JPH1052030A - Thyristor driving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reliable thyristor driving circuit for feeding a desired gate current, along with a simple constitution and a small body. SOLUTION: A resistor 3 is connected in parallel with an RC serial circuit of a resistor 2 and a capacitor 4. The parallel circuit made up of the resistor 3 and the RC serial circuit, the primary side of a pulse transformer 5, and a switching element 6 are connected serially to a constant current and voltage DC power supply 1. The secondary side of the pulse transformer 5 is connected to the gate and cathode of a thyristor through a gate connection terminal G and a cathode connection terminal K. A secondary current of the pulse transformer 5 is fed as a gate current for turning on the thyristor. Then, when the current transformer ratio is made 1:1, the same gate current as a resultant current ic made up of a current ia at the RC serial circuit and a current ib at the resistor 3 is fed to the gate of the thyristor. In a simple constitution, a desired gate current is fed by adjusting the values of resistors 2 and 3, and the capacitor 4 adequately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a thyristor drive circuit, particularly a circuit such as a power semiconductor, which uses a large-capacitance element in which a current rises quickly, from the viewpoint of di / dt countermeasures. The present invention relates to a thyristor drive circuit capable of high gate drive.

[0002]

2. Description of the Related Art Conventionally, in a GTO (gate turn-off) thyristor or the like, a high gate drive is performed to turn on the thyristor quickly. That is, a gate current that is considerably larger than the steady gate current flows at the beginning,
After the lapse of a predetermined time, only a small value of the steady gate current is allowed to flow. FIG. 6 (see the Toshiba Thyristor catalog) and FIG. 7 (see the Mitsubishi Electric Power Semiconductor Data Book) show a timing chart of the gate current by such a high gate drive.

FIGS. 3, 4 and 5 show thyristor driving circuits for realizing the above high gate driving. FIG. 3 is a configuration diagram of a thyristor drive circuit of a first conventional example (refer to the Toshiba thyristor catalog). In FIG. 3, G and K are thyristors (not shown) to be driven respectively.
Is a terminal connected to the gate and cathode. In this thyristor drive circuit, the charge stored in the capacitors 12 and 14 is applied to the gate of the switching element 11 by a pulse 19.
Is applied, the switching element 11 is turned on to discharge. Since the discharge current is discharged through the primary side of the pulse transformer 15, a gate current is generated on the secondary side of the pulse transformer 15. The discharge current flowing to the primary side of the pulse transformer 15 is a combined current of the discharge current of the capacitor 12 and the discharge current of the capacitor 14 of the LC series circuit. The discharge current of the capacitor 12 forms a pulse having a large peak current and a short period, and the discharge current of the capacitor 14 forms a pulse having a long period and a suppressed peak due to the inductance 13. , The current shown in FIG. In FIG. 3, 16 is a diode, and 17 and 18 are resistors.

FIG. 4 shows a second conventional example (Japanese Patent Laid-Open No. 5-1299).
FIG. 21 is a configuration diagram of a thyristor drive circuit of Japanese Patent Publication No. 21). The gate drive circuit 21 includes an on-gate current generation circuit 22 that supplies an on-gate current to the thyristor 33, an off-gate current generation circuit 23 that supplies an off-gate current, DC power supplies 24 and 25 that supply power to them, and a one-shot such as a monostable multivibrator. And a circuit 26. The thyristor 33 is connected with a snubber circuit 35 and a free wheel diode 36 in parallel.

The on-gate current generating circuit 22 includes current limiting resistors 27 and 28 and switching elements 29 and 30. The resistor 27 and the switching element 29 constitute a high gate current generating circuit 31 for supplying a high gate current to a thyristor 33. , Resistor 28 and switching element 30
Constitutes a steady-state gate current generating circuit 32 for passing a steady-state gate current to the thyristor 33. The resistance value of the resistor 27 is set smaller than the resistance value of the resistor 28 so that a relatively large current can flow through the gate of the thyristor 33.

In the on-gate current generating circuit 22, when the on signal 34 for the thyristor 33 rises, the switching elements 29 and 30 are simultaneously turned on. After the ON signal 34 rises due to the operation of the one-shot circuit 26, the switching element 29 maintains the ON state only for a fixed time (about 10 to 20 μs), and then turns OFF. Also,
The switching element 30 keeps the on state continuously while the on signal 34 is at the high level, and turns off when the on signal 34 falls. Switching element 30
Is turned on, a steady gate current flows from the DC power supply 24 to the gate of the thyristor 33 through the resistor 28 and the switching element 30. When the switching 29 is turned on, a high gate current flows from the DC power supply 24 to the gate of the thyristor 33 through the resistor 27 and the switching 29. Therefore, when the ON signal 34 rises, a current obtained by adding the high gate current to the steady gate current flows for a certain time immediately after the ON signal 34, and only the steady gate current flows until the ON signal 34 falls after the elapse of the certain time. Will be. As a result, a current shown in FIG. 6 is formed.

FIG. 5 shows a third conventional example (Japanese Patent Laid-Open No. 1-1703).
FIG. 66 is a configuration diagram of a thyristor drive circuit. A DC power supply 42, a pulse transformer 46, and a switching element 44 are arranged in series to form a wide on-gate circuit. Similarly, a DC power supply 43, a pulse transformer 47, and a switching element 45 are arranged in series to form an overdrive circuit. And combine the outputs of both to form a thyristor 41
In addition to the gate. If the wide on-gate is replaced with a steady gate and the overdrive is replaced with a high gate, the function is the same as in FIG. FIG. 5 does not show a wide-width pulse forming circuit, an overdrive pulse forming circuit, or a circuit for synchronizing the two, but it is needless to say that these circuits are required by an ON signal. The reason why the pulse transformers 46 and 47 are used is to ensure insulation between the ON signal system and the thyristor 41 system, and is not directly related to the high gate drive. In FIG. 5, 48,
49 is a switching element, 50 to 54 are diodes, 5
5, 56 are thyristors, 57 to 59 are resistors, 60, 61
Is a capacitor.

[0008]

In the first conventional example shown in FIG. 3, although the circuit configuration is simple, the factors that determine the peak values and the durations of the high gate current and the steady current are the inductance 13 and the inductance. Under the resonance condition of the series LC circuit of the capacitor 14, when the high gate drive as shown in FIG.
5, it is extremely difficult to select the capacitors 12, 14 and the inductance 13, and even if the numerical values are determined experimentally,
It is extremely difficult to maintain stable quality in mass production. In addition, since the discharge of the capacitors 12 and 14 is used, each capacitor 12 and 14 needs to be recharged every time a gate pulse is output. At that time, a charging current flows to the primary side of the pulse transformer 15. Erroneous firing of the thyristor occurs.
Since a new circuit is required to avoid this false firing, the circuit configuration is actually complicated.

The second and third conventional examples shown in FIGS. 4 and 5 can be easily realized even when a high gate drive as shown in FIG. 7 is required. However, a one-shot circuit such as a monostable multivibrator is used. 26, a wide-width / narrow-width pulse forming circuit, and the like are required, and the circuit configuration becomes complicated. In addition, the thyristor drive circuit needs to be placed near the thyristor in order to prevent noise and turn on the thyristor at high speed. The drive circuit of a large-capacity thyristor must have a highly reliable gate circuit from the viewpoint of both thermal and electromagnetic interference when the thyristor is turned on. However, in the conventional example shown in FIGS. In consideration of the above, not only is the system more complicated, the reliability is remarkably reduced, but also the size is increased, so that there are restrictions on the installation.

It is an object of the present invention to provide a thyristor drive circuit which can supply a desired gate current, can be reduced in size with a simple circuit configuration, and has high reliability.

[0011]

A thyristor drive circuit according to the present invention comprises a constant voltage DC power supply, a series circuit of a first resistor and a capacitor, a parallel circuit of a second resistor, and a switching element connected in series. The gate of the thyristor is triggered by a current flowing through the switching element when the switching element is turned on.

According to this configuration, when the switching element is turned on, a combined current of a current flowing through the series circuit of the first resistor and the capacitor and a current flowing through the second resistor flows through the switching element. The gate of the thyristor is triggered by the current. At this time, the current supplied to the gate of the thyristor is initially a high gate current having a high peak value, and becomes a low value steady gate current after a lapse of a predetermined time. The high gate current is the sum of the current flowing in the second resistor and the current flowing in the series circuit of the first resistor and the capacitor, and the peak value is equal to the resistance value of the first resistor forming the series circuit with the capacitor. Dependent. Also,
The duration of the high gate current is determined by the time constant of the series circuit of the first resistor and the capacitor. Further, the current value of the steady gate current depends on the resistance value of the second resistor. Thus, by setting the values of the first resistor, the capacitor, and the second resistor, desired high gate current and steady gate current can be easily realized.

When the switching element is turned off, the charged capacitor is quickly discharged by the series circuit composed of the capacitor and the first and second resistors, so that there is no false firing of the thyristor and the next thyristor does not fire. Gate drive. In addition, since the number of elements is small and the circuit configuration is simple, the reliability and size can be improved, the device can be installed near the thyristor, and the thyristor can be easily turned on at high speed.

[0014]

FIG. 1 is a block diagram of a thyristor driving circuit according to an embodiment of the present invention. In FIG. 1, 1 is a constant-voltage DC power supply, 2, 3, and 10 are resistors, 4, 9 are capacitors, 5 is a pulse transformer, 6 is a switching element composed of a transistor, 7, 8 are diodes, and G and K are respectively driven. A terminal connected to the gate and cathode of the thyristor (not shown), and S _ON is an ON signal for turning on the switching element 6 to turn on the thyristor (not shown).

The thyristor drive circuit includes a constant-voltage DC power supply 1 and a resistor (first resistor) 2 and an R
A parallel circuit of a C series circuit and a resistor (second resistor) 3, a primary side of a pulse transformer 5 and a switching 6 are connected in series, and a secondary side of the pulse transformer 5 is connected to a gate connection terminal G and a cathode connection terminal. K connects the gate and cathode of a thyristor (not shown) to supply the secondary current of the pulse transformer 5 as a gate current for turning on the thyristor. The diodes 7, 8, the capacitor 9, and the resistor 10 connected to the secondary side of the pulse transformer 5 are general noise prevention elements.

When the ON signal S _ON is input to the switching element 6, the constant voltage DC power supply 1 supplies an RC series circuit (resistor 2).
A current flows into the primary side of the pulse transformer 5 through the parallel circuit of the capacitor 4) and the resistor 3 and returns to the constant voltage DC power supply 1 via the switching element 6. As a result, a current corresponding to the current transformation ratio is induced on the secondary side of the pulse transformer 5, so that the primary current _{ic of the} pulse transformer 5 is supplied from the gate connection terminal G and the cathode connection terminal K to the gate of the thyristor. A current similar to the above flows.

FIG. 2 is a timing chart of the current of each part showing the operation of the thyristor drive circuit of FIG. FIG.
2A shows _a current ia flowing through the RC series circuit of the resistor 2 and the capacitor 4, FIG. _2B shows a current ib flowing through the resistor 3, and FIG. 2C shows a primary current of the pulse transformer 5. _ic . The primary current _ic of the pulse transformer 5 is
The combined current of the current i _a and the current i _b.

If a gate current is to be caused by a high gate drive as shown in FIG. 7, it can be designed as follows. The voltage of the constant voltage DC power supply 1 is 24 V, the current transformer ratio of the pulse transformer 5 is 1: 1, and the steady gate current I shown in FIG.
When the _GT and 0.5A, since the constant gate current is the same as the current i _b flowing through the resistor 3, the resistance value of the resistor 3 may be a 24 ÷ 0.5 = 48 (Ω) .

The high gate current is the sum of the current flowing through the resistor 3 and the current flowing through the RC series circuit of the resistor 2 and the capacitor 4. As is clear from the electric circuit theory, the peak current of the RC series circuit is Since only the resistance 2 is used, the peak value of the high gate current is set to 1.5 A in FIG. 7 and the resistance value of the resistance 2 may be set to 24 ÷ (1.5−0.5) = 24 (Ω).

Since the duration of the high gate current is the same as the time constant of the RC series circuit, the time constant is set to 50 from FIG.
As μs, the capacity of the capacitor 4 may be set to 50 ÷ 24 ≒ 2 (μF). The DC resistance and inductance of the pulse transformer 5 are so small that they can be ignored, and the ON resistance and ON voltage of the switching element 6 are so small that they can be ignored.

The duration of the steady gate current is the same as the ON duration of the _ON signal S _ON , so that the ON signal S ON
_{The ON} pulse width may be 300 μs. Also, the rise time of the high gate current is 1.5 μs in FIG. 7. This is to make the internal impedance of the constant voltage DC power supply 1 sufficiently small and to select the switching element 6 having a short switching time. With the overdrive drive by passing a sufficient base current with
It can be easily realized, and can be realized even if it is considerably shorter than 1.5 μs.

As described above, according to this embodiment, by appropriately setting the resistance value and the capacitance value of each element,
A desired gate current, for example, a gate current by high gate driving as shown in FIG. 7 can be supplied. Also,
From the moment when the _ON signal S _ON is turned off, the electric charge charged in the capacitor 4 becomes equal to the resistance 3, the resistance 2 and the capacitor 4
Is discharged by the series circuit of. The time constant at this time is (48 + 24) × 2 = 144 (μs) using the above-mentioned numerical value, and does not pose any problem in practical use. Further, since the discharge is performed by a circuit not passing through the pulse transformer 5, there is no possibility that the thyristor is erroneously fired by the discharge.

Furthermore, in the above-described design, since the impedance of each part is sufficiently low, malfunction does not occur due to electromagnetic induction due to thyristor switching surge or the like. Further, since there is no circuit such as a one-shot multivibrator circuit whose internal state is easily inverted by an external disturbance pulse, there is no possibility of malfunction.

Further, since the number of elements to be used is small, the reliability is improved by one digit compared to the configurations of FIGS. In addition, since the number of elements is small, the device can be reduced in size, and can be easily installed in the vicinity of the thyristor, and the thyristor can be easily turned on at high speed. Further, since only one switching element 6 is required, a switching element synchronization circuit which is inevitably required for a plurality of switching elements is not required.

The pulse transformer 5 is not always necessary for operation. The switching element 6 may be a bipolar transistor, a thyristor, or a GTO.
(Gate turn-off) With a high-speed switching element such as a thyristor or a field-effect transistor, an equivalent effect can be obtained. As a thyristor connected to the gate connection terminal G and the cathode connection terminal K, a GTO thyristor can be used.

[0026]

A thyristor drive circuit according to the present invention comprises a constant voltage DC power source, a series circuit of a first resistor and a capacitor, a parallel circuit of a second resistor, and a switching element connected in series. The gate of the thyristor is triggered by the current flowing through the switching element when turned on, and the first resistor, the capacitor, and the second
By appropriately setting the resistance value of the thyristor, a desired high gate current and a steady gate current supplied to the gate of the thyristor can be easily realized when the switching element is turned on.

When the switching element is turned off, the charged capacitor is quickly discharged by the series circuit including the capacitor and the first and second resistors, so that there is no false firing of the thyristor and the next thyristor does not fire. Gate drive. In addition, since the number of elements is small and the circuit configuration is simple, the reliability and size can be improved, the device can be installed near the thyristor, and the thyristor can be easily turned on at high speed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a thyristor drive circuit according to an embodiment of the present invention.

FIG. 2 is a timing chart of a current of each unit according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of a thyristor drive circuit of a first conventional example.

FIG. 4 is a configuration diagram of a thyristor drive circuit of a second conventional example.

FIG. 5 is a configuration diagram of a thyristor drive circuit of a third conventional example.

FIG. 6 is a timing chart of a gate current by high gate driving.

FIG. 7 is a timing chart of a gate current by high gate driving.

[Description of Signs] 1 Constant voltage DC power supply 2, 3 Resistance 4 Capacitor 5 Pulse transformer 6 Switching element G Gate connection terminal K Cathode connection terminal

Claims (1)

[Claims] 1. A constant voltage DC power supply, comprising a series circuit of a first resistor and a capacitor and a parallel circuit of a second resistor, and a switching element connected in series, wherein the switching element is turned on when the switching element is turned on. A thyristor drive circuit that performs a gate trigger of the thyristor by a current flowing through the thyristor.