Linear stabilizers have a common drawback - this is a low efficiency and high heat generation. Powerful devices that create a load current over a wide range have significant dimensions and weight. To compensate for these shortcomings, switching regulators have been developed and are being used.

A device that maintains a constant voltage on a current consumer by adjusting an electronic element operating in the key mode. Switching stabilizer voltage, as well as linear, there is a series and parallel type. The role of the key in such models is played by transistors.

Since the active point of the stabilizing device is almost constantly located in the cutoff or saturation region, passing through the active region, little heat is released in the transistor, therefore, the switching regulator 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 frequency-pulse, and in other words, width regulation. Switching stabilizers operate in a combined pulsed mode.

In stabilization devices with pulse-width control, the pulse frequency has a constant value, and the duration of the pulses is a non-constant value. In devices with frequency-pulse 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, respectively, it is not suitable for supplying the consumer. Before power is applied to the load of the consumer, it must be leveled. To do this, leveling capacitive filters are mounted at the output of switching stabilizers. They are multi-link, L-shaped and others.

The average voltage applied to the load is calculated by the formula:

• Ti is the length of the period.
• ti is the pulse duration.
• Rн - the value of the resistance of the consumer, Ohm.
• I(t) - the value of the current passing through the load, amperes.

The current may stop flowing through the filter by the beginning of the next pulse, depending on the inductance. In this case, we are talking about the mode of operation with alternating current. The current can also flow further, in which case we mean operation with direct current.

With increased sensitivity of the load to power pulses, perform the mode direct current, 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 switching regulator includes a switching converter with an adjustment device, a generator, an equalizing filter that reduces voltage pulses at the output, a comparing device that supplies a signal for the difference between the input and output voltages.

The 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 the comparing device with the base voltage. The result is a proportional signal. It is fed to the generator, after amplifying it.

When regulated in the generator, the differential analog signal is modified into pulsations with a constant frequency and variable duration. When regulating the frequency-pulse, the duration of the pulses has a constant value. It changes the pulse frequency of the generator 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 the theory, in devices with frequency and width adjustment, voltage pulses on the consumer may be absent.

With the relay principle of operation, the signal that is controlled by the stabilizer is generated using a trigger. When a constant voltage is supplied to the device, the transistor operating as a key is open and increases the output voltage. the comparing device determines the difference signal, which, having reached a certain upper limit, will change the state of the trigger, and the control transistor will switch to cutoff.

The output voltage will 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 enter saturation. The potential difference across the device load will increase. Therefore, with a relay type of stabilization, the output voltage rises, thereby leveling off. The trigger limit is adjusted by adjusting the amplitude of the voltage value on the comparator.

Relay-type stabilizers have an increased reaction speed, unlike devices with frequency and width regulation. 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 step-up stabilizers are used together 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 step-up stabilizers are called boost converter. The main parts of such a device:

The transistor saturates, and the current passes through the circuit from the positive pole through the storage inductor, the transistor. In this case, energy is accumulated in the magnetic field of the inductor. The load current can only create a discharge of capacitance C1.

Turn off the turn-off voltage from the transistor. At the same time, it will enter the cut-off position, and therefore the 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 load.

At this moment, the magnetic field of the inductive choke produces energy, and the capacitance C1 reserves energy to maintain the voltage at the consumer after the transistor enters saturation mode. The inductor is for energy reserve and does not work as a power filter. When voltage is applied to the transistor again, it will open, and the whole process will begin again.

Stabilizers with Schmitt trigger

This kind impulse device has its own characteristics with the smallest set of components. The main role in the design is played by the trigger. It includes a comparator. The main task of the comparator is to compare the magnitude of the output potential difference with the highest allowable.

The principle of operation of the device with a Schmitt trigger is that with an increase in the highest voltage, the trigger is switched to the zero position with the opening of the electronic key. At one time, the throttle is discharged. When the voltage reaches the lowest value, then switching is performed by one. This ensures the closure of the key and the passage of current to the integrator.

Such devices differ in their simplified circuit, but they can be used in special cases, since switching regulators are only step-up and step-down.

Step Down Stabilizer

Switching type stabilizers operating with voltage reduction are compact and powerful electric current 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 constantly less than the input voltage. The diagram of a step-down type switching stabilizer is shown in the figure.

Connect a voltage to drive the source and gate of the transistor, which will go into saturation. It will carry current through the circuit from the positive pole through the equalization choke and the load. No current flows through the diode in the forward direction.

Turn off the control voltage, which turns off the key transistor. After that, it will be in the cut-off position. The inductive emf of the equalizing inductor will block the path for changing the current, which will go through the circuit through the load from the inductor, along the common conductor, the diode, and again come to the inductor. The capacitance C1 will be discharged and will hold 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 whole chain will repeat again.

Inverting Stabilizer

Switching regulators of the inverting type are used to connect consumers with a constant voltage, the pole of which has the opposite direction of the pole of the potential difference at the output of the device. Its value can be above the mains, and below the mains, depending on the settings of the stabilizer. There is no galvanic isolation between the power supply and the load. Imported devices of the inverting type are called buck-boost converter. At the output of such devices, the voltage is always lower.

Let's connect the 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 positive through the transistor, choke to minus. In this process, the inductor reserves energy with the help of its magnetic field. Turn off the control potential difference from the key on the transistor, it will close. The current will go from the inductor through the load, the diode, and return to its original position. The reserve energy on the capacitor and the magnetic field will be consumed for the load. Let's power up the transistor again to the source and gate. The transistor will saturate again and the process will repeat.

Advantages and disadvantages

Like all devices, the modular switching regulator is not perfect. Therefore, it has its pros and cons. Let's take a look at the main benefits:

• Easily achieve alignment.
• Smooth connection.
• Compact dimensions.
• Output voltage stability.
• Wide range of stabilization.
• Increased efficiency.

Disadvantages of the device:

• Complicated design.
• Many specific components that reduce the reliability of the device.
• The need to use compensating power devices.
• The complexity of the repair work.
• Generation of a large amount of frequency interference.

Permissible frequency

The operation of a switching stabilizer is possible with 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 interval will be 20-80 kilohertz. But when choosing PWM and key devices, it is necessary to take into account the high harmonics of the currents. The upper limit of the parameter is limited by certain requirements that apply to radio frequency devices.

Schemes of home-made pulsed DC-DC voltage converters on transistors, seven examples.

Due to their high efficiency, switching voltage stabilizers have recently become more and more widespread, although they are usually more complex and contain a larger number of elements.

Since only a small fraction of the energy supplied to the pulse stabilizer is converted into thermal energy, its output transistors heat up less, therefore, by reducing the heat sink area, the weight and dimensions of the device are reduced.

A noticeable disadvantage of switching stabilizers is the presence of high-frequency ripples at the output, which significantly narrows their range. practical use- Most often, switching stabilizers are used to power devices on digital microcircuits.

Step-down switching voltage regulator

A stabilizer with an output voltage lower than the input voltage can be assembled on three transistors (Fig. 1), two of which (VT1, VT2) form a key regulatory element, and the third (VTZ) is an error signal amplifier.

Rice. 1. Scheme of a switching voltage regulator with an efficiency of 84%.

The device operates in self-oscillating mode. The positive feedback voltage from the collector of the composite transistor VT1 through the capacitor C2 enters the base circuit of the transistor VT2.

The element of comparison and the amplifier of the mismatch signal is a cascade on the VTZ transistor. Its emitter is connected to a reference voltage source - the zener diode VD2, and the base - to the output voltage divider R5 - R7.

In switching stabilizers, the regulating element operates in the key mode, so the output voltage is regulated by changing the duty cycle of the key.

Turning on / off the transistor VT1 by the signal of the transistor VTZ controls the transistor VT2. At the moments when the transistor VT1 is open, in the inductor L1, due to the flow of load current, electromagnetic energy is stored.

After closing the transistor, the stored energy through the diode VD1 is given to the load. The output voltage ripple of the stabilizer is smoothed out by the filter L1, NW.

The characteristics of the stabilizer are entirely determined by the properties of the transistor VT1 and the diode VD1, the speed of which should be maximum. With an input voltage of 24 V, an output voltage of 15 V, and a load current of 1 A, the measured efficiency was 84%.

The inductor L1 has 100 turns of wire with a diameter of 0.63 mm on a K26x16x12 ferrite ring with a magnetic permeability of 100. Its inductance at a bias current of 1 A is about 1 mH.

Step-down DC-DC voltage converter to +5V

A diagram of a simple switching regulator is shown in fig. 2. Inductors L1 and L2 are wound on plastic frames placed in B22 armored magnetic cores made of M2000NM ferrite.

Choke L1 contains 18 turns of a bundle of 7 wires PEV-1 0.35. A gasket 0.8 mm thick is inserted between the cups of its magnetic circuit.

The active resistance of the inductor winding L1 is 27 mΩ. Choke L2 has 9 turns of a bundle of 10 wires PEV-1 0.35. The gap between its cups is 0.2 mm, the active resistance of the winding is 13 mΩ.

Gaskets can be made of hard heat-resistant material - textolite, mica, electric cardboard. The screw fastening the cups of the magnetic circuit must be made of non-magnetic material.

Rice. 2. Scheme of a simple key voltage regulator with an efficiency of 60%.

To establish a stabilizer, a load with a resistance of 5 ... 7 Ohms and a power of 10 watts is connected to its output. By selecting the resistor R7, the nominal output voltage is set, then the load current is increased to 3 A and, by selecting the value of the capacitor C4, the generation frequency is set (approximately 18 ... 20 kHz) at which the high-frequency voltage surges on the capacitor C3 are minimal.

The output voltage of the stabilizer can be increased to 8 ... 10V by increasing the value of the resistor R7 and setting a new value for the operating frequency. In this case, the power dissipated by the VTZ transistor will also increase.

In circuits of switching stabilizers, it is desirable to use electrolytic capacitors K52-1. The required capacitance value is obtained by parallel connection of capacitors.

Main technical characteristics:

• Input voltage, V - 15 ... 25.
• Output voltage, V - 5.
• Maximum load current, A - 4.
• Output voltage ripple at a load current of 4 A in the entire range of input voltages, mV, not more than - 50.
• Efficiency, %, not less than - 60.
• Operating frequency at an input voltage of 20 b and a load current of 3A, kHz - 20.

An improved version of the switching regulator for + 5V

In comparison with the previous version of the switching stabilizer in the new design of A. A. Mironov (Fig. 3), such characteristics as efficiency, output voltage stability, duration and nature of the transient process under the influence of an impulse load have been improved and improved.

Rice. 3. Scheme of a switching voltage regulator.

It turned out that during the operation of the prototype (Fig. 2), the so-called through current arises through a composite key transistor. This current appears at those moments when, at the signal of the comparison node, the key transistor opens, and the switching diode has not yet had time to close. The presence of such a current causes additional losses for heating the transistor and diode and reduces the efficiency of the device.

Another drawback is a significant ripple of the output voltage at a load current close to the limit. To combat ripples, an additional output LC filter (L2, C5) was introduced into the stabilizer (Fig. 2).

It is possible to reduce the instability of the output voltage from a change in the load current only by reducing the active resistance of the inductor L2.

Improving the dynamics of the transient process (in particular, reducing its duration) is associated with the need to reduce the inductance of the inductor, but this will inevitably increase the output voltage ripple.

Therefore, it turned out to be advisable to exclude this output filter, and increase the capacitance of capacitor C2 by 5 ... 10 times ( parallel connection several capacitors in a battery).

The circuit R2, C2 in the original stabilizer (Fig. 6.2) practically does not change the duration of the decline in the output current, so it can be removed (close the resistor R2), and the resistance of the resistor R3 can be increased to 820 ohms.

But then, with an increase in the input voltage from 15 6 to 25 6, the current flowing through the resistor R3 (in the original device) will increase by 1.7 times, and the dissipation power will increase by 3 times (up to 0.7 W).

By connecting the lower resistor R3 according to the output circuit (on the circuit of the modified stabilizer this is the resistor R2) to the positive terminal of the capacitor C2, this effect can be weakened, but the resistance R2 (Fig. 3) must be reduced to 620 Ohm.

One of the effective ways to deal with the through current is to increase the rise time of the current through the opened key transistor.

Then, when the transistor is fully opened, the current through the VD1 diode will decrease to almost zero. This can be achieved if the shape of the current through the key transistor is close to triangular.

As the calculation shows, to obtain such a form of current, the inductance of the storage inductor L1 should not exceed 30 μH.

Another way is to use a faster switching diode VD1, for example, KD219B (with a Schottky barrier). Such diodes have higher speed and less voltage drop at the same forward current compared to conventional silicon high-frequency diodes. Capacitor C2 type K52-1.

An improvement in the parameters of the device can also be obtained by changing the operating mode of the key transistor. A feature of the operation of a powerful VTZ transistor in the original and improved stabilizers is that it operates in an active mode, and not in a saturated one, and therefore has a high current transfer coefficient and closes quickly.

However, due to the increased voltage on it in the open state, the dissipated power is 1.5 ... 2 times higher than the minimum achievable value.

You can reduce the voltage on the key transistor by applying a positive (relative to the positive power wire) bias voltage to the emitter of the VT2 transistor (see Fig. 3).

The required value of the bias voltage is selected when adjusting the stabilizer. If it is powered by a rectifier connected to a mains transformer, then a separate winding on the transformer can be provided to obtain the bias voltage. However, in this case, the bias voltage will change along with the mains voltage.

Converter circuit with stable bias voltage

To obtain a stable bias voltage, the stabilizer must be modified (Fig. 4), and the inductor must be turned into a transformer T1 by winding an additional winding II. When the key transistor is closed and the diode VD1 is open, the voltage on the winding I is determined from the expression: U1=UByx + U VD1.

Since the voltage at the output and across the diode at this time changes slightly, regardless of the value of the input voltage on the winding II, the voltage is almost stable. After rectification, it is fed to the emitter of the transistor VT2 (and VT1).

Rice. 4. Scheme of a modified switching voltage regulator.

Heating losses decreased in the first version of the modified stabilizer by 14.7%, and in the second - by 24.2%, which allows them to operate at a load current of up to 4 A without installing a key transistor on the heat sink.

In the stabilizer of option 1 (Fig. 3), the L1 choke contains 11 turns wound with a bundle of eight PEV-1 0.35 wires. The winding is placed in the B22 armored magnetic circuit made of 2000NM ferrite.

Between the cups you need to lay a gasket made of textolite with a thickness of 0.25 mm. In the stabilizer of option 2 (Fig. 4), the transformer T1 is formed by winding two turns of wire PEV-1 0.35 over the inductor coil L1.

Instead of a germanium diode D310, you can use silicon, for example, KD212A or KD212B, while the number of turns of winding II must be increased to three.

DC Voltage Regulator with PWM

The pulse-width controlled stabilizer (Fig. 5) is similar in principle to the stabilizer described in, but, unlike it, has two feedback circuits connected in such a way that the key element closes when the load voltage is exceeded or the current increases consumed by the load.

When power is applied to the input of the device, the current flowing through resistor R3 opens the key element formed by transistors VT.1, VT2, as a result of which a current appears in the circuit transistor VT1 - inductor L1 - load - resistor R9. Capacitor C4 is charged and energy is stored by inductor L1.

If the load resistance is large enough, then the voltage across it reaches 12 B, and the VD4 zener diode opens. This leads to the opening of transistors VT5, VTZ and the closing of the key element, and due to the presence of the diode VD3, the choke L1 gives the accumulated energy to the load.

Rice. 5. The scheme of the stabilizer with pulse-width control with an efficiency of up to 89%.

Specifications of the stabilizer:

• Input voltage - 15 ... 25 V.
• Output voltage - 12 V.
• Rated load current - 1 A.
• Output voltage ripple at a load current of 1 A - 0.2 V. Efficiency (at UBX \u003d 18 6, In \u003d 1 A) - 89%.
• Current consumption at UBX = 18 V in the mode of closing the load circuit - 0.4 A.
• Output short circuit current (at UBX = 18 6) - 2.5 A.

As the current through the inductor decreases and the capacitor C4 is discharged, the voltage at the load will also decrease, which will lead to the closing of the transistors VT5, VTZ and the opening of the key element. Further, the process of the stabilizer is repeated.

Capacitor C3, which reduces the frequency of the oscillatory process, increases the efficiency of the stabilizer.

With a low load resistance, the oscillatory process in the stabilizer occurs differently. An increase in the load current leads to an increase in the voltage drop across the resistor R9, opening the transistor VT4 and closing the key element.

In all modes of operation of the stabilizer, the current consumed by it is less than the load current. Transistor VT1 should be installed on a heat sink with dimensions of 40x25 mm.

Inductor L1 is 20 turns of a bundle of three PEV-2 0.47 wires placed in a B22 cup magnetic circuit made of 1500NMZ ferrite. The magnetic core has a 0.5 mm thick gap made of non-magnetic material.

The stabilizer is easy to rebuild for a different output voltage and load current. The output voltage is set by choosing the type of zener diode VD4, and the maximum load current is set by a proportional change in the resistance of the resistor R9 or by applying a small current to the base of the VT4 transistor from a separate parametric stabilizer through a variable resistor.

To reduce the level of output voltage ripple, it is advisable to use an LC filter similar to that used in the circuit in Fig. 2.

Switching voltage regulator with conversion efficiency 69...72%

The switching voltage regulator (Fig. 6) consists of a trigger unit (R3, VD1, VT1, VD2), a reference voltage source and a comparison device (DD1.1, R1), a DC amplifier (VT2, DD1.2, VT5), transistor key(VTZ, VT4), an inductive energy storage device with a switching diode (VD3, L2) and filters - input (L1, C1, C2) and output (C4, C5, L3, C6). The switching frequency of the inductive energy storage, depending on the load current, is in the range of 1.3...48 kHz.

Rice. 6. Scheme of a switching voltage stabilizer with a conversion efficiency of 69 ... 72%.

All inductors L1 - L3 are the same and are wound in B20 armored magnetic circuits made of 2000NM ferrite with a gap between the cups of about 0.2 mm.

The rated output voltage is 5 V when the input voltage changes from 8 to 60 b and the conversion efficiency is 69...72%. Stabilization factor - 500.

The amplitude of the output voltage ripple at a load current of 0.7 A is no more than 5 mV. Output impedance - 20 mΩ. The maximum load current (without heat sinks for the VT4 transistor and the VD3 diode) is 2 A.

Switching voltage regulator for 12V

Switching voltage regulator (Fig. 6.7) at an input voltage of 20 ... 25 V provides a stable voltage of 12 V at the output at a load current of 1.2 A.

Output ripple up to 2 mV. Due to the high efficiency, the device does not use heat sinks. The inductance of the inductor L1 is 470 μH.

Rice. 7. Scheme of a switching voltage regulator with small ripples.

Transistor analogs: VS547 - KT3102A] VS548V - KT3102V. Approximate analogues of transistors VS807 - KT3107; BD244 - KT816.

Switching voltage regulators have recently become quite popular due to their compact size and relatively high efficiency, and in the near future they will completely replace the good old analog circuits.
Now, for a couple of dollars in China, you can buy a ready-made DC-DC converter module that provides output voltage regulation, has the ability to limit current, and operates in a fairly wide range of input voltages.

The most popular chip on which such stabilizers are built is the LM2596. The maximum voltage is up to 35 volts, with a current of up to 3 amperes. The microcircuit works in a pulsed mode, the heating on it is not very strong at quite impressive loads, it is compact and costs a penny.

By adding an op-amp, you can also get the output current limitation, I will say more - current stabilization, in other words - the current will be kept at the specified level regardless of the voltage.
Such modules are quite compact and can be built into any home-made design of the power supply and charger. By connecting a digital voltmeter to the output, we will know what voltage is at the output. .

The board itself has trimmer resistors to limit the output current and adjust the voltage. The input voltage range will make it possible to introduce such a module into a car by directly connecting 12 volts to the on-board network. What will it give us?

1. 1) Universal Charger with high current. You can charge any smartphones, tablets, players and other players, navigators and portable security systems, moreover, you can connect, say, 2-3 smartphones to the device at the same time and all of them will be equally well charged.

2. 2) Connect the device, say, to a laptop adapter, set the output to 14-15 Volts and safely charge the battery! 3 amps is quite a considerable current for charging a car battery, although the converter board itself will have to be installed on a small radiator.

You can't argue with the usefulness of the board, and it costs a penny (no more than 2-3 US dollars). The same board can be made at home, with certain components, although the finished module is much cheaper than individual components.

A dual operational amplifier, a current limiting unit is built on the first element of the op-amp, and an indication is built on the second. The microcircuit itself with a strapping, a power inductor that can be wound independently and a pair of regulators. The circuit almost does not overheat at low currents - but a small heat sink will not hurt.

The adjustable switching voltage stabilizer is designed both for installation in amateur radio devices with a fixed output voltage, and for a laboratory power supply with an adjustable output voltage. Since the stabilizer operates in a pulsed mode, it has a high efficiency and, unlike linear stabilizers, does not need a large heat sink. The module is made on a board with an aluminum substrate, which allows you to remove the output current up to 2 A for a long time without installing an additional heat sink. For currents over 2 A, a radiator with an area of ​​at least 145 sq. cm must be attached to the rear side of the module. The radiator can be attached with screws, for this purpose two holes are provided in the module, for maximum heat transfer use KPT-8 paste. If it is not possible to use mounting screws, the module can be attached to the heatsink/metal part of the device using an autosealant. To do this, apply sealant to the center of the back of the module, grind the surfaces so that the gap between them is minimal and press for 24 hours. The device has thermal protection and output current limitation from 3 to 4 A. The output voltage cannot exceed the input voltage. In order to start operating the stabilizer, it is necessary to solder a variable resistor from 47 to 68 KΩ to the contacts on the R1 board. The variable resistor should not be connected on long wires. For installation in devices with a fixed output voltage, in place of R1, you need to install a constant resistor using the formula R1 = 1210 (Uout / 1.23-1), where Uout is the required output voltage. The module can operate in the current stabilizer mode, for this, instead of R2, you need to install an external resistor, calculated by the formula R = 1.23 / I, where I is the required output current. The resistor must be of the appropriate power. When powering the module from a step-down transformer and a diode bridge, a filter capacitor of at least 2200 uF must be installed at the output of the diode bridge. Specifications Parameter Value Input voltage, no more than 40 V Output voltage 1.2..37 V Output current over the entire voltage range, no more than 3 A Output current limitation 3..4 A Conversion frequency 150 kHz Module temperature without heatsink at tamb = 25° С, Uin = 25 V, Uout = 12 V at out. current 0.5 A 36 ° C at the output. current 1 A 47 ° C at the output. current 2 A 65 ° C at the output. current 3 A 115 ° C efficiency at Uin = 25 V, Uout = 12 V, Iout = 3A 90% Operating temperature range -40. .85° С Reverse polarity protection no Module dimensions 43 х 40 х 12 mm Module weight 15 g Wiring diagram with voltmeter SVH0043 Wiring circuit with current stabilizer 1.6 A Overall dimensions

Switching power supply 200W Step-Down on the TL494 chip - schematic diagram, printed circuit board and description. This is an improved version of the switching regulator on the popular m / s TL494.

• Input voltage 2x18~30V AC
• The output voltage is adjustable with a potentiometer in the range 0-25 V DC
• Current limit adjustable by potentiometer
• For R=0.01 Ohm - 5~20 A
• For R=0.1 Ohm - 0.1~5 A

Large currents cause too much power loss on the resistor R, so we reduce its resistance. The efficiency of the converter circuit is very good, at 100 watts the heatsink only heats up a little. The red LED indicates current stabilization, and the green LED indicates voltage stabilization. Tested with 10 A resistive load. Works as expected.

Scheme of a pulse regulated inverter

The second version of the scheme

Circuit board - drawing

The stabilizer shown in the diagram is set to 14.4 volts and is used as a charger, therefore capacitors with a voltage of 16 V are used. 35 V at the input - 14.4 V at the output. The transformer is wound with a margin of turns, so that if desired, you can raise the voltage. But over 38 is too much. The microcircuit can withstand only 44 VDC according to the datasheet. The operating frequency of the converter is 100 kHz.