JP2013198222A - Power semiconductor switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an improved power semiconductor switching device, in which a short-circuited capacitor can be separated before a sound capacitor is discharged.SOLUTION: The power semiconductor switching device has a gate driver 2 for turning a thyristor 1 on/off. The gate driver 2 has a plurality of capacitors connected in parallel, and a switching transistor connected in series with the capacitor. A power supply unit 4 is connected with the capacitors, respectively, via a breaker. A plurality of diodes are connected between the switching transistor and each capacitor. The breaker separates a short-circuited capacitor. The diodes block a reverse current flowing into the capacitor from a load.

Description

  The present invention relates to a power semiconductor switching device, and more particularly to a power semiconductor switching device including a circuit for isolating a shorted capacitor.

  The power semiconductor switching device is provided with a gate driver and controls the thyristor on and off. The gate driver has a plurality of capacitors connected in parallel and a plurality of switching transistors (MOSFETs) connected in series to each capacitor.

  A conventional power semiconductor switching device is shown in FIG. 1 of Japanese Patent Publication No. 2005-333444. This conventional power semiconductor switching device includes a thyristor 101, a driver 102, a plurality of capacitors 104 connected in parallel, a switching transistor 105 connected in series to each capacitor, and a power supply 106 for charging the capacitor.

  In operation, first, the capacitor 104 is charged to the voltage VC by the charger 106. When the driver 102 generates a turn-on signal, a forward bias current flows through the gate of the thyristor 101, and the thyristor 101 is turned on. A signal is then sent from the driver 102 through each resistor to provide a discharge current from the switching transistor 105 and a turn-off signal to the gate, thereby providing a reverse bias current − to the gate of the thyristor 101. IG flows and thyristor 101 is turned off.

  During operation, if one of the capacitors is shorted to become a defective capacitor, the charge on the healthy capacitor is discharged through the shorted capacitor. That is, the power semiconductor switching device is interrupted by one shorted capacitor.

  Furthermore, depending on the type of load connected to the thyristor 101, a reverse current may be applied to the anode. Then, the parasitic reverse diode between the anode and the gate of the thyristor 101 is activated, and a reverse current is applied to the gate. Such a gate current flows as a reverse current Ib through the gate driver, charges the capacitor 104, and an avalanche diode between the gate and the cathode of the thyristor works to limit the increase in voltage. As a result, the capacitor 104 receives an excessive voltage and is overcharged. With these overcharged capacitors, an avalanche voltage is applied to the gate of the thyristor. As a result, excessive stress is applied to the thyristor, and a countermeasure to eliminate it is required. That is, it is necessary to provide a separate discharge circuit.

Japanese Unexamined Patent Publication No. 2005-333444 published on December 2, 2005

  The first problem of the conventional power semiconductor switching device is that when one capacitor is short-circuited, the sound capacitor is discharged and the power semiconductor switching device is shut off.

  The second problem with conventional power semiconductor switching devices is that when a reverse current flows, the capacitor needs to be large enough to withstand it, and a separate discharge circuit is required to reduce the gate voltage of the thyristor. There is a point.

  It is an object of the present invention to provide an improved power semiconductor switching device that can isolate a shorted capacitor before the healthy capacitor is discharged.

  Another object of the present invention is to provide an improved power semiconductor switching device capable of preventing reverse current from flowing into a capacitor.

  A power semiconductor switching device according to the present invention includes a switching element having an anode, a cathode and a gate, a power supply device having a positive potential line and a negative potential line, a driver for producing an on signal and an off signal for controlling the switching element, At least one switching transistor for receiving the off signal, a plurality of diodes, a plurality of capacitors, a reverse bias driver means having a plurality of breakers, wherein one diode, one capacitor and one breaker Are connected by a Y connection having a central connection point J, wherein the switching transistor, the diode, and the capacitor are connected in series between the gate and cathode of the switching element, and further wherein the breaker is The center connection point J and the positive potential line and negative potential line The power semiconductor switching device is characterized in that it is connected to either one of them.

  According to the present invention, a short-circuited capacitor can be separated by a breaker and a diode provided in each capacitor.

  According to the present invention, it is possible to prevent the backflowing current from flowing into the capacitor by the diode. Therefore, it is possible to avoid overcharging the capacitor.

  By using the present invention, it is sufficient that the capacitor has a capacity capable of supplying a current necessary for turning off the switching element. Moreover, it is not necessary to consider the current flowing backward from the load.

FIG. 1 is a circuit diagram of a conventional power semiconductor switching device. FIG. 2A is a circuit diagram of the power semiconductor switching device according to the first embodiment of the present invention. FIG. 2B is a timing chart showing turn-on and turn-off of the power semiconductor switching element of FIG. 2A. FIG. 2C is a timing chart showing a gate current of the power semiconductor switching element of FIG. 2A. FIG. 2D is a timing chart showing discharging and charging of the pulse capacitor in FIG. 2A. FIG. 3 is a circuit diagram of the first embodiment of the breaker. FIG. 4 is a circuit diagram of a second embodiment of the breaker. FIG. 5 is a circuit diagram of a third embodiment of the breaker. FIG. 6 is a circuit diagram of a fourth embodiment of the breaker. FIG. 7 is a circuit diagram of a fifth embodiment of the breaker. FIG. 8 is a circuit diagram of a sixth embodiment of the breaker. FIG. 9 is a circuit diagram of a seventh embodiment of the breaker. FIG. 10 is a circuit diagram of a surplus monitor circuit used in the circuit of FIG. 2A. FIG. 11 is a circuit diagram of a power semiconductor switching device according to a second embodiment of the present invention. 12 is a circuit diagram showing a first modification of the apparatus shown in FIG. FIG. 13 is a circuit diagram showing a second modification of the apparatus shown in FIG. FIG. 14 is a circuit diagram showing a third modification of the apparatus shown in FIG.

  FIG. 2A shows a power semiconductor switching device according to Embodiment 1 of the present invention. The power semiconductor switching device according to the first embodiment includes a switching element 1 and a driver 2, and the driver 2 outputs a turn-on signal via a line 12 and a turn-off signal via a line 13. The power semiconductor switching element 1 has an anode 26 and a cathode 28, and a load (not shown) is connected between them. The switching element 1 is a thyristor, for example, a GCT (gate commutation turn-off) thyristor, a GTO (gate turn-off) thyristor, or an electrostatic induction thyristor (SITH). Line 12 is connected to the gate of switching element 1, line 13 is connected to each of gate resistors R1, R2,..., And further to the gates of switching transistors F1, F2,. Each of the switching transistors F1, F2,... Is composed of, for example, an N-MOSFET. The drain of each switching transistor is connected to the gate 14 of the switching element 1. Power to the driver 2 is supplied from the power supply 4 via the line 20. A control signal 24 is added to the driver 2 to control the frequency and timing of the output control signal.

  The power supply 4 generates predetermined DC power between the positive potential line 18 and the negative potential line 16. Breaker B1-1 and capacitor C1-1 are connected in series between charging line 16 and line 18, and capacitor C1-1 is charged through breaker B1-1. Further, a diode D1-1 is connected between one side of the capacitor C1-1 and the source of the switching transistor F1, and restricts the flow of current only in one direction from the switching transistor F1 to the capacitor C1-1.

  There are a plurality of breakers B1-1, B1-2, ..., B1n and a plurality of capacitors C1-1, C1-2, ..., C1-n, which are the charging lines 16 and lines as described above 18 are connected in series, and capacitors C1-1, C1-2,..., C1-n are charged. In addition, a plurality of capacitors C1-1, C1-2,..., C1-n are connected to diodes D1-1, D1-2,. Connected to line 17-1 and further to the source of switching transistor F1. The positive potential line 18 functions as the positive bus line 18 and is paired with the negative bus line 17-1. Further, all the negative bus lines 17-1,..., 17-m may be connected to each other.

  The combination of capacitor C1-1, breaker B1-1, and diode D1-1 is referred to as capacitor structure CA1-1. Similarly, the combination of the capacitor C1-2, the breaker B1-2, and the diode D1-2 constitute another capacitor structure CA1-2. Each capacitor structure CA has one capacitor, one breaker and one diode, which are connected by Y connection, that is, star connection, capacitor free end FE1, breaker free end FE2, and diode free end Has FE3. The capacitor is connected between the center connection point J of the Y connection and the first free end FE1, the breaker is connected between the center connection point J and the second free end FE2, and the diode is connected to the center connection point Between J and the third free end FE3, the third free end FE3 is connected in the direction to the center connection point J.

  n capacitor structures CA1,..., CAn are provided to cooperate with one switching transistor F1. The capacitor free end FE1 of each capacitor structure CA is connected to the positive bus line 18, the breaker free end FE2 of each capacitor structure CA is connected to the negative potential line 16, and the diode free end of each capacitor structure CA FE3 is connected to the negative bus line 17-1.

  A combination of one switching transistor F1 and the capacitor structures CA1,..., CAn that cooperate with the switching transistor F1 is referred to as a reverse bias driver RD1. A plurality of reverse bias drivers RD1,..., RDm are provided, which are connected in parallel between the gate 14 and the cathode 28 of the power semiconductor switching element 1.

  In one example, the number m of the reverse bias drivers RD is 4 or more, for example, 8. Further, the number n of the capacitor structures CA is 10 or more, for example, 50. Note that such a number can be changed by design.

  The number of capacitors C1-1 and other capacitors is not limited to one and may be a plurality of capacitors connected in parallel. Further, the capacitor C1-1 and other capacitors may be ceramic capacitors.

  The operation of the power semiconductor switching device will be described with reference to FIGS. 2B, 2C, and 2D.

  It is assumed that the switching element 1 (for example, GCT) is on at time t0. And all the capacitors C1-1, C1-2, ..., C1-n, ..., Cm-1, Cm-2, ..., Cm-n are set to a predetermined voltage VC1. It shall be charged. At time ta, a turn-off signal is generated from driver 2 and applied to the gates of MOSFETs F1,..., Fm via line 13 and resistors R1,. Therefore, MOSFETs F1, ..., Fm are all turned on, and the discharge current IG from all capacitors C1-1, ..., Cm-n passes through cathode 28 and gate 14 of switching element 1, and further Flows through MOSFETs F1, ..., Fm. Therefore, at time ta, the capacitors C1-1,..., Cm-n are discharged, and the turn-off pulse 109 (FIG. 2C) appears at the gate 14 of the switching element 1 and the voltage drop 110 (FIG. 2D). ) Occurs. Therefore, at the time ta, the GCT is blocked as indicated by the sharp drop line 108. Since the charging current is continuously provided from the power supply 4, the capacitors C1-1,..., Cm-n rapidly, that is, as shown by the voltage increase line 111 and the saturation line 112. It is charged to a predetermined voltage VC1 within a predetermined period tCmin from ta.

  At time tb, the driver 2 generates a turn-on signal. MOSFETs F1,..., Fm are turned off and a turn-on signal is applied to the gate of switching element 1 via line 12. Therefore, the switching element 1 is turned on again.

  Thereafter, at time tc, a second turn-off signal is generated, and the switching element 1 is turned off in the same manner as described above. The time difference between two successive turn-off signals from driver 2, specifically the two turn-off pulses 109 and 114, depends on the control signal 24 but is equal to or greater than the time tCmin . For example, the time tCmin is about 100 μs to 200 μs. Therefore, according to the present invention, the time for the power supply 4 to charge the capacitors C1-1,..., Cm-n to the predetermined voltage VC1 is within the time tCmin (that is, within 100 μs).

  Here, it is assumed that one of the capacitors C1-1,..., Cm-n, for example, the capacitor C1-1 is a defective capacitor and thus a short-circuit failure occurs. The current from the power supply and the discharge current from the remaining capacitors C1-2,..., Cm-n flow into breaker B1-1 and shorted capacitor C1 via lines 16 and 18. Here, the breaker B1 immediately cuts off the discharge current and prevents the current from flowing into the shorted capacitor C1. Therefore, the remaining capacitors C1-2,..., Cm-n are kept charged. Then, the subsequent turn-on and turn-off of the switching element 1 can be executed without any time delay without any problem.

  FIG. 3 shows an example of a first capacitor structure CA, which includes a breaker B, which includes a MOSFET 30 and a comparator 32. The MOSFET 30 is connected between the free end FE2 and the center connection point J. The comparator 32 takes the difference between the voltages at both ends of the capacitor C, and controls the MOSFET 30 on and off. When the capacitor C is charged, the difference between the voltages across the capacitor C is a predetermined voltage. In this case, the comparator 32 generates a HIGH level signal and maintains the MOSFET 30 in the ON state. Therefore, the capacitor C is appropriately charged with the current from the free end FE2 connected to the negative potential line 16. When capacitor C causes a short circuit and becomes a defective capacitor, an abnormal current begins to flow through defective capacitor C. For this reason, the voltage across the defective capacitor C is 0 or almost equal to 0. Therefore, the comparator 32 generates a LOW level signal and turns off the MOSFET 30. In this case, since the current path leading to the free end FE2 is interrupted by the breaker B, nearby healthy capacitors are not discharged by the short-circuited defective capacitor. Diode D prevents discharge current from flowing from a healthy capacitor to the defective capacitor via free end FE3 and negative bus line 17. The function of the diode D for preventing the discharge current also applies to the other cases described with reference to FIGS.

  FIG. 4 shows an example of a second capacitor structure CA, which includes a breaker B, which includes a MOSFET 30 and a comparator 33. The MOSFET 30 is connected between the free end FE2 and the center connection point J. Further, the comparator 32 takes the difference between the voltages at both ends of the diode D and performs on / off control of the MOSFET 30. If capacitor C is operating properly without a short circuit, the voltage across diode D will be zero or nearly equal to zero. Therefore, the comparator 33 generates a HIGH level signal and maintains the MOSFET 30 in the ON state. Therefore, the capacitor C is appropriately charged with the current from the free end FE2 connected to the negative potential line 16. When capacitor C causes a short circuit and becomes a defective capacitor, an abnormal current begins to flow through defective capacitor C. For this reason, the voltage across the diode D becomes HIGH. Therefore, the comparator 33 generates a LOW level signal and turns off the MOSFET 30. In this case, since the current path leading to the free end FE2 is interrupted by the breaker B, nearby healthy capacitors are not discharged by the short-circuited defective capacitor.

  FIG. 5 shows an example of a third capacitor structure CA, which includes a breaker B, which is composed of a current limiter. The current limiter includes a MOSFET 35, resistors 37 and 39, and a Zener diode 41. The resistor 37 and the MOSFET 35 are connected in series between the free end FE2 and the center connection point J. Zener diode 41 and resistor 39 are connected in series between free end FE2 and free end FE1. When the capacitor C is charged, a predetermined HIGH voltage appears at the free end FE1. This HIGH voltage is applied to the gate of the MOSFET 35 through the resistor 39, and the MOSFET 35 is turned on. Therefore, the capacitor C is appropriately charged with the current from the free end FE2 connected to the negative potential line 16. When capacitor C causes a short circuit and becomes a defective capacitor, an abnormal current begins to flow through defective capacitor C. For this reason, the voltage of the resistor 37 rises, and the gate-source voltage of the MOSFET 35 is reduced. This limits the current to a safe amount.

  FIG. 6 shows an example of a fourth capacitor structure CA, which includes a breaker B, which is composed of a current limiter. The current limiter includes MOSFET 42, resistors 34, 36, 38, and 40, and transistor 44. The resistor 34 and the MOSFET 42 are connected in parallel between the free end FE2 and the center connection point J. Resistor 36 is connected between free end FE 2 and the gate of MOSFET 42. The resistors 38 and 40 are connected in series between both ends of the capacitor C. The transistor 44 is connected between the gate of the MOSFET 42 and the free end FE1, and its base is connected between the resistors 38 and 40. When capacitor C is charged, current flows through resistor 38, turning on transistor 44. Accordingly, the HIGH voltage at the free end FE1 is applied to the gate of the MOSFET 42, turning on the MOSFET 42. Therefore, the capacitor C is appropriately charged with the current from the free end FE2 connected to the negative potential line 16. When capacitor C causes a short circuit and becomes a defective capacitor, an abnormal current begins to flow through defective capacitor C. For this reason, the current flowing through the resistor 38 is stopped. As a result, the voltage across resistor 40 goes low, turning off transistor 44. Therefore, the LOW voltage at the free end FE2 is applied to the gate of the MOSFET 42 via the resistor 36, turning off the MOSFET 42.

  FIG. 7 shows an example of a fifth breaker B, which is composed of a resistor 46 and a fuse 48. The resistor 46 and the fuse 48 are connected in series between the free end FE2 and the center connection point J. In normal operation, capacitor C is charged with current through resistor 46 and fuse 48. When the capacitor C causes a short circuit accident and becomes a defective capacitor, an abnormal current starts to flow toward the defective capacitor C from the power supply and the sound capacitor. For this reason, the fuse 48 is blown immediately.

  FIG. 8 shows an example of a sixth capacitor structure CA, which includes a breaker B, which includes a resistor 50 having a fuse function, which includes a free end FE2 and a central connection point J. Connected between. In normal operation, capacitor C is charged with a current through resistor 50. When the capacitor C causes a short circuit accident and becomes a defective capacitor, an abnormal current starts to flow toward the defective capacitor C from the power supply and the sound capacitor. For this reason, the resistor 50 having the fuse function is immediately cut off.

  FIG. 9 shows an example of a seventh capacitor structure CA, which includes a breaker B, which includes a PTC (positive temperature characteristic) resistor 52, which is centrally connected to the free end FE2. Connected between points J. The PTC resistor 52 has a characteristic that the resistance value increases as the temperature rises. In normal operation, capacitor C is charged with a current through PTC resistor 52. When the capacitor C causes a short circuit accident and becomes a defective capacitor, an abnormal current starts to flow toward the defective capacitor C from the power supply and the sound capacitor. For this reason, as the temperature rises, the resistance value of the PTC resistor 50 increases and the abnormal current is cut off.

  FIG. 10 shows a surplus monitor circuit. The surplus monitor circuit generates a warning signal when a predetermined number or more of capacitors are short-circuited and become defective. In addition, the warning signal can send a message to the service team to take preventive measures in the next service step. The surplus monitor circuit includes a comparator 54, resistors 55, 56, 57 and detection resistors R1-1, R1-2,..., R1-n. Resistors 55 and 56 are connected in series between the negative potential line 16 and the positive potential line 18, and generate a threshold voltage at the connection point between the resistors 55 and 56. The threshold voltage is applied to one input of the comparator 54. One end of the resistor 57 is connected to the negative potential line 16, and the other end is connected to each end of the detection resistors R1-1, R1-2,..., R1-n. The other ends of the detection resistors R1-1, R1-2,..., R1-n are connected to the center connection point of the capacitor structure CA. The other end of the capacitor 57 is also connected to the other input of the comparator 54.

  If no capacitor has caused a short circuit accident, the voltage at the other end of resistor 57 is equal to the voltage on negative potential line 16. If one capacitor causes a short circuit accident, the voltage at the other end of resistor 57 will rise. As the number of capacitors causing the short circuit increases, the voltage at the other end of the resistor 57 increases stepwise. When the number of short-circuited capacitors reaches a predetermined number, the voltage at the other end of the resistor 57 becomes larger than the threshold voltage. Thus, the comparator 54 generates a HIGH signal that is sent to the driver 2 from which the message is sent.

  FIG. 11 shows a power semiconductor switching device according to the second embodiment of the present invention. Compared with the first embodiment shown in FIG. 2A, in the second embodiment, the negative bus lines 17-1,..., 17-m (which may be a single line) are negative potentials. Integrated with line 16. All other configurations are the same. In other words, the negative potential line 16 is incorporated in the negative bus lines 17-1, ..., 17-m.

  The circuits shown in FIGS. 3 to 10 can also be applied to the second embodiment.

  According to the present invention, the breaker B that cooperates with each capacitor C can efficiently isolate the capacitor that caused the short-circuit accident, and as a result, the power semiconductor switching device is not cut off by the short-circuited capacitor. Disappear.

  According to the present invention, the diode D can prevent a current flowing backward from the load from flowing into the capacitor. Accordingly, overcharging of the capacitor can be avoided.

  By using the present invention, it is sufficient for the capacitor to have a voltage rating to the extent necessary to supply the turn-off current to the switching element 1, and it is not necessary to consider the current flowing back from the thyristor. . The modification described below is applicable to the first and second embodiments.

  FIG. 12 shows a first modification applied to the second embodiment. In the reverse bias drivers RD1, ..., RDm, the positions of the switching transistors F1, ..., Fm and the capacitor structure CA are interchanged. Thus, the source S of the switching transistor is connected to line 28 and the drain D is connected to the positive bus line 18. The negative bus line 17 is connected to the gate line 14 of the thyristor 1.

  FIG. 13 shows a second modification applied to the second embodiment. In each of the capacitor structures CA, the positions of the capacitor and the diode are interchanged. The breaker B is connected not between the negative bus line 17 and the connection point J but between the positive bus line 18 and the connection point J.

  FIG. 14 shows a third modification applied to the second embodiment. Instead of using N-channel MOSFETs as shown in FIG. 11, P-channel MOSFETs are used for the switching transistors F1,..., Fm.

  Although the present invention has been described according to a preferred embodiment with reference to the accompanying drawings, various modifications and variations will be apparent to those skilled in the art. Such obvious modifications and variations are included in the scope of the present invention.

  The present invention can be used in a power semiconductor switching device.

1 ... switching element, 2 ... driver, 4 ... power supply, RD ... reverse bias driver, CA ... capacitor structure, F ... switching transistor, C ... Capacitor, D ... Diode, B ... Breaker

Claims (12)

A power semiconductor switching device,
A switching element having an anode, a cathode and a gate,
A power supply having a positive potential line and a negative potential line;
A driver for producing an on signal and an off signal for controlling the switching element;
Reverse bias driver means having at least one switching transistor for receiving the off signal, a plurality of diodes, a plurality of capacitors, and a plurality of breakers;
Including
Here, one diode, one capacitor, and one breaker are connected by a Y connection having a central connection point,
Here, the switching transistor, the diode, and the capacitor are connected in series between the gate and the cathode of the switching element,
Further, here, the breaker is connected to the central connection point and one of a positive potential line and a negative potential line.
A power semiconductor switching device. The power semiconductor switching device according to claim 1, wherein a series connection of the diode and the capacitor is connected between the positive potential line and the negative potential line. The power semiconductor switching device according to claim 1, wherein the breaker includes a fuse. The power semiconductor switching device according to claim 1, wherein the breaker includes a resistor having a fuse function. The power semiconductor switching device according to claim 1, wherein the breaker includes a PTC resistor. The power semiconductor switching device according to claim 1, wherein the breaker includes a current limiter. The power semiconductor switching device according to claim 1, wherein the breaker includes a MOSFET and a comparator that controls the MOSFET, and the comparator compares potentials at both ends of the capacitor. The power semiconductor switching device according to claim 1, wherein the breaker includes a MOSFET and a comparator that controls the MOSFET, and the comparator compares potentials at both ends of the diode. The breaker includes a MOSFET, a Zener diode, and a resistor, and the MOSFET is connected between a central connection point and a negative potential line, and the Zener diode and the resistor are connected to a free end of a capacitor, a negative potential line, The power semiconductor switching device according to claim 1, wherein a connection point between the Zener diode and the resistor is connected to a gate of the MOSFET. The breaker includes a MOSFET, a transistor, and a pair of resistors, the MOSFET is connected between a central connection point and a negative potential line, and the transistor is connected between a free end of a capacitor and the gate of the MOSFET. The power semiconductor switching device according to claim 1, wherein the pair of resistors are connected in series between both ends of the capacitor, and a connection point between the pair of resistors is connected to a base of the transistor. The power semiconductor switching device according to claim 1, further comprising a surplus monitor circuit that issues a warning signal when a predetermined number of capacitors cause a short circuit accident. The surplus monitor circuit includes a comparator, a threshold generator for applying a threshold voltage to one input of the comparator, and a plurality of resistors respectively connected to a plurality of capacitors. The power semiconductor switching device according to claim 11, wherein a current is received when short-circuited, and each resistor is connected to the other input of the comparator.

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