Nippon Precision Circuits Inc.

Matsushita Electric Industrial Co., Ltd.

Toshiaki Tsujikawa

Masataka Saitoh

Electric power consumed by a laser diode when an optical disk or magneto-optical disk is played back is reduced. A laser diode control circuit () causes the laser diode to emit continuously rather than intermittently, even if a PCK signal is supplied to the laser diode control circuit (), when an optical display player or magneto-optical disk drive does not yet stabilize and is being pulled into a phase-locked state. When the focus is locked, the player is in a phase-locked state, and the operation is stable, a mode-switching circuit () included in the laser diode control circuit () switches the mode of operation from continuous operation to intermittent operation according to an FLOCK signal. The frequency of the PCK is multiplied by a frequency multiplier circuit (), and the pulse width is adjusted by a pulse width-adjusting circuit (). A laser diode driver circuit () produces intermittent current of this adjusted pulse width. The laser diode is started to emit intermittently.

Method of controlling laser diode in optical disk player and circuit therefor

Automatic slice level control response to differential input signals is provided to remove in-phase noise and effects on S/N ratio Analog differential input signals Vinp and Vinn are inverted with respect to each other and applied to input terminals in and in of a comparator via resistors R and R . A data stream is provided giving DSV&equals;0. A charge pump is driven by a digital signal from the comparator. A transconductance amplifier produces output current Itrc and Itrc that are mutually differential signals and in proportion to the voltage difference between the output voltage Vcp from the charge pump and a reference voltage Vref. The output currents are supplied to the input terminals in and in of the comparator to provide a DSV&equals;0. The analog differential input signals are binarized by the comparator to remove in-phase noise

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Tokyo, Japan

Toshiaki Tsujikawa