JP3596096B2 - GTO thyristor gate drive circuit - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a GTO thyristor gate drive circuit for turning on and off a GTO thyristor (gate turn-off thyristor) used for a switching element or the like of a PWM (pulse width modulation) inverter device, and particularly to a gate current when the GTO thyristor is turned on. To improve the rise slope of the vehicle.
[0002]
[Prior art]
Since a steep gradient is required for the anode current when the GTO thyristor is turned on, a high value is required for the rising gradient [di / dt] of the gate current by the gate drive circuit that turns on the GTO thyristor. That is, if the rising gradient [di / dt] of the gate current for turning on the GTO thyristor is small, the time required for the GTO thyristor to rise to the rated gate current becomes long, and the GTO thyristor may be destroyed by current concentration at turn-on. It is required that the rising gradient [di / dt] be larger than the value at which this destruction can be avoided.
[0003]
Therefore, from the above demand, a high gate current which is considerably larger than the steady state gate current flows between the gate and the cathode of the GTO thyristor to turn on the GTO thyristor and turns on the GTO thyristor. A high-gate drive type in which only a gate current flows is used. This type of GTO thyristor gate drive circuit applies a rated positive voltage of a DC power supply to a gate of the GTO thyristor via a switch element and a current limiting resistor, and allows a high gate current to flow from the gate of the GTO thyristor to a cathode, thereby causing the GTO thyristor to operate. Turned on. Further, when the GTO thyristor is in an on state, a DC power supply voltage having a polarity opposite to that at the time of turn-on is applied between the gate and the cathode through a switch element, thereby turning off the GTO thyristor.
[0004]
As described above, in the GTO thyristor gate drive circuit for turning on the GTO thyristor, the rising gradient [di / dt] of the gate current is reduced by the current-limiting resistance at the time of turn-on. Therefore, a GTO thyristor gate drive circuit in which the rising slope [di / dt] of the gate current is increased by directly applying the DC power supply voltage to the gate of the GTO thyristor without using a resistor and turning on the GTO thyristor is disclosed in Jpn. No. 6135 discloses this. An example of the basic circuit is shown in FIG. 3 and described.
[0005]
The GTO thyristor gate drive circuit of FIG. 1 includes a first DC power supply 1 for turn-on and a second DC power supply 2 for turn-off, which are connected in series. A first positive electrode of the DC power source 1 is connected via a first switching element SW ₁ to the gate G of the GTO thyristor 3, the first negative electrode of the DC power source 1 is connected to the cathode K of the GTO thyristor 3. A second positive electrode of the DC power source 2 is connected to the cathode K of the GTO thyristor 3, the second negative electrode of the DC power source 2 is connected to the gate G of the GTO thyristor 3 through the second switching element SW _2. The third series circuit of switching elements SW ₃ and the first resistor R ₁ is connected between the second gate G of the negative electrode and the GTO thyristor 3 of the DC power source 2, a second resistor between the gate and cathode of the GTO thyristor 3 R ₂ is connected.
[0006]
Each of the switch elements SW _{1 to} SW ₂ is a field-effect transistor or the like which is turned on / off by an external GTO thyristor on / off command signal shown in FIG. The first resistor R ₁ and the second resistor R ₂ are voltage dividing resistors determined by the rated negative bias value of the GTO thyristor 3.
[0007]
When the second switching element SW ₂ and the third switching element SW ₃ is turned off, the first switch element SW ₁ is turned on a predetermined time as shown in FIG. 4 (b), the first DC power supply 1 of the DC voltage _{V ON} There is applied between the gate and cathode of the GTO thyristor 3, the Highgate current example about 50 amps rated current I _H flows in the cathode K from the gate G, GTO thyristor 3 is turned on. After this turn-on, a rated steady-state gate current of, for example, about 5 amps flows between the gate and the cathode, so that the ON state of the GTO thyristor 3 is stably continued. Note that a steady-state current circuit for flowing a steady-state gate current to the GTO thyristor 3 is a circuit or the like in which a switch element and a resistor are combined, and is not shown because it is not directly related to the present invention.
[0008]
When the first switching element SW ₁ is the second switch element SW ₂ when the GTO thyristor 3 off are kept on a steady gate current, turn on a predetermined time as shown in FIG. 4 (c), GTO thyristor The reverse polarity DC voltage V _OFF of the second DC power supply 2 is applied between the gate and the cathode of the transistor 3, current is drawn from the gate G, and the GTO thyristor 3 is forcibly turned off. At this time the third switching element SW _3, the is turned on as shown in FIG. 4 (d), a negative bias voltage by the first resistor R ₁ and determined by the second voltage dividing resistor R ₂ is applied to the gate G, A negative bias current flows between the gate and the cathode, and the OFF state of the GTO thyristor 3 is stably maintained.
[0009]
The turn-on and turn-off of the GTO thyristor 3 are alternately repeated based on the on-off command signal in FIG. The gate current waveform of the GTO thyristor 3 at the time of turning on and off includes a repetitive waveform of a turn-on waveform indicating a steep rising as shown in FIG. 4F and a turn-off waveform indicating a steep falling.
[0010]
[Problems to be solved by the invention]
By the way, the rising gradient [di / dt] of the high gate current for turning on the GTO thyristor 3 is proportional to the DC voltage V _ON of the first DC power supply 1, and the wiring of the high gate current generating circuit and the lead wire of the gate electrode of the GTO thyristor 3 are provided. in inverse proportion to the stray inductance L _S of the driving circuit etc., it is given by the following equation.
[0011]
(Di / dt) = (V _ON −V _gk / L _S )
[0012]
However, since the gate-cathode voltage V _gk in the above equation is much smaller than the power supply voltage V _ON, it can be ignored and is roughly given by the following equation.
[0013]
(Di / dt) = (V _ON / L _S )
[0014]
Therefore, as means for the rising gradient [di / dt] above standard value, due to the stray inductance L is _S to the lower as much as possible, but reduction improvement of stray inductance L _S and is limited to the structure of the circuit wiring There is a problem that it is difficult to increase the rising gradient [di / dt]. Also, the rising gradient [di / dt] of the high gate current can be increased by increasing the DC power supply voltage V _ON , but the larger the power supply voltage V _ON is, the higher the power supply voltage V _ON is, given the relationship with the rated value I _H of the high gate current. There is a problem that the power supply capacity of the DC power supply 1 increases and the cost increases. At present, the increase of the rising gradient [di / dt] due to the power supply voltage V _ON has already reached the limit.
[0015]
SUMMARY OF THE INVENTION An object of the present invention is to provide a GTO thyristor in which the rising gradient of a high gate current for turning on a GTO thyristor is increased without particularly reducing the stray inductance of a driving circuit and without increasing a DC power supply voltage for supplying a high gate current. It is to provide a gate drive circuit.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a first DC power supply for supplying a turn-on current for turning on a GTO thyristor to a gate of the GTO thyristor via a first switch element, and a second off-current for turning off the GTO thyristor. A second DC power supply for supplying to the gate of the GTO thyristor via the switch element; a capacitor connected in series with the first switch element between the positive electrode of the first DC power supply and the gate of the GTO thyristor; A configuration is provided that includes a diode in which the first series power supply is connected in parallel with a positive pole in the forward direction, and a charging circuit that charges the capacitor with the second series power supply when the first switch element is turned off and the GTO thyristor is turned off. .
[0017]
In the present invention, if the charging circuit is provided with a variable resistor for variably adjusting the rated charging voltage of the capacitor, the gate current rising gradient at the time of turning off the GTO thyristor can be adjusted.
[0018]
[Action]
When the first switch element is turned off, the second and third switch elements are turned on, and the GTO thyristor is turned off, the capacitor is charged with the second DC power supply voltage. In this state, the first switch element is turned on, and the second and third switch elements are turned on. When the third switch element is turned off and the GTO thyristor is turned on with the first DC power supply voltage, the charge of the capacitor discharges and flows to the gate of the GTO thyristor, and the discharge current is superimposed on the high gate current solely from the first DC power supply. I do. By the superposition of these two currents, the rising gradient of the high gate current is further increased as compared with the case where there is no charge / discharge. In addition, by charging the capacitor with the second DC power supply that turns off the GTO thyristor, the burden on the first DC power supply that turns off the GTO thyristor can be reduced.
[0019]
If a variable resistor is provided in the charging circuit for charging the capacitor and the charging voltage of the capacitor is adjusted with this variable resistance value, the rising gradient of the high gate current that turns on the GTO thyristor can be adjusted.
[0020]
【Example】
One embodiment of the present invention applied to the GTO thyristor gate drive circuit of FIG. 3 is shown in FIG. 1 and its operation waveform diagram is shown in FIG. The same reference numerals are given to the same or corresponding parts of the driving circuit of FIG. 1 as those of FIG. 3, and the description is omitted.
[0021]
The GTO thyristor gate drive circuit in the embodiment of FIG. 1 is characterized in that a capacitor C, a diode D, and a charging circuit 4 are added to the drive circuit of FIG. Further, Figure 1 drive circuit, by installing the variable resistor R _X in the charging circuit 4, thereby enabling adjusting the charging voltage of the capacitor C.
[0022]
Capacitor C is connected in series between the first gate G of the switching elements SW ₁ and the GTO thyristor 3. The diode D is connected in parallel to the capacitor C in a forward direction in which a gate current from the first DC power supply 1 flows through the gate G. The charging circuit 4, the capacitor C in the DC voltage V _OFF of the second DC power supply 2 when the GTO thyristor 3 is turned off, the circuit for charging and the first switching element SW ₁ side in the negative electrode, the capacitor C and the which are connected 1 to the midpoint of the switching elements SW ₁ to the variable resistor _{R X.} Variable resistor R _X corresponds to those obtained by replacing the first resistor R ₁ of Figure 3 the variable resistor, the variable resistor R _X and charged to H side circuit 4 of Figure 1 is connected to the resistor in the charging circuit 4 value becomes zero, the resistance value in the charging circuit 4 and the charging circuit 4 is connected to the L side is the first resistance value of the resistor R _1.
[0023]
The on / off timing of each of the switch elements SW _{1 to} SW ₂ in the drive circuit of FIG. 1 may be the same as that of the drive circuit of FIG. 3, and specific examples thereof are shown in FIGS. The operation of the circuit will be described.
[0024]
When conventional similarly first switching element SW ₁ is turned on based on the on-off command signals of FIG. 2 (a), the first DC voltage V _ON of the DC power supply 1 is applied between the gate and cathode of the GTO thyristor 3, the rated current flows to the cathode K from the gate G of the GTO thyristor 3 Highgate current I _H via the first switching element SW ₁ and the diode D, GTO thyristor 3 is turned on. Thereafter, a rated steady gate current flows between the gate and the cathode of the GTO thyristor 3 by a steady current circuit (not shown), and the ON state of the GTO thyristor 3 is continued. At the beginning of the turn-on, the charge of the capacitor C charged when the GTO thyristor 3 is turned off is discharged, and the rising gradient [di / dt] of the high gate current is increased. This will be described in detail after the next turn-off operation.
[0025]
When the second switching element SW ₂ is turned on when the GTO thyristor 3 is kept in the ON state, forcibly turned off GTO thyristor 3 is with a reverse polarity DC voltage V _OFF of the second DC power source 2, also, the 3 negative bias current flows between the gate and cathode of the GTO thyristor 3 with oN of the switch element SW _3, off of the GTO thyristor 3 is maintained.
[0026]
For Figure 1 drive circuit, the DC voltage V _OFF of the second DC power supply 2 is applied through a variable resistor R _X in the capacitor C when the GTO thyristor 3 is turned off, the capacitor C is charged by the second DC power supply 2 You. When the variable resistor R _X is at the H side of FIG. 1, a capacitor C as shown in FIG. 2 (e) is charge to a DC voltage V _OFF of the second DC power source 2. The variable resistor R _X is when in the L-side of FIG. 1, the capacitor C is charged to a voltage obtained by dividing the DC voltage V _OFF a variable resistor R _X and a second resistor R _2. Charging voltage V _C of the rating of such capacitor C, the cathode side of the diode D becomes positive polarity is maintained until GTO thyristor 3 is turned on.
[0027]
Charging of the capacitor C is carried out in a short time, when after that first turns on the switching element SW ₁ to turn on the GTO thyristor 3, the charging voltage V _C of the capacitor C to the first DC voltage V _ON of the DC power supply 1 The superimposed DC voltage [V _ON + V _C ] is applied between the gate and the cathode of the GTO thyristor 3, and a high gate current of the rated current I _H is applied to the gate of the GTO thyristor 3 via the first switch element SW ₁ and the capacitor C. G flows to the cathode K, and the GTO thyristor 3 turns on. At the beginning of the turn-on, the charge of the capacitor C is discharged to become a gate current, and the discharge at this time greatly improves the rising gradient [di / dt] of the high gate current as compared with the drive circuit in FIG. That is, the rising gradient [di / dt] of the high gate current in the drive circuit of FIG. 1 is roughly given by the following equation.
[0028]
_{(Di / dt) = (V} ON + V C) / L S
[0029]
Accordingly, by the amount of the charging voltage _{V C} of the capacitor C rising gradient [di / dt] is increased. When the variable resistor _{R X} is at the H side of FIG. _{1, V C =} V _OFF rising gradient [di / dt] at the greatest, turn waveform at this time is shown in solid line in FIG. 2 (f). It should be noted that the broken line in the waveform of FIG. 2F corresponds to the conventional waveform of FIG. 4F, from which it can be clearly seen that the rising gradient [di / dt] is increased. When the variable resistor _RX is moved to the L side in FIG. 1, V _C = V _OFF × [R ₂ / (R ₁ + R ₂ )], and the rising gradient [di / dt] is arbitrarily adjusted. You.
[0030]
When the GTO thyristor 3 is turned on and the discharge of the capacitor C is completed, the diode D is forward-biased and a gate current flows through the diode D. Thereafter, the diode D is turned on similarly to the drive circuit of FIG. Then, when the GTO thyristor 3 is turned off, charging of the capacitor C is repeatedly performed.
[0031]
【The invention's effect】
According to the present invention, when the GTO thyristor is turned off, the capacitor is charged with the second DC power supply voltage for turning off, and when the GTO thyristor is turned on, the charge of the capacitor is discharged to the gate of the GTO thyristor. Since the GTO thyristor is turned on by the superimposed voltage of one DC power supply voltage and the capacitor charging voltage, the rising gradient of the high gate current at this time can be further increased as compared with the case where there is no capacitor. Therefore, it is easy to increase the rising gradient of the high gate current that turns on the GTO thyristor without particularly reducing the stray inductance of the drive circuit and without increasing the DC power supply voltage for supplying the high gate current. A high-performance GTO thyristor gate drive circuit that is advantageous in terms of capital investment can be provided. Further, since the capacitor is charged by the second DC power supply that turns off the GTO thyristor, the burden on the first DC power supply for turning on can be reduced.
[0032]
In addition, since a variable resistor is installed in the charging circuit for charging the capacitor and the charging voltage of the capacitor is adjusted by the variable resistance value, the rising gradient of the high gate current that turns on the GTO thyristor can be adjusted arbitrarily. A GTO thyristor gate drive circuit with excellent versatility can be provided.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing an embodiment of a GTO thyristor gate drive circuit according to the present invention. FIG. 2 is a time chart of each part of the circuit shown in FIG. 1. FIG. 3 is a circuit diagram of a conventional GTO thyristor gate drive circuit. 4 is a time chart of each part of the circuit shown in FIG.
DESCRIPTION OF SYMBOLS 1 1st DC power supply 2 2nd DC power supply 3 GTO thyristor 4 Charging circuit SW ₁ 1st switch element SW ₂ 2nd switch element C Capacitor D Diode _RX Variable resistance

Claims (2)

A first DC power supply for supplying a turn-on current for turning on the GTO thyristor to the gate of the GTO thyristor via the first switch element, and a turn-off current for turning off the GTO thyristor to the gate of the GTO thyristor via the second switch element. A second DC power supply for supplying, a capacitor connected in series with a first switch element between a positive electrode of the first DC power supply and a gate of the GTO thyristor, and a first series power supply connected to the capacitor in a forward direction with a positive pole. A GTO thyristor gate drive circuit, comprising: a diode connected in parallel with the above; and a charging circuit for charging a capacitor with a second series power supply when the first switch element is turned off and the GTO thyristor is turned off. 2. The GTO thyristor gate drive circuit according to claim 1, wherein a variable resistor for variably adjusting a rated charging voltage of the capacitor is provided in the charging circuit.

Images