JPH03145809A - High dielectric strength driving circuit - Google Patents

Abstract

PURPOSE:To realize a high dielectric strength driving circuit with high accuracy and low current by employing a base current compensation type high dielectric strength current mirror circuit for a gate driving circuit in a high dielectric strength driving circuit for a thyristor applied with a high voltage. CONSTITUTION:A current source is a highly accurate constant current source. When a voltage lower than a reference voltage VTH is applied to a control terminal IN of a current changeover circuit 10 comprising transistors(TRs) T1, T2, the current I1 of the current source passes through the TR T2. The current I1 of the current source is inputted to a base current compensation current mirror circuit 20 comprising TRs T3, T4, T5 and outputted from the TR T5. The output current flows to a gate terminal as a gate driving current of a thyristor S1 via a high dielectric strength diode D1 to turn on the thyristor S1. Since the constant current source I1 is formed to be a low voltage, the current accuracy is improved. Thus, a highly accurate gate driving current is realized, then the gate driving current is set to a required minimum value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a high breakdown voltage drive circuit for a thyristor to which a high voltage is applied.

[Conventional technology] A conventional high-voltage drive circuit of this type is shown in FIG.

As shown in the figure, in the conventional high voltage drive circuit, when 0 volts is applied to the control terminal IN, a collector current flows through the high voltage transistor T6.

This current flows through the high voltage diode D1 to the gate terminal as a gate drive current of the thyristor S1, thereby turning on the thyristor S1.

Here, the gate drive current I changes the forward voltage of the diode G DD to v, ■, 2', respectively.
3 F2 F3 The resistance value of resistor R is R, and the emitter current ■ and collector current I of transistor T7. The ratio (Io/I) to α, the transistor T
7, the emitter-to-emitter voltage is v8E.

The current flowing to the B terminal is the sum of the forward current I of the thyristor S1 and the gate drive current I, and therefore the current flowing between the A terminal and the B terminal is:
The error will be the gate drive current.

[Problems to be Solved by the Invention] In the conventional high-voltage drive circuit described above, since the high-voltage transistor T7 has a high breakdown voltage, α is 0.6 to 0°9, and therefore the gate drive current ■ is large G. There was a drawback that the forward current I of the thyristor S1 was greatly affected by the fluctuation.

[Means for Solving the Problems] An object of the present invention is to solve the problems of the prior art described above and to provide a high-precision, low-current, high-voltage driving circuit.

The present invention provides a high withstand voltage drive circuit for a thyristor to which a high voltage is applied. The present invention is characterized in that it includes a base current compensation type current mirror circuit in which input/output transistors are formed of transistors.

[Example] Next, a high breakdown voltage drive circuit of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of a high voltage driving circuit according to the present invention.

The current source used in the figure is a highly accurate constant current source. When a voltage lower than the reference voltage TH is applied to the control terminal IN of the current switching circuit 10 composed of transistors T1 and T2, the current I of the current source changes to
It will pass through 2.

The current 11 of the current source further flows through transistors T3 and T4.
, T5, and output from the transistor T5. This output current flows through the high voltage diode D1 to the gate terminal as a gate drive current of the thyristor S1, turning on the thyristor S1.

Transistor T5 is a high voltage transistor, and transistor T4#J is a high voltage transistor that requires matching. The current amplification factor of the low voltage transistor T3 is β3(
= 100), and the current amplification factor of the high voltage transistor TT is β β (β4'5 4゛ 54 ; β5 = β = 2~10), then the gate drive current ■ is G, and α is 0.990~0. It becomes 998.

Since the constant current source 11 can be configured in a low breakdown voltage section, the ta accuracy is improved. In this way, a highly accurate gate drive current can be achieved, and therefore the gate drive current can be set to the minimum necessary value.

[Effects of the Invention] As explained above, the present invention has the effect of realizing a high-precision, low-current, high-voltage drive circuit by using a high-voltage base current compensation type current mirror circuit in the gate drive circuit. There is.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of a high voltage driving circuit according to the present invention. FIG. 2 is a circuit diagram showing a conventional high-voltage driving circuit. T1, T2...NPN) transistors T3, T6... low voltage PNP transistors T4, T5
, T7...High voltage PNP transistor D1...High voltage diode Sl...Thyristor ■...Power supply C ■TH...Reference voltage IN...Control input terminals R1-R3...Resistor D2, D3...diode

Claims (1)

[Scope of Claim] A high voltage drive circuit for a thyristor to which a high voltage is applied, comprising: a constant current source; a current switching circuit that switches the current of the constant current source; and an output of the current switching circuit that transmits to the thyristor. A high-voltage drive circuit comprising: a base current compensation current mirror circuit whose input/output transistors are constituted by high-voltage transistors;