Discharge device control circuit including a thyristor
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorsSuzuo Kojima, Yoshio Fujimaru
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Abstract
A main capacitor is connected across a series combination of a flash discharge lamp and a thyristor to flash the flash discharge lamp through the thyristor in its ON state. A commutation circuit connected to the thyristor includes a commutation capacitor and another thyristor turned on upon a flashing light from the flash discharge lamp reaching a predetermined magnitude. When turned on, the latter thyristor permits the commutation capacitor to supply a reverse voltage to the first thyristor to turn it off. A semiconductor diode is connected between the commutation capacitor and the first thyristor to prevent that capacitor from applying a forward voltage to the first thyristor.
Claims7
A control circuit for controlling an electric discharge device, comprising, in combination:
- a first circuit branch comprising an electric discharge device and a thyristor connected in series with said discharge device for controlling current flowing through said discharge device and flowing through the node at which said discharge device and said thyristor are connected;
- a second circuit branch connected in parallel with said first circuit branch, said second circuit branch comprising an impedance element connected to said discharge device and a switching element connected to said thyristor and to said impedance element to define a node therewith;
- and
- a third circuit branch connected between the node defined by said discharge device and said thyristor and the node defined by said impedance element and said switching element, said third circuit branch comprising a commutation capacitor for storing and applying a reverse voltage to said thyristor under control of said switching element to bias said thyristor from a conducting to a nonconducting state, and a diode connected in series with said commutation capacitor and having a polarity effective to prevent a voltage opposite the polarity of said reverse voltage and stored on said commutation capacitor from being applied to said thyristor.
A control circuit for a discharge device comprising, in combination:
- an electric discharge device;
- a thyristor connected in series with said electric discharge device to control a current flowing through said electric discharge device;
- a commutation circuit including a commutation capacitor and a switching element for controlling the discharge of said commutation capacitor through said thyristor;
- said switching element being connected between said thyristor and said commutation capacitor to supply a reverse voltage stored in said commutation capacitor to said thyristor to bias said thyristor from a conductive to a nonconductive state;
- a semiconductor diode connected between said commutation capacitor and said thyristor to prevent an electrical charge with a polarity opposite that of the reverse voltage accumulated on said commutation capacitor from discharging through said thyristor;
- and a resistor connected in parallel with said semiconductor diode.
A control circuit for a discharge device comprising, in combination:
- an electric discharge device;
- a thyristor connected in series with said electric discharge device to control a current flowing through said electric discharge device;
- a commutation circuit including a commutation capacitor and a switching element for controlling the discharge of said commutation capacitor through said thyristor;
- said switching element being connected between said thyristor and said commutation capacitor to supply a reverse voltage stored in said commutation capacitor to said thyristor to bias said thyristor from a conductive to a nonconductive state;
- a semiconductor diode connected between said commutation capacitor and said thyristor to prevent an electrical charge with a polarity opposite that of the reverse voltage accumulated on said commutation capacitor from discharging through said thyristor;
- and a resistor and a reactor connected in series, and wherein the series combination of said resistor and reactor is connected in parallel with said diode.
Dependencies are inferred from the claim text.