Powerful switching power supply for 3842. Simple switching power supply for UC3842 - Power supplies (switching) - Power supplies. Scheme of a switching power supply based on a PWM controller UC3842

At least once in a lifetime, every motorist is faced with the problem of a dead battery. To prevent such a malfunction, it is necessary to properly maintain the battery and charge it in time using a charger. What is a pulsed charger for a car battery, what is its principle of operation and how to build a device with your own hands - read on.

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Device characteristic

Devices designed for batteries are divided into several types - transformer and pulse. Transformer chargers for car batteries have a large weight and size, while their efficiency is much lower than that of other devices. As a result, the demand for such chargers has gradually decreased. To date, the pulse charger is the most popular type.

Device and principle of operation

Any pulse charger for a car battery is a device designed to restore charge.

Structurally, the pulse memory consists of the following elements:

• transformer (pulse);
• rectifier devices;
• stabilizer device;
• display elements;
• the main unit designed to control the charge procedure.

It should be noted that all the elements that make up the pulse charger are small in size when compared with transformer chargers. In principle, it is not so difficult to build such a device for charging a car battery with your own hands - this will only require a board that will control the transistor. As a result of the fact that the design of this type of device is quite simple, and the components for manufacturing are easily available, pulse chargers are popular among our car enthusiasts.

As for the principle of operation, the charging procedure itself can be carried out by one of several methods:

• by voltage at direct current;
• voltage of constant parameters;
• combined method.

In principle, the way to stress constant values ​​is the most correct from a theoretical point of view. This is because pulse chargers for car batteries can automatically control the current strength parameters only if the voltage is constant. If you want to ensure that the charge level is as high as possible, the discharge parameter must also be taken into account.

As for the voltage method at direct current, this option is not the most optimal. This is because during the operational charging of the battery, obtained as a result of exposure to direct current, the plates of the device can simply crumble. And it will be impossible to restore them.

The combined battery charging option is one of the most gentle. When applying this method, a direct current first passes, and at the very end of the procedure, it begins to change to an alternating current. Further, this parameter is gradually reduced to zero, thus stabilizing the voltage level. According to experts, such a scheme of work allows you to prevent or minimize the likelihood of a car battery boiling. In addition, with this approach, the likelihood of outgassing is also reduced.

Aspects of equipment selection

If you want to ensure that the car battery works properly, you need to think in advance about buying the necessary charger for charging.

There are certain nuances of this issue that it is desirable to take into account:

1. First of all, many consumers are interested in the question - can the charger, working according to its own scheme, restore a completely discharged car battery. Here it must be borne in mind that not all chargers sold in car dealerships can cope with this task. Therefore, when buying this moment, you need to check with the sellers.
2. The second, important aspect is the level of the maximum current parameter that the charger gives out during operation. In addition, you need to take into account the voltage to which the car battery will be charged. For example, if you opt for a pulse charger, then keep in mind that it should have a shutdown option or a support function that turns on automatically when fully charged (video by ChipiDip).

When operating the memory with your own hands, you need to consider several points. First of all, it is a sequence of actions. To begin with, it is recommended to dismantle the cover of the device and unscrew the plugs. If it is necessary to add electrolyte to the system, use distilled water for this, this must be done before the charging procedure is carried out.

Consider a few options:

1. Voltage level. The maximum indicator in this case should be no more than 14.4 volts.
2. Current strength. This parameter is adjustable, for this, take into account the level of battery discharge. For example, if the car battery is 25% discharged, then when the charger is activated, the current strength parameter may increase.
3. Auto battery charge time. In the event that there are no indicators on the memory, then you can understand when the car battery is charged by the current value. In particular, if this parameter does not change for three hours, this will indicate that the battery is charged.

Never charge the device for more than 24 hours, this will cause the electrolyte to simply boil, and a short circuit will occur inside the circuit.

Do-it-yourself instructions for making a pulsed memory

To build a charger for a car battery with your own hands, the IR2153 scheme is used. This scheme differs from the conventional memory production scheme in that instead of two capacitors connected to the midpoint, only one electrolyte is used. It should be noted that this do-it-yourself manufacturing scheme allows you to make a charger for a car battery, designed for low power. But this problem can also be solved by using more powerful elements.

In the diagram above, keys of the 8N50 type are used, equipped with an insulated housing. As for diode bridges, it is better to use those that are installed in computer power supplies. If you don’t have such circuit elements, then you can try to assemble a diode bridge from four rectifier diodes (the author of the video on creating a charger for a car battery is Blaze Electronics).

Now let's move on to the power supply circuit of the circuit device. To equip this component with your own hands, a resistor is used to dampen the current, use an 18 kOhm device. After the resistor in the circuit, there is a conventional rectifier component mounted on a single diode, while the power itself will in any case be supplied to the board. An electrolyte is directly on the power supply, which is connected in parallel to a capacitor (this element can be either film or ceramic). The use of a capacitor is necessary in order to provide the most optimal smoothing of pulses and noise.

As for the transformer, it can also be dismantled from the PC power supply. It should be noted that such a transformer is excellent for creating a battery charger, since it allows you to provide a good output current. In addition, a transformer of this type can simultaneously provide several output voltage parameters. The diodes themselves should only be pulsed, since standard elements will not be able to function as a result of too high a frequency.

The filter can not be added to the circuit, but instead it is desirable to install several containers and the inductor itself. To reduce the level of input surges to the filter element, it is advisable to add a 5 ohm thermistor to the circuit. This element can also be pulled out with your own hands from the PC power supply. An important point will be the installation of an electrolytic capacitor. It must be selected based on a special ratio of 1 watt - 1 microfarad, the voltage level should be 400 volts.

In general, such a scheme in its design is quite simple. In practice, if you approach this issue correctly, then it will not be so difficult to build, even if you have no experience. And given that you will have material with all the necessary diagrams and symbols at hand, it will be easier than ever to cope with such a task. Of course, if you can't tell a transformer from a resistor, it's best to just go to the store and buy the right charger.

Video "Making a pulse charger with your own hands"

All the nuances that need to be taken into account, as well as detailed step-by-step instructions for making a pulse charger for a car battery, are given below (the author of the video is Soldering Iron TV).

A fairly simple circuit of a laboratory power supply or charger, for example, for a battery. It is implemented quite simply, as can be seen from the diagram. A unique feature of the circuit is the fact that it is possible to adjust not only voltage, but also current, which even many purchased chargers do not have.

The circuit is built on 4 transistors, the main role is played by the power transistor V4 (see diagram), in this case 2N3055 is taken, which can be completely replaced with the domestic analogue KT803. In general, the output power of the device and the possible maximum current will ultimately depend on this transistor, so if you need more significant currents, it is enough to replace V4 with a more powerful transistor. It is clear that the power transistor is necessarily installed on the heat sink.

Another feature of such a charger is its efficiency, all the elements will cost you 100-200 rubles. When using the 2N3055 transistor shown in the diagram or its domestic counterpart KT803, the current can be accelerated to 6 A. Although the transistor itself will draw 15 A in its characteristics, we do not recommend loading it to such an extent. A limiting resistor R2 with a nominal value of 1 Ohm is taken with a power of at least 5 W, the rest of the resistors of 0.25 W are enough.

So far, we have considered only the part of the circuit responsible for regulating voltage and current. However, it is clear that the device needs to be powered by something, especially with a constant voltage, therefore, a power source is needed capable of delivering sufficient output power, with a constant voltage of up to 16 V and a current of up to 10 A. In principle, for power supply from a 220V network, 50 Hz was it would be enough to wind a step-down transformer and put a bridge at its output. However, even a superficial calculation shows that a transformer is needed with a power of up to 200 watts.

The core for it can be obtained from old tube TVs, but not everyone has such an opportunity, and if you buy it, it will be very expensive. Plus, the use of such a scheme will greatly increase the dimensions of the device itself. Therefore, to reduce the dimensions of the transformer, we will use the presented circuit of a switching power supply that increases the frequency to 50 kHz, which ultimately leads to a reduction in the dimensions of the output transformer.

The only thing, but the transformer was taken from a computer power supply designed for bipolar voltage, we understand that one polarity is enough. The ratings and types of elements are indicated on the diagram.

The circuit has protection against short circuit, when it is triggered, the LED lights up, which is also very useful when working with a source. When winding the output transformer, the primary winding consists of 37 turns with a wire with a cross section of at least 0.5 mm?, the secondary 6 turns with a cross section of at least 2.5 mm?, can be wound with three wires with a wire of 0.8 mm?. The core can be taken from any computer power supply. The diodes of the rectifier bridge at the output must be high-frequency, we advise you to take KD213.

To adjust the limiting current (protection operation), it is enough to change the value of the resistor R10; the smaller its value, the greater the protection operation current and vice versa. All transistors involved in the circuit must be installed on separate heat sinks or isolated from each other.

After the first rectifier bridge, the filter capacitors should be 100 to 470 uF with voltage ratings up to 400 V.

16-03-2015

UC3842

Rzhevsky Alexander

A simple switching voltage regulator with overload and short circuit protection for charging high-capacity batteries (from 55 ampere hours) can be made from common radio components dismantled from old computer monitors and power supplies. A feature of the proposed stabilizer is high efficiency and, as a result, minimal heating of the components. The schematic diagram of the device is shown in Figure 1.

The stabilizer is based on a PWM modulator chip in a standard switching circuit with a transistor inverter in the feedback circuit. For more reliable control of the MOSFET, a transistor driver has been added to the circuit, which contributes to the accelerated discharge of the gate capacitance when switching high pulse currents.

Overcurrent protection is built in a standard way. The current sensor is resistor R9 with a resistance of 0.1 ohm.

The short-circuit protection circuit is highlighted in blue in the diagram. During the operation of the stabilizer, it turned out that when the output is short-circuited, the diode 16C40 starts to heat up and fails, if the short circuit is not eliminated. To protect the diode from overheating, the modulator chip is blocked with a certain time delay. In the event of a short circuit, the capacitor C6 begins to charge, and after about 4 seconds the transistor opens, blocking the operation of the microcircuit at pin 3. To restart the stabilizer, it is necessary to eliminate the short circuit and briefly disconnect it from the power supply.

The output voltage is regulated by a trimming resistor R7. You can expand the control range by increasing the resistance of the resistor R6.

More about the design

The inductor is wound on a yellow ring magnetic circuit, dismantled from a computer power supply. Contains 28 turns of PEL-0.8 wire. At a current of 5 A, it heats up to 40 degrees. To avoid crackling and whistling, the windings should be impregnated with superglue.

Resistor R9 is wound from nichrome wire with a diameter of 0.7 mm and a length of 60 mm. The edges of the wire are cleaned, wrapped with copper wire 0.8 mm in 3 turns with a step of 0.2 mm, crimped with pliers and soldered. At a current of 5 A, the resistor heats up to 60 degrees.

Figure 2. Voltage stabilizer printed circuit board.

Figure 2 shows the circuit board of the device (without the diode protection circuit). The transistor and diode are soldered to copper from the side of the conductors, which, together with the base of the board, performs the function of their radiators, and a choke is attached to the opposite side.

The PCB is shown from the solder side. The following colors have been used:

• green - copper tracks,
• blue - arrangement of elements,
• white - marking of circuit elements,
• yellow - jumpers.

Version: PDIP8. Current Mode PWM Controller Package Type: PDIP-8 Topology: Boost, Buck, Flyback, Forward Control Mode: Current Frequency...

Provider	Manufacturer	Name	Price
RIV Electronics	STMicroelectronics	UC3842BD1013TR	10 rub.
AliExpress		RM6204 UC3842B AM-22A BP3126 UC3845B TL081 TL081CP SM7055 SM7055-12 MAX483CPA MAX483EPA OB2538AP VIPER12A	10 rub.
Kim	Infineon	UC3842AMSMD	14 rub.
MosChip	Texas Instruments	UC3842ANANDUC2842ANG	on request

• ... 1. I suggest the author to revise the blue section of the circuit 2. put 10-12k on paw 6 3. put 10-12k on the zener shutter 4. for smooth running, connect 5k in series with P7 ...
• Is a short circuit an overcurrent? Why then added "in blue" if there is R9? I understand that during a short circuit, an inductance is connected by a load, and reverse currents are shunted through a heated diode. But why then R9 ... and it is necessary to regulate mainly not the voltage, but the current ...
• As I understand it ... the blue circuit is for setting the initial output voltage, and R9 ... current protection ... it's just that everything is connected to one input ... and how stable it will work ... question ...
• The article also says
• I want to thank the author for the idea of ​​​​using such a classy IC in devices of this kind. Let me make a few remarks, in my opinion: it seems to me that the key that stands for the discharge of the gate capacitance is not needed. The collector current 361 is 250 mA, and 3842 (according to the datasheet Io = + -1A) if you use 34063 then you definitely need to. It is better to implement output voltage control on a current mirror, although it is troublesome to set up, you can simply put a voltage-to-current converter: i.e. In the chain of the emitter of the same according to scheme 361, turn on a 12k resistor (for example), connect the base through 33-51 Ohm to the output. thus, the emitter will have the output Uout of the source. The collector current will be Ik = Uout / 12k. It remains to calculate Uin =1mA.
• My God, how everything is running. I can create a class D amplifier based on the UC3842 PWM controller, and a parametric stabilizer from the amplifier, but I'm still friends with my head
• hi all. I wonder who needs this extremely confusing and crooked - inverted scheme. who sees it and understands it a little, probably comes in shock. an additional transistor is not needed there, it is a weak micro 1 ampere output - they already wrote the en-channel transistor itself, it must be set to plus, as elsewhere in ds-ds lowerers. for the frequency of this turn, it is not enough twice or 10 turns more, approximately for a ring of 23.5mm, if 27mm, then it may be abnormal. for some reason, it’s also not mentioned anywhere about the diameter of ferit zholtogo. that people - it’s not possible to get a kinder world everyone who wants to repeat this scheme, get worn out and will arrive for 1-2 months without a mood and then leave everything without receiving minimal satisfaction while collecting it and still need recharge on the 3rd leg it will not start. also on the first leg you can make a smooth start, you need 3 parts - there are in the pdefs. be kind and we won’t need the junk from the whale, it often flies and is not repairable, since all the details are mowing - believe me, and as a rule, the names of the chips are erased.
• Is there really no place on the forums of a really working circuit ds ds lowering that this is some kind of secret thing, let's discuss a really working circuit - in the studio
• So it doesn’t control the output voltage in your opinion ... and doesn’t set the initial response threshold? ... :mad: Not everything that is written on a sleigh team ... true ... :p
• Available: http://forum.cxem.net/index.php?showtopic=77467 http://kazus.ru/forums/showthread.php?p=137986 http://radiokot.ru/forum/viewtopic.php? f=11&t=39128 But not for such illiterate people. For "mines walk in pairs" ...
• please translate the statement for the illiterate - For "the miserable pairs walk" - you are a very smart person, and many come here and come in illiterate. and why did you give 3 links about atx ups on tl494 - it’s not a topic here we are talking about an iron transformer and a stub, like we are discussing a ds ds stabilizer lowering for VS3843-42. .and here 3843 10aper is like a scooter, and even 6ampere is enough for a powerful computer. Plus, the iron trans is nephonite and does not interfere like an UPS at 494 if the stub is correctly diluted. let the jelly be eating more by 20 watts, but also normal. I also realized that when a person has nothing to say in response, he writes with sayings. I wrote the truth about this scheme and many people understand this.
• can someone come in handy for a program for calculating the throttle of the yellow-white ring on the internet on the forums everywhere - it shows twice as many turns when calculating the byaku and also compared the inductance of the throttle with its ds ds board of the company, the well-known and high-quality compad from the store found it and sniffed it out with a specialist. but maybe I'm confusing it with the frequency cp-chain. and I don’t remember which micra was 3843 90 percent filling or 3845 like 50 percent - direct me who knows what kind of micra should be in a ds ds lowering - with a 50 percent filling of the sine wave or 90. I just know that the power supply of the field workers who are on the compad board is approx 12 volts. then which micro to put from two with a start pressure of 8.4v. :confused:
• 1 Blue circuit for fans of checking the output voltage by short circuiting the output (if it sparks, it works). 2 There was a case that, at the time of charging, the insulation of the wire connecting the battery and charging melted. A short circuit occurred and, as if evil, the wires stuck together, melted from the battery side, and a short circuit remained from the charging side. If there is a guarantee to avoid the above cases, then the blue insert is not needed at all. If a duty cycle of up to 50% is guaranteed, then 315 is not needed in the gate. But this condition is not feasible at the initial time of the battery charge.

Every car enthusiast has for a 12 V battery. All these old chargers work and perform their functions with varying degrees of success, but they have a common drawback - they are too large in size and weight. This is not surprising, because a 200-watt power transformer alone can weigh up to 5 kg. Therefore, I decided to assemble a pulse charger for a car battery. On the Internet, or rather on the Kazus forum, I found a diagram of this memory.

Schematic diagram of the memory - click to increase the size

Got it, works great! I charged a car battery, set the charger to 14.8 V and a current of about 6 A, there is no overcharging or undercharging, when the voltage at the battery terminals reaches 14.8 V, the charging current drops automatically. I also charged a helium lead battery from a PC uninterruptible power supply - it's normal. This charger is not afraid of short circuits at the output. But from a polarity reversal it is necessary to do protection, he did it on a relay.

See the printed circuit board, datasheets for some radio elements and other files on the forum.

In general, I advise everyone to do it, since this memory has many advantages: small size, the base of radio elements is not in short supply, you can buy a lot, including a ready-made pulse transformer. I bought it myself in the online store - they sent it quickly and cheaply. I’ll make a reservation right away, instead of the VD6 Schottky diode (thermal stabilization), I just put a resistance of 100 Ohms, a charger and it works great with it! The circuit was assembled and tested:Demo.

Charger on UC3842/UC3843 with voltage and current regulation

The charger described here is designed for charging lead-acid batteries. There are two adjustments: voltage and current. When one of these adjustments is triggered, the corresponding LED lights up, which is very convenient. Schematic and PCB taken from the radiocat forum:

The device is assembled on a common UC3842/UC3843 chip. We have already described its use in power supplies. In this circuit, the adjustment occurs on 1 output. The power part is typical, the microcircuit is powered by a separate winding on the return stroke.

click to enlarge
Voltage and current adjustment is made according to the scheme from the forum member FolksDoich. A reference voltage source is assembled on the TL431. On the halves of the LM358 op-amp, voltage and current adjustments are made. If LEDs are used as VD6 and VD7, they will indicate the current adjustment with their glow, which can be useful. For example, if the VD7 LED is on, then the current is limited. The same with VD6, but in terms of voltage.

This circuit is designed to charge the battery with a current of up to 6 amperes, so it is proposed to parallelize four electrolytic capacitors at the output, because. one at high current will not work for long. Of course, they must all be LOW ESR.

How can this scheme be improved? If you use it to assemble not a charger, but a power supply regulated within certain limits, then you can make the already familiar improvements described in the previous article. In particular, it is possible to power the UC3842/UC3843 chip in the forward direction, and use a separate transformer winding to power the op-amp and PC817. All this is justified only if it is required to expand the range of voltage regulation.

In addition to LEDs, the circuit can be supplemented with an ammeter and a voltmeter, both pointer and digital, showing the value of voltage and current, and, possibly, also counting the load power and controlling the cooling fan.

With the right choice of power field effect transistor, its heating should be negligible. It should be mentioned that in the diagram they forgot to draw a 2.2 nF capacitor between the hot and cold parts.

PCB: charger_12v_6a.lay6

There is another version of this scheme in this form:

click to enlarge
Printed circuit boards from FolksDoich for devices of different power, the second board - up to 10 amps. The UC384x chip is located on a separate small scarf, mounted vertically on the main one.