| 摘要 |
PURPOSE:To decrease the time for reconduction at overcurrent by detecting the presence of an overcurrent detection signal synchronously with a detection pulse having a period shorter than that of a projected optical pulse after the input of a first projected optical pulse. CONSTITUTION:A pulse generating circuit 5 generates a projected optical pulse P7a and a detection pulse P7b having a shorter period than that of the pulse P7a. An overcurrent detection circuit 14 detects an overcurrent of an output switching element 1 to output an overcurrent detection signal S14. An overcurrent discrimination circuit 15 detects the presence of the signal S14 synchronously with the pulse P7b after the input of a first pulse P7a after the input of a reception signal S12 and outputs an interruption signal S17 in case of the 'presence'. A counter 19 outputs a counter signal S19 when a prescribed number of the pulses P7a is counted and reset by the signal S17. A state discriminating circuit 21 outputs a drive signal S24 turning on the element 1 immediately after the signal S12 is inputted, stops the output of the signal S24 when the signal S17 is inputted and outputs the signal S24 on the condition of the input of the signal S12 when the signal S19 is inputted. Thus, the element 1 is turned off with a delay of nearly one projected period after the element 1 is turned on. Then the signal S24 is outputted at every input of the signal S19 to turn on the element 1 and to turn off the element 1 synchronously with the pulse P7b. |
