JP2009232545A - Protective circuit of double chopper circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a protection circuit for a chopper circuit advantageous to circuit compaction by detecting shut-down of one of two chopper circuits operating in parallel based on the combined current of the chopper circuits so that failure of the other circuit is prevented. <P>SOLUTION: When chopper circuits 101 and 102 operate according to gate signals g1 and g2 generated based on triangular waves having different phases, the combined current of the chopper circuits 101 and 102 has a ripple frequency of two times to that of the triangular waves. The protective circuit comprises a current detector 110 for detecting the combined current, a band-pass filter 104 which passes the components of one half of the frequency of a ripple current contained in the detected combined current, i.e., those in a predetermined range centering the frequency of a triangular wave, and a control circuit 109 for stopping the chopper circuits 101 and 102 when the frequency component of the ripple current detected by the band-pass filter 104 exceeds a preset threshold. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a protection circuit for a chopper circuit that protects the other chopper circuit when a failure occurs in one of the two chopper circuits operated in parallel.

The chopper circuit is a circuit that adjusts the average value of the output voltage by opening and closing the output circuit and changing the time ratio between the open state and the closed state. When two chopper circuits are operated in parallel, if it is not detected that one chopper circuit has failed and stopped, only the other chopper circuits operate.
For example, two chopper circuits that operate in parallel usually operate with a load current of 50%. For this reason, when one of the chopper circuits fails, a load that is twice the normal load is applied to the chopper circuit that has not failed, resulting in an overload state, which may cause a failure. In order to prevent secondary failure of the chopper circuit on the healthy side, it is conceivable to double the capacity per one chopper circuit. However, increasing the capacity is disadvantageous for reducing the size of the circuit, and thus cannot be said to be an optimal method.

  In order to prevent the chopper circuit from failing, a chopper circuit protection circuit has been proposed. As a conventional example of such a protection circuit, for example, the configuration shown in FIG. The illustrated protection circuit includes a chopper circuit 1 including an IGBT (Insulated Gate Bipolar Transistor) 11, a freewheeling diode 21, a DC reactor 31, a double chopper of a chopper circuit 2 including an IGBT 12, a freewheeling diode 22, and a DC reactor 32. This circuit protects the circuit. The chopper circuit 1 is provided with a current detector 51, the chopper circuit 2 is provided with a current detector 52, and currents flowing through the two chopper circuits are individually detected.

  Further, the low-pass filter 81, the comparator 91, and the setting device 93 constitute the overcurrent detection circuit 3, and the low-pass filter 82, the comparator 92, and the setting device 94 constitute the overcurrent detection circuit 4. The overcurrent detection circuits 3 and 4 receive the individually detected currents and detect overcurrents. When an overcurrent is detected, a stop signal is output from the OR circuit 20. The control circuit 109 inputs a stop signal and stops the operation of the chopper circuits 1 and 2.

In this configuration, the thresholds of the comparators 91 and 92 are set based on the current in a state where, for example, 50% of the load is applied to the chopper circuits 101 and 102, respectively. In this way, when any one of the chopper circuits stops, the chopper circuits 1 and 2 can individually detect and stop the overload state, so that the secondary side of the healthy chopper circuit can be stopped. Failure can be prevented.
The following techniques are disclosed regarding the protection circuit of the chopper device.
JP 2006-271069 A JP-A-11-289755

Patent Document 1 of the above prior art is provided with a current detector in each chopper circuit to detect and protect the current flowing through the chopper circuit individually. The protection circuit of Patent Document 2 uses an insulation converter. To do. For this reason, in the case of two chopper circuits operating in parallel, the number of detectors is doubled, leading to an increase in circuit size and an increase in the number of parts.
The present invention has been made in view of the above points, and by detecting abnormality of the chopper circuit based on the combined current of the chopper circuits operating in parallel with each other, the sound side chopper circuit can be made secondary. An object of the present invention is to provide a protection circuit for a chopper circuit that is advantageous for downsizing the circuit in order to protect it from failure.

  In order to solve the above problems, a protection circuit for a chopper circuit according to claim 1 of the present invention is a protection circuit for a double chopper circuit including two chopper circuits, and the two chopper circuits are in phase with each other. The combined current obtained by combining the output currents of the two chopper circuits has a ripple frequency that is twice the frequency of the triangular wave. Current detecting means for detecting a combined current flowing in the wiring common to two chopper circuits, and a band for passing a ripple current in a predetermined range centered on the frequency of the triangular wave among the combined current detected by the current detecting means The magnitude of the triangular wave frequency component of the ripple current passed by the pass filter and the band pass filter is not less than a predetermined value. If, characterized in that it comprises a chopper circuit stopping means for stopping the operation of the double chopper circuit.

  The chopper circuit protection circuit according to claim 2 is the invention according to claim 1, wherein the current detected by the current detection means is less than or equal to an allowable current value by one chopper circuit. When one healthy chopper circuit continuously operates and exceeds the allowable current value, the chopper circuit stopping means stops the operation of the double chopper circuit.

According to the first aspect of the present invention, it is detected that one chopper circuit is stopped by one current detector from a change in the frequency and magnitude of the ripple current of the combined current obtained by synthesizing the output currents of the two chopper circuits. it can. For this reason, it can be set as the structure advantageous for size reduction of a circuit and reduction of a number of parts. Further, by stopping the operation of the healthy chopper circuit promptly after one of the double chopper circuits is stopped, a secondary failure of the healthy chopper circuit can be prevented.
According to the second aspect of the present invention, even if one of the two chopper circuits is stopped, it is possible to continuously supply power to the load of one chopper circuit. When the current is less than or equal to the allowable current value of one chopper circuit, the operation can be continued without stopping the entire apparatus by continuing the operation with one chopper circuit on the sound side.

Hereinafter, a protection circuit for a chopper circuit according to the present invention will be described with reference to the drawings.
(Circuit configuration)
FIG. 1 is a diagram for explaining a protection circuit for a double chopper circuit according to the first embodiment. The illustrated configuration shows the chopper circuits 101 and 102 and the protection circuit 100 that protects the chopper circuits 101 and 102. The chopper circuits 101 and 102 constitute a double chopper circuit that operates in parallel. The chopper circuit 101 includes an IGBT 111, a free wheel diode 112, and a DC reactor 113. The chopper circuit 102 includes an IGBT 121, a freewheeling diode 122, and a DC reactor 123.

In the double chopper circuit, the input terminals of the two chopper circuits 101 and 102 are connected to the DC power supply 114, the smoothing capacitor 103 is connected between the output terminals of the two chopper circuits, and the two chopper circuits 101 and 102 are connected. The common wiring part 115 is connected to the anode side of the free-wheeling diodes 112 and 122.
The gate signals g1 and g2 that are switching signals of the chopper circuits 101 and 102 have phases different from each other by 180 degrees. The gate signal g1 and the gate signal g2 will be described later.
On the other hand, the protection circuit 100 detects a current (combined current) obtained by combining the output currents of the chopper circuit 101 and the chopper circuit 102 flowing through the wiring unit 115 shared by the chopper circuit 101 and the chopper circuit 102 with the current detector 110. .

  The protection circuit 100 includes a band-pass filter 104, a rectifier 105, a low-pass filter 106, a comparator 107, and a control circuit 109. The band-pass filter 104 is configured to pass only a current having a frequency within a predetermined range among components having various frequencies included in the detected combined current. In the first embodiment, the band-pass filter 104 is configured to pass the gate signals g1, g2 It is centered on the frequency of the triangular wave used to generate. The rectifier 105 rectifies the ripple frequency component of the combined current detected by the band-pass filter 104, converts the high frequency component of the rectified ripple frequency component into a direct current amount by removing it with the low-pass filter 106, and inputs it to one side of the comparator 107. .

The comparator 107 compares a specific ripple frequency component of the combined current output from the low-pass filter 106 with a value serving as a threshold set by the setting unit 108. The threshold is determined based on the magnitude of the ripple frequency component of the combined current that flows when one of the chopper circuits 101 and 102 is not operating normally. The comparator 107 determines that one of the chopper circuits is abnormal when the ripple frequency component of the combined current is greater than the threshold value, and outputs a stop signal.
The control circuit 109 detects the voltage across the smoothing capacitor 103 (hereinafter referred to as the voltage value V), and performs feedback control so as to match the voltage command value that is the target value of the output voltage. When the stop signal is input, the gate signals g1 and g2 are turned off to stop the operation of the chopper circuits 101 and 102.

  FIG. 2 is a diagram for explaining the details of the control circuit 109 shown in FIG. The control circuit 109 includes an adjuster 203. The adjuster 203 is a circuit that performs AVR control for controlling the detected voltage value V to a constant voltage. For this reason, the voltage value V0 that is the target value and the voltage value V that is the detection value are input to the adjuster 203. Then, the difference between the voltage value V0 and the voltage value V is taken, and an AVR output signal S1 based on this difference is output.

The AVR output signal S1 is input to the comparators 205 and 206. The comparators 205 and 206 receive carrier signals c1 and c2. The comparator 205 compares the carrier signal c1 with the AVR output signal S1, and outputs a signal S2 that becomes “H” when the AVR output signal S1 becomes equal to or higher than the carrier signal c1. The comparator 206 compares the carrier signal c2 with the AVR output signal S1, and outputs a signal S3 that becomes “H” when the AVR output signal S1 becomes equal to or higher than the carrier signal.
The signals S2 and S3 output from the comparators 205 and 206 are input to the logic gate circuits 207 and 208. The logic gate circuit 207 is an AND circuit that inputs the stop signal and the signal S2 and outputs the gate signal g1. The logic gate circuit 208 is an AND circuit that inputs the stop signal and the signal S3 and outputs the gate signal g2.

(Circuit operation)
FIGS. 3A to 3D are diagrams for explaining the relationship among the carrier signal c1, the carrier signal c2, the AVR output signal S1, the gate signal g1, and the gate signal g2 described above. The vertical axis of each signal shown in the figure indicates the output value of the signal, and the horizontal axis indicates time t. As shown in the figure, the carrier signals c1 and c2 are both triangular waves, and the phases are 180 degrees different from each other. The AVR output signal S1 shown in the figure is a signal having a constant value, and the gate signals g1 and g2 are pulse signals having a rectangular waveform.

  The comparator 205 compares the carrier signal c1 and the AVR output signal S1 as shown in FIG. The output of the comparator 205 becomes high level (“H”) only when the AVR output signal is larger than the carrier signal c1, and becomes low level (“L”) at other timings. That is, the comparator 205 outputs the signal S2 shown in FIG. A stop signal is input to the inverting input terminal of the logic gate circuit 207. Therefore, the gate signal g1 shown in FIG. 3C is output from the logic gate circuit 207 at a timing when the stop signal is not output (the stop signal is “L”).

  Further, as shown in FIG. 3B, the comparator 206 compares the carrier signal c2 with the AVR output signal S1. The output of the comparator 206 becomes “H” only when the AVR output signal is larger than the carrier signal c2, and becomes “L” at other timings. That is, the comparator 206 outputs the signal S3 shown in FIG. A stop signal is input to the inverting input terminal of the logic gate circuit 208. Therefore, the gate signal g2 shown in FIG. 3D is output from the logic gate circuit 208 at a timing when the stop signal is not output (the stop signal is “L”).

  Since the gate signals g1 and g2 which are switching signals are generated based on the carrier signals c1 and c2 which are 180 degrees out of phase with each other, they have phases different from each other by 180 degrees. Gate signals g1 and g2 are input to gate terminals of the IGBTs 111 and 121 of the chopper circuits 101 and 102, respectively. Since the IGBTs 111 and 121 are turned on and off in accordance with the pulses of the gate signals g1 and g2, the chopper circuits 101 and 102 operate in parallel at a timing different from each other by 180 degrees.

  In such a configuration, when the stop signal is output (the stop signal is “H”), the inverting input terminals of the logic gate circuits 207 and 208 become “H”, so that the outputs of the gate signals g1 and g2 are Stop. The chopper circuits 101 and 102 are stopped by stopping the gate signals g1 and g2. Therefore, the chopper circuit protection circuit according to the first embodiment can quickly stop the chopper circuits 101 and 102 by outputting the stop signal.

(Stop signal)
4A and 4B are diagrams for explaining the generation of the stop signal, where the vertical axis indicates the current level I and the horizontal axis indicates time t. Also, the current a shown in the figure is the output current of the chopper circuit 101, and the current b is the output current of the chopper circuit 102. A current c indicates a combined current obtained by combining the current a and the current b. FIG. 4A shows currents a to c when the chopper circuits 101 and 102 are operating normally. FIG. 4B shows currents a to c in a state where the chopper circuit 102 is not operating.

As described above, the IGBTs 111 and 121 of the chopper circuits 101 and 102 are turned on and off according to the gate signals g1 and g2 and output current. For this reason, the frequencies of the current a and the current b are substantially equal to the frequencies of the carrier signals c1 and c2 used to generate the gate signals g1 and g2.
Further, as shown in FIG. 3, the chopper circuits 101 and 102 perform switching operations in parallel according to the gate signals g1 and g2 whose phases are different by 180 degrees. For this reason, when the chopper circuits 101 and 102 are operating normally, as shown in FIG. 4A, the ripple frequency (the frequency of the pulsating component of the direct current) of the current c that is the combined current is the current a, b Twice the frequency of. On the other hand, when one of the chopper circuits 101 and 102 is not operating (for example, the chopper circuit 102), the ripple frequency of the current c is equal to the current a as shown in FIG.

  The current c is input to the comparator 107 via the band pass filter 104, the rectifier 105, and the low pass filter 106. Here, as described above, the comparator 107 is configured to pass a frequency in a predetermined range centered on the frequencies of the carrier signal c1 and the carrier signal c2. For this reason, when the chopper circuits 101 and 102 are operating normally, the signal passing through the band-pass filter 104 is relatively small and increases when one of the chopper circuits 101 and 102 is stopped.

  The comparator 107 inputs the signal that has passed through the band pass filter 104 via the rectifier 105 and the low pass filter 106. And it compares with the threshold value preset by the setting device 108, and a stop signal is output when the input signal is larger than a threshold value. In the setting device 108, when either one of the chopper circuits 101 and 102 is not operating, a size that can be detected is set as a threshold value.

  In the first embodiment described above, one of the two chopper circuits is stopped by a single current detector by detecting the frequency component of the ripple current of the combined current obtained by synthesizing the output currents of the two chopper circuits. Can be detected. That is, the detected combined current is passed through a bandpass filter and a current having a frequency in a predetermined range centered on the frequency of the triangular wave is passed, and the magnitude of the frequency component of the ripple current that has passed is equal to or greater than a predetermined value. Thus, it can be determined that one of the two chopper circuits is not operating. As described above, the protection circuit can be configured by one current detector, which is advantageous for downsizing and reduction of the number of parts. In addition, by stopping the operation of the double chopper circuit after this detection, the operation of the double circuit is stopped immediately from one stop of the double chopper circuit to prevent secondary failure on the healthy side. it can.

(Embodiment 2)
FIG. 5 is a diagram for explaining the second embodiment of the present invention. Among the illustrated configurations, configurations similar to those described in FIG. 1 of the first embodiment are denoted by the same reference numerals, and a part of the description is omitted.
The protection circuit for the chopper circuit of the second embodiment is detected when the current detected by the current detector 110 is less than or equal to the allowable current value of one chopper circuit, and the one chopper circuit on the sound side continues to operate. When the current exceeds the allowable current value, the operation of the double chopper circuit is stopped.

That is, even if it detects that one of the two chopper circuits has stopped, the protection circuit of the chopper circuit of the second embodiment continues to operate if it is below the allowable value of the healthy chopper circuit. For this reason, the overcurrent detection circuit 40 configured by the low pass filter 84, the comparator 96, and the setting unit 98 sets the overcurrent of the entire apparatus as a set value, for example, 150%. An overcurrent detection circuit 30 comprising a comparator 95 and a setting device 97 is provided. In the overcurrent detection circuit 30, for example, 75% of the combined current is set as an allowable value for one unit, and the overcurrent detection circuit 30 determines whether the magnitude of the combined current exceeds the allowable value for one unit. When it is less than the allowable value, detection by the frequency component of the ripple current is masked by the AND circuit 209, and when it is more than that, it is validated. The outputs of the AND circuit 209 and the overcurrent detection circuit 40 are input to the OR circuit 210, and the output of the OR circuit 210 is input as a stop signal for the control circuit 109. This makes it possible to perform a degenerate operation using the redundancy of the two chopper circuits without stopping the entire apparatus.
Further, if the fact that one chopper circuit is stopped is output to the display 116, it can be used for maintenance.

It is a figure for demonstrating the protection circuit of the chopper circuit of Embodiment 1 of this invention. It is a figure for demonstrating the structure of the control circuit shown in FIG. FIG. 3 is a diagram for explaining a relationship among a carrier signal c1, a carrier signal c2, an AVR output signal S1, a gate signal g1, and a gate signal g2 illustrated in FIG. (A) is a figure which shows the electric current in the state where the chopper circuit shown in FIG. 1 is operating normally, (b) is a figure which shows the electric current in the state where one of the chopper circuits is not operating. It is a figure for demonstrating the protection circuit of the chopper circuit of Embodiment 2 of this invention. It is a figure for illustrating the protection circuit of the conventional chopper circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Protection circuit 101,102 Chopper circuit 103 Smoothing capacitor 105 Rectifier 107 Comparator 108 Setter 109 Control circuit 110 Current detector 112,122 Free-wheeling diode 113,123 DC reactor 115 Wiring part

Claims (2)

A protection circuit for a double chopper circuit including two chopper circuits,
The two chopper circuits operate in accordance with a switching signal generated based on a triangular wave that is 180 degrees out of phase with each other, and a combined current obtained by synthesizing the output currents of the two chopper circuits is twice the frequency of the triangular wave. Ripple frequency of
Current detection means for detecting a combined current flowing in a wiring common to the two chopper circuits;
Among the combined current detected by the current detection means, a bandpass filter that passes a current in a predetermined range centered on the frequency of the triangular wave;
Chopper circuit stopping means for stopping the operation of the double chopper circuit when the magnitude of the current passed by the bandpass filter is equal to or greater than a predetermined value;
A double chopper circuit protection circuit comprising:   When the current detected by the current detection means is less than or equal to an allowable current value in one chopper circuit, one sound side chopper circuit continuously operates, and exceeds the allowable current value, 2. The double chopper circuit protection circuit according to claim 1, wherein the chopper circuit stop means stops the operation of the double chopper circuit.

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