DE3523666A1 - Circuit arrangement for the floating switching-on of a GTO thyristor or bipolar transistor using an impressed control current - Google Patents

Abstract

The invention relates to a circuit arrangement for the floating switching-on of a GTO thyristor or bipolar transistor with an impressed control current, having at least one pulse transformer to whose primary winding at least one switch is connected, and having a voltage source to which the primary winding of the pulse transformer is connected. The invention consists of a switchable current source having a feedback resistor being arranged in the connecting line of the switching-on control circuit to the GTO thyristor, in the GTO control line on the cathode side. <IMAGE>

Description

The invention relates to a circuit arrangement for floating Switch on a GTO thyristor or bipolar transistor with an embossed Control current according to the preamble of claim 1.

Switch-on control circuits for igniting thyristors are already known. In a typical pulse amplifier for driving GTO thyristors Three stages are generally included via pulse transformers. The first stage is a start-up control circuit with an AC voltage source, which can be switchable with one or two pulse transformers, with a rectifier and with a resistor or an RC network for setting the level and timing of the ignition current. Second, a shutdown control circuit with a switchable DC voltage source, a pulse transformer and decoupling diodes included therein. The third stage is a negative bias voltage source with an im general non-switchable AC voltage source, a Transformer, a rectifier and a resistor are used.

For the necessary decoupling of the switch-on control circuit from the switch-off control circuit and the negative bias source during the lockout period inserted a decoupling network. This is either a passive decoupling provided with a zener diode or a series diode connection or an active decoupling with a transistor switch that  still e.g. can be controlled via optocouplers (N.Seki et al. "Present Condition of High Power GTO Applications ", Proceedings of PCI, September 1982, page 391 ff).

Since the gate cathode voltage of a GTO thyristor is used, among other things, by the gate Current and temperature is dependent and has a wide range, requires compliance with the desired narrow gate current tolerances in the conventional gate current settings with resistors a high voltage at the output of the rectifier. This leads to one high power requirement.

The task is to create a circuit arrangement for floating Switch on a GTO thyristor or bipolar transistor with an embossed Specify control current with which a circuit simplification and an improvement in the ignition conditions of the GTO thyristor and the reduction the power requirement of the pulse amplifier can be achieved. The object is achieved according to the invention by the in the claims specified measures solved.

The invention is described below using exemplary embodiments with reference to Drawings explained in more detail. In the figures is the start-up control circuit shown in detail while the shutdown control circuit and the circuit for the negative bias voltage source are only hinted at.

The switch-on control circuit ( Fig. 1) contains a pulse transformer T with tapped windings. The primary winding of the pulse transformer T is connected to the voltage source via the center tap. The voltage source is bridged by a capacitor C 1 . In addition, switches Q 2 and Q 3 are located on the primary winding.

On the secondary winding of the pulse transformer T are diodes D 1 and D 2 , which rectify the current. The ignition current i _{G is} passed from them to the GTO thyristor. The center tap of the secondary winding of the pulse transformer T is connected to a switchable current source Q 1 via a resistor R 4 to be added if necessary. The resistor R 4 serves for negative feedback. The switchable current source Q 1 can be a transistor. Depending on whether the switchable current source Q 1 is arranged in the cathode-side GTO control line, as in FIG. 1, or in the gate line as in FIG. 2, either an NPN transistor, an NPN Darlington transistor or N-channel FET or a PNP transistor, a Darlington transistor or P-channel FET is used.

The control voltage U _ST is derived from the rectifier output voltage U _{A with} little effort via a voltage divider circuit R 5 , R 6 .

The required timing of the ignition current can be set by adding an RC element to the voltage divider R 5 , R 6 ( FIG. 3) or by a time-dependent negative feedback network ( FIG. 4). In addition - with further reduction of the losses - the time course of the ignition current can be formed by staggered switching on of different voltage sources on the primary side (without figure).

The advantage of the invention is that the targeted tight Gate current tolerances with reduced power requirements with small circuit complexity can be met.

Claims (2)

1. Circuit arrangement for potential-free switching on of a GTO thyristor or bipolar transistor with an impressed control current, with at least one pulse transformer, at the primary winding of which there is at least one switch, and with a voltage source to which the primary winding of the pulse transformer is connected, characterized in that in the connecting line the switch-on control circuit with the GTO thyristor in the cathode-side GTO control line a switchable current source ( Q 1 ) is arranged with a negative feedback resistor ( R 4 ) to be added if necessary. 2.Circuit arrangement for potential-free switching on of a GTO thyristor or bipolar transistor with an impressed control current, with at least one pulse transformer, at the primary winding of which there is at least one switch, and with a voltage source to which the primary winding of the pulse transformer is connected, characterized in that in the connecting line the switch-on control circuit with the GTO thyristor in the gate line is a switchable current source ( Q 1 ) with a negative feedback resistor ( T 4 ) to be added if necessary.