JPH02202354A - Gate driver device for thyristor - Google Patents

Abstract

PURPOSE:To enable heat generation to be suppressed gate-driving many thystors with a less power loss by effectively utilizing excitation energy of a gate transformer and charging a capacitor. CONSTITUTION:A capacitor C1 connects between its terminals the first DC power source E1 through a charging resistor R1 and the second DC power source E2, having voltage lower than that of the first DC power source E1, through a diode D1 of forward direction. The capacitor C1 is charged up to the voltage of the first DC power source E1; when a switching element Q1 conducts, the capacitor C1 is discharged of its electric charge through a drive winding, generating a large gate current of sharp riseup. When the capacitor C1 obtains its terminal voltage equal to the voltage of the second DC power source E2, a gate pulse signal of large width with a sharp riseup is supplied to thyristors Th1 to Thn by the second DC power source. Thus, high reliability of gate driving can be contrived.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to gate driving of a SIRISK used in a power converter such as an inverter, and particularly to a device suitable for driving the gates of a large number of SIRISKS.

<Prior Art> In recent years, the capacity of power conversion devices using thyristors has been increased dramatically, and in particular, nuclear fusion devices and the like are being designed to have higher voltages and larger currents. On the other hand, the increase in the capacity of SIRISK cannot keep up with the increase in the capacity of power conversion equipment, so large numbers of SYRISKs are connected in series or parallel, or multi-phased to cope with the increase in capacity. Hundreds of devices
Currently, it is not uncommon to use individual Cyrisks.

In a large power conversion device using such a large number of thyristors, the gate drive device thereof also becomes large in size, resulting in an increase in heat generation and a decrease in reliability.

When using a large number of these thyristors, the conditions for the gate current are to prevent turn-off due to a large current gate pulse with a steep rise and an oscillating current when turning on the thyristors of other phases, in order to prevent variations at turn-on. Therefore, the most important point is a gate pulse with a small current and a long time width.

As this type of device, for example, those shown in FIGS. 3 and 4 have been proposed. The former (snoring figure 3) is
To two DC power supplies Ea, Eb (however, Ea>Eb), via series resistors Ra, Rb and diodes Da, Db,
A capacitor Ca is connected between the terminals of the capacitor Ca, and the primary winding of the gate transformer Ta is connected to the transistor Qa.
A diode D is connected between the terminals of the above primary winding.
It is constructed by inserting c.

When the transistor Qa is in the cut-off state, the capacitor Ca is charged to Ea by the DC power supply Ea, and when the transistor Qa becomes conductive, the charge in the capacitor Ca is discharged through the primary winding of the gate transformer Ta. Since the resistor Ra is set to a sufficiently large value, the current supplied from the DC amount aEa is sufficiently small compared to the discharge current of the capacitor Ca.When the terminal voltage of the capacitor Ca becomes equal to the DC amount 6Eb, the gate transformer Ta
The energizing current 10 is the DC amount i! By continuing to flow the gate pulse signal from iEb during the conduction period of the transistor Qa, a gate pulse signal with a large rising current and a small wide current is supplied to the thyristor Tha, as shown in Fig. 3(b). It is.

In the latter (Fig. 4), a series circuit consisting of a diode Dd, a series resistor Rc, and a capacitor cb, and a series circuit consisting of a diode De, a DC reactor La, and a transistor Qb are connected to the DC power supply Ec. The above resistance R
A diode D is provided between the connection point between c and capacitor cb and the connection point between DC reactor La and transistor Qb.
Both terminals of f are connected to the primary winding of gate transformer Tb.

Assuming that the capacitor cb is charged to Ed (Ed>Ec), the conduction of the transistor Qb causes the charge in the capacitor cb to be discharged through the primary winding of the gate transformer Tb.

The discharge continues until the voltage of the capacitor cb becomes equal to the DC power supply Ec, after which the diode Dd becomes conductive and the DC power supply Ec causes a current i to flow to the primary winding of the gate transformer Tb via the resistor Rc. As shown in FIG. 4(b), a gate pulse signal having a large rising current and a small wide current is supplied to the thyristor Thb. On the other hand, from the moment the transistor Qb becomes conductive, a current i starts flowing through the DC reactor La from the DC power supply Ec, and this current ILa increases with the passage of time. When the transistor Qb is cut off, the current iLa from the DC reactor La, that is, the current due to the excitation energy accumulated in the inductance, passes through the diode D[ and charges the capacitor cb, raising the terminal voltage of the capacitor cb to Ed. (Special Publication No. 63-37712).

<Problem to be solved by the invention> However, in the former case, in order to supply the gate pulse signal, the terminal voltage of the capacitor Ca must be set to Ea.
It must be charged by DC power supply Ea through resistor Ra until
a-Eb)! When driving the gates of many thyristors, it requires energy of
This has the problem of increasing heat generation. In addition, the current due to the excitation energy accumulated in the gate transformer Ta is reduced by circulating through the diode DC when the transistor Qa is cut off, which increases heat generation and increases the excitation inductance L. Since it decreases with an L/R time constant with the winding resistance R, it does not reach zero suddenly. Therefore, if the repetition frequency is high, the gate transformer will be magnetically saturated when the next gate pulse signal is supplied, and the desired value will not be reached. The problem is that the gate pulse signal cannot be supplied, and there is a risk that the turn-on of a large number of thyristors may vary, resulting in a decrease in reliability.

Furthermore, in the latter case, in addition to the gate transformer, a DC reactor with an iron core of the same size is required, and when driving the gates of a large number of thyristors, the device becomes large. .

Moreover, the energy stored in the gate transformer is not used, and therefore does not suddenly become zero as in the former case, and the excitation energy of the DC reactor simply charges the capacitor with DC current [a voltage Ed higher than Ec]. Since they are used only for this purpose, these power losses are large, and in devices that gate drive a large number of thyristors, there is a problem in that heat generation becomes large. Also, the voltage Ed charged in the capacitor (Ed>Ec)
is performed by the excitation energy of the DC reactor, so the first gate pulse signal solves the problem of not being able to obtain a pulse with a large rising current because the terminal voltage of the capacitor is only charged up to the DC power supply Ec. Moreover, since general power supplies use SI risk to turn off the load manually and phase control, the load off time, that is, the gate off period, is not constant, and as this period becomes longer, the capacitor In addition to the self-discharge of thyristors, the first gate pulse signal becomes low, which poses a problem in that reliability is significantly reduced in devices that gate drive a large number of thyristors. Furthermore, since the capacitor Φ charging voltage Ed is determined by the value of the DC reactor and the gate pulse width, the variation in the charging voltage becomes extremely large.In order to stabilize this, increasing the accuracy of the DC reactor would be expensive, and the pulse width would be increased. If the control circuit for making the signal constant is multi-phase, it takes time and effort to adjust it, resulting in a high cost and a lack of versatility.

The present invention has been made in view of the above-mentioned points, and its purpose is to save power and reduce the size of a gate pulse signal that has a large current with a steep rise and a wide width of a small current. The object of the present invention is to provide a device that can be supplied with high reliability of gate drive, and has high versatility.

Means for Solving the Problems> In order to achieve the above objects, the present invention provides one of the gate transformers.
On the next side, a reset winding and a drive winding are connected in series, and the common end of both windings is connected to the other end of a discharging capacitor whose end is grounded to the circuit. A cathode of a diode whose anode is grounded to the circuit is connected to the other end of the capacitor, the other end of the drive winding is grounded to the circuit via a switching element, and a charging resistor is connected between the terminals of the capacitor. The first DC power supply is connected to the first DC power supply, and a second DC power supply having a voltage lower than that of the first DC power supply is connected via a forward diode.

Function> When the capacitor is charged to the voltage of the first DC power supply and the switching element becomes conductive, the capacitor discharges the charge through the drive S line and generates a large gate current with a steep rise. When the terminal voltage of the capacitor becomes equal to the voltage of the second DC power supply, the gate transformer is excited by the second DC ta, and a wide and small gate current is generated, resulting in a steep rise and a wide width of the sirisk. The gate pulse signal is supplied. When the switching element is cut off, the current generated by the excitation energy of the gate transformer charges the capacitor through the reset winding and circulates.
Rapidly decrease to zero.

Thereafter, the gate pulse signal is supplied by the discharge of the capacitor charged by the excitation energy of the gate transformer and the second DC power supply.

<Example> Embodiments of the present invention will be described with reference to FIGS. 1 and 2.

In FIG. 1, Th,, Th.

Th, is a large number of thyristors inserted into the main circuit to which a load (not shown) is connected. 1.1゜・---1---
-----・- is a first DC power supply E, and a second DC power supply Et with a lower voltage (El > Et
), the thyristors Th, , Th.

This is a drive circuit configured to output a gate pulse signal to each gate of Th. In this case, a reset winding N and a drive winding N are connected in series on the primary side of a gate transformer T which has an output winding N on the secondary side, and this reset winding N The other end of the discharging capacitor C, whose one end is grounded to the circuit, is connected to the common @ (connection point of N and N1) of the drive winding N1 and the drive winding N1, and the anode is connected to the other end of the reset winding N2, whose anode is grounded to the circuit. The cathode of a diode Dz is connected to the other end of the drive winding N1, and the collector of a transistor Q whose emitter is grounded is connected to the other end of the drive winding N1. A gate transformer T is connected to a DC power supply E through a forward diode D1.

from the output winding N3 to the diode D and the gate resistor R2.
A gate pulse signal is output through the .

Next, the operation of the thyristor Th will be explained.

In addition, the thyristors T h , T h , -----
- The operation for Th7 is performed in the same way, so the explanation will be omitted.

Now, the transistor Q is in a cut-off state, the charge on the capacitor C1 is also zero, and the DC power supply E is turned on.

When E2 is supplied, capacitor C1 is connected to diode D
, conducts and is charged by the DC power source E2, and is also charged by the DC amount a E l via the resistor R1 with a time constant of C, R, and the charging voltage becomes the voltage V of the DC amount aE2.
. When the voltage becomes higher, the diode D1 becomes non-conductive, and the DC power supply E thereafter becomes non-conductive.

is charged to the voltage Vt+ of E.

In this state, FIG. At the time transistor Q1
When conductive, the capacitor C1 discharges its charge to the gate transformer T (Fig. 2(e)), and as a result, a high current ivt with a rising or steep peak value flows through the drive winding N1.
flows (Fig. 2 (C)), and a gate current i with a steep rise and high peak value is output from the output winding N3 to the gate of the thyristor T h l via the diode D and the resistor R (the second (b)), the thyristor Th, is turned on.

Then, when the capacitor C8 is discharged, its terminal voltage becomes the DC power supply E! This continues until the voltage VEX becomes equal to the voltage VEX (Fig. 2, t1), after which the diode D becomes conductive, and the DC power supply E2 causes the current itl to flow through the drive winding N of the gate transformer T1 (Fig. 2 (Fig. 2)). C)) As a result, the gate current iG maintains a value t sufficiently higher than the gate trigger current ISF of the thyristor T h during the conduction period of the transistor Q (Fig. 2(a)), and the output winding N3
to the gate of the thyristor Th (Fig. 2(b)
)).

On the other hand, from the time the transistor Q becomes conductive, an excitation current fax flows through the gate transformer T, and this increases with the passage of time (FIG. 2(C)).

Transistor Q1 is shown in FIG. When the state is cut off at this point, the electric current a tvz due to the excitation energy accumulated in the gate transformer T1 by the excitation current 1eX passes through the reset winding N and N! →C.

→D2→Nt, it circulates and flows, charging the capacitor CI, and changing its terminal voltage Vc to the voltage VEI of the DC amount BB.
(Fig. 2(e)), and at the same time, the excitation energy is used to charge the capacitor CI, so that the current 1. rapidly decreases to zero (Fig. 2(c)).

Thereafter, the gate pulse signal for the thyristor T h + is applied to the capacitor C1 charged by the excitation energy.
This is done by the discharge of , and the DC amount #f, .

<Effects of the Invention> According to the present invention, since the excitation energy of the gate transformer is effectively used to charge the capacitor, power loss can be extremely reduced, and a large number of thyristors can be gate driven. It is possible to extremely reduce heat generation even if the Furthermore, unlike in the past, there is no need for a series reactor as an energy charger, making it possible to make the paternal side smaller and cheaper. In addition, since the first DC power supply (higher voltage power supply) is only used for initial charging of the capacitor, the charging resistor can also be set to a high resistance, and the first DC power supply The second DC power supply, which has a lower voltage than the power supply, only needs to be a power supply that is sufficient to output a gate current that is sufficient to maintain the gate trigger current of the thyristor, so the power supply capacity can be made smaller and the power consumption can be reduced. It can be made extremely small. Furthermore, since it is charged by the first DC power supply during rest, it is possible to accurately output a stable gate pulse signal, further increasing reliability even when driving the gates of a large number of thyristors. Furthermore, the current due to the excitation energy of the gate transformer charges the capacitor and makes it circulate, so it can be rapidly reduced to zero, and the current can be bridge-connected and phase-controlled. Even when driving the thyristor gate with double pulses, the desired gate pulse signal can be accurately output, and even if the pulse width becomes small and the excitation energy decreases, the first direct lit source can perform auxiliary charging. Therefore, there is no need to keep the pulse width constant, and there is no need to make any adjustments, thereby expanding the scope of application and further improving versatility.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is an explanatory diagram of its operation, and Fig. 3 shows a conventional example.
a) is a circuit diagram, FIG. 4(b) is an explanatory diagram of its operation, and FIG. 4 shows another conventional example; FIG.
b) is an explanatory diagram of the operation. E,,'E shit: 11th second DC power supply R1: Charging resistor C1: Discharging resistor DD,: Diode T1 Nigate transformer Ql Niswitching element

Claims (1)

[Claims] A reset winding and a drive winding are connected in series on the primary side of the gate transformer, and a discharge capacitor whose one end is grounded to the circuit is connected to the common end of both windings. The cathode of a diode whose anode is grounded to the circuit is connected to the other end of the reset winding, the other end of the drive winding is grounded to the circuit via a switching element, and a charging resistor is connected between the terminals of the capacitor. A gate drive device for a thyristor, characterized in that a first DC power supply is connected through the thyristor, and a second DC power supply having a lower voltage than the first DC power supply is connected through a forward diode. .