 1. Diesel engine. 2. Electromagnetic clutch. 3. Special brushless Laboratory work 1 AC rectifier Purpose: to study the operation of half-wave and full-wave rectifiers and their characteristics. A rectifier is a device for converting voltage Laboratory work 2 Study of the smoothing filter of the secondary power supply The purpose of the work is to study methods for reducing the ripple of the rectified voltage of the secondary power supply of electronic