CIRCUIT FOR DETECTING ABNORMAL OPERATION IN SWITCH DRIVEN POWER SUPPLY

摘要

PURPOSE: A circuit for detecting abnormal operation in a switch driven power supply is provided to monitor output voltage of the power supply directly and simply to protect primary input circuit and secondary output circuit. CONSTITUTION: A circuit for detecting abnormal operation in a switch driven power supply has the photo coupler(210), the counter part(220) and frequency abnormality detecting part. The photo coupler(210) is supplied with the square wave switched in the power supply as input signal. The counter part(220) executes the operation of counting numbers of pulse represented at the output terminal of the photo coupler(210) for define interval periodically. The frequency abnormality detecting part compares the counted value and predefined value and outputs the abnormal operation signal when the counted value is got out of the predefined value.