Voltage regulator on the field circuit. Voltage stabilizer on a field-effect transistor - circuit design. Powerful field stabilizer
A simple circuit for regulating and stabilizing voltage is shown in the picture above; even a novice in electronics can assemble it. For example, 50 volts are supplied to the input, and at the output we get 15.7 volts or another value up to 27V.
Main radio component of this device is a field-effect (MOSFET) transistor, which can be used as IRLZ24/32/44 and others like that. They are most commonly produced by IRF and Vishay in TO-220 and D2Pak packages. It costs about $0.58 UAH at retail; on ebay 10psc can be purchased for $3 ($0.3 per piece). Such powerful transistor has three terminals: drain, source and gate, it has the following structure: metal-dielectric (silicon dioxide SiO2)-semiconductor. The TL431 stabilizer chip in the TO-92 package provides the ability to adjust the value of the output electrical voltage. I left the transistor itself on the radiator and soldered it to the board using wires.
The input voltage for this circuit can be from 6 to 50 volts. At the output we get 3-27V with the ability to regulate with a 33k substring resistor. The output current is quite large, up to 10 Amps, depending on the radiator.
Smoothing capacitors C1, C2 can have a capacity of 10-22 μF, C3 4.7 μF. Without them, the circuit will still work, but not as well as it should. Don't forget about voltage electrolytic capacitors at the input and output, I took everything designed for 50 Volts.
The power that can be dissipated by this cannot be more than 50 watts. The field-effect transistor must be installed on a radiator, the recommended surface area of which is at least 200 square centimeters (0.02 m2). Don’t forget about thermal paste or rubber backing so that the heat transfers better.
It is possible to use a 33k substring resistor like WH06-1, WH06-2; they have fairly precise resistance adjustment, this is what they look like, imported and Soviet.
For convenience, it is better to solder two pads onto the board rather than wires, which are easily torn off.
Discuss the article VOLTAGE STABILIZER ON A FIELD TRANSISTOR
I. NECHAYEV, Kursk
This regulator allows you to control the amount of heat generated by the electric heater. The principle of its operation is based on changing the number of periods of the mains voltage supplied to the heater, with switching on and off occurring at moments close to the transition of the instantaneous value of the mains voltage through zero. Therefore, the regulator creates virtually no switching interference. Unfortunately, it is not suitable for dimming incandescent lamps, which will flicker noticeably.
The device diagram is shown in Fig. 1.
As switching elements, it uses field-effect transistors IRF840 with a permissible drain-source voltage of 500 V, a drain current of 8 A at a case temperature of 25 ° C and 5 A at a temperature of 100 ° C, a pulse current of 32 A, an open channel resistance of 0.85 Ohm and dissipated power of 125 W. Each transistor contains an internal protective diode connected parallel to the channel in reverse polarity (cathode to drain). This allows you to connect two transistors in back-to-back series to switch alternating voltage.
Elements DD1.1, DD1.2 are used to assemble a generator of adjustable duty cycle pulses running at a frequency of approximately 1 Hz. On DD1.3, DD1.4 - voltage comparator. DD2.1 is a D-trigger, and DD1.5, DD1.6 are buffer stages. Quenching resistor R2, diodes VD3 and VD4, zener diode VD6, capacitor C2 form a parametric voltage stabilizer. Diodes VD5, VD7 suppress voltage surges at the gates of transistors VT1, VT2.
Timing diagrams of signals at various points of the regulator are shown in Fig. 2.
The positive half-wave of the mains voltage, passing through diodes VD3, VD4 and resistor R2, charges capacitor C2 to the stabilization voltage of the zener diode VD6. The voltage at the anode of diode VD4 is a sinusoid limited from below by a zero value, and from above by the stabilization voltage of the zener diode VD6 plus the forward voltage drop across the diode itself. The comparator on elements DD1.3, DD1.4 makes the voltage drops steeper. The pulses generated by it are supplied to the synchronization input (pin 11) of the DD2.1 trigger, and to its input D (pin 9) - pulses with a frequency of approximately 1 Hz from the output of the generator on elements DD1.1, DD1.2.
The output pulses of the trigger are fed through elements DD1.5 and DD1.6 connected in parallel (to reduce the output resistance) to the gates of transistors VT1 and VT2. They differ from generator pulses by “tying” time differences to the network voltage crossing a level close to zero, in the direction from plus to minus. Therefore, the opening and closing of transistors occurs only at the moments of such intersections (which guarantees low level interference) and always for an integer number of periods of mains voltage. As the variable resistor R1 changes the duty cycle of the generator pulses, the ratio of the duration of the on and off state of the heater, and therefore the average amount of heat generated by it, also changes.
Field-effect transistors can be replaced with others that are suitable for the permissible voltage and current, but must be equipped with protective diodes. K561 series microcircuits, if necessary, are replaced with functional analogues of the 564 series or imported ones. Zener diode D814D - any medium power with a stabilization voltage of 10...15 V.
Most of the device parts are located on printed circuit board from one-sided foil fiberglass shown in Fig. 3.
When the heater power is more than 500 W, transistors VT1 and VT2 must be equipped with heat sinks.
The board is installed in a housing made of insulating material, on the wall of which a socket XS1 and a variable resistor R1 are mounted. A handle made of insulating material must be placed on the resistor axis.
When setting up the regulator, check the voltage on capacitor C2 throughout the entire power adjustment range. If it changes noticeably, the value of resistor R2 will have to be reduced.
Radio No. 4 2005.
Triac power regulator.
A.STASChoke L1 is any noise-suppressing device used in such devices, corresponding to the load. You can, in principle, do without it, especially if the load is inductive in nature. Capacitors CI, C2 - for a voltage of at least 250 V. Diodes VD1...VD4 - any silicon for a reverse voltage of at least 300 V.
Transistors VT1, VT2 are also, in principle, any silicon with the appropriate type of conductivity.
This circuit works with any type of triacs for the appropriate voltage. The most powerful one we were able to test was TS142-80-10.
Radio amateur 8/97
Step power regulator.
K. MOVSUM-ZADE, TyumenThe proposed device is distinguished by accessible parts with a small number and uncritical ratings. Step regulation: 2/2, 2/3, 2/4, 3/7, 3/8, 3/9 and 3/10 of the full load power.
The regulator diagram is shown in Fig. 1.
It consists of a power unit (diodes VD2, VD6, zener diode VD1, resistor R3, capacitor C1), a control unit (resistors R1, R2, R4, R5, switch SA1, decimal counter DD1, diodes VD3-VD5) and a power unit on field effect transistor VT1 and diode bridge VD7-VD10, it also includes resistor R6.
Suppose switch SA1 is set to position 2/3. During the first positive half-cycle of the mains voltage, diodes VD2 and VD6 are open. The current flowing through the zener diode VD1 forms a pulse with an amplitude of 15 V with a steep rise and fall. This pulse charges capacitor C1 through diode VD2, and through resistor R1 enters the CN input of counter DD1. At the edge of this pulse, a high level will be set at output 1 of the counter, which, through diode VD4 and resistor R4, will go to the gate of field-effect transistor VT1 and open it. As a result, a positive half-wave of current flows through the load.
During the negative half-cycle, the diodes VD2 and VD6 are closed, but the voltage of the charged capacitor C1 (it is then recharged by each positive half-cycle) continues to power the counter DD1, the state of which does not change. Transistor VT1 remains open, and current continues to flow through the load.
With the beginning of the next positive half-cycle, the level at output 1 of the counter will become low, and at output 2 - high. Transistor VT2, whose gate-source voltage has become zero, will be closed, and the load will be disconnected from the network for the entire period.
In the third positive half-cycle, the high level set at output 3 will flow through switch SA1 to the R input of the counter, which will immediately go into its initial state with a high level at output 0 and low at all other outputs. The voltage supplied through diode VD3 and resistor R4 to the gate of transistor VT1 will open it. At the end of this period the cycle will repeat. In other positions of switch SA1, the device operates similarly, only the number of periods during which the load is connected to the network and disconnected from it changes.
The regulator almost does not create radio interference, since the switching of the counter, and with it the opening and closing of the transistor VT1, occurs at moments when the instantaneous value of the mains voltage is very close to zero - it does not exceed the stabilization voltage of the zener diode VD1. Resistor R6 suppresses voltage surges that occur when switching an inductive load, which reduces the likelihood of breakdown of transistor VT1.
The regulator is assembled on a printed circuit board made of one-sided foil-coated PCB (Fig. 2).
It is designed for MLT resistors and similar ones with the power indicated on the diagram, and the resistor ratings may differ several times from those indicated. Capacitor C1 - K50-35 or other oxide. The KS515G zener diode can be replaced with KS515Zh or KS508B, the KD257B diodes with imported 1N5404, and the KP740 transistor with IRF740.
Switch SA1 is a P2G-3 11P1N biscuits, of which only seven positions are used. The switch terminals are connected by flexible wires to unmarked contact pads located on the printed circuit board around the DD1 chip.
It is advisable to check the assembled device by connecting it to the network through an isolation transformer with a voltage on the secondary winding of 20...30 V and replacing the actual load with a 1.5...3 kOhm resistor. Only after making sure proper operation, connect it to the network directly. After this, it is dangerous to touch any elements of the device (except for the insulated switch handle) - they are under mains voltage.
The regulator has been tested with loads up to 600 W. Field-effect transistor VT1, due to the low resistance of the open channel, heats up very little, however, it is advisable to provide it with a small heat sink.
This article describes two circuit diagrams regulators based on direct current, which are implemented on the basis of the K140UD6 operational amplifier.
PWM voltage regulator 12 volts - description
A feature of these circuits is the ability to use virtually any available operational amplifiers, with a supply voltage of 12 volts, for example, or.
By changing the voltage at the non-inverting input of the operational amplifier (pin 3), you can change the output voltage. Thus, these circuits can be used as a current and voltage regulator, in dimmers and also as a DC motor speed regulator.
The circuits are quite simple, they consist of simple and accessible radio components and, if installed correctly, they immediately begin to work. A powerful field-effect n-channel transistor is used as a control switch. The power of the field-effect transistor, as well as the area of the radiator, must be selected according to the current consumption of the load.
To prevent breakdown of the gate of the field-effect transistor, when using a PWM regulator with a supply voltage of 24 volts, it is necessary to connect a resistance of 1 kOhm between the gate of VT2 and the collector of transistor VT1, and connect a 15-volt zener diode in parallel with resistance R7.
If it is necessary to change the voltage on a load, one of the contacts of which is connected to ground (this occurs in a car), then a circuit is used in which the drain of an n-channel field-effect transistor is connected to the plus of the power source, and the load is connected to its source.
It is desirable to create conditions under which the field-effect transistor will open fully, the gate control circuit should contain a node with an increased voltage of the order of 27...30 volts. In this case, the voltage between source and gate will be more than 15 V.
If the load current consumption is less than 10 amperes, then it is possible to use powerful field-effect p-channel transistors in the PWM regulator.
In the second scheme PWM voltage regulator 12 volts The type of transistor VT1 also changes, and the direction of rotation of the variable resistor R1 also changes. So, in the first version of the circuit, a decrease in the control voltage (the handle moves to the “-” power source) causes an increase in the output voltage. The second option has everything reversed.
Power regulators alternating current with phase-pulse control have become widespread both in industrial automation devices and in amateur radio designs. The regulating element of such devices is a triode thyristor, the opening moment (angle) of which is regulated by applying a pulse or voltage level to the control electrode,
and closing occurs at the moment the current flowing through the thyristor decreases to zero (with an active load - at the moment the mains voltage passes through zero). Such control is called incomplete, since only the opening angle of the thyristor can be adjusted, and the closing moment is not adjustable. Designed in last years high-power field-effect transistors with insulated gate ( MOSFET ) allow you to build a simple switch for switching alternating current with full control, i.e. opening and closing the key.
The power regulator circuit is shown in Fig. 1.The power switch is made on transistors VT1, VT2, connected in back-to-back series. The presence of an internal protective diode in each transistor, connected parallel to the channel in reverse polarity (anode to source, cathode to drain), allows current to flow in the load during positive and negative half-cycles of the mains voltage.
A pulse generator with adjustable duty cycle is made on three logical elements of the DD1 microcircuit. The pulse frequency is about 2 kHz (significantly higher than the mains voltage frequency). In the presence of high level at the output of the inverter DD1.3, the transistor switch is open and current flows through the load. In this case, in the positive half-cycle, the current flows through the open channel of transistor VT1 and the protective diode of transistor VT2, and in the negative half-cycle, on the contrary, through the protective diode of transistor VT1 and the open channel of transistor VT2. If the output DD1.3 is low, then both transistors are closed and the load is de-energized. Timing diagrams of the regulator operation are shown in Fig. 2. Obviously, changing the duty cycle of the pulses allows change the load power from zero to maximum value, corresponding to the full network voltage.
The DD1 microcircuit is powered from a half-wave rectifier with a parametric stabilizer assembled on elements R2 VD3, VD4, C2. Please note that the voltage stabilizer is connected to the sources of the field-effect transistors and to the common wire of the microcircuit, so the voltage is applied to the gates of the transistors relative to their sources
Advantage this method power regulation before phase-pulse is that the load is switched with a much higher frequency than in thyristor-based regulators, this makes it possible to regulate power for low-inertia loads.
The IRF840 field-effect transistors indicated in the diagram have the following parameters: drain current - 8 A, maximum voltage between drain and source - 500 V, channel resistance in the open state - 0.85 Ohm, power dissipation - 125 W. These transistors can be replaced with IRF740, IRFP450, IRFP460, IRFPC50, IRFPC60, IRFP350, IRFP360 BUZ80. Before installing it into the device, you should make sure that the transistor has a protective diode (this can be easily done with an ohmmeter). The maximum load power is determined by the maximum current of the open transistor, while the power released on the open channel should not exceed the maximum permissible. The generator frequency, if necessary, can be changed by selecting capacitance C1.
Literature
1. Koldunov A MOSFET transistors. - Radiomir, 2004, N4 C 26
2 Semenov B.Yu. Power electronics for amateurs and professionals - M. SOLON-R 2001
A. EVSEEV,
PHASE POWER REGULATOR ON THE KEY FIELD TRANSISTOR is a negative resistor, which reduces the speed of the switch, since an RC circuit is formed consisting of this resistance and gate capacitance, or the output of the control circuit is made more powerful.
Typically, phase AC power regulators are based on a thyristor or triac. These schemes have long become standard and have been repeated many times both by radio amateurs and on a production scale. But thyristor and triac regulators, as well as switches, have always had one important drawback, the limitation of the minimum load power. That is, typical thyristor regulator for a maximum load power of more than 100W cannot well regulate the power of a low-power load that consumes units and fractions of watts. Key field-effect transistors differ in that the physical operation of their channel is very similar to the operation of a conventional mechanical switch; in a fully open state, their resistance is very small and amounts to fractions of an ohm, and in the closed state, the leakage current is microamperes. And this practically does not depend on the voltage on the channel. That is, just like a mechanical switch. That is why the key stage on a key field-effect transistor can switch a load with a power from units and fractions of watts, up to the maximum permissible current value. For example, the popular IRF840 field-effect transistor without a radiator, operating in switching mode, can switch power from almost zero to 400W. In addition, the switching FET has a very low gate current, so very low static power is required for control.
True, this is overshadowed by the relatively large gate capacitance, so at the first moment of switching on, the gate current may turn out to be quite large (current per charge of the gate capacitance). This is dealt with by switching the current limiter in series with the gate. The power regulator circuit is shown in the figure. The load is powered by a pulsating voltage, as it is connected through a diode bridge VD5-VD8. This is suitable for powering an electric heating device (soldering iron, incandescent lamp). Since the negative half-wave of the pulsating current is “turned” upward, pulsations with a frequency of 100 Hz are obtained. But they are positive, that is, a graph of the change from zero to a positive amplitude voltage value. Therefore, adjustment is possible from 0% to 100% Value maximum power the load in this circuit is limited not so much by the maximum current of the open channel VT1 (this is ZOA), but by the maximum forward current of the diodes of the rectifier bridge VD5-VD8.
When using KD209 diodes, the circuit can operate with a load of up to 100W. If you need to work with a more powerful load (up to 400W), you need to use more powerful diodes, for example, KD226G, D.
The inverters of the D1 microcircuit contain a control pulse generator that opens the transistor VT1 in a certain half-wave phase. Elements D1.1 and D1.2 form a Schmitt trigger, and the remaining elements D1.3-D1.6 form a high-power output inverter. The output had to be strengthened to compensate for the troubles caused by the current jump to charge the gate capacitance VT1 at the moment it was turned on.
The low-voltage power supply system of the microcircuit is divided into two parts using the VD2 diode, the actual power supply part,