| 摘要 |
PURPOSE:To make the prevention of the breakdown of semiconductor elements possible by feeding the detected quantity of rectified output back to controlling circuits to operate a switching circuit in preference to the controlling circuits thereby turning off the elements according to the current values of the elements. CONSTITUTION:While the frequency of a switching circuit 2 is under controlling by the 1st controlling circuit 7, transistors 20, 21 are turned on and off successively while the outputs of (f), (g) are inverted with periods T1-T3 as half cycles. The off time TOFF formed fixedly by a timer 73 corresponds to the periods T1-T2 when the circuit 7 is under operation. When the 2nd controlling circuit 8 operates, first the output of a comparing amplifier 81 goes to a high level, and resets a pulse generator 71. At this moment, the supply of pulses from the generator 71 to a flip-flop (FF) 72 is stopped, and the operation of the circuit 7 is stopped as well. On the other hand, the FF72 is inverted by an amplifier 81, and the TRs which begin to flow abnormal currents are turned off. |
