PURPOSE: To make it possible to prevent the going out of a discharge lamp at the light control by providing a control means to shorten the on-time of a switching element so as to adjust the light of the discharge lamp and a means to reduce the inductance or the capacitance of a resonant circuit at the light control.
CONSTITUTION: An oscillation capacitor C1 consists of two capacitors C11, C12, and contact [r1] of a relay Ry1 is used for a switch which makes the connection and the disconnection of the capacitor C12, and the contact [r1] is closed when the lamp is fully lighted. A control circuit CO has a terminal to output a light control Dim signal which controls the continuity of a transistor Q2 to control the operation of the relay Ry1. The constants of the other circuit elements are similar to conventional values, and the capacitance of the oscillation capacitor C1 is made to be C11+C12=C1.
MIYAGI HIDEO
KUBOTA SATOSHI
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