A power control circuit of a variable-frequency opto-interrupter for a printer has a plurality of impedances electrically connected with a receiving terminal of the opto-interrupter in parallel for multi-stage variable adjustment, an IR photodiode having stronger penetration and adopted to a transmitting terminal, and a variable frequency generator generating variable frequency signal and electrically connected with a negative pole pin of the IR photodiode through a switching transistor. Accordingly, the emitting intensity of the opto-interrupter is significantly enhanced so that various printing media are penetrated through by infrared beams and the emitting intensity is adjusted to adapt to acquire a broader dynamic range of the load of the receiving terminal.

Claims data not available