| 摘要 |
PROBLEM TO BE SOLVED: To provide a current mode control type step-up converter wherein a minimum duty ratio can be reduced to a sufficiently small value and a maximum duty ratio can be easily set. SOLUTION: The step-up converter includes: a current detector 9 that generates a current detection signal Vc corresponding to the current of a rectifier 4; an error amplifier 8 that generates an error signal Ve corresponding to output direct-current voltage Vo; and a control circuit 10 that turns on/off a main switch 3 based on the current detection signal Vc and the error signal Ve. The control circuit 10 includes a comparator 11 and a timer circuit 12. With this construction, the on time of the main switch 3 is set to a predetermined value and the valley value of an inductor current that increases and decreases like a triangular wave is controlled. Therefore, it is the off time of the main switch to be adjusted for output stabilization. The on time of the main switch can be freely set, and the minimum duty ratio can be reduced to zero or a sufficiently small value. COPYRIGHT: (C)2008,JPO&INPIT
|
