| 摘要 |
<P>PROBLEM TO BE SOLVED: To enhance power supply conversion efficiency under light-load by easily changing the light-load detection level, or the switching stop period in a switching element. <P>SOLUTION: When the voltage level VFB of a feedback terminal FB becomes light-load level, a light-load detection comparator OP2 turns a transistor Q5 off, and a current I1 is compensated from a resistor R1. Voltage drop of the resistor R1 increases by "current I1×resistor R1", and the voltage level VFB becomes "resistor R2×current I2-resistor R2×current I1". The voltage drop "resistor R1×current I1" increased by the resistor R1 becomes the hysteresis voltage for adjusting the switching off period of a switching transistor. When the resistance of a resistor R5 connected with the adjustment signal terminal adj of a drive signal controller 10 is decreased, the current I1 flowing through a transistor Q3 increases. Since the hysteresis voltage increases, the switching off period of a transistor can be prolonged. <P>COPYRIGHT: (C)2013,JPO&INPIT |
