JP2007215324A - Surge voltage suppression circuit - Google Patents

Abstract

Provided is a power converter that uses a power converter equipped with a high-frequency transformer to remove a surge generated on the output side of the high-frequency transformer with a simple circuit configuration and control when converting from a DC power supply to AC power. To do.
An inverter 12, a high-frequency transformer 13, and a bidirectional switch 15 are provided, and a positive and negative rectangular wave pulse train boosted by the high-frequency transformer 13 is rectified by the bidirectional switch 15 to form a rectangular wave pulse train of the same polarity. In the power conversion device to be converted, two series circuits of the power switch element AS1 and the capacitor C1 and two series circuits of the power switch element AS2 and the capacitor C2 opposite to the series circuit are provided at both ends on the output side of the high-frequency transformer 13. With the above connection, the power switch elements AS1 and AS2 operate in synchronization with the polarity of the output voltage of the high frequency transformer 13, and the surge voltage generated in the output voltage of the transformer 13 is clamped to the voltage of the capacitors C1 and C2.
[Selection] Figure 1

Description

  The present invention comprises an inverter that converts a DC voltage into a positive and negative rectangular wave pulse train, a high-frequency transformer connected to the output side of the inverter, and a bidirectional switch connected to the output side of the high-frequency transformer. The present invention relates to a power converter for rectifying a positive and negative rectangular wave pulse train boosted by the bidirectional switch to convert it into a rectangular wave pulse train of the same polarity, and in particular, a surge voltage generated in an output voltage of a high frequency transformer due to commutation The present invention relates to a surge voltage suppression circuit that absorbs noise.

  A power converter provided with a high-frequency transformer is known in the case where DC power from a DC power source is converted into AC power linked to, for example, a commercial AC power supply system by an inverter. As shown in FIG. 7, the power conversion apparatus includes an inverter 12 that converts a DC voltage of a DC power source 11 into a positive and negative rectangular wave pulse train, a high-frequency transformer 13 connected to the output side of the inverter, A bidirectional switch 15 connected to the output side is provided, and positive and negative rectangular wave pulse trains boosted by the high-frequency transformer 13 are rectified by the bidirectional switch 15 and converted into rectangular wave pulse trains of the same polarity.

  As a result, a PWM waveform corresponding to the frequency of the power supply system is obtained, and the high frequency component is removed by the filter 16 so as to be converted into low frequency AC power corresponding to the frequency of the power supply system. Then, AC power converted from DC power is supplied to the power supply system (load) 17.

  However, in such a power conversion device, a surge voltage is generated at both ends of the bidirectional switch due to energy accumulated in leakage inductance of the high-frequency transformer and parasitic inductance such as wiring. When this surge voltage exceeds the withstand voltage of the power switch element of the bidirectional switch, there is a problem that the element may be destroyed.

Therefore, an RC snubber circuit is generally provided to suppress the surge voltage, but there is a problem that a loss due to the resistance of the RC snubber circuit is large. In order to reduce the loss, for example, it has been proposed to add an energy regenerative circuit in parallel to the bidirectional switch to absorb the surge voltage without loss (Patent Document 1). However, this method has a problem that both the control and the circuit are complicated.
Japanese Patent No. 2723928

  The present invention solves such a problem. When a power converter equipped with a high-frequency transformer is used when converting from a DC power supply to AC power, a surge voltage generated on the output side of the high-frequency transformer can be simplified. An object of the present invention is to provide a surge voltage suppression circuit that can be economically removed by a simple circuit configuration and control.

  The surge voltage suppression circuit of the present invention comprises an inverter that converts a DC voltage into a positive and negative rectangular wave pulse train, a high-frequency transformer connected to the output side of the inverter, and a bidirectional switch connected to the output side of the high-frequency transformer. A positive and negative rectangular wave pulse train boosted by the high frequency transformer is rectified by the bidirectional switch and converted into a rectangular wave pulse train of the same polarity, a surge voltage is applied across the output side of the high frequency transformer. Two or more series circuit of a power switch element and a capacitor to absorb, the power switch element operates in synchronization with the polarity of the output voltage of the high-frequency transformer, the surge voltage generated in the output voltage of the transformer, It is characterized by clamping to the voltage of the capacitor.

  Here, an auxiliary winding is provided on the secondary side of the high-frequency transformer, an output synchronized with the polarity of the output voltage of the high-frequency transformer is taken out from the auxiliary winding, and the output is used as a drive signal for the power switch element. Is preferred.

  According to the present invention, two or more series circuits of a power switch element and a capacitor and a series circuit of a power switch element and a capacitor opposite to the series circuit are provided at both ends of the output side of the high-frequency transformer, and the power switch By operating the element in synchronization with the polarity of the output voltage of the high-frequency transformer, positive and negative surge voltages generated in the output voltage of the high-frequency transformer are connected in series in the opposite direction to the series circuit corresponding to the polarity. It can be absorbed by clamping to a constant voltage of each capacitor of the circuit. As a result, destruction of the power element of the bidirectional switch can be prevented by the same control as a circuit configuration without a conventional surge voltage suppression circuit without having a special control mode to absorb a simple circuit and surge. And a highly reliable power conversion device can be provided.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, in each figure, the same code | symbol is attached | subjected to the member or element which has the same effect | action or function, and the overlapping description is abbreviate | omitted.

  1 and 2 show a power conversion apparatus according to a first embodiment of the present invention and an operation example thereof. The DC power supply 11 is a DC power supply such as a fuel cell or a solar cell, and has a DC voltage of about 20-30 V as an example. Both ends of the DC power supply 11 are connected to an inverter 12 that converts a DC voltage into a positive and negative rectangular wave-shaped high-frequency voltage. The inverter 12 has power switch elements Q1 to Q4 connected in series and parallel, repeats on / off of the required pulse width for each carrier frequency cycle time, and is a positive and negative rectangular pulse train of the required pulse width for each carrier frequency cycle time. A certain PWM waveform Vp is formed. As the carrier frequency, for example, a frequency of about 10-100 kHz is adopted, and the peak value of the rectangular pulse train is about ± 20-30V.

  A high frequency transformer 13 is connected to the output side of the inverter 12, a surge absorbing circuit 14 is connected to the output side of the high frequency transformer 13, and a bidirectional switch 15 and a filter 16 are further connected. From the high-frequency transformer 13, the positive and negative rectangular wave pulse train is boosted to a boost ratio of 1: n and output. The step-up ratio of the high-frequency transformer 13 is set so that the peak value of the rectangular wave pulse train of the same polarity after rectification becomes a voltage that can obtain an AC commercial power system voltage waveform of, for example, 200V or 400V.

  The surge absorption circuit 14 absorbs a surge voltage generated by commutation due to leakage inductance of the high-frequency transformer 13 and protects the power switch element of the bidirectional switch 15 at the subsequent stage. The surge absorbing circuit 14 is connected to both ends of the output side of the high-frequency transformer 15 by connecting a series circuit of the power switch element AS1 and the capacitor C1, and a series circuit C2 of the capacitor and the power switch element AS2 opposite to the series circuit in reverse parallel. Configured.

  The bidirectional switch 15 has power switch elements S1 to S4 connected as shown in the figure, rectifies the positive and negative rectangular wave pulse train output from the high-frequency transformer, and converts it into a PWM voltage waveform of a rectangular wave pulse train of the same polarity. . That is, in the case of a positive pulse, the power switch elements S1 and S4 are turned on, and in the case of a negative pulse, the power switch elements S2 and S3 are turned on. As a result, the negative polarity pulse is converted into the positive polarity pulse, or the positive polarity pulse is converted into the negative polarity pulse, and the PWM voltage waveform of the rectangular wave pulse train of the same polarity is alternately formed every half cycle of the system power supply. .

  The filter 16 composed of the inductor L1 and the capacitor C3 removes the high-frequency component of the PWM voltage waveform, thereby converting the PWM voltage waveform into low-frequency AC power and outputting the AC power to the commercial AC power supply system (load) 17. The

  Next, the operation of the surge absorbing circuit 14 will be described in detail. The output voltage Vp of the inverter 12 is a voltage of a positive and negative rectangular waveform PWM waveform (crest value E) formed from the DC voltage of the DC power supply 11 by the inverter 12. The output voltage Vout of the high-frequency transformer 13 is obtained by boosting the output voltage Vp of the inverter according to the boost ratio 1: n of the high-frequency transformer (crest value nE). The voltages Vc1 and Vc2 at both ends of the capacitors C1 and C2 are charged to the output voltage Vout (crest value nE) of the high-frequency transformer 13 when the power switch elements AS1 and AS2 are turned on.

  Assuming that the surge absorbing circuit 14 does not exist (the power switch elements AS1 and AS2 are always in an off state), the leakage inductance of the high-frequency transformer 13 is formed during the formation (commutation) of a positive and negative rectangular wave pulse voltage (crest value nE). A surge voltage is generated at both ends of the high-frequency transformer 13 due to the energy accumulated in the parasitic inductance such as the wiring, and is applied to the bidirectional switch 15. As described above, the surge voltage may exceed the withstand voltage of the power switch element of the bidirectional switch 15 and may lead to element destruction.

  Therefore, the power switch elements AS1 and AS2 of the surge absorbing circuit 14 are on / off controlled in synchronization with the pulse polarity of the output voltage Vout of the high-frequency transformer 13. That is, when the output voltage Vout of the high frequency transformer 13 is a positive pulse, the power switch element AS1 is turned on, and when the output voltage Vout is a negative pulse, the power switch element AS2 is turned on. When Vout = 0V, the power switch elements AS1 and AS2 are controlled to be turned off.

  Specifically, when the output voltage Vout of the high-frequency transformer 13 is a positive pulse, this is detected by a detection unit (not shown) and used as a drive signal for turning on the power switch element AS1. Therefore, when a surge voltage exists in the output voltage Vout of the high-frequency transformer 13 and is equal to or higher than the voltage of the capacitor C1, the current Ic1 flows into the capacitor C1, and when it is equal to or lower than the voltage of the capacitor C1, the current Ic1 is The voltage flowing out from the capacitor C1 and the output voltage Vout of the high-frequency transformer 13 are clamped to the voltage of the capacitor C1. If the output voltage Vout of the high-frequency transformer 13 is a negative pulse, this is detected by the detector, and the power switch element AS2 is turned on. As a result, when the surge voltage is present in the output voltage Vout of the high-frequency transformer 13 and is equal to or higher than the voltage of the capacitor C2, the current Ic2 flows into the capacitor C2, and when it is equal to or lower than the voltage of the capacitor C2, the current Ic2 Flows out of the capacitor C2, and the output voltage Vout of the high-frequency transformer 13 is clamped to the voltage of the capacitor C2. When the output voltage Vout of the high-frequency transformer 13 is 0 V, the power switch elements AS1 and AS2 are both turned off and the capacitors C1 and C2 are cut off.

  That is, by turning on / off the power switch elements As1 and As2 in synchronization with the timing of the transformer output pulse, the surge voltage generated at the rising timing of the transformer output pulse voltage can be clamped to the voltage of the capacitors C1 and C2. it can. When the transformer output voltage is higher than the capacitors C1 and C2, the currents Ic1 and Ic2 flow in the direction of charging the capacitors C1 and C2, and when the transformer output voltage is low, the currents Ic1 and Ic2 flow in the direction of discharging from the capacitors C1 and C2. Energy due to the surge voltage is temporarily stored in the capacitors C1 and C2, and then regenerated to the load side.

  The power switch elements AS1 and AS2 can also be controlled on / off in synchronization with the inverters Q1 to Q4. When Q1 and Q4 are on, the power switch element AS1 is turned on and Q2 and Q3 are turned on. In this case, the power switch element AS2 is controlled to be turned on. When all of Q1 to Q4 are turned off, or when Q1 and Q3 are turned off and Q2 and Q4 are turned off, the power switch elements AS1 and AS2 are controlled to be turned off. In this case, the control signals for the power switch elements AS1 and AS2 can be shared with the control signals for Q1 to Q4, and the polarity detection means for the transformer Vout is not required.

  The above description is for the case where the power switch elements AS1 and AS2 are controlled in synchronization with the transformer output voltage or the inverter, but the time for delay of T1 is determined in advance without being completely synchronized, Control may be performed in the same manner as described above by adding a predetermined time to the synchronization signal.

  Therefore, it is only necessary to configure the voltage clamp circuit by combining the power switch element and the capacitor and connect the both ends of the high frequency transformer secondary side to drive the power switch element of the voltage clamp circuit in synchronization with the output of the high frequency transformer. The surge voltage generated at the time of commutation of the high-frequency transformer output can be suppressed without requiring a complicated control / circuit.

  3 and 4 show a power conversion device according to the second embodiment of the present invention and an operation example thereof. Also in this embodiment, an inverter 12 that converts a DC voltage into a positive and negative rectangular wave-shaped high frequency voltage, a high frequency transformer 13 connected to the output side of the inverter, and a bidirectional switch 15 connected to the output side of the high frequency transformer. And a power converter that outputs a positive and negative rectangular wave pulse train from the high-frequency transformer 13 and rectifies it by the bidirectional switch 15 to convert it into a rectangular wave pulse train of the same polarity. A series circuit of the power switch element AS1 and the capacitor C1 and a series circuit of the power switch element AS2 and the capacitor C2 opposite to the series circuit are connected in antiparallel to both ends on the output side of the high-frequency transformer 13, and the power switch element AS1 and AS2 operate in synchronization with the polarity of the output voltage of the high-frequency transformer 13, and include a surge absorption circuit 14 that clamps the surge voltage generated in the output voltage at the time of commutation of the transformer 13 to the voltage of the capacitors C1 and C2. This is also common in that

  However, in this embodiment, the auxiliary winding 13a is provided on the secondary side of the high-frequency transformer 13, an output synchronized with the polarity of the output voltage of the high-frequency transformer 13 is taken out from the auxiliary winding 13a, and the output is output to the power switch element AS1. , AS2 drive signal. The output voltages Vas1 and Vas2 of the auxiliary winding 13a are set to a turn ratio such that a voltage suitable for the drive voltage of the power switch element is obtained, and for example, an output of about 15V is obtained.

  When the output voltage Vas1 of the auxiliary winding 13a is positive, the power switch element AS1 is turned on. When the output voltage Vas2 of the auxiliary winding 13b is negative, the power switch element AS2 is turned on. Therefore, the power switch elements AS1 and AS2 can be turned on / off in synchronization with the positive and negative pulses of the transformer output voltage Vout. As a result, the output from the auxiliary winding of the high-frequency transformer is used as a drive signal for the power switch elements AS1 and AS2, whereby a more simplified circuit configuration can be achieved.

  The operation of the surge absorbing circuit of the second embodiment of the present invention is the same as that shown in FIG. 2, but in this embodiment, auxiliary winding output voltages Vas1 and Vas2 are obtained in synchronization with the output voltage Vout of the transformer. When the auxiliary winding output voltage Vas1 is in a high state, the power switch element AS1 is turned on, and when the auxiliary winding output voltage Vas2 is in a high state, the power switch element AS2 is turned on. As a result, the surge voltage generated by the commutation is clamped to the voltage of the capacitors C1 and C2, the surge currents Ic1 and Ic2 flow only in the capacitors C1 and C2, and the surge voltage does not affect the bidirectional switch 15 side. It is shown.

  5 and 6 show a power conversion device according to a third embodiment of the present invention and an operation example thereof. In this embodiment, an operation example in the case where the secondary side of the high-frequency transformer 13 is a center tap type rectifier circuit is shown. The surge absorption circuit 14 has a series circuit of a power switch element AS1 and a capacitor C1 at both ends of the output winding st1 of the high-frequency transformer 13 provided with a center tap on the output side, and a power switch element AS1 at opposite ends of the output winding st2. The power switch element AS2 and a capacitor series circuit C2 are connected.

  As shown in the figure, the bidirectional switch 15 is connected to both ends of the output windings st1 and st2 of the high-frequency transformer 13 provided with a center tap on the output side. The power switch elements S1 and S2 rectify the positive and negative rectangular wave pulse train output from the high-frequency transformer by performing on / off control corresponding to the polarity, and convert it into a PWM voltage waveform of the rectangular wave pulse train of the same polarity. That is, when Vout1 and Vout2 are positive pulses, the power switch element S1 is turned on, and when Vout1 and Vout2 are negative pulses, the power switch element S2 is turned on. As a result, the negative polarity pulse is converted into the positive polarity pulse, or the positive polarity pulse is converted into the negative polarity pulse, and the PWM voltage waveform of the rectangular wave pulse train of the same polarity is alternately formed every half cycle of the system power supply. .

  In the case of center tap rectification, the number of bidirectional switches can be reduced to half compared to full-bridge rectification, and only one bidirectional switch is required to conduct during rectification, so that switch conduction loss can be reduced.

  The filter 16 composed of the inductor L1 and the capacitor C3 removes the high-frequency component of the PWM voltage waveform, thereby converting the PWM voltage waveform into low-frequency AC power and outputting the AC power to the commercial AC power supply system (load) 17. The

  The operation of the surge absorbing circuit 14 is basically the same. The output voltage Vp of the inverter 12 is boosted according to the step-up ratio of the high-frequency transformer 13, and the voltage of the positive and negative rectangular waveform PWM waveform (crest value E) formed from the DC voltage of the DC power supply 11 by the inverter 12. Output voltages Vout1 and Vout2 are formed. The voltages Vc1 and Vc2 across the capacitors C1 and C2 are charged to the output voltages Vout1 and Vout2 of the high-frequency transformer 13 when the power switch elements AS1 and AS2 are turned on.

  The power switch elements AS1 and AS2 of the surge absorbing circuit 14 are controlled to be turned on / off in synchronization with the pulse polarity of the output voltages Vout1 and Vout2 of the high-frequency transformer 13. That is, when the output voltages Vout1 and Vout2 of the high-frequency transformer 13 are positive pulses, the power switch element AS1 is turned on, and when the output voltages Vout1 and Vout2 are negative pulses, the power switch element AS2 is turned on. When Vout1 and Vout2 = 0V, the power switch elements AS1 and AS2 are controlled to be turned off.

  Therefore, when a surge voltage exists in the output voltage Vout1 of the high-frequency transformer 13 and is equal to or higher than the voltage of the capacitor C1, the current Ic1 flows into the capacitor C1, and when it is equal to or lower than the voltage of the capacitor C1, the current Ic1 is The voltage Vout1 flowing out from the capacitor C1 is clamped to the voltage of the capacitor C1. When the output voltages Vout1 and Vout2 of the high-frequency transformer 13 are negative pulses, a surge voltage exists in the output voltage Vout2 of the high-frequency transformer 13 and is equal to or higher than the voltage of the capacitor C2, the current Ic2 flows into the capacitor C2. When the voltage is equal to or lower than the voltage of the capacitor C2, the current Ic2 flows out of the capacitor C2, and the output voltage Vout2 of the high frequency transformer 13 is clamped to the voltage of the capacitor C2. When the output voltages Vout1 and Vout2 of the high-frequency transformer 13 are 0V, the power switch elements AS1 and AS2 are both turned off and the capacitors C1 and C2 are cut off.

  That is, by turning on / off the power switch elements As1 and As2 in synchronization with the timing of the transformer output pulse, the surge voltage generated at the rising timing of the transformer output pulse voltage can be clamped to the voltage of the capacitors C1 and C2. it can. When the transformer output voltage is higher than the capacitors C1 and C2, the currents Ic1 and Ic2 flow in the direction of charging the capacitors C1 and C2, and when the transformer output voltage is low, the currents Ic1 and Ic2 flow in the direction of discharging from the capacitors C1 and C2. Energy due to the surge voltage is temporarily stored in the capacitors C1 and C2, and then regenerated to the load side.

  Therefore, it is only necessary to configure the voltage clamp circuit by combining the power switch element and the capacitor and connect the both ends of the high frequency transformer secondary side to drive the power switch element of the voltage clamp circuit in synchronization with the output of the high frequency transformer. The surge voltage generated at the time of commutation of the high-frequency transformer output can be suppressed without requiring a complicated control / circuit.

  In the above embodiment, as an example in which the power switch elements AS1 and AS2 of the surge absorbing circuit operate in synchronization with the polarity of the output voltage Vout of the high-frequency transformer 13, an auxiliary winding is provided in the high-frequency transformer, and the output thereof is used as a drive signal. However, it is a matter of course that a detection unit other than the auxiliary winding may be provided to detect the polarity of the output voltage Vout and use the output as a drive signal. Similarly, in the case of the center tap rectification method, it is possible to provide an auxiliary winding and use the output as a drive signal.

  Further, according to the operation example in which the inverter 12 is configured as a full bridge, the synchronization between the power switch elements AS1 and AS2 and the inverters Q1 to Q4 has been described. However, the power switch that configures the inverter 12 even in cases other than the full bridge If the polarity of Vout can be determined by the on / off state of the element, AS1 and AS2 can be controlled in synchronization with the power switch element of the inverter 12.

  Although one embodiment of the present invention has been described so far, the present invention is not limited to the above-described embodiment, and may of course be implemented in various forms within the scope of the technical idea.

It is a circuit diagram showing the power converter of a 1st embodiment of the present invention. It is a time chart which shows operation | movement of the surge absorption circuit of the said power converter device. It is a circuit diagram which shows the power converter device of 2nd Embodiment of this invention. It is a time chart which shows operation | movement of the surge absorption circuit of the said power converter device. It is a circuit diagram which shows the power converter device of 3rd Embodiment of this invention. It is a time chart which shows operation | movement of the surge absorption circuit of the said power converter device. It is a circuit diagram which shows the conventional power converter device.

Explanation of symbols

11 DC power supply 12 Inverter 13 High-frequency transformers 13a and 13b Auxiliary winding 14 Surge absorption circuit 15 Bidirectional switch 16 Filter 17 Load

Claims (4)

An inverter that converts a DC voltage into a positive and negative rectangular wave pulse train, a high-frequency transformer connected to the output side of the inverter, and a bidirectional switch connected to the output side of the high-frequency transformer are boosted by the high-frequency transformer In a power converter that rectifies positive and negative rectangular wave pulse trains with the bidirectional switch and converts them into rectangular wave pulse trains of the same polarity,
Two or more series circuits of power switch elements and capacitors that absorb surge voltage are provided at both ends of the output side of the high-frequency transformer,
A surge voltage suppression circuit, wherein the power switch element operates in synchronization with the polarity of the output voltage of the high-frequency transformer, and clamps a surge voltage generated in the output voltage of the transformer to the voltage of the capacitor.   An auxiliary winding is provided on the secondary side of the high-frequency transformer, an output synchronized with the polarity of the output voltage of the high-frequency transformer is extracted from the auxiliary winding, and the output is used as a drive signal for the power switch element. The surge voltage suppression circuit according to claim 1.   When the series circuit and the series circuit opposite to the series circuit are connected in antiparallel, a surge absorption circuit is configured, and when the output voltage of the high-frequency transformer is positive, the power switch element of one of the series circuits is The surge voltage suppression circuit according to claim 1, wherein the power switch element of the other series circuit is turned on when the polarity is negative.   A center tap is provided on the output side of the high-frequency transformer, a series circuit of a power switch element and a capacitor is connected to both ends of one output winding, and a power switch element opposite to the power switch element is connected to both ends of the other output winding When the output voltage of the high-frequency transformer is positive, the power switch element of one series circuit is turned on. When the output voltage of the high-frequency transformer is negative, the power switch element of the other series circuit is turned on. The surge voltage suppression circuit according to claim 1.

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