Electrical thyristor circuit
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorHideo Iwamoto
Life of this patent
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Abstract
An electrical circuit comprising at least one thyristor having an anode, cathode and gate; an ignition circuit for applying an ignition signal between the gate and cathode of the thyristor when turning on the thyristor; a turn-off circuit for turning off the thyristor which applies a reverse voltage between the anode and cathode of the thyristor when turning off the thyristor and which comprises an inverse bias circuit; said inverse bias circuit comprising a first path across the gate and cathode of the thyristor and a second path acrosss the gate and anode of the thyristor; and said bias circuit applying a reverse bias voltage having opposite polarity to the ignition signal between the gate and the cathode of the thyristor.
Claims22
An electrical circuit comprising at least one thyristor having an anode, cathode and gate;
- an ignition circuit for applying an ignition signal between the gate and cathode of the thyristor when turning on the thyristor;
- a turn-off circuit for turning off the thyristor which applies a reverse voltage between the anode and cathode of the thyristor when turning off the thyristor and which comprises an inverse bias circuit;
- said turn off circuit comprising a commutation capacitor connected by switch means across the anode and cathode of the thyristor, means for reverse charging the commutation capacitor while the thyristor conducts so that upon actuation of the switch means the commutation capacitor applies voltage to the anode of the thyristor which is negative with respect to the voltage applied by the commutation capacitor to the cathode of the thyristor;
- said inverse bias circuit comprising a first path across the gate and cathode of the thyristor and a second path across the gate and anode of the thyristor;
- and
- said inverse bias circuit applying a reverse bias voltage having opposite polarity to the ignition signal between the gate and cathode of the thyristor.
An electrical circuit comprising:
- a DC power source having first and second terminals;
- a transformer having an input coil and an output coil;
- said input coil having a middle terminal disposed between its first and second terminals and being connected to the first terminal of said DC power source;
- a load connected to the output coil of said transformer;
- a first thyristor connected between the first terminal of said input coil and the second terminal of said DC power source;
- a second thyristor connected between the second terminal of said input coil and the second terminal of said DC power source;
- each of said thyristors having an anode, cathode, and gate;
- a commutation capacitor between the first and second terminals of said input coil;
- said commutation capacitor being reverse charged while each of the thyristors conducts to apply a reverse voltage between the anode and cathode of each of said thyristors to give a positive polarity to the cathode when turning off each of said thyristors;
- a first inverse bias circuit connected to the first thyristor and a second inverse bias circuit connected to the second thyristor whereby the reverse bias voltage is applied between the gate and cathode of each of said thyristors to give a positive polarity to the cathode when turning off said thyristors.
The electrical circuit according to claim 18 wherein the first paths of the first and second inverse bias circuits each include a diode connected in series to the zener diode with each diode being connected so as to impart a forward direction characteristic to the inverse bias voltage.
An electrical circuit comprising:
- a first thyristor connected in series to a load and a DC power source;
- said first thyristor having an anode, cathode, and gate;
- an ignition circuit for applying an ignition signal between the gate and cathode of the first thyristor when turning on the first thyristor;
- a turn-off circuit for turning off the first thyristor;
- said turn-off circuit comprising a commutation capacitor and a second thyristor;
- said commutation capacitor being reverse charged while the first thyristor conducts to apply a reverse voltage between the anode and cathode of the first thyristor to give a positive polarity to the cathode during the turn-on of the second thyristor;
- said turn-off circuit comprising an inverse bias circuit which has a first path across the gate and cathode of the first thyristor and a second path across the gate and anode of the first thyristor;
- said inverse bias circuit applying a reverse bias voltage having a polarity opposite to the ignition signal between the gate and cathode of the first thyristor.
Dependencies are inferred from the claim text.