Sharp Kabushiki Kaisha Corporation

Yoshihiro Ohtsuka

Yoshifumi Masuda

Yoshihumi Masuda

A pulse light-receiving circuit includes a pair of preamplifiers made up of the same circuit components, a difference amplifier for amplifying the outputs from the preamplifiers, and a pair of peak value-detecting circuits made up of the same circuit component for obtaining the amplitude of an input pulse signal. The median of that amplitude is used as a reference voltage for comparison with an output from the difference amplifier.

Pulse light-receiving circuit with means to minimize power source noise

A light receiving section of a photocoupler according to the present invention has, for example, a light receiving element, a converting circuit, an oscillator, an updown (U/D) counter, a decoder and a clock signal supply control circuit, and those devices are monolithically integrated therein. When the light receiving element receives light from a light generating section, an output of the converting circuit becomes High. At this time, an output of the decoder is delayed until the U/D counter has counted up to the preset number a clock signal supplied by the clock signal supply control circuit. On the other hand, upon having Low of the output of the converting circuit, the output of the decoder is delayed until the U/D counter has counted down to '0' the clock signal supplied by the clock signal supply control circuit. Therefore, even in the case where noise interferes the output of the converting circuit, since the output of the decoder is delayed until the count value of the U/D counter has reached the preset number or '0' in spite of switching of the operation of the U/D counter, it is not adversely affected by the noise. This results in improved anti-noise characteristics of the photocoupler.

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Nara, Japan

Yoshihiro Ohtsuka