| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To surely detect a light-load state. <P>SOLUTION: A first controller 10 generates a first pulse signal S<SB POS="POST">PWM</SB>. A second controller 20 generates a second pulse signal S<SB POS="POST">PFM</SB>. A driver 30 drives a switching transistor M1 and a synchronous rectification transistor M2 on the basis of the first pulse signal S<SB POS="POST">PWM</SB>in a normal mode and on the basis of second pulse signal S<SB POS="POST">PFM</SB>in a light-load mode. A light-load detection comparator 40 generates a comparison signal S1 that is asserted when a detection current I<SB POS="POST">M1</SB>flowing through the switching transistor M1 exceeds a first threshold current I<SB POS="POST">TH1</SB>. A control circuit 100 is set to be the normal mode when the comparison signal S1 is asserted, and set to be the light-load mode when the comparison signal S1 is not asserted. <P>COPYRIGHT: (C)2013,JPO&INPIT</p> |
