RU87304U1 - VOLTAGE INVERTER WITH PREVENTION OF ONE-SIDED SATURATION OF TRANSFORMER - Google Patents

Abstract

A voltage inverter with prevention of one-sided saturation of the transformer, comprising a DC to AC converter with a bridge switch connected to terminals for a power source; an output transformer, the primary winding of which is connected to the output of the bridge switch of the DC-AC converter; a clock generator that sets the period of the output voltage, having first and second outputs with a shift of the output pulses of the second output by half the period relative to the pulses at the first output, characterized in that the output transformer contains a measuring winding, an input means for detecting a voltage proportional to the magnetizing EMF of the magnetic circuit a transformer having one common output for both the first half-cycle and the second half-cycle; to control the start of the start of formation of each half-cycle, electrical connections were introduced for the triggering pulses from the outputs of the clock generator: to the start input of the DC / AC converter with a bridge switch, to the start input of the calculator of the actual voltage value of the first half period, to the start input of the calculator of the average voltage value of the first half period, to the start input of the calculator of the average voltage value of the second half-cycle, to the start input of the storage device; a calculator of the effective value of the voltage generated in the first half-period, connected by a measuring input to the output of the means for detecting the voltage proportional to the magnetizing EMF of the transformer magnetic circuit, and by the input to start the start

Description

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

Known devices for converting DC voltage to AC by periodically switching the polarity of the voltage supplied to the primary winding of the output transformer, from the output of which the AC 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 methods and 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 current transformer circuit. In particular, control of the beginning of saturation of the magnetic circuit is carried out by monitoring the voltage at the output of the current transformer and determining the second derivative of the outflow 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 inverters leads to a deterioration in weight and size indicators.

There is a method of preventing saturation of a transformer, implemented in an inverter for operation with a capacitive load - a fluorescent lamp [3]. The inverter contains control circuits for the constant and variable components when controlling transistor switches and means to prevent saturation of the transformer. The disadvantage is unsatisfactory weight and size indicators and design complexity.

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

There is also known a solution, patent of the Russian Federation [5], according to which the device for limiting the one-sided saturation of the transformer of a pulse voltage converter contains means that detect a signal proportional to the magnetizing current of the transformer, compare it with a given signal proportional to the maximum permissible magnetizing current, and generate a control signal, correcting mode of magnetization reversal of the transformer.

The disadvantage of this device is the complexity of its implementation in the design, since this requires a special signal sensor proportional to the magnetization current of the transformer, i.e. it is required to carry out a current measurement in a short-circuited coil, covering part of the transformer magnetic circuit, which complicates the design of both the magnetic circuit itself and the converter as a whole, requiring an additional current transformer.

The closest known analogue is a patent of the Russian Federation [6]. The inverter [6] with protection against one-sided saturation of the voltage transformer transformer with means to prevent one-sided saturation of the voltage transformer transformer is made as follows.

The output transformer contains a magnetizing EMF measurement winding connected to the input of the measuring voltage shaper proportional to the magnetizing EMF of the first and second half-periods, which has two outputs. The corresponding inputs of the two measurement channels and the formation of the first and second voltage half-periods are connected to these outputs.

The first channel is designed to measure the current voltage values of the first half-cycle and calculate the current and average voltage values. The second channel is designed to measure the current voltage values of the second half-cycle and calculate the average voltage value. The signals from the outputs of these channels are transmitted to a DC-to-AC converter containing a bridge switch.

The disadvantage of the device of this inverter - a DC-to-AC converter is the difficulty of ensuring the identity of the transient characteristics of the circuits for both outputs of the measuring voltage shaper of the first and second half-cycles. Each channel of this shaper has its own systematic and random errors, various dependences on temperature and other influences in the structure. Ensuring the identity of the circuits of both outputs complicates both the design scheme and its adjustment.

The problem to which the claimed technical solution is directed is to reduce errors and simplify the design.

For this, a solution was used that made it possible to detect a measuring voltage proportional to the EMF of the magnetization of the first and second half-cycles, with one output common to the inputs of both measurement channels and the formation of the first and second half-periods of voltage.

The proposed solution is a voltage inverter, made as follows.

The voltage inverter with the prevention of one-sided saturation of the transformer contains a number of well-known technical solutions and a set of new technical solutions.

The inverter contains the following well-known technical solutions.

A DC to AC converter with a bridge switch 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 of the DC / AC converter.

A clock generator that sets the period of the output voltage, having first and second outputs with a shift of the output pulses of the second output by half the period relative to the pulses at the first output.

The signs that distinguish the proposed solution from the known, the following.

The output transformer contains a measuring winding, means for detecting a voltage proportional to the magnetization EMF of the transformer magnetic circuit connected to the input, having one common output for both the first half-period and the second half-period;

To control the start of the formation of each half-cycle, electrical connections for triggering pulses from the outputs of the clock generator are introduced:

to the start input of the DC / AC converter, to the start input of the calculator of the actual voltage value of the first half period, to the start input of the calculator of the average voltage value of the first half period, to the start input of the calculator of the average voltage value of the first half period,

to the start input of the storage device.

A calculator of the effective value of the voltage generated in the first half-period, connected by a measuring input to the output of the voltage detection means proportional to the EMF of magnetization of the transformer magnetic circuit, and by the input to start the measurement to the first output of the clock generator.

The reference voltage source is proportional to the specified value of the effective voltage value, which should be generated in the first half-cycle.

The first comparator compares the actual value of the current voltage of the first half-cycle with the reference voltage of the reference voltage source, connected to the voltage comparison inputs to the reference voltage source and to the output of the calculator of the actual voltage value generated in the first half-cycle, and the output of the first comparator is connected to the input of the bridge switch, which is designed to complete the voltage generation of the first half-cycle.

A calculator of the average value of the voltage generated in the first half-cycle, connected by a measuring input to the output of the voltage detection means proportional to the magnetizing EMF of the transformer magnetic circuit, and by the input to start the measurement to the first output of the clock generator.

A memory device that remembers the average value of the voltage generated in the first half-cycle, connected by a signal input to the output of the average voltage calculator of the first half-cycle, an input to start the start of storage - to the first output of the clock generator, and an input to complete the storage and switch to storage mode - to the output the first comparator comparing the current value of the current voltage of the first half-cycle with the reference voltage of the reference voltage source;

a calculator of the average voltage value of the second half-cycle generated in the primary winding, connected by a measuring input to the output of a means for detecting a voltage proportional to the magnetizing EMF of the transformer magnetic circuit, and by an input to start the measurement to the second output of the clock generator;

the second comparator compares the average value of the current voltage of the second half-cycle with the stored average voltage value of the first half-cycle, connected to the voltage comparison inputs to the output of the calculator of the average value of the current voltage of the second half-cycle, and to the output of a storage device that stores the average value of the voltage generated in the first half-cycle, and the output of the second the comparator is connected to the input of the bridge switch, which is designed to complete the voltage generation of the second oluperioda.

The circuit of the voltage inverter with the prevention of one-sided saturation of the transformer is shown in figure 1, where the following designations of the elements and assemblies of which the inverter is made are taken.

1, 2 - input;

3, 4 - output;

5 - DC to AC converter with a bridge switch;

6 - output transformer;

7 - primary winding;

8 - output winding;

9 - winding measuring the EMF magnetization;

10 - means for detecting the measuring voltage proportional to the EMF magnetization of the transformer magnetic circuit in the first and second half-periods;

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

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

11 is a clock pulse generator controlling the frequency of the Converter 5;

14 - calculator of the effective voltage value of the first half-cycle;

15 - calculator of the average voltage value of the first half-cycle;

16 - calculator of the average voltage value of the second half-cycle;

17 is a reference voltage source equivalent to the required effective voltage of the first half-cycle;

18 - the first comparator compares the current effective voltage of the first half-cycle with the reference;

19 - storage device;

20 is a second comparator comparing the current average voltage of the second half-cycle with the average voltage value of the first half-cycle.

The voltage inverter with the prevention of one-sided saturation of the transformer is made as follows.

In the inverter circuit of Fig. 1, input terminals 1, 2 are intended for supplying a constant voltage to the inverter from a power source, and output terminals 3, 4 are intended for connection to a load inverter. The findings 1, 2 connected to the Converter 5 DC to AC with a bridge switch. The output transformer 6 with the primary winding 7 is connected to the output of the bridge switch of the converter 5. The output transformer 6 contains an output winding 8 connected to the terminals 1, 2, and a measuring winding 9, which is used to detect the voltage proportional to the magnetization EMF of the transformer magnetic circuit. The output winding 8 of the transformer 6 is connected to the output terminals 3, 4 for connecting the load. The output terminals 3, 4 of the inverter are designed to supply an external load with an alternating voltage, stabilized by the value of the effective value with a given error, and in the range from minimum to maximum value.

To the measuring winding 9 is connected a means 10 for detecting a voltage proportional to the EMF magnetization of the magnetic circuit of the output transformer 6; this tool has one output for a voltage proportional to that generated in the first and second half-periods. Clock generator 11 sets the frequency of the output voltage. The clock generator 11 has first and second outputs, with a shift of the output pulses of the second output by half the period relative to the pulses at the first output.

To control the start of the beginning of the formation of each half-cycle, the following electrical connections have been introduced to transmit trigger pulses from the outputs of the clock generator 11:

to the start input of the DC-to-DC converter 5 with a bridge switch - from the first output of the clock generator 11 for the first half-cycle, and from the second output of the clock generator 11 for the second half-cycle;

to the input of the start of the calculator 14 of the current voltage value of the first half-cycle from the first output of the clock generator 11;

to the input of the start of the calculator 15 of the average voltage of the first half-cycle from the first output of the clock generator 11;

to the input of the start of the storage device 19 - from the first output of the clock generator 11;

to the input of the launch of the calculator 16 of the average voltage of the second half-cycle from the second output of the clock generator 11.

The calculator 14 of the current value of the voltage generated in the first half-cycle is connected by a measuring input to the output of the means 10 for detecting the voltage proportional to the magnetization EMF of the magnetic core of the transformer 6, and by the input to start the measurement to the first output of the clock generator 11.

The reference voltage source 17, which is proportional to the specified value of the rms voltage value that must be generated in the first half-cycle, and the output of the rms voltage value calculator 14, formed in the first half-cycle, are connected to the voltage comparison inputs of the first comparator 18 for comparing the current effective voltage of the first half-cycle with the reference voltage . The output of the first comparator 18 is connected to that input of the DC / AC converter 5 with a bridge switch, which is designed to complete the voltage generation of the first half-cycle.

The calculator 15 of the average voltage generated in the first half-period is connected by a measuring input to the output of the means 10 for detecting the voltage proportional to the magnetization EMF of the magnetic circuit of the output transformer 6, and the input to start the measurement is connected to the first output of the clock generator 11. The output of the calculator 15 calculates the average voltage the first half-cycle is connected to the input of the storage device 19, which stores the average value of the voltage generated in the first half-cycle.

The calculator 16 of the average voltage value of the second half-cycle generated in the primary winding 7 is connected by a measuring input to the output of the means 10 for detecting the voltage proportional to the magnetization EMF of the transformer 6 magnetic circuit; and the input for starting the start of measurements to the second output of the clock generator 11. The output of the calculator 16 of the average voltage of the second half-cycle is connected to the first input of the voltage comparison of the second comparator 20 comparing the current average voltage of the second half-cycle with the average value of the voltage of the first half-period stored in the storage device 19. The second voltage comparison input of the second comparator 20 is connected to the output of the storage device 19, which stores the average value of the voltage generated about in the first half period. The output of the second comparator 20 is connected to that input of the DC / AC converter 5, which is designed to complete the voltage generation of the second half-cycle.

The circuit of figure 1 works as follows.

At the inputs 1, 2 from the power source of the inverter serves a constant voltage.

From outputs 3, 4, an alternating voltage stabilized by the value of the effective value with a given error, i.e., lying in the range from minimum to maximum, is removed to the inverter load.

The direct voltage supplied to the inputs 1, 2 from the power source, the DC-to-AC converter 5 with a bridge switch converts to alternating voltage with a given frequency. Alternating voltage from the output of the bridge switch of the converter 5 is supplied to the output transformer 6 through the primary winding 7.

The output winding 8 of the transformer 6 is connected to the output terminals 3, 4 of the inverter, through which the voltage generated by the inverter is supplied to the load.

Signals are taken from the measuring winding 9 to measure the current voltage value, which is proportional to the magnetization EMF of the transformer core.

Connected to the winding 9 means 10 for detecting the measuring voltage proportional to the EMF of magnetization of the transformer magnetic circuit in the first and second half-periods, contains the load resistance of the winding 9, a rectifier of the first and second half-periods of the generated voltage, and a matching amplifier. The means 10 for detecting the measuring voltage proportional to the EMF of magnetization of the transformer magnetic circuit in the first and second half-periods has one common output on both channels 12 and 13, from which the measuring voltage is supplied to the input circuits of channels 12 and 13, intended for measuring current voltage values and calculations. According to the results of these calculations, the separate formation of stresses in the first and second half-periods in the converter 5 is controlled.

The frequency of the output voltage of the inverter is set by the clock of periodic pulses 11, the output signals of which control the converter 5. The formation of the voltages of the first and second half-cycles begins with the arrival of pulses of the clock generator 11 at the input of the converter 5, and ends with the arrival of control signals from the outputs of channels 12 and 13.

With the beginning of the formation of voltages of the first and second half-periods, a current flows through the transformer winding 7.

At the same time, signals are measured from the measuring winding 9 for measuring the current value of the voltage proportional to the magnetizing EMF of the transformer core, which are fed to the input of the measuring voltage shaper 10, which is proportional to the magnetizing EMF of the transformer magnetic circuit in the first and second half-periods.

From the output of circuit 10, the output signals are fed to channels 12 and 13, in which computational operations are carried out and the necessary pulse duration of the first and second half-periods is formed.

The output signals during the first half-cycle from the output of the shaper 10 are sent to channel 12, which contains two means - 14 and 15 for calculating the parameters of the current voltage generated in the first half-cycle:

- to the measuring first input of the calculator of the effective voltage value 14,

- to the measuring first input of the calculator of the average voltage value 15.

During the beginning of the first half-cycle, a rectangular pulse from the first output of the clock generator 11 is supplied to the first input of the start of the DC-to-DC converter 5, and a current begins to flow in the primary winding 7 - the formation of the first half-cycle begins.

During the beginning of the first half-cycle, a rectangular pulse from the first output of the clock generator 11 also arrives at the control inputs of the start-up enable of the calculator 14 of the effective voltage value of the first half-cycle, and the calculator 15 of the average voltage of the first half-cycle.

In addition, during the first half-cycle, a rectangular pulse from the output of the clock generator 11 is supplied to the control input of the storage device 19 to start the operation. In this case, the front of this rectangular pulse, the storage device 19 is set to the initial state of readiness for storing voltage from the computer 15 of the average voltage value of the first half-cycle.

During the beginning of the second half-cycle, a rectangular pulse from the second output of the clock generator 11 is supplied to the second input of the start of the DC-to-DC converter 5, and then a current begins to flow in the primary winding 7 - the formation of the second half-cycle begins.

In addition, during the start of the second half-cycle, the rectangular pulse from the second output of the clock generator 11 also arrives at the control input of the start-up permission of the calculator 16 of the average voltage of the second half-cycle.

The calculators 14, 15, 16 begin to perform calculations from the moment the signal arriving from the output of the means 10 for detecting the measuring voltage, which is proportional to the EMF of magnetization of the transformer magnetic circuit in the first and second half-periods, only if there are corresponding enable pulses from the clock generator 11. And since these enable signals for the first and second half-cycles go from different outputs of the clock generator 11 and therefore are shifted by half a period, then from the output signal of the means 10 is automatically allocated to already half-cycle, and therefore in the tool 10 two separate outputs for each half-cycle is not required.

Computing devices 14, 15, 16 after each completion of the calculations for the corresponding half-cycle are automatically set to the initial state of readiness for the next calculations by signals from the clock generator 11.

The inverter contains a reference voltage source 17, which sets the value of the effective voltage value generated in the first half-cycle; its output is connected to the first input of the first comparator 18, and the second input of the first comparator 18 receives a signal from the calculator of the actual value 14, and the calculated effective value of the voltage at the output of the calculator 14 is compared with the reference voltage of the reference voltage source 17. When the equality of the effective voltage value is reached with a reference voltage from the output of the first comparator 18 to the third input of the reset of the Converter 5 receives a signal to complete the formation of voltage; in addition, the same signal is supplied to a separate input of the storage device 19, and with this signal, the storage device 19 is transferred to the storage mode of the stored voltage.

The processes of calculating stresses by the average voltage calculator 15 and the current voltage calculator 14 begin and end simultaneously.

The calculated average voltage value from the output of the calculator 15 is sent to channel 13, to the signal input of the means for storing the average voltage value - a memory device 19, where this value is stored and used during the voltage generation process of the second half-cycle.

When the output signals of the second half-cycle from the output of the means 10 for detecting the measuring voltage, which is proportional to the magnetization EMF of the transformer magnetic core, are fed to the input of the average voltage calculator 16, the latter starts to perform the calculations. From the output of the calculator 16, a voltage proportional to the average voltage value is supplied to the first input of the second comparator 20, and a voltage from the output of the storage device 19, which is proportional to the average voltage value generated in the first half-cycle, is supplied to its second input. If these voltages are equal, the pulse is generated at the output of the second comparator 20, which is fed to the second input of the converter by the arrival of this pulse, the formation of the voltage of the second half-cycle is completed.

Computing devices 14, 15, 16 after each completion of the calculations for the corresponding half-cycle are set to the initial state of readiness for the next calculations by the signals from the outputs of the clock pulse generator 11.

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

The described calculations and operations can be performed by means of analog or digital technology.

In this case, the output voltage is within the specified tolerances. The output voltage may have asymmetric tolerances with respect to the specified reference voltage if the output transformer has an voltage inequality of the first and second half-periods, caused either by the power source and circuit elements, or by a non-linear load.

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 proposed solution allows the means for detecting the measuring voltage proportional to the magnetization EMF in the first and second half-periods to be performed with one output and exclude the second stage with the second output, which reduces the conversion errors and simplifies the design.

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 No. 2273087, IPC Н02М 7/538, Method of protection against unilateral saturation of a voltage transformer transformer.

Claims (1)

A voltage inverter with preventing one-sided saturation of the transformer, comprising a DC to AC converter with a bridge switch connected to terminals for a power source; an output transformer, the primary winding of which is connected to the output of the bridge switch of the DC-AC converter; a clock generator that sets the period of the output voltage, having first and second outputs with a shift of the output pulses of the second output by half the period relative to the pulses at the first output, characterized in that the output transformer contains a measuring winding, an input means for detecting a voltage proportional to the magnetizing EMF of the magnetic circuit a transformer having one common output for both the first half-cycle and the second half-cycle; to control the start of the start of formation of each half-cycle, electrical connections were introduced for the triggering pulses from the outputs of the clock generator: to the start input of the DC / AC converter with a bridge switch, to the start input of the calculator of the effective voltage value of the first half period, to the start input of the calculator of the average voltage value of the first half period, to the start input of the calculator of the average voltage value of the second half-cycle, to the start input of the storage device; a calculator of the effective value of the voltage generated in the first half-period, connected by a measuring input to the output of the means for detecting the voltage proportional to the magnetizing EMF of the transformer magnetic circuit, and by the input to start the measurement to the first output of the clock generator; a reference voltage source proportional to a predetermined value of the effective voltage value, which should be generated in the first half-cycle; a first comparator comparing the effective value of the current voltage of the first half-cycle with the reference voltage of the reference voltage source connected to the voltage comparison inputs to the reference voltage source and to the output of the calculator of the actual voltage value generated in the first half-cycle, and the output of the first comparator is connected to the input of the bridge switch, which is designed to complete the voltage generation of the first half-cycle; a calculator of the average value of the voltage generated in the first half-period, connected by a measuring input to the output of the means for detecting the voltage proportional to the EMF of magnetization of the transformer magnetic circuit, and by the input to start the measurement to the first output of the clock generator; a memory device that stores the average value of the voltage generated in the first half-cycle, connected by a signal input to the output of the calculator of the average voltage of the first half-cycle, the input to start the start of memorization - to the first output of the clock generator, and the input to complete the memorization and switch to storage mode - to the output the first comparator comparing the current value of the current voltage of the first half-cycle with the reference voltage of the reference voltage source; a calculator of the average voltage value of the second half-cycle generated in the primary winding, connected by a measuring input to the output of the means for detecting the voltage proportional to the magnetizing EMF of the transformer magnetic circuit, and by the input to start the measurement to the second output of the clock generator; the second comparator compares the average value of the current voltage of the second half-cycle with the stored average voltage value of the first half-cycle, connected to the voltage comparison inputs to the output of the calculator of the average value of the current voltage of the second half-cycle, and to the output of a storage device that stores the average value of the voltage generated in the first half-cycle, and the output of the second the comparator is connected to the input of the bridge switch, which is designed to complete the voltage generation of the second oluperioda.