| 摘要 |
PURPOSE:To stabilize dimming of a discharge lamp by providing a gate circuit with a capacity type impedance for making a gate current to a thyrister advance from a stabilizer. CONSTITUTION:Conduction signals from a trigger circuit 6 is fed to a thyrister 4 via a gate circuit 7, whereby the thyrister 4 is controlled in its conduction phase and supply power to a discharge lamp 3 is controlled resulting in that the lamp 3 is dimmed. An input current flowing through the thyrister 4 is made advance phase with a stabilizer 1 having an advance phase condenser. A current whose phase is the same as or more than that of an input current, however, flows to the gate of a thyrister 4 by a capacity type impedance 8 which advances the gate current of the gate circuit 7. Irrespective of the level of the conduction angle, therefore, the thyrister 4 is surely made off at the termination of semi-cycle to enable a stable dimming. |
