Patent ID: 7012344

Claim:
A switch control circuit, applied to an auto laser power control circuit of a laser diode driving system, the switch control circuit being coupled to a driving circuit and a feedback amplifying circuit, the switch control circuit comprising: a first electronic switch, having a first terminal coupled to the feedback amplifying circuit, a second terminal and a control terminal; a second electronic switch, having a first terminal coupled to a first power supply, a second terminal and a control terminal; a third electronic switch, having a first terminal, a second terminal coupled to the driving circuit and a control terminal; a fourth electronic switch, having a first terminal, a second terminal and a control terminal, wherein the second terminal of the first electronic switch, the second terminal of the second electronic switch, the first terminal of the third electronic switch and the first terminal of the fourth electronic switch are coupled together; and a resistor, having a first terminal coupled to the second terminal of the fourth electronic switch and a second terminal coupled to the second terminal of the third electronic switch; wherein the control terminals of the first, second, third and fourth electronic switches receive a first control signal, and when the first control signal is enabled, the first and third electronic switches conduct and the second and fourth electronic switches are turned off, and when the first control signal is disabled, the first and third electronic switches are turned off and the second and fourth electronic switches conduct.