RU2234791C1 - Dc-to-ac converter - Google Patents

Abstract

FIELD: converter engineering; power systems for automatic-control devices and electric drives.

SUBSTANCE: proposed converter designed to convert low dc voltage into high sine-wave voltage that has transformer 4, first and second transistor switches 2 and 3, respectively, control unit 12, rectifier bridge 6, third and fourth transistor switches 7 and 8, respectively, and capacitor 10 is provided in addition with double-coil reactor 9 whose first-coil first lead is connected to common point of input of transistor switch 7 and output of transistor switch 8; input of the latter is connected to second output of rectifier bridge 6; second lead of first coil of double-coil reactor 9 is connected to first output lead of converter, to first lead of capacitor 10 whose second lead is connected to second output lead of converter, and to first lead of second coil of double-coil reactor 9;, second lead of this coil being connected to secondary-winding center tap of transformer 4; common bus of converter is connected to integrated inputs of first and second transistor switches 4 and 3, respectively.

EFFECT: enhanced efficiency and reliability of converter.

1 cl, 4 dwg

Description

The present invention relates to a conversion technique and can be used in power systems to convert a low DC voltage to a high alternating voltage sinusoidal shape in the development of various automation devices, electric drives.

A device is known for generating alternating current from direct current, comprising two or more bridge converters connected in series, each of the branches of which consists of a transistor shunted by a diode, the first diagonal of the bridge converter is connected to a power source, the first output of the second diagonal of the first bridge converter is connected to the first inductance terminal , the second output of which is connected to the second output of the second diagonal of the last bridge converter (see p. WO No. 105022, N 02 M 6 7/5387, 2001 g.)

The disadvantage of the device for generating is the low reliability due to the large number of control keys.

Known transistor inverter containing the first and second transistors, the inputs of which are combined and connected to a common bus, the outputs of which are connected to the primary winding of the first transformer, the midpoint of which is connected to a power source, as well as a bridge transistor voltage converter, each branch of which contains a transistor, shunted a diode, the control input of each transistor is connected to its input through the base diode and one of the four secondary windings of the first transformer, as well as through the series but the connected resistor and the secondary winding of the second transformer, the primary winding of the second transformer is connected to the output of the master oscillator, while the control inputs of the first and second transistors are connected through the corresponding counter-connected first and second diodes to the common bus and to the first and second output of the secondary winding of the third transformer, the primary winding of which is included in the diagonal of the bridge voltage converter (see.with. USSR No. 729784, N 02 M 6 7/5387, 1972)

The disadvantages of the inverter are low reliability due to the large number of control keys, large dimensions.

The closest in technical essence to the proposed one is a DC-to-AC converter containing a transformer, the beginning and end of the primary winding of which are connected respectively to the outputs of the first and second transistor switches, the inputs of which are combined and connected through the first current sensor to the first input of the converter, the second input of which connected to the midpoint of the transformer primary winding, the control inputs of the first and second transistor switches are connected respectively to the first and to the second outputs of the first control unit, the secondary winding of the transformer is connected to the input of the rectifier bridge, the first output of which is connected to the first output of the capacitor and the first input of the bridge voltage converter, the second output of the rectifier bridge is connected to a common bus, to the second output of the capacitor and through the second current sensor to the second the input of the bridge voltage converter, each branch of which contains a transistor switch, the outputs of the first and second transistor switches are combined and connected to the first the bridge voltage converter, to the second input of which the combined inputs of the third and fourth transistor switches are connected, the input of the first and the output of the third transistor switches are combined and connected to the first output of the DC-DC converter to AC, to the second output of which the combined input of the second and fourth transistor switches are connected , the control inputs of the transistor switches of the bridge voltage converter are connected to the outputs of the second control unit, respectively (with . P. USA No. 4706177, NKI 363-24, 1987).

The disadvantages of the converter are the presence of a two-stage conversion system (preliminary conversion of constant low voltage to high constant voltage), large dimensions due to the presence of a large capacitor and low reliability due to the large number of controlled keys, low efficiency due to the use of a two-stage conversion system.

The technical result of the invention is to increase efficiency, increase reliability.

The result is achieved by the fact that the DC-to-AC converter contains a transformer, the beginning and end of the primary winding of which are connected respectively to the outputs of the first and second transistor switches, the inputs of which are combined, their control inputs are connected respectively to the first and second outputs of the control unit, the middle point the transformer primary winding is connected to the converter input, the transformer secondary winding is connected to the input of the rectifier bridge, to the first output of which the output of the third transistor switch is switched on, the input of which is connected to the output of the fourth transistor switch, the control inputs of the third and fourth transistor switches are connected respectively to the third and fourth outputs of the control unit, as well as a capacitor and a common bus, a double-winding inductor is introduced, the first output of the first winding of which is connected to the connection point of the input of the third and the output of the fourth transistor switches, the input of the last of which is connected to the second output of the rectifier bridge, the second output of the first the two winding chokes are connected to the first output terminal of the converter, to the first output of the capacitor, the second terminal of which is connected to the second output terminal of the converter and to the first terminal of the second winding of the two winding inductor, the second terminal of which is connected to the midpoint of the secondary winding of the transformer, while the common bus of the converter is connected to the combined inputs of the first and second transistor switches.

The studies on patent and scientific and technical literature give reason to believe that the proposed technical solution is still unknown, which allows us to conclude that the claimed technical solution is new.

The use of a combination of features that distinguish the claimed technical solution from the well-known in the study of this and related areas of the technology section for converting low DC voltage to alternating voltage of a sinusoidal shape for the same purpose has not been identified, which ensures the claimed technical solution meets the criterion of "significant differences".

Figure 1 presents a block diagram of a DC-AC voltage converter (sinusoidal), figure 2 shows timing diagrams explaining its operation (a, b, c, d - respectively, the control signals at the inputs of the first, second, third and fourth semiconductor switches; d - the voltage at the output of the converter), 3 is an exemplary embodiment of the control unit 4 are timing charts for explaining its operation (a ₁ - the output voltage of the sawtooth generator, and ₂ - the output voltage pervog rectifier, b - voltage at the output of the comparator, c - voltage at the first output of the first inverter, g - voltage at the second output of the first inverter, d - voltage at the output of the first element And, e - voltage at the output of the second element And, w - voltage at the first the output of the second inverter, s is the voltage at the second output of the second inverter.

The DC-to-AC converter contains the input 1 of the converter, the first 2 and second 3 transistor switches, the inputs of which are combined and connected to the common bus 5 of the converter, their outputs are connected to the first and second terminals of the primary 4 ₁ transformer winding, the middle point of which is connected to input 1 , the secondary winding _{2 April} it is connected to the input of the rectifier bridge 6 to the first output of which is connected to the output 7 of the third transistor switch to its second output connected to a fourth input of the transistor switch 8, vyho which is combined with the input of the third 7 transistor switch and connected to the first terminal of the first September ₁ winding two winding inductor 9, a second terminal which is connected to the first terminal of the capacitor 10, to first output terminal 11 converter to the second output terminal of which is connected the second terminal of the capacitor 10 and the first a second output winding ₉ February two winding inductor 9, a second terminal which is connected to the midpoint of the secondary winding of the transformer _{2 April} 4, wherein the control inputs of the semiconductor switches connected to the corresponding 1-4 conductive unit 12 outputs control.

The rectifier bridge 6 consists of four branches, each of which contains a diode, the connection point of the anode of the first 6 ₁ diode and the cathode of the second 6 _{2 is} connected to the first input terminal of the bridge 6, its second input terminal is connected to the connection point of the anode of the third 6 ₃ diode and the cathode of the fourth 6 ₄ diodes, cathodes of diodes 6 ₁ and 6 _{3 are} combined and connected to the first output terminal of bridge 6, anodes of diodes 6 ₂ and 6 _{4 are} combined and connected to the second output terminal of bridge 6.

The control unit 12 contains a clock generator 13, the output of which is connected to the output of a sawtooth voltage generator 14, the output of which is connected to the first input of the comparator 15, to the second input of which is connected through the first 19 rectifier the output of the sinusoidal pulse generator 18, the input of which is connected to the output of the generator 13 clock pulses and to the input of the divider 20, the output of which is connected to the input of the first 21 inverter, the first (inverse) output of which is connected to the first input of the first 16 element And, its second output is connected is connected to the first input of the second 17 And elements, the second inputs of the elements 16 and 17 are connected to the output of the comparator 15, the outputs of the first 16 and second 17 elements And are connected respectively to the first 12 and second 12 outputs of the control unit 12, the third 123 and fourth 124 of which outputs are connected respectively, to the first (inverse) and second outputs of the second 24 inverter, the input of which is connected through the second 22 rectifier to the output of the sinusoidal pulse generator 18 and through the resistor 23 to the common bus 25 of the control unit 12, which is connected to the common bus 5 Vatel.

The sawtooth voltage generator 14 and the sinusoidal voltage generator 18 can be performed on R-2R matrices, the comparator 15 on the operational amplifier, the divider 20 on the triggers.

Converter DC to AC sinusoidal shape works as follows.

When applying a clock pulse generator 13 starts the voltage ramp generator 14 and voltage generator 18, a sinusoidal voltage, the inputs of the comparator 15 is supplied with a sawtooth voltage generator 14 (4a _1), and the rectified voltage of the generator 18 (4a _2). As a result of comparing the two voltages, pulses appear at the output of the comparator 15 (Fig. 4b), the duration of which during the half-cycle changes according to the law of a sinusoid, in the middle of the half-cycle the pulse duration reaches its maximum value, and by the beginning and the end of the half-cycle it is minimal. Upon receipt of pulses from the direct and inverse outputs of the first inverter 21 to the first inputs of the elements 16 and 17 (Figs. 4c, 4d), and to the second inputs of their pulses from the comparator 15, the outputs 16 and 17 of the elements also receive pulses with a variable duration, varying in the law of the sinusoid (fig.4d, e).

The voltage of the sinusoidal form from the output of the generator 18 is supplied through the second rectifier 22 to the input of the second 24 inverter, converted at its first (inverse) and second outputs into pulses with a period equal to the period of the sinusoidal voltage (Fig.4g, h).

The pulses from the control unit 12 are supplied to the inputs of the transistor switches 1-4 in accordance with the timing diagrams shown in FIGS. 2a-d.

During the time interval t ₀ -t _n the formation of a positive half-wave of the output sinusoidal voltage across the capacitor 10.

During the time interval t ₀ -t _n the formation of a positive half-wave of the output sinusoidal voltage across the capacitor 10.

During the entire time interval t ₀ -t _{n, the} third 7 transistor switch is open (Fig.2c), and the fourth 8 transistor switch is closed (Fig.2g).

At time t ₀ in accordance with the signals from the control unit 12 to the control input of the first 2 transistor switch (figa) key 2 is opened. The current flows from the source 1 through the first 4 ₁₁ primary winding of the transformer 4, the key 2 to the common bus 5. In accordance with the phasing of the windings on the first secondary winding 4 _{21 of the} transformer 4 appears a voltage proportional to the voltage of the power source and the transformation ratio. Under the influence of this voltage, a current flows through the first diode 6 _{1 of the} rectifier bridge 6, the open key 7, the first 9 ₁ winding of the inductor 9, the capacitor 10 and the second 9 ₂ winding of the inductor 9, which charges the capacitor 10 to a certain value with voltage of positive polarity.

At time t _{1, the} first 2 transistor switch closes. In this case, the inductor 9 will be a current source. The current of the inductor 9 continues to flow along the same circuit and charge the capacitor 10.

At time t ₂ opens the second 3 transistor switch (Fig.2B). The current flows from the source 1 through the second 4 ₁₂ primary winding of the transformer 4, key 3 to the common bus 5. In accordance with the phasing of the windings on the second 4 ₂₂ secondary winding of the transformer 4, a voltage proportional to the voltage of the power source and the transformation ratio appears. Under the influence of this voltage, a current flows through the third diode 6 ₃ , the open key 7, the first 9 ₁ winding of the inductor 9, the capacitor 10 and the second 9 ₂ winding of the inductor 9, which continues to charge the capacitor 10 with a voltage of positive polarity.

At time t _{3 the} second 3 transistor switch is closed. In this case, the current of the inductor 9 continues to flow along the same circuit and charge the capacitor 10.

At time t ₄ opens the transistor switch 2 and the processes are repeated until the time t _n . The duration of the open state of the transistor switches 2 and 3 increases in accordance with the algorithm for the formation of the growing section of the sinusoidal voltage (fig.2d).

Upon reaching the middle of the time interval t ₀ -t _{n the} duration of the open state of the transistor switches 2 and 3 reach their maximum value and then decrease to the end of the interval in accordance with the algorithm for the formation of the falling section of the sinusoidal voltage.

At time t _n , the stage of forming a positive half-wave of the output alternating (sinusoidal) voltage across the capacitor 10 ends.

On the time interval t _n -t _k the formation of a negative half-wave of the output alternating (sinusoidal) voltage across the capacitor 10.

At the same time, during the entire time interval t _n -t _{k, the} fourth 8 transistor switch is open (Fig. 2d), and the third 7 transistor switch is closed (Fig. 2c).

At time t _{n, the} transistor switch 2 opens. The current flows from the source 1 through the primary 4 ₁₁ winding of the transformer 4, the key 2 to the common bus 5. In accordance with the phasing of the windings on the second 4 ₂₂ secondary winding of the transformer 4 appears a voltage proportional to the voltage of the power source 1 and the transformation ratio. Under the influence of this voltage, a second current flows through the second 9 ₂ winding of the inductor 9, the capacitor 10, the first 9 ₁ winding of the inductor 9, the open key 8 and the fourth 6 ₄ diode of the rectifier bridge 6, which charges the capacitor 10 to a certain value with negative polarity voltage.

At time t _{5, the} first 2 transistor switch is closed. In this case, the inductor 9 will be a current source. The current of the inductor 9 continues to flow along the same circuit and charge the capacitor 10.

At time t _{6 the} second 3 transistor switch opens. Current flows from the source 1 through the second 4 ₁₂ primary winding of the transformer 4, the transistor switch 3 to the common bus 5. In accordance with the phasing of the windings, a voltage proportional to the voltage of the power supply 1 and the transformation ratio appears on the first 4 ₂₁ secondary winding of the transformer 4. Under the influence of this voltage, a current flows through the second 9 ₂ winding of the inductor 9, the capacitor 10, the first 9 ₁ winding of the inductor 9, the public key 8 and the second 6 ₂ diode of the rectifier bridge 6, which continues to charge the capacitor 10 with a voltage of negative polarity.

At time t _{7, the} second 3 transistor switch closes. In this case, the current of the inductor 9 continues to flow along the same circuit and charge the capacitor 10.

At time t ₈ , the first 2 transistor switch is opened (Fig. 2a) and the processes are repeated until time t _k . The duration of the open state of the transistor switches 2 and 3 increases in accordance with the algorithm for the formation of the falling section of the sinusoidal voltage.

Upon reaching the middle of the time interval t _n -t _{k, the} duration of the open state of the transistor switches 2 and 3 reaches its maximum value and then decreases to the end of the interval in accordance with the algorithm for generating an increasing section of the sinusoidal voltage.

At time t _k , the stage of formation of the negative half-wave of the output alternating (sinusoidal) voltage across the capacitor 10 (Fig.2d) ends.

The proposed technical solution allows you to abandon the two-stage conversion system and get the conversion of low DC voltage to high AC in one conversion stage (combined conversion of DC voltage at high frequency and conversion to AC voltage at a frequency of 50 Hz), which significantly increases the efficiency of the device, in addition, the reliability of the converter increases (the number of controlled keys is reduced and transistor switches 7 and 8 operate at a frequency of 50 Hz), arity due to the lack of a large capacitor.

Claims (1)

A DC / AC converter containing a transformer, the beginning and end of the primary winding of which are connected respectively to the outputs of the first and second transistor switches, the inputs of which are combined, their control inputs are connected respectively to the first and second outputs of the control unit, the input of the converter connected to the midpoint of the primary transformer windings, the secondary winding of which is connected to the input of the rectifier bridge, to the first output of which the output of the third transistor is connected a key whose input is connected to the output of the fourth transistor key, the control inputs of the third and fourth transistor keys are connected respectively to the third and fourth outputs of the control unit, as well as a capacitor and a common bus, characterized in that a double-winding inductor is introduced, the first output of the first winding of which is connected to the connection point of the input of the third and the output of the fourth transistor switches, the input of the last of which is connected to the second output of the rectifier bridge, the second output of the first winding the other choke is connected to the first output terminal of the converter, to the first terminal of the capacitor, the second terminal of which is connected to the second output terminal of the converter and to the first terminal of the second winding of the double winding inductor, the second terminal of which is connected to the midpoint of the secondary winding of the transformer, while the common bus of the converter is connected to the combined inputs of the first and second transistor switches.

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