WO2011054137A1

WO2011054137A1 - Direct current-alternating current voltage converting circuit

Info

Publication number: WO2011054137A1
Application number: PCT/CN2009/001556
Authority: WO
Inventors: 陆元成; 洪伟弼
Original assignee: 纽福克斯光电科技（上海）有限公司
Priority date: 2009-11-05
Filing date: 2009-12-25
Publication date: 2011-05-12
Also published as: CN101702591A; CN101702591B

Abstract

A direct current-alternating current voltage converting circuit is used for converting a direct current low voltage to output an alternating current output voltage. The voltage converting circuit includes a boost circuit (201) for inverting and boosting the direct current low voltage into a high frequency alternating current high voltage, a bridge rectifier circuit (202) for rectifying the high frequency alternating current high voltage to obtain a direct current high voltage, a first capacitor (C1) and a second capacitor (C2) connected in series across the output ends of the bridge rectifier circuit (202), a first switch (S1) and a second switch (S2) connected in series across the output ends of the bridge rectifier circuit (202), a waveform generation circuit (206) for controlling the first switch (S1) and the second switch (S2), and an alternating current output circuit (204) for outputting the alternating current output voltage. A first output end (A) of the alternating current output circuit (204) is connected to a common node (5) of the first capacitor (C1) and the second capacitor (C2), and a second output end (B) is connected to a common node (6) of the first switch (S1) and the second switch (S2). Since the voltage converting circuit utilizes only two switch elements at the output side and does not need a high voltage drive circuit, the circuit is simple relatively and can save cost and space.

Description

DC-AC voltage conversion circuit

The present invention relates to a voltage conversion circuit, and more particularly to a conversion circuit for converting a direct current voltage into an alternating current voltage.

Background technique

The DC-AC voltage conversion circuit is a static semiconductor power device that converts DC power such as a battery, a solar cell or a fuel cell into a constant voltage (50 Hz, 60 Hz, 400 Hz, etc.) constant current (50 Hz > 60 Hz, 400 Hz, etc.) The converter device is used for AC load or connected to the AC to generate electricity. This inverter technology plays a vital role in the development and application of new energy.

Figure 1 shows a common circuit for a DC-AC voltage conversion circuit currently used to convert a DC DC low voltage into an AC AC high voltage. The working principle is as follows: input DC DC low voltage to supply a high frequency oscillating circuit and corresponding high frequency power amplifying circuit, the high frequency oscillating circuit outputs a high frequency switching signal, and the high frequency switching signal is sent to the power amplification The primary of the high-frequency transformer T1; after the high-frequency transformer T1 is boosted, the required high-frequency alternating current high voltage is obtained in the high-frequency transformer secondary; the high-frequency alternating current high voltage is rectified by the high-frequency high-voltage bridge rectifier circuit, and is resistant High-voltage large-capacity smoothing filter obtains DC high-voltage HV (High Voltage); This DC high-voltage HV is connected to a bridge-type inverter switching circuit composed of four power switching elements S1~S4, and obtains a constant voltage HV constant frequency (such as 50Hz, 60Hz or 400Hz, the specific frequency depends on the AC output of the waveform generator): When VC1 and VC3 are high voltage and VC2 and VC4 are low voltage, switches S1 and S3 are turned on and switches S2 and S4 are turned off, DC high voltage HV is switched S1 to point A, then connected to point B via load ZL, and then connected to DC ground by switch S3; when VC1 and VC3 are low voltage and VC2 and VC4 are high voltage, switch S1 S3 is turned off and switches S2 and S4 are turned on, DC high voltage HV is switched to S point B to B point, then connected to point A via load ZL, and then connected to DC ground by switch S2; DC high voltage HV is loaded by ZL to waveform generator The frequency alternates from point A to point B and then from point B to point A to form a constant voltage HV constant frequency (such as 50 Hz, 60 Hz or 400 Hz, the specific frequency depends on the waveform generator) AC voltage AC, thereby obtaining DC-to-AC Conversion.

However, in this circuit, the DC-AC inverter circuit requires four power switches S1, S2, S3 and S4, and the operating voltages of the switches SI and S4 are between HV and GND, in order to enable the switches S1 and S4 to be turned on, The high-voltage body circuit 1 and the high-voltage drive circuit 2 are often required to complete the high-voltage drive, which results in more power control switches for such circuit forms, and the high-voltage drive control circuit is also more complicated and costly.

In summary, it can be seen that the prior art requires four power switches and a high-voltage driving circuit to convert the DC voltage into an AC voltage, which complicates the high-voltage driving control circuit and has a high cost. Therefore, it is necessary to propose an improved technical means. , To solve this problem. Summary of the invention

In order to overcome the above various shortcomings of the prior art, the main object of the present invention is to provide a DC-AC conversion circuit that can convert DC low voltage into AC high by using only two switching elements and without requiring a high voltage driving circuit. The purpose of the voltage.

To achieve the above and other objects, a DC-AC voltage conversion circuit of the present invention electrically connects a DC voltage, and converts the DC voltage output to provide a stable AC output voltage, which includes:

a boosting circuit electrically connected to the DC voltage, the DC voltage obtaining a high frequency AC high voltage after the boosting circuit; a bridge rectifier circuit having two AC input terminals and two DC output terminals, the rise The voltage circuit is connected between the two AC input terminals, and the high frequency AC high voltage is sent to the bridge rectifier circuit for rectification to obtain a positive and negative DC high voltage and a reference midpoint voltage of the positive and negative DC high voltage ;

a filter capacitor group is connected between two positive and negative DC output terminals of the bridge rectifier circuit and a reference midpoint for filtering the positive and negative DC high voltages; - an AC output circuit for outputting AC a power frequency output voltage, the first output end of the AC output circuit is connected to the reference midpoint;

a switching circuit is connected between the two positive and negative DC output ends of the bridge rectifier circuit and connected to the second output end of the AC output circuit;

A waveform generating circuit is connected to the switching circuit for controlling the turning on and off of the switching circuit.

The boosting circuit includes at least a high frequency transformer connected to the bridge rectifier circuit.

The boosting circuit includes a high frequency switching circuit and a high frequency transformer, the high frequency switching circuit includes a high frequency oscillating circuit and a high frequency power amplifying circuit, and the DC voltage is amplified by the high frequency switching circuit and sent to the High frequency transformer.

The filter capacitor group includes at least a first capacitor and a second capacitor connected in series, and the first capacitor and the second capacitor in series are connected between two DC output terminals of the bridge rectifier circuit, the first capacitor and the first capacitor A reference midpoint common to the two capacitors is coupled to the first output of the AC output circuit.

The high frequency transformer secondary has a center tap, and a common node of the first capacitor and the second capacitor is connected to the center tap. The first capacitor and the second capacitor are both high voltage and large capacitors.

The switching circuit includes a first switch and a second switch connected in series, and the first switch and the second switch connected in series are connected between two positive and negative DC output ends of the bridge rectifier circuit, the first switch and the first switch The common node of the second switch and the AC input The second output of the output circuit is connected.

The second output is a reference ground.

The first switch and the second switch are both power stage transistor switches, and the first switch and the second switch are complementary polarity switching elements.

The waveform generating circuit is a waveform generator, and the waveform generator is respectively connected to the first switch and the second switch. At least a third capacitor is further disposed between the waveform generator and the second switch for changing a control signal of the waveform generator to the second switch to a negative polarity control signal having a negative voltage.

A clamping circuit is further disposed between the third capacitor and the second switch for clamping the control signal to a negative voltage. The clamping circuit is a diode, the diode is grounded, and the anode is connected between the third capacitor and the second switch. The first switch and the second switch may also be an N-channel MOS tube or an NPN tube, and one end of the corresponding waveform generator is connected to the first switch through an optocoupler, and the other end of the waveform generator and the second switch connection.

Compared with the prior art, the DC-AC voltage conversion circuit of the present invention connects the second output end of the AC output circuit to two by connecting the first output end of the AC output circuit to the common node of the two high-voltage capacitors connected in series. a common node of the series switch, and directly driving the two series switches by a waveform generating circuit, thereby achieving the purpose of converting the DC low voltage into the power frequency AC high voltage, because the present invention The output circuit uses only two switching elements, and does not require a high voltage driving circuit, so that the DC-to-AC output circuit of the present invention becomes very simple, saving the cost and space of the circuit. DRAWINGS

1 is a circuit diagram of a prior art DC-AC voltage conversion circuit.

2 is a circuit diagram of a DC-AC voltage conversion circuit of the present invention.

Fig. 3 is a schematic diagram showing voltage waveforms of respective nodes in Fig. 2.

4 is a circuit diagram of another DC-AC voltage conversion circuit of the present invention.

Fig. 5 is a schematic diagram showing voltage waveforms of respective nodes in Fig. 4. detailed description

The embodiments of the present invention will be described by way of specific examples and the accompanying drawings, and those skilled in the art can readily understand the advantages and advantages of the present invention. The invention may also be embodied or applied by other different specific examples, and the details in the specification may also be based on different viewpoints and applications without departing from the essence of the invention. God made various modifications and changes.

2 is a circuit diagram of a DC-AC voltage conversion circuit according to the present invention. As shown in FIG. 2, a DC-AC voltage conversion circuit is electrically connected to a low voltage DC, and the DC low voltage DC is converted and outputted to provide a stable AC output voltage AC, which includes a boost circuit 201. The bridge rectifier circuit 202, the filter capacitor bank 203, the 'outflow output circuit 204, the switch circuit 205, and the waveform generation circuit 206. ,

The boosting circuit 201 is connected to the bridge rectifier circuit 202. The boosting circuit 201 includes a high frequency switching circuit and a high frequency transformer. The high frequency switching circuit can be composed of a high frequency oscillation circuit and a high frequency power amplifying circuit. The booster circuit 201 receives the DC low voltage, and forms a high frequency amplified signal through the high frequency oscillator circuit. The high frequency amplified signal is amplified by the high frequency power amplifier circuit and sent to the high frequency transformer. After the high-frequency transformer is boosted, a required high-frequency AC high voltage is obtained in the high-frequency transformer secondary; the bridge rectifier circuit 202 is a bridge rectifier circuit composed of four rectifier diodes, which has two AC input terminals and Two positive and negative DC output terminals, the high frequency AC high voltage output passes through the bridge rectifier circuit 202, and obtains a positive and negative DC high voltage +HV, -HV and a reference midpoint voltage of the positive and negative DC high voltage.

The filter capacitor group 203 is connected between the two positive and negative DC output terminals of the bridge rectifier circuit 202, and includes a first capacitor C1 and a second capacitor C2 connected in series, the first capacitor C1 and the second capacitor C2. The capacitors are all high voltage resistant capacitors, and are connected in series between the two positive and negative DC output terminals of the bridge rectifier circuit 202. The common node 5 serving as the reference midpoint is not only the first one of the AC output circuit 204. The output terminal A is connected, and is connected to the center tap of the high frequency transformer. After the high voltage direct current is filtered by the filter capacitor group 203, a relatively smooth positive and negative high voltage direct current is obtained; the switch circuit 205 is also connected to the bridge rectifier. The two positive and negative DC output terminals of the circuit 202 are connected in parallel with the filter capacitor, and are connected in series and connected between the positive and negative DC output terminals of the bridge rectifier circuit 202. The first switch S1 and the common node 6 of the second switch S2 are connected to the second output terminal B of the AC output circuit 204. In the present invention, the second output terminal B is simultaneously referenced, and the first switch S1 and the second switch are simultaneously S2 The waveform generating circuit 206 is connected to the waveform generating circuit 206 to generate a corresponding control signal to control the on or off of the first switch S1 and the second switch S2 to control the output of the AC output circuit 204 to 50HZ/60HZ/ The 400 Hz AC power frequency output voltage AC (the specific frequency depends on the waveform generation circuit 206).

It should be noted that the DC-AC voltage conversion circuit of the present invention may further provide a fourth capacitor C4 between the DC low voltage DC input and the booster circuit 201, which functions to smooth the DC power supply or the spike interference pulse. Filtering to provide better quality DC power is a common practice and will not be described in detail here.

The working principle of the invention is as follows: after the DC low voltage DC is input to the boosting circuit 201, after the high frequency converter is boosted, a required high voltage alternating current high voltage is obtained, and then the high frequency alternating current high voltage is output. Feeding into the bridge rectifier circuit 202 The rectification is performed to obtain a positive and negative DC high voltage +/- HV. When the first switch S1 is turned on by the waveform generation circuit 206, and the second switch S2 is turned off, the first capacitor C1 is positively grounded, due to the voltage on the capacitor. It cannot be abruptly changed. At this time, the voltage on the first capacitor C1 is still HV, so the anode voltage of the first capacitor C1 is equivalent to -HV; and when the waveform generation circuit 206 controls, the first switch S1 is turned off, and the second switch S2 is guided. At this time, the second capacitor C2 is at the ground, and the voltage on the capacitor C2 is still HV, so the cathode voltage of the second capacitor C2 is equivalent to +HV. Thus, under the control of the control signal of the positive or negative voltage alternately generated by the waveform generating circuit 206, the two points of AB can output a constant voltage HV constant frequency (such as 50 Hz, 60 Hz or 400 Hz, the specific frequency of which depends on Waveform generator) AC power frequency output voltage AC.

Hereinafter, a preferred embodiment of the present invention will be further described with reference to FIG. Compared with the prior art, the high frequency transformer in the preferred embodiment of the present invention needs to use a center tapped secondary, and the corresponding secondary total number of turns is twice the original; the bridge rectifier circuit 202 is composed of four rectifier diodes. High-frequency high-voltage bridge rectifier circuit, wherein D1-D4 are rectifier diodes, D1 and D3 cathodes are connected, common node 1 is DC output positive pole, D2 and D4 anode are connected, and common node 2 is DC output negative pole, in the present invention The common node 1 and the common node 2 are both defined as DC output terminals; the D1 anode is connected to the D4 cathode and connected to one of the secondary ends of the high frequency transformer, and the D3 anode is connected to the D2 cathode and connected to the other end of the high frequency transformer secondary. , but the rectified DC output is 2 HV, the common node 4 of D1 and D4 and the common node 3 of D2 and D3 are defined as the AC input terminal; the high voltage resistant large capacitor first capacitor C1 and the second capacitor C2 are connected in series, The common node 5 is connected to the secondary center tap of the high frequency transformer, and the common node 5 is also connected to the first output terminal A of the constant voltage constant frequency AC output voltage AC; The first switch S1 and the second switch S2 are connected in series, wherein the first switch S1 is an NPN power transistor (or an N-channel MOS transistor or other equivalent device, for convenience of description, only the triode switch is described below), and the second switch S2 is PNP power transistor (or P-channel MOS transistor or other complementary equivalent device, for convenience of description, only the transistor switch is described below), the common node 6 is connected to the second output terminal B of the constant voltage constant frequency AC output voltage AC, The node B is simultaneously defined as the ground of the waveform generator; the waveform generating circuit 206 is a waveform generator that generates control voltages NC1, VC2, the control voltage VC1 is connected to the first switch S1, and the control voltage VC2 is connected to the second switch. S2, controlling the first switch S1 and the second switch S2 to be turned on or off by the control voltages VC1, VC2. Preferably, a third capacitor C3 is connected between the control voltage VC2 and the second switch S2 for changing the control voltage VC2 to a negative voltage control signal VC2, and the negative pulse of the control signal enables the second The switch S2 is turned on. In addition, the preferred embodiment further includes a clamp circuit, specifically a diode D5. The anode of the diode D5 is connected to the output end of the third capacitor C3 and the cathode of the second switch S2. Grounding is used to clamp the positive control signal output by the waveform generating circuit 206 to a negative control signal to drive the second switch S2.

3 is a schematic diagram of voltage waveforms of respective nodes, wherein VC1 and VC2 are respectively generated corresponding to the waveform generation circuit 206. Control voltages VC1 and VC2; VC2 is the voltage after VC2 is blocked by the third capacitor C3 and diode D5, that is, the actual control voltage of the second switch S2; AC represents the output between the output terminals AB of the AC output circuit 204. AC power frequency output voltage. Referring to FIG. 2 at the same time, the driving signal VC1 of the first switch S1 is a high level, and t1 is an on-time; the control signal VC2 of the second switch S2 is a low level, and 12 is an on-time; The control voltage VC1 and the control voltage VC2 generated as the driving signal generated by the waveform generating circuit 206 do not allow the on-times t1 and t2 to overlap in timing, otherwise a short circuit is formed, which may damage the device and cause a danger. The second output terminal B is referred to as ground. In the time t1, the control voltage VC1 is at a high level, and the control voltages VC2 and VC2 are at a high level. During this period, the first switch S1 is turned on, and the second switch S2 is turned off. The positive pole of the first capacitor C1 is ground. Since the voltage on the capacitor cannot be abruptly changed, the voltage on the first capacitor C1 is still HV, so the anode voltage of the first capacitor C1 is equivalent to -HV; during the time t2, the control voltage VC1 When the level is low, the control voltage VC2 is low level, and the actual control voltage VC2 of the second switch S2 is a negative voltage. During this period, the first switch S1 is turned off, and the second switch S2 is turned on, and the second capacitor C2 is negative. Extremely, since the voltage across the capacitor cannot be abrupt, the voltage on the second capacitor C2 is still HV, so the positive voltage of the second capacitor C2 is equivalent to +HV. Thus, the voltage at the first output terminal A is alternately positive or negative with respect to the frequency of the control signal generated by the waveform generator at the second output terminal B, and the constant voltage HV constant frequency (for example, 50 Hz) can be output at two points of AB. , 60Hz or 400Hz, the specific frequency depends on the AC power frequency output voltage AC of the waveform generator).

4 is a circuit diagram of another DC-AC voltage conversion circuit of the present invention, which is compared with the DC-AC voltage conversion circuit shown in FIG. 2, a booster circuit 201, a bridge rectifier circuit 202, a filter capacitor bank 203, and an AC output. The circuit 204 and the waveform generating circuit 206 are the same except that the first switch S1 and the second switch S2 in the switch circuit 205 are both N-channel MOS transistors or NPN tubes, and the second switch S2 is connected to the waveform through a resistor R2. At the output of the control voltage VC2 of the circuit 206, the second switch S2 is directly driven by the control voltage VC2. The first switch SI is driven by the control voltage VC1 through the optocoupler 01. The specific connection is as follows: The common node 6 is connected to the emitter of the triode in the optocoupler 01, and the first switch S1 is connected to the collector of the triode in the optocoupler 01. The diode D5 of the optocoupler 01 is grounded, and the anode is connected to the output of the control voltage VC1 of the waveform generating circuit 206 through a resistor R3. The collector and the emitter of the transistor in the optocoupler 01 are also respectively connected to a resistor R1 and a resistor. Capacitor C5, the resistor R1 and the other end of the capacitor C5 are connected in parallel and connected to the voltage +Vcc through a diode.

FIG. 5 is a schematic diagram of voltage waveforms of respective nodes. Referring to FIG. 4 at the same time, when the control voltage VC1 is at a high level, the aperture 01 is turned on, and the first switch S1 is turned off; when the control voltage VC1 is at a low level, the first switch S1 is turned on. When the control voltage VC2 is at a high level, the second switch S2 is turned on, and when the control voltage VC2 is at a low level, the second switch S2 is turned off. During the time t2, the control voltages VC1 and VC2 are both at the high level, and the first switch S1 is turned off during the period, and the second switch S2 is turned off. Turn on, at this time, the second capacitor C2 is grounded, because the voltage on the capacitor cannot be abrupt, the voltage on the second capacitor C2 is still HV, so the positive voltage of the second capacitor C2 is equivalent to +HV; The control voltages VC1 and VC2 are both low level. During this period, the first switch S1 is turned on, the second switch S2 is turned off, and the first capacitor C1 is positively ground. Since the voltage on the capacitor cannot be abrupt, the first capacitor C1 is at this time. The voltage on the voltage is still HV, so the negative voltage of the first capacitor C1 is equivalent to -HV. In this way, the voltage at the first output terminal A is alternately positive or negative with respect to the frequency of the control signal generated by the waveform generator at the second output terminal B, and the constant voltage HV constant frequency (for example, 50 Hz) can be output at two points of AB. , 60Hz or 400Hz, the specific frequency depends on the AC power frequency output voltage AC of the waveform generator).

Through the invention, the DC-AC voltage conversion circuit can be made very simple, saving the cost and space of the circuit. The above-described embodiments are merely illustrative of the principles of the invention and its advantages, and are not intended to limit the invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be as set forth in the claims.

Claims

Rights request

A DC-AC voltage conversion circuit electrically connecting a DC voltage to convert the DC voltage output to provide a stable AC output voltage, comprising:

a boosting circuit electrically connected to the DC voltage, the DC voltage obtaining a high frequency AC high voltage after the boosting circuit; a bridge rectifier circuit having two AC input terminals and two positive and negative DC output terminals, The boosting circuit is connected between the two AC input terminals, and the high frequency AC high voltage is sent to the bridge rectifier circuit for rectification to obtain a positive and negative DC high voltage and a reference of the positive and negative DC high voltage. Point voltage

a filter capacitor group is connected between the two positive and negative DC output ends of the bridge rectifier circuit and a reference midpoint for filtering the positive and negative DC high voltages;

An AC output circuit for outputting an AC power frequency output voltage, wherein the first output end of the AC output circuit is connected to the reference midpoint;

a switching circuit is connected between the two positive and negative DC output terminals of the bridge rectifier circuit, and is connected to the second output end of the AC output circuit;

2. The DC-AC voltage conversion circuit according to claim 1, wherein the boosting circuit comprises at least a high frequency transformer connected to the bridge rectifier circuit.

3. The DC-AC voltage conversion circuit according to claim 1, wherein the boosting circuit comprises a high frequency switching circuit and a high frequency transformer, the high frequency switching circuit comprising a high frequency oscillation circuit and a high frequency And a power amplifier circuit, wherein the DC voltage is amplified by the high frequency switching circuit and sent to the high frequency transformer.

The DC-AC voltage conversion circuit according to claim 2 or 3, wherein the filter capacitor group comprises at least a first capacitor and a second capacitor connected in series, and the series connected first capacitor and second capacitor are connected A reference midpoint common to the first capacitor and the second capacitor is coupled to the first output of the AC output circuit between the two DC outputs of the bridge rectifier circuit.

5. The DC-AC voltage conversion circuit according to claim 4, wherein the high frequency transformer secondary has a center tap, and the common node of the first capacitor and the second capacitor is connected to the center tap.

6. The DC-AC voltage conversion circuit according to claim 5, wherein the first capacitor and the second capacitor are both high voltage and large capacitors.

7. The DC-AC voltage conversion circuit according to claim 6, wherein the switching circuit comprises a first switch and a second switch connected in series, and the first switch and the second switch connected in series are connected to the bridge. Two positive and negative straight Between the stream outputs, the common node of the first switch and the second switch is connected to the second output of the AC output circuit.

8. The DC-AC voltage conversion circuit according to claim 7, wherein the second output terminal is a reference ground.

9. The DC-AC voltage conversion circuit according to claim 8, wherein the first switch and the second switch are both power stage transistor switches, and the first switch and the second switch are of complementary polarity Switching element.

10. The DC-AC voltage conversion circuit according to claim 9, wherein the waveform generating circuit is a waveform generator, and the waveform generator is connected to the first switch and the second switch, respectively.

11. The DC-AC voltage conversion circuit according to claim 10, wherein at least a third capacitor is further disposed between the waveform generator and the second switch, and the waveform generator is configured to The control signal of the two switches becomes a control signal containing a negative voltage.

12. The DC-AC voltage conversion circuit according to claim 11, wherein a clamping circuit is further disposed between the third capacitor and the second switch for clamping the control signal to a negative voltage. .

13. The DC-AC voltage conversion circuit according to claim 12, wherein the clamping circuit is a diode, the diode cathode is grounded, and the anode is connected between the third capacitor and the second switch.

The DC-AC voltage conversion circuit according to claim 8, wherein the first switch and the second switch are both N-channel MOS transistors or NPN transistors.

The DC-AC voltage conversion circuit according to claim 14, wherein the waveform generating circuit is a waveform generator, and one end of the waveform generator is connected to the first switch through an optical coupler, and the waveform is generated. The other end of the device is connected to the second switch.