| 摘要 |
<p>A photoelectrical switching circuit (l000) suitable for circuit integration and circuit-size reduction for producing a pulse-modulated light according to light emission pulse signals (gl) and detecting presence of an object by checking if the light is interrupted or reflected by the object, comprises a frequency divider circuit (200) and a signal output circuit (500) and may comprise further a control circuit (600). The frequency divider circuit (200) includes a counter formed by flip-flop and an operation stop circuit, wherein the counter generates light emission pulse signals with variable period and read pulse signals to pick up light sensing signals (p) and outputting the state of the final stage flip-flop as an operation signal, and the operation stop circuit stops the operation of the final stage flip-flop after the operation signal is input. The signal output circuit (500) which provides output signals after the operation signal is input, includes a shift register for shifting the light sensing signals (p) in step with clock pulses (a), a set output AND circuit (549), and a reset output AND circuit (553). The output AND circuit provides a logical product of a set output of the final stage and a set output of the m-th stage of the shift register to direct set terminals of the m + l-th and subsequent stages of the shift register, the reset output AND circuit (553) performs the same operation with the reset outputs and the reset terminals of the shift register, and then the signal output circuit (500) outputs output signals of the final stage of the shift register. The control circuit for making the period of pulse signals of the frequency divider circuit (200) fixed for a predetermined length of time. <IMAGE></p> |
