Patent ID: 7346088

Claim:
A voltage dividing apparatus for preventing sudden increases in power to a laser diode, comprising: a laser diode module, including: a laser diode, for receiving a driving current to emit light; and a photo diode, for receiving light emitted from the laser diode and converting the received light into a voltage signal; a feedback amplifying circuit having an input coupled to the photo diode for providing a feedback voltage signal responsive to the voltage signal from the photo diode to automatically balance power of the laser diode; a laser-driving unit having an output connected to the laser diode, and an input coupled to an output of the feedback amplifying circuit for controlling a current of the laser diode responsive to the feedback voltage signal; a voltage distribution circuit providing coupling between the feedback amplifying circuit and the laser driving unit, the voltage distribution circuit including two series connected voltage-dividing resistors connected with the laser-driving unit for proportionally distributing the feedback voltage signal into each component of the laser-driving unit; and a feedback voltage monitoring circuit having an input coupled to the feedback amplifying circuit and an output coupled to the voltage distribution circuit and the laser-driving unit, the feedback voltage monitoring circuit including (a) a transistor coupled to the voltage-dividing resistors and the laser driving unit, and (b) a Zener diode coupled between the output of the feedback amplifying circuit and the transistor, wherein a short circuit causing the feedback voltage signal to exceed a Zener breakdown voltage of the Zoner diode enables conduction of the transistor to thereby disable the laser-driving unit to protect the laser diode from output of excessive power.