| 摘要 |
PROBLEM TO BE SOLVED: To give fold-back current limiting characteristics to the load of a flyback switching power source by adding a simple circuit to the primary side of the power source. SOLUTION: In a control and protection circuit 40, a circuit composed of a reference power source 41, a comparator 42, a changeover switch 43, and resistances 44 and 45 is added and when the collector voltage of a transistor 8 of a photocoupler 9 as the feedback signal from a feedback circuit 6 exceeds the voltage of the reference power source 41, the changeover switch 43 is operated to the side of resistances 44 and 45 electrified from VCC to make the ON period of a power MOSFET 3 shorter and reduce the drain current, thereby giving the bent type drooping characteristics to the load connected across a capacitor 5.
|
