Centralization type light change circuit for LED illuminating system

The invention discloses a centralized light modulation circuit in LED illumination system, which comprises a central controller and a multipath LED drive circuit; The central controller comprises a thyristor SCR and a light modulation control trigger circuit; the light modulation control trigger circuit comprises a hand-operated brightness adjusting trigger circuit, and/or a ambient brightness detecting and brightness adjusting trigger circuit, and/or a timing control adjusting trigger circuit, and outputs hand-operated and/or time controlled light modulation signals; and each LED drive circuit comprises a main circuit, a signal detection shaping and converting circuit, a current adjusting and constant current controlling circuit. In the invention, the small-ranged variation of conduction angle of controlled silicon in the central controller can obtain wide range light modulation effect; and the invention has simple circuit and low cost, generate no great harmonic wave, and reduces harmonic wave pollution.