To provide a synchronism detection circuit for light control device capable of removing notched wave-form included in power source wave-form of a synchronism detection circuit, generating synchronous signal pulse having little phase difference against a basic wave of a voltage wave-form generated between voltage-impressed wires and neutral wire of a three-phase 4 wire type power source.
A reference phase point of firing phase angle of a thyristor is settled on the basis of output terminal voltage (V1) of the an LC filter circuit (a), by providing an LC filter circuit (a) connected between power input terminals 8a, 8b of the synchronism detection circuit 1, and by correcting phase drift of a synchronizing signal pulse by attenuating distorted wave-form contained in voltage wave form (V0) of an alternating current power source 7 by the LC filter circuit (a).
| JP2005235573A | 2005-09-02 | |||
| JP2004146366A | 2004-05-20 | |||
| JPH0591199U | 1993-12-10 |
Ishiwatari Eibo
Nakamura Masamichi