Patent ID: 8742672

Claim:
A light source dimming control circuit, comprising: a voltage signal generator for generating a first voltage signal between a predetermined voltage level and a ground level; a reference voltage signal generator for generating a reference voltage signal at an output end according to the first voltage signal and a second voltage signal lower than the predetermined voltage level, the reference voltage signal generator comprising: a first diode with an anode end coupled to the voltage signal generator, and a cathode end coupled to the output end; and a second diode with an anode end receiving the second voltage signal, and a cathode end coupled to the output end; a first switch with a first end coupled to an output end of a light source; a first resistor with a first end coupled to a second end of the first switch, and a second end coupled to a ground end; a switch controller coupled to the first switch and the voltage signal generator for turning on the first switch when a sawtooth signal is lower than the first voltage signal, and for turning off the first switch when the sawtooth signal is higher than the first voltage signal; and a current controller coupled to the output end of the reference voltage signal generator and the first end of the first resistor for controlling current flowing through the first resistor according to the reference voltage signal.