Patent ID: 7649919

Claim:
An automatic power control (APC) circuit applicable to controlling a laser generation module, the laser generation module comprising a laser generator for generating laser and a photosensor for outputting a detection result corresponding to the power of the laser, the APC circuit comprising: a comparator, coupled to the photosensor and biased by a first voltage level, for comparing the detection result and a reference signal to generate a comparison result, wherein the comparator is not biased by a second voltage level, and the first voltage level is a maximum voltage level applied to the comparator; a level shifter, coupled to the comparator, for shifting an intermediate voltage level controlled by the comparison result to generate a control voltage, wherein the level shifter is not biased by the first voltage level; and a driver, coupled to the level shifter and the laser generator, for driving the laser generator according to the control voltage and the second voltage level, wherein the second voltage level is a maximum voltage level applied to the driver.