JP4307698B2 - Gate drive device for gate commutation type turn-off thyristor element and gate commutation type turn-off thyristor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gate drive device for a gate commutated turn-off (hereinafter referred to as GCT) thyristor element, which is a high power semiconductor device, and in particular, the main circuit current is the maximum of the GCT thyristor element. The present invention relates to a control technique for protecting a GCT thyristor element from an overcurrent turn-off when an overcurrent exceeding a rated controllable on-current is reached.
[0002]
[Prior art]
The GCT thyristor element is a development of the GTO (Gate Turn-off) thyristor element, and the configuration and operation principle thereof are disclosed in, for example, Japanese Patent Application Laid-Open No. 9-201039 (US Pat. No. 5,777,506) and Japanese Patent Application Laid-Open No. 8-330572. (US Pat. No. 5,777,351). The characteristics are summarized as follows. That is, in the GCT thyristor element, the shape of the gate terminal that is in contact with the ring gate electrode and drawn out of the insulating cylinder is replaced with the ring shape from the lead shape of the conventional GTO thyristor element, and the GCT thyristor element and the gate drive circuit This connection is also improved from a GTO thyristor element lead wire configuration to a multilayer substrate configuration. As a result, the inductance of the gate terminal and the gate wiring is reduced to about 1/100 of the inductance of the GTO thyristor element, and the reverse gate current flowing at the time of turn-off is more isotropic than the entire circumferential surface of the gate electrode. This makes it possible to reduce the turn-off accumulation time. As for the wafer structure of the GCT thyristor element, in the same way as the wafer structure of the conventional GTO thyristor element, several thousand segments are arranged concentrically in parallel in several stages, and the gate electrode and A gate electrode region forming an interface is disposed.
[0003]
Conventionally, in designing a gate drive device for a GTO thyristor element or GCT thyristor element, when the main circuit current flowing through the element becomes an overcurrent state, the element causes the overcurrent to turn off as it is. In order to protect the circuit, a method is employed in which the use conditions are determined in advance with a sufficient margin so that the main circuit current is less than the maximum rated controllable on-current.
[0004]
As another conventional technique, when the main circuit is driven by three-phase alternating current, the main circuit is short-circuited, and a short-circuit current flows to the GCT (or GTO) thyristor element in a certain one-phase path. In this case, a short circuit state of the main circuit is immediately detected by a sensor provided on the main circuit side, and the gate signal of the other two-phase GCT (or GTO) thyristor element is obtained by forced firing based on the detection result. By switching from the off-state to the on-state, the overcurrent is distributed to the other two-phase GCT (or GTO) thyristor element side to protect the GCT (or GTO) thyristor element from the overcurrent turn-off. It has been broken.
[0005]
[Problems to be solved by the invention]
However, with respect to the former prior art, it is unnecessary to set a margin in the first place, and even if the main circuit current reaches the maximum rated value of the controllable on-current, the GCT thyristor element can still be turned off, while the main circuit current When the value exceeds the maximum rated value of the controllable on-current, it has been demanded to realize such control that the protection of the GCT thyristor element is automatically activated.
[0006]
Also, the latter prior art has a problem that the protection timing is likely to be delayed because the detection of the overcurrent state is detected by the sensor on the main circuit side, and when the protection timing is delayed like that, the GCT The thyristor element turns off the overcurrent, and the device characteristics may be significantly deteriorated due to the turn-off failure.
[0007]
The present invention has been made to overcome such a problem, and in the event that the main circuit current flowing through the GCT thyristor element exceeds the maximum rated value of the controllable on-current, even if no margin is taken in advance. Is intended to automatically protect the GCT thyristor element from an overcurrent turn-off without causing a delay in protection timing.
[0008]
[Means for Solving the Problems]
In the gate drive device for a gate commutation type turn-off thyristor element according to the first aspect of the present invention, the main circuit current at the start of turn-off of the gate commutation type turn-off thyristor element is directly measured by measuring the turn-off gate current after the start of the turn-off. by monitoring, when detecting when said main circuit current exceeds a maximum rated value of the controllable oN-state current of the gate commutated turn-off thyristor element is smaller than the maximum rated value of the controllable oN-state current In addition, the gate commutation type turn-off thyristor element is continuously turned on, and the gate commutation type turn-off thyristor element is turned on. After the transition, only the limited turn-off gate current is turned off and the gate is turned off. Characterized in that to keep the flow turn-off thyristor element to the ON state.
[0009]
A gate commutation type turn-off thyristor device according to a second aspect of the present invention includes a gate commutation type turn-off thyristor element and the gate driving device according to the first aspect.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
(Viewpoints)
The GCT thyristor element is turned off by commutating all of the main circuit current to the gate circuit when turned off. Therefore, the value of the main circuit current can be directly monitored by measuring the gate current flowing in the gate driving device at the start of turn-off (corresponding to the gate reverse current when viewed from the turn-on). By utilizing this point, when it is detected from the monitoring result that the main circuit current is in an overcurrent state exceeding the maximum rated value of the controllable on-current of the GCT thyristor element, the gate drive device performs the turn-off operation. The state of the GCT thyristor element that has just been started can be immediately switched from the turn-off operation to the on state, and the GCT thyristor element can be protected from an overcurrent turn-off. More specifically, the gate driving device instantaneously turns off the off-gate signal controlled to be turned on at the start of turn-off, and switches on the on-gate signal controlled to be turned off at the start of turn-off according to the monitoring result. Thus, the operation of the GCT thyristor element is controlled such that the GCT thyristor element does not turn off the overcurrent. In this way, since the value of the main circuit current is directly monitored and the gate drive device of the GCT thyristor element is instantaneously controlled based on the monitoring result, the timing of protection is lost. This does not happen.
[0011]
Hereinafter, each embodiment will be described with reference to the drawings.
[0012]
(Embodiment 1)
FIG. 1 is a circuit diagram schematically showing the configuration of the GCT thyristor device according to the present embodiment. This apparatus is roughly divided into a GCT thyristor element 1, a gate drive circuit or gate drive apparatus 2, and a gate drive circuit control circuit (not shown). Among these, the GCT thyristor element 1 has an anode terminal 1A, a gate terminal 1G, and a cathode terminal 1K connected to the main circuit (not shown) side.
[0013]
On the other hand, the gate drive circuit 2 includes an on-gate MOSFET (first switching element) 21 (Tr1), an on-gate power supply capacitor 22, an off-gate MOSFET (second switching element) 23 (Tr2), and an off-gate power supply capacitor 24. An off-gate current detection circuit (current sensor or the like) 25, a current-limiting circuit 26 connected in parallel with the off-gate MOSFET 23 (Tr2), and a wiring 29. The on-gate MOSFET 21 (Tr1), the on-gate power supply capacitor 22 and the wiring 29 constitute an on-gate circuit. The off-gate current detection circuit 25, the off-gate MOSFET 23 (Tr2), the current limiting circuit 26, and the off-gate power supply capacitor 24. The wiring 29 constitutes an off-gate circuit.
[0014]
Here, the current limiting circuit 26 is a current limiting circuit MOSFET (third switching element) 261 (Tr3) and a current limiting circuit whose value is set so that the input impedance of the current limiting circuit 26 becomes high impedance. And a resistor 262.
[0015]
Note that each of the switching elements 21, 23, and 261 may be formed of a bipolar transistor instead of the MOSFET.
[0016]
The gate drive circuit control circuit (not shown) is connected to the output terminal of the off-gate current detection circuit 25 and the gate terminals of the switching elements 21, 23, 261, and has a preset controllable on-current. The maximum rated value is compared with the monitor result of the input off-gate current detection circuit 25, and gate signals of the switching elements 21, 23, and 261 are generated and output according to the comparison result.
[0017]
As described above, the main circuit current can be monitored by measuring the gate current (turn-off gate current) iG flowing in the gate driving circuit 2 at the time of turn-off. When the turn-off gate current iG exceeds the maximum rated value of the controllable on-current of the GCT thyristor element 1, if the GCT thyristor element 1 tries to turn off this overcurrent, the characteristics of the GCT thyristor element 1 are significantly deteriorated due to the turn-off failure. There is a case. For this reason, it is necessary to perform protection control of the GCT thyristor element 1 so that the GCT thyristor element 1 is not turned off.
[0018]
The operation of the GCT thyristor device of FIG. 1 at the time of turn-off will be described below.
[0019]
First, at the start of turn-off, the turn-off gate current iG is measured by the off-gate current detection circuit 25 in the gate drive circuit 2 and the main circuit current iA is monitored.
[0020]
i) When the main circuit current iA is less than or equal to the maximum rated value of the controllable on-current In this case, the gate drive circuit control circuit controls each transistor Tr1, Tr2, Tr3 as shown in FIG. The thyristor element 1 turns off the main circuit current iA. That is, the gate drive circuit control circuit controls the gate signals of the transistors Tr1, Tr2, and Tr3 to be off, on, and on at the start of turn-off t1, respectively, and maintains the above levels of the gate signals during the turn-off operation period. to continue. Accordingly, during the turn-off operation period, the turn-off gate current IGM flows in the off-gate circuit through the off-gate MOSFET 23 (Tr2) and the current limiting circuit 26.
[0021]
2 is the value of the main circuit current iA in the on state, VAK is the anode-cathode voltage (also referred to as the anode voltage), and the absolute value of the turn-off gate current IGM is the main circuit current IT. equal.
[0022]
ii) When the main circuit current iA exceeds the maximum rated value of the controllable on-current In this case, as shown in FIG. 3, the off-gate MOSFET 23 (Tr2) of the off-gate circuit is instantaneously controlled to the off state. Therefore, the turn-off gate current IG1 is allowed to flow only through the current limiting circuit 26. If the off-gate MOSFET 23 (Tr2) turns off the large current turn-off gate current IGM (= IT) as it is, the surge voltage at turn-off increases, and the characteristics of the MOSFET 23 (Tr2) and the GCT thyristor element 1 may be significantly degraded. Therefore, the current limiting circuit 26 is used to prevent this. Here, since the input impedance of the current limiting circuit 26 is set to a high impedance, the turn-off gate current that can flow through the current limiting circuit 26 is remarkably suppressed, and the turn-off gate is sufficiently smaller than the turn-off gate current IGM (= IT). The current IG1 only flows in the off-gate circuit via the current limiting circuit 26. In addition, since the current limiting circuit 26 is connected in parallel to the off-gate MOSFET 23 (Tr2), the loop inductance Ls of the off-gate MOSFET 23 (Tr2) -current limiting circuit 26-off-gate MOSFET 23 (Tr2) is set small. . As a result, the surge voltage when the off-gate MOSFET 23 (Tr2) is turned off is suppressed to a sufficiently small value. In addition, the time T1 from the time when the main circuit current iA exceeds the maximum rated value of the controllable on-current to the timing t2 when the off-gate MOSFET 23 (Tr2) is turned off is set as small as possible, and the anode voltage The gate signals of the transistors Tr1, Tr2, and Tr3 are controlled while the VAK is sufficiently small, and thus the instantaneous loss applied to the GCT thyristor element 1 does not increase. The operation will be described below based on the timing chart of FIG.
[0023]
First, at the timing of the turn-off start time t1, the gate drive circuit control circuit controls the gate signals of the transistors Tr1, Tr2, and Tr3 to be off, on, and on, respectively. As a result, the turn-off gate current iG flows in the off-gate circuit with a steep slope and exceeds the maximum rated value of the controllable on-current. At this time, in response to the monitoring result output from the off-gate current detection circuit 25, the gate drive circuit control circuit detects that the main circuit current iA exceeds the maximum rated value of the controllable on-current, and quickly receives the time t2. In this case, only the gate signal of the off-gate MOSFET 23 (Tr2) is controlled to be turned off. As a result, the turn-off gate current that has flowed in the off-gate circuit as the current value IGM (= IT) is forced to flow only through the current limiting circuit 26 thereafter, and the turn-off gate current is rapidly suppressed. The current value is IG1. Furthermore, the gate drive circuit control circuit quickly controls to turn on only the gate signal of the on-gate MOSFET 21 (Tr1) at time t3. As a result, the turn-on gate current and the turn-off gate current are mixed and flow through the gate driving circuit 2. After time t2, in the GCT thyristor element 1, the same anode current as the main circuit current iA is restricted from flowing to the gate driving circuit 2 side by the current limiting action of the gate driving circuit 2, and as a result, to the gate driving circuit 2 The amount of current (iA-IG1) that can no longer flow flows to the cathode 1K side, and the GCT thyristor element 1 is suddenly turned on. In this case, almost the entire surface of the GCT thyristor element 1, that is, between the gate and the cathode of each segment is in a forward bias state, and the GCT thyristor element 1 is turned on. At this time, an overcurrent flows through the GCT thyristor element 1. At this timing t4 (time (t4-t3) is arbitrarily set), the gate drive circuit control circuit turns off the current limiting circuit 26 and keeps the on-gate circuit on, so that the GCT thyristor element 1 is stable. The ON state can be maintained.
[0024]
If the impedance (resistance, inductance, etc.) of the main circuit is appropriately set so that the overcurrent is less than the rated value of the surge-on current of the GCT thyristor element 1, the GCT thyristor element 1 Will not cause any problems.
[0025]
After the overcurrent flows through the GCT thyristor element 1, when the junction temperature of the GCT thyristor element 1 becomes sufficiently low and the GCT thyristor element 1 is found to have returned to the normal state, the gate drive circuit control circuit again The gate signals of the transistors Tr1, Tr2, and Tr3 are controlled to be off, on, and on, respectively. Thereby, the GCT thyristor element 1 can be returned to the OFF state.
[0026]
As described above, according to the present apparatus shown in FIG. 1, the gate current iG is measured by the off-gate current detection circuit 25 after the turn-off is started, and the main circuit current iA is monitored. When the maximum rated value of the controllable on-current is detected, the off-gate MOSFET 23 is instantaneously switched from on to off and the on-gate MOSFET 21 is switched from off to on, so that the current limiting circuit 26 By the action, the GCT thyristor element 1 is shifted to the on state without being turned off. Thereby, it is possible to protect the GCT thyristor element 1 from being overturned off.
[0027]
In the above description, the GCT thyristor element 1 for one phase is automatically protected from overcurrent turn-off. However, for example, when the main circuit is driven by three-phase AC, the GCT thyristor for each phase is used. If a GCT thyristor device as shown in FIG. 1 is provided for each element and the turn-off operation of each GCT thyristor element is controlled by the same method, the overcurrent is distributed to the GCT thyristor elements of each phase that has been turned on. The advantage that it can be made is obtained. This also applies to the second and third embodiments described below.
[0028]
(Embodiment 2)
FIG. 4 is a circuit diagram showing a GCT thyristor device according to the second embodiment. In this embodiment, the voltage detection circuit 27 in the gate drive circuit 2 measures the on-voltage at both ends when the off-gate MOSFET 23 (Tr2) is turned off, and the on-voltage is converted into a current by a conversion circuit (not shown). By doing so (see FIG. 5), the main circuit current iA is monitored. Other configurations are the same as those of the apparatus of FIG. Therefore, when it is detected from the monitoring result that the main circuit current iA exceeds the maximum rated value of the controllable on-current of the GCT thyristor element 1, the same control as in the first embodiment is performed, whereby the GCT thyristor element 1 can be protected from overcurrent turn-off.
[0029]
(Embodiment 3)
FIG. 6 is a circuit diagram showing a GCT thyristor device according to the third embodiment. In this embodiment, the voltage detection circuit 28 in the gate drive circuit 2 measures the voltage at both ends of the off-gate power supply capacitor 24 when it is turned off (see FIG. 7), and the reduced value ΔVC of the voltage at both ends is converted into a conversion circuit (not shown). The main circuit current iA is monitored by converting the current into a current (see FIG. 8). Other configurations are the same as those of the apparatus of FIG. Therefore, when it is detected from the monitoring result that the main circuit current iA exceeds the maximum rated value of the controllable on-current of the GCT thyristor element 1, the same control as in the first embodiment is performed, whereby the GCT thyristor element 1 can be protected from overcurrent turn-off.
[0030]
【The invention's effect】
According to the first and second aspects of the invention, it is possible to provide a control system that can reliably and automatically protect the GCT thyristor element from an overcurrent flowing through the GCT thyristor element.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a GCT thyristor device according to a first embodiment of the present invention.
FIG. 2 is a diagram showing the operation of the GCT thyristor device according to Embodiment 1 when the main circuit current is equal to or less than the maximum rated value of the controllable on-current of the GCT thyristor element.
FIG. 3 is a diagram showing the operation of the GCT thyristor device according to Embodiment 1 when the main circuit current exceeds the maximum rated value of the controllable on-current of the GCT thyristor element.
FIG. 4 is a circuit diagram showing a GCT thyristor device according to a second embodiment of the present invention.
FIG. 5 is a diagram showing voltage and current characteristics of an off-gate MOSFET.
FIG. 6 is a circuit diagram showing a GCT thyristor device according to a third embodiment of the present invention.
FIG. 7 is a diagram illustrating a voltage drop of an off-gate power supply capacitor.
FIG. 8 is a diagram illustrating a relationship between a voltage drop of an off-gate power supply capacitor and an off-gate current.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 GCT thyristor element, 2 Gate drive circuit, 21 On-gate MOSFET, 22 On-gate power supply capacitor, 23 Off-gate MOSFET (Tr2), 24 Off-gate power supply capacitor, 25 Off-gate current detection circuit, 26 Current limiting circuit, 261 Current limiting circuit MOSFET (Tr3), 262 current limiting circuit resistor, 27 off-gate MOSFET voltage detection circuit, 28 off-gate power supply capacitor voltage detection circuit.

Claims (2)

By directly monitoring the main circuit current at the start of turn-off of the gate commutation type turn-off thyristor element by measuring the turn-off gate current after the start of the turn-off , the main circuit current can be used for the gate commutation type turn-off thyristor element. If it is detected that the maximum rated value of the control on-current is exceeded, the value is smaller than the maximum rated value of the controllable on-current and the gate commutation type turn-off thyristor element is limited to a value that cannot be turned off. The turned-off gate current continues to flow, and then the turn-on current continues to flow to shift the gate commutation type turn-off thyristor element to the on state, and then only the limited turn-off gate current is turned off to turn off the gate switching. The flow-type turn-off thyristor element is kept on ,
Gate drive device for gate commutation type turn-off thyristor element. A gate commutation type turn-off thyristor element;
The gate driving device according to claim 1,
Gate commutation type turn-off thyristor device.

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