| 摘要 |
PURPOSE:To make an improvement in efficiency and to protect an excess current by a method wherein the second comparison circuit, where the oscillation on an oscillation circuit is broken when the sum of the first comparison circuit output and a current detecting circuit output exceeds a reference voltage, is provided. CONSTITUTION:An output voltage VD and the first reference voltage V2 are compared, the first comparison circuits Q2 and R3 which turn out power in proportion to the deviation value obtained is provided and also a current detecting circuit R4 which detects a peak current iT of a choke transformer T is provided. And the second comparison circuits Q3 and R1 which apply a triggar signal to an oscillation circuit (base emitter of transistor Q1 on secondary wiring N2) when the sum of an output V2 of the R4 and an output V1 of the R3 exceeds the second reference voltage VBE, is provided. Thus the switching transistor Q1 can be interrupted speedily, efficiency is improved by reducing a power dissipation, an output voltage is turned to a drooping type characteristic when a load RL grows heavier and an overcurrent protecting function can be accomplished. |
