RU84173U1 - BRIDGE INVERTER WITH OUTPUT TRANSFORMER PROTECTION FROM ONE-SIDED SATURATION - Google Patents

Abstract

A bridge inverter with protection of the output transformer from one-sided saturation, intended for converting direct voltage to alternating current with stabilization of the effective value of the output voltage, comprising: a bridge switch for converting direct current into alternating current, connected to the terminals for a power source; output transformer, the primary winding of which is connected to the output of the bridge switch; electronic key for short-circuiting this winding with open keys of the bridge switch; a clock pulse generator that sets the frequency of the generated output voltage, characterized in that the inputs of the means for detecting the open state of all the keys of the bridge switch are connected to the keys of the bridge switch, and the output of this tool is connected to the input of the electronic key for short-circuiting the primary winding of the transformer; the output transformer contains two identical measuring windings that act as EMF sensors for magnetizing the transformer magnetic circuit; the first means of detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the first half-period is connected to the first measuring winding; connected to the second measuring winding is a second means for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the second half-period; a calculator of the effective value of the voltage generated in the first half-period is connected to the output of the first means for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the first

Description

This technical solution relates to the field of electrical engineering, and is intended primarily for use in DC-AC converters.

Inverters are known - devices for converting direct voltage to alternating voltage by periodically switching the polarity of the voltage supplied to the primary winding of the output transformer, from the output of which the alternating voltage is removed to connect the load. They have a drawback - the appearance of one-sided saturation of the output transformer magnetic circuit with changes in input voltage, load asymmetry, or circuit elements. Known devices for eliminating this drawback with the detection of magnetic saturation of the magnetic circuit of the output transformer by controlling the output voltage are additionally introduced into the circuit by a current transformer. In particular, control of the beginning of saturation of the magnetic circuit

carried out by monitoring the voltage at the output of the current transformer and determining the second derivative of the current in the output transformer [1]. However, in a DC / AC converter, such a solution requires a separate transformer current sensor and sophisticated high-speed means of monitoring the second derivative.

Known schemes to prevent asymmetric saturation of the magnetic core of the output transformer by compensating for the saturation current in the opposite direction with additional power to the transformer winding with a current of opposite polarity [2]. However, this leads to a complication of the design, and in powerful voltage converters leads to a deterioration in weight and size indicators.

A known option to prevent saturation of the transformer, implemented in the voltage Converter for operation with capacitive load - fluorescent lamp [3]. The voltage converter contains control circuits for the constant and variable components when controlling transistor switches and means to prevent saturation of the transformer. The disadvantage is the complexity of the design and unsatisfactory weight and size

indicators.

It is also known the use of two saturation sensors to combat saturation of the transformer, however, this significantly complicates the design [4].

It is also known to limit the one-sided saturation of a transformer of a pulse voltage converter, RF patent [5], when a signal proportional to the magnetizing current of a transformer is detected, it is compared with a predetermined reference signal proportional to the maximum permissible magnetization current, and a control signal is generated that corrects the magnetization reversal mode of the transformer.

The disadvantage of this solution lies in the complexity of implementation, since a special sensor is needed for the signal proportional to the magnetization current of the transformer, it is necessary to measure the current in a short-circuited coil, covering part of the transformer magnetic circuit, which complicates the design of the voltage converter.

The closest known analogue is a RF patent [6], according to which a voltage inverter with transformer protection against one-sided saturation of the output transformer with two identical primary windings connected in series, the connection point of which is connected to one output of the power source, and the ends of the windings through controlled

the switches are connected to the second terminal of the power source. To control the alternate connection of these windings to the power source when generating the output voltage, the switch management tool is used. In order to eliminate the residual magnetization of the transformer magnetic circuit, the circuit contains a key controlled by the switch control means for short-circuiting the transformer primary winding when the power switches of the first and second windings are simultaneously open, when these windings are disconnected from the power source. The combined use of such a complex of technical solutions provides high quality voltage conversion, however, the overall dimensions are low due to the bulky transformer, which is a drawback. In addition, the disadvantage is the design complexity of the transformer due to the need to ensure the identity of the parameters of the primary windings used both in the formation of the required voltages and in measurements of the voltage proportional to the EMF magnetization of the transformer magnetic circuit.

The problem to which the claimed technical solution is directed is to eliminate these drawbacks, to reduce the size and weight, to prevent one-sided saturation of the output transformer

voltage converter, with protection against residual magnetization of the transformer magnetic circuit.

For this, a solution was used that provides approximate stabilization of the effective voltage value at the output of the voltage converter with predetermined limit values. One-sided saturation is prevented due to the equality of the volt-second areas of the output voltages in the positive and negative half-periods, and additional protection against residual magnetization of the transformer magnetic circuit. In this case, the output transformer is made with a primary winding having only two outputs.

This bridge inverter with the protection of the output transformer from one-sided saturation is designed to convert the constant voltage of the power source to alternating voltage, with stabilization of the effective value of the output voltage, as follows.

The bridge inverter contains a number of well-known technical solutions.

A bridge switch for converting direct current into alternating current connected to the terminals for a power source.

The output transformer, the primary winding of which is connected to the output of the bridge switch.

An electronic key for short-circuiting this winding when the keys of the bridge switch are open.

A clock pulse generator that sets the frequency of the generated output voltage.

Signs that distinguish this bridge inverter from the known ones are contained in the following solutions.

The keys of the bridge switch are connected to the inputs of the means for detecting the open state of all the keys of the bridge switch, and the output of this tool is connected to the input of the electronic key for short circuiting the primary winding of the transformer.

The output transformer contains two identical measuring windings that act as EMF sensors for magnetizing the transformer magnetic circuit.

The first means of detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the first half-period is connected to the first measuring winding.

A second means for detecting EMF proportional voltages is connected to the second measuring winding.

magnetization of the magnetic core of the transformer in the second half-cycle.

The calculator of the effective value of the voltage generated in the first half-period is connected to the output of the first means for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the first half-period.

The source of the reference voltage equivalent to the required value of the effective value of the voltage generated in the first half-cycle.

A comparator comparing the magnitude of the effective voltage value generated in the first half-cycle with the voltage of the reference voltage source is connected by inputs to the output of the calculator of the effective voltage value generated in the first half-cycle and to the output of the reference voltage source.

The calculator of the average voltage generated in the first half-period is connected to the output of the first means for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the first half-period.

A storage device for storing the value of the average voltage value generated in the first half-cycle, and storing this value during the formation of the second half-period, is connected to the output of the calculator

the average voltage generated in the first half-cycle.

The calculator of the average value of the voltage generated in the second half-period is connected to the output of the second means for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the second half-period.

A comparator comparing the average voltage value generated in the second half-cycle with the stored average voltage value generated in the first half-time is connected to the output of the average voltage calculator generated in the second half-time and to the output of the storage device for storing the average voltage value generated in first half period.

The output of the comparator comparing the magnitude of the effective voltage generated in the first half-cycle with the reference voltage is connected to those input circuits of the bridge switch, which serve to control the connection of the primary winding of the output transformer to the power source during the formation of the first half-cycle.

The output of the comparator comparing the average voltage value generated in the second half-cycle, with the stored value of the average voltage value generated in the first half-cycle, is connected to those input circuits of the bridge

the switch, which are used to control the keys of the bridge switch connecting the primary winding of the output transformer to the power source during the formation of the second half-cycle.

The drawing of figure 1 presents a diagram of the proposed bridge inverter with the protection of the output transformer from one-sided saturation.

In the drawing, the following notation is used for the elements and assemblies of which the bridge inverter is made.

1, 2 - input;

3, 4 - output;

5 - bridge switch;

6 - output transformer;

7 - primary winding;

8 - output winding;

9 - the first measuring winding;

10 - second measuring winding;

11 - the first means of detecting voltages proportional to the EMF of magnetization of the magnetic circuit;

12 - a second means of detecting voltages proportional to the EMF of magnetization of the magnetic circuit;

13 - electronic key for short circuit the primary winding of the transformer;

14 - clock pulse generator;

15 - channel for measuring the current voltage values of the first half-cycle and calculating the current and average voltage values;

16 - channel for measuring the current voltage values of the second half-cycle and calculating the average voltage value;

17 - calculator of the effective value of the voltage generated in the first half-cycle;

18 - calculator of the average voltage generated in the first half-cycle;

19 is a voltage reference source;

20 is a comparator comparing the magnitude of the current value of the voltage generated in the first half-cycle with the voltage of the reference voltage source;

21 is a storage device for storing the value of the average voltage value generated in the first half-cycle;

22 - calculator of the average voltage generated in the second half-cycle;

23 is a comparator comparing the magnitude of the average voltage generated in the second half-period, with a stored value

the average voltage generated in the first half-cycle.

The bridge inverter with the protection of the output transformer from one-sided saturation when converting DC voltage to AC with stabilization of the effective value of the output voltage is as follows.

At the input 1, 2 terminals for the power source connected bridge switch 5 for converting direct current to alternating current.

The primary winding 7 of the output transformer 6 is connected to the output of the bridge switch 5.

To the inputs of the start of operation of the bridge switch 5 when forming the first and second half-periods, the outputs are connected to a clock pulse generator 14, which sets the frequency of the generated output voltage.

In parallel to the winding 7, an electronic key 13 is connected for short circuiting the winding 7 with the keys of the bridge switch 5 open.

The keys of the bridge switch 5 are connected to the inputs of the built-in means for detecting the open state of all the keys of the bridge switch 5, and the output of this tool

connected to the input of the electronic key 13 for short circuit of the primary winding 7 of the transformer 6.

The output transformer 6 contains two identical measuring windings 9 and 10, which act as EMF sensors for magnetization of the transformer magnetic circuit - winding 9 for the first half-cycle, and winding 10 for the second half-cycle.

To the first measuring winding 9 is connected the first means 11 for detecting voltages proportional to the EMF of magnetization of the magnetic core of transformer 6 in the first half-cycle.

To the second measuring winding 10 is connected a second means 12 for detecting voltages proportional to the EMF magnetization of the magnetic core of the transformer 6 in the second half-cycle.

To the output of the first means 11 for detecting voltages proportional to the EMF of magnetization of the magnetic circuit of the transformer 6 in the first half-period, a calculator 17 of the effective voltage value generated in the first half-period is connected.

To the output of the calculator 17 of the effective voltage value generated in the first half-cycle, and to the output of the reference voltage source 19, which is equivalent to the required value of the effective voltage value, formed in the first

a half-period is connected to the inputs of a comparator 20 comparing the magnitude of the effective value of the voltage generated in the first half-period with the voltage of the reference voltage source 19.

To the output of the first means 11 for detecting voltages proportional to the EMF of magnetization of the magnetic circuit of the transformer 6 in the first half-period, a calculator 18 of the average voltage generated in the first half-period is connected.

A memory 21 is connected to the output of the calculator 18 of the average voltage value generated in the first half-period to store the value of the average voltage value generated in the first half-cycle and to store this value during the formation of the second half-period. To the output of the second means 12 for detecting voltages proportional to the magnetization EMF of the magnetic circuit of the transformer 6 in the second half-period, a calculator 22 of the average voltage value generated in the second half-period is connected.

To the output of the calculator 22 of the average voltage value generated in the second half-cycle, and to the output of the storage device 18 for storing the value of the average voltage value generated in the first half-cycle, is connected

a comparator 23 for comparing the magnitude of the average voltage generated in the second half-cycle with the stored value of the average voltage generated in the first half-cycle.

The output of the comparator 20 comparing the magnitude of the effective voltage generated in the first half-cycle with the reference voltage is connected to those input circuits of the bridge switch 6, which serve to control the connection of the primary winding 7 of the output transformer 6 to the power source during the formation of the first half-cycle.

the output of the comparator 23 comparing the magnitude of the average voltage generated in the second half-cycle with the stored value of the average voltage formed in the first half-cycle, is connected to those input circuits of the bridge switch 6, which are used to control the keys of the bridge switch connecting the primary winding 7 of the output transformer 6 to the source power during the formation of the second half-cycle.

Means 17, 18, 19, 20 form a channel 15 for measuring the current voltage values of the first half-cycle and calculating the current and average voltage values.

Means 21, 22, 23 form a channel 16 for measuring the current voltage values of the second half-cycle and calculating the average voltage value.

The output winding 8 of the output transformer 6 is connected to the output 3, 4.

The principle of operation of a bridge inverter with protection against one-sided saturation of the output transformer when converting direct voltage to alternating current, with stabilization of the effective value of the output voltage, is as follows.

The voltage of the first polarity is formed for the first half-cycle. Then a voltage of the second, opposite, polarity is formed for the second half-cycle.

The effective value of the voltage generated in the first half-cycle is made equal to a given reference value.

In addition, the average value of the voltage generated in the first half-cycle is calculated and stored.

In the second half-cycle, a voltage is formed, the average value of which is equal to the stored average value of the voltage generated in the first half-cycle preceding it.

Moreover, when calculating the current and average voltage values, the current voltage is used, which is proportional to the magnetizing EMF of the transformer magnetic circuit, which are removed from two separate measuring windings of the output transformer loaded with active resistances. This reduces the measurement error in comparison with the use of a single winding with further half-wave rectification and distribution of signals over the channels.

This ensures the equality of the volt-second areas of the generated voltages and eliminates the one-sided saturation of the transformer magnetic circuit.

On the resistances connected to the measuring windings of the output transformer, measure the current voltage proportional to the magnetization EMF of the transformer magnetic circuit, and then form the voltages of the first and second half-cycles with the first polarity.

The current voltage proportional to the magnetization EMF of the transformer magnetic core is also measured, its effective value is calculated, the result is compared with the aforementioned set value of the reference signal, and when the current value is equal to the reference value, voltage generation of the first half-cycle with the first polarity is completed.

In addition, the average voltage value for the first half-cycle is calculated, and the result is stored for use in the process of generating a voltage pulse of the second half-cycle with a different, opposite polarity.

In the second half-cycle, a second voltage pulse is formed having a different, opposite polarity.

When forming the voltage of the second half-cycle, the current voltage is proportional to the EMF of the magnetization of the transformer magnetic circuit, its average value is calculated, the result is compared with the stored value of the calculated average voltage value generated for the previous first half-cycle, and when the equality is reached, the second pulse is completed.

In the formation of pulses of subsequent periods, all operations are repeated.

As a result of this, the average values of voltages and volt-second areas of the generated pulses of the first and second polarity are equal during the first and second half-periods, and, consequently, magnetic fluxes in the magnetic circuit, which eliminates the danger of one-sided saturation of the transformer magnetic circuit.

In the first half-cycle, a voltage is formed that satisfies the conditions for the effective value

voltage, and, in addition, calculate the average value of the voltage and remember the result.

In the second half-cycle, a voltage is formed that satisfies the conditions for the average value so that it is equal to the previously stored value of the average voltage value of the first half-cycle.

In subsequent periods, the operation is repeated.

Implementing the above principle, the circuit is depicted in figure 1, and works as follows.

A constant voltage is applied to inputs 1, 2 from the power supply of the bridge inverter.

The clock pulse generator 14 starts to work, setting the frequency of the generated output voltage. It is connected by outputs to the inputs of the start of operation of the bridge switch 5 during the formation of the first and second half-periods. The corresponding keys of the bridge switch 5 are opened and the current of the first half-cycle being formed begins to flow through the primary winding 7. The first formed half-cycle will end upon receipt of a signal from channel 15 measuring the current voltage values of the first half-cycle and calculating the current and average voltage values at

reaching the required value of the effective value of the generated voltage.

The second half-cycle then begins with the arrival of the second half-cycle pulse generated by the clock generator 14, and ends when the signal from channel 16 arrives when the average value of the generated voltage of the second half-cycle is equal to the average voltage of the first half-cycle generated in channel 15.

Further cycles are repeated.

In this case, the bridge inverter as a whole and the circuits in channels 15 and 16 work as follows.

From the outputs 3, 4 of the bridge inverter, an alternating voltage is removed for a connected external load, stabilized by the value of the effective value with a given error, and lying in the allowable range from minimum to maximum value.

The DC voltage supplied to the inputs 1, 2 from the power source, the bridge switch 5 converts to AC. Alternating voltage from the output of the bridge switch 5 is supplied to the output transformer 6 through the primary winding 7.

From the output winding 8 of the output transformer 6 to the output terminals 3, 4, the output voltage of the bridge inverter is supplied.

The signals used to measure the current voltage proportional to the magnetization EMF of the transformer 6 magnetic core in the first half-cycle are taken from the first measuring winding 9, which functions as an EMF magnetization sensor.

Connected to the first measuring winding 9, the first means 11 for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the first half-cycle contains the load resistance of the winding 9, and a rectifier, from which the current measuring voltage is removed for calculations. The signals from the output of the means 11 then enter the channel 15 measuring the current voltage values of the first half-cycle and calculating the current and average voltage values, and calculations are performed. From the calculator 17 of the effective voltage value generated in the first half-cycle, a signal is continuously supplied to one of the inputs of the comparator 20 for comparing the value of the effective voltage value generated in the first half-cycle with the voltage of the reference voltage source 19. The reference signal from the source is supplied to the second input of the comparator 20

the reference voltage 19, equivalent to the required value of the effective value of the voltage generated in the first half-cycle. When the equality of the signals received at the input of the comparator 20 is reached, a signal to complete the formation appears at its output. This signal serves to open the keys of the bridge switch 5, and is transmitted to those input circuits of the bridge switch 5, which during the formation of the first half-cycle serve to control the connection of the primary winding 7 of the output transformer 6 to the terminals of the input 1, 2 for the power source.

The processes of calculating stresses by the average voltage calculator 18 and the current voltage calculator 17 start and end simultaneously.

Calculators 17 and 18 after completion of calculations by built-in means are automatically reset to the initial state of readiness for the next calculations.

The frequency of the output voltage of the voltage Converter is set by the clock generator 14 periodic pulses, the outputs of which control the triggering circuit of the keys of the bridge switch 5. The formation of voltages of the first and second half-cycles begins when pulses from the first or second outputs of the clock generator 14 to the corresponding inputs of the bridge switch

5a and ends with control signals from the outputs of channels 15 or 16. With the beginning of the formation of voltages of the first and second half-periods, a current flows through the winding 7 of the transformer 6.

The output signals related to the first half-cycle from the first output of the means 11 for detecting voltages proportional to the magnetizing EMF of the transformer magnetic core are fed to channel 15 for measuring the current voltage values of the first half-cycle and for calculating the current and average voltage values, containing two means for measuring the current voltage generated in the first half-cycle , and necessary calculations:

- to the measuring input of the calculator 17 of the effective voltage value generated in the first half-cycle,

- to the measuring input of the calculator 18 of the average voltage generated in the first half-cycle.

The output signals from the output of the second means 12 for detecting voltages proportional to the EMF of the magnetization of the magnetic core related to the second half-cycle are fed to channel 16 for measuring the current voltage values of the second half-cycle and for calculating the average voltage — to the input of the computer 22 of the average voltage generated in the second half-period. Channel 16 only contains

one means of calculating the parameters of the current voltage generated in the second half-cycle.

The calculated average voltage value of the first half-cycle from the output of the calculator 18 goes to channel 16, to the input of the storage device 21 for the average voltage value generated in the first half-cycle, where this value is stored until the voltage generation process of the second half-cycle is completed and then automatically reset.

Calculators 17, 18, as well as 22, begin to perform calculations from the moment the signals arriving at their inputs begin, respectively, from the outputs of the first 11 and second 12 means for detecting voltages proportional to the EMF of magnetization of the magnetic circuit.

When the voltage related to the second half-cycle comes from the output of the means for detecting voltages 12 proportional to the magnetizing EMF of the magnetic core of the transformer 6, to the input of the average voltage calculator 22, the latter starts to calculate from the moment the signal starts. From the output of the calculator 22, a voltage proportional to the average voltage of the second half-cycle is supplied to the first input of the comparator 23 for comparing the current average voltage of the second half-cycle with the voltage

the output of the storage device 21 for the average value of the voltage generated in the first half-cycle. The second input of the comparator 23 is supplied with voltage from the output of the storage device 21, which is proportional to the average value of the voltage generated in the first half-cycle. If these voltages are equal, the output signal of formation is generated at the output of the comparator 23, which is fed to the second input of the bridge switch 5, and the voltage generation of the second half-cycle is completed. Simultaneously with the output of the comparator 23, a signal is also supplied to the second input of the storage device 21 for the average voltage value generated in the first half-cycle, setting it in the initial state of readiness for the next storage.

Computing devices 17, 18, 22 after each completion of the calculations for the corresponding half-cycle, the built-in tools are automatically set to the initial state of readiness for the next calculations.

As a result, the average values of the pulses generated in the first and second half-periods are equal.

The key 13 is a short circuit of the primary winding 7 at those times when it is disconnected from the power source - the keys of the bridge switch 5 are open.

After the completion of the formation of each half-cycle, the keys of the bridge switch 5 are open for some time. In this period of time, the key 13 closes, which opens until the next key closure of the bridge switch 5. This eliminates the possible residual magnetization of the transformer magnetic circuit.

The bridge switch 5 contains means for preventing through currents through the managed switches contained therein, and means for preventing the simultaneous short-circuiting of said converter switches and an electronic switch for short-circuiting the primary winding of the transformer. Such means are known, for example, prohibition schemes and the formation of pauses between switching times in bridge circuits. Such schemes are applicable to protect the entire complex of the mentioned keys of the bridge switch 5 together with the key 13.

Known devices usually solve the problem of stabilizing the voltage so that the output voltage is equal to a certain predetermined value with some tolerances, usually symmetrical with respect to the required rating.

According to the proposed solution, the output voltage is within the specified tolerances. In this case, the output voltage may have asymmetrical tolerances relative to the specified

reference voltage, if the output transformer has a voltage inequality of the first and second half-cycles caused by the power source and circuit elements or non-linear load.

Errors of the magnitude of the effective voltage at the output of the voltage converter according to the proposed method are within acceptable limits for practical applications.

For each pair of pulses in one period, the parameters of the first pulse exactly correspond to the required value, at which the required effective value is provided.

The difference in the parameters of the second pulse and the first pulse leads to a slight absolute error of the effective value at the output of the voltage converter, in comparison with the known options for ensuring the equality of the effective values in both half-periods.

The proposed solution allows us to simplify the cumbersome and complex circuitry solutions for monitoring and control used in known circuits of voltage converters in order to prevent one-sided saturation of the transformer.

Information sources.

1. US patent No. 6617839, Method for detecting current transformer saturation.

2. US Patent No. 4017786, Transformer saturation control circuit for a high frequency switching power supply.

3. US Patent No. 5317497, Internally excited, controlled transformer saturation, inverter circuitry.

4. RF patent No. 2027297, IPC Н02М 7/539, DC / AC Converter of a given shape.

5. RF patent No. 2035833, IPC Н02М 7/538, Method for limiting one-sided saturation of a transformer of a pulse voltage converter.

6. RF patent №2282934, IPC Н02М 7/42, Voltage inverter with transformer protection from one-sided saturation.

Claims (1)

A bridge inverter with protection of the output transformer from one-sided saturation, intended for converting direct voltage to alternating current with stabilization of the effective value of the output voltage, comprising: a bridge switch for converting direct current into alternating current, connected to the terminals for a power source; output transformer, the primary winding of which is connected to the output of the bridge switch; electronic key for short-circuiting this winding with open keys of the bridge switch; a clock pulse generator that sets the frequency of the generated output voltage, characterized in that the inputs of the open-circuit detection means of all the keys of the bridge switch are connected to the keys of the bridge switch, and the output of this tool is connected to the input of the electronic key for short-circuiting the primary winding of the transformer; the output transformer contains two identical measuring windings that act as EMF sensors for magnetizing the transformer magnetic circuit; the first means of detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the first half-period is connected to the first measuring winding; to the second measuring winding is connected a second means for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the second half-period; a calculator of the effective value of the voltage generated in the first half-period is connected to the output of the first means for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the first half-period; a reference voltage source equivalent to the required value of the effective voltage value generated in the first half-cycle; a comparator comparing the magnitude of the rms value of the voltage generated in the first half-cycle with the voltage of the reference voltage source, connected to the outputs of the calculator of the rms value of the voltage generated in the first half-cycle, and to the output of the reference voltage source; a calculator of the average value of the voltage generated in the first half-period is connected to the output of the first means for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the first half-period; a storage device for storing the value of the average voltage value generated in the first half-cycle, and storing this value during the formation of the second half-period, connected to the output of the calculator of the average voltage value generated in the first half-period; a calculator of the average value of the voltage generated in the second half-period is connected to the output of the second means for detecting voltages proportional to the EMF of magnetization of the transformer magnetic circuit in the second half-period; a comparator comparing the average voltage value generated in the second half-cycle with the stored average voltage value generated in the first half-time, connected to the output of the average voltage calculator generated in the second half-time, and to the output of the storage device for storing the average voltage value generated in first half period; the output of the comparator comparing the magnitude of the effective voltage generated in the first half-cycle, with the reference voltage connected to those input circuits of the bridge switch, which serve to control the connection of the primary winding of the output transformer to the power source during the formation of the first half-cycle; the output of the comparator comparing the average voltage generated in the second half-cycle, with the stored value of the average voltage formed in the first half-cycle, is connected to those input circuits of the bridge switch, which are used to control the bridge switch keys that connect the primary winding of the output transformer to the power source during formation second half period.