| 摘要 |
PROBLEM TO BE SOLVED: To obtain a protective circuit which can protect the power factor improving circuit of a PWM controller without stopping the operations of the power factor improving circuit, when an overcurrent occurs in the power factor improving circuit. SOLUTION: A protective circuit is provided with a PWM controller 11 having a switch element 5, a current detector which detects the current flowing to the controller 11, a current level setter 13 which sets the current to first and second current levels, a comparator 14 which compares the set current level values with detected current values, an operation interrupter 15 which interrupts the operation of the switch element 5 within one period of the carrier of the controller 11 when the current value is equal to or higher than the first current level and lower than the second current level, and an interruption canceler 16 which cancels the interrupting operation of the interrupter 15 whenever each cycle of the carrier is started. The interrupter 15 inhibits the interruption cancellation of the interruption canceler 16, when the detected current value is equal to or higher than the second input current level. |
