Patent ID: 8198880
Filing Date: 2012-06-12
Classification: H02M

Abstract:
1. A control circuit for constant on-time converters, comprising: a timer for providing timing signal with a constant time; a minimum off-time circuit for providing a minimum off-time signal; a feedback loop for feeding back the output signal of the converter and providing a feedback signal; a comparison circuit for providing a comparison signal in response to the feedback signal, a reference signal and a compensation signal; a logic circuit for providing a logical signal in response to the timing signal, the minimum off-time signal and the comparison signal; wherein the logic circuit comprises: a first AND gate, operable to receive the minimum off-time signal and the comparison signal; an inverter, coupled to the output terminal of the first AND gate, operable to provide an inverted signal; a second AND gate, operable to receive the timing signal and the inverted signal; a RS flip-flop, operable to provide the logical signal in response to the output signals of the first AND gate and the second AND gate, a driver for providing driving signals to the output stage of the converter in response to the logical signal; and a compensation circuit for providing the compensation signal, wherein the compensation circuit comprise a first current source, a second current source, a first switch, a second switch, and a capacitor, wherein the first current source, the first switch and the capacitor are coupled in series, the second switch and second current source are coupled in parallel with the capacitor.