SWITCHING CONVERTER AND METHOD FOR PROTECTING IT FROM OVERLOAD

摘要

PROBLEM TO BE SOLVED: To protect a switching element and the entire circuit when an overcurrent appears in a resonance converter circuit. SOLUTION: When it is detected by a comparator 54 that the voltage appearing across an impedance element 53 in proportion to current which flows in a main circuit exceeds a specified threshold value 55, an oscillation frequency of an oscillator circuit is changed to a specified direction and thereby switching stress to be applied to a switching element is lessened. When it is detected by an overcurrent time measuring circuit 56 that an overcurrent state continues more than a first specified period of time, a pulse drive circuit is controlled by an intermittent oscillator circuit 57 and the power transmission is held down in such an intermittent driving state. Furthermore, when it is detected by an intermittent time measuring circuit 58 that the intermittent drive state continues more than a second specified period of time, the operation of a drive circuit 11 is stopped and thereby the operation of the entire circuit is stopped to protect the entire circuit.