Patent ID: 9577531
Date: 2017-02-21
CPC Classifications: H02M,Y02B

Claim:
1. A control circuit, used for controlling a switching regulator of a buck-boost converter, the switching regulator having an inductor, a first switch, a second switch, a third switch, and a fourth switch, the inductor having a first end and a second end, an end of the first switch coupled to the first end, another end of the first switch configured for receiving an input voltage generated from an input end, an end of the second switch coupled to the first end, another end of the second switch coupled to ground, an end of the third switch coupled to the second end, another end of the third switch coupled to ground, an end of the fourth switch coupled to the second end, and another end of the fourth switch configured for transmitting an output voltage to an output end, the control circuit comprising: a feedback compensator, coupled between the fourth switch and the output end, configured for detecting the output voltage, and generating a compensation signal indicating the output voltage; a determining element, coupled to the feedback compensator, configured for receiving the compensation signal and a current signal flowing through the inductor, and determining whether the current signal is lower than the compensation signal, wherein when the current signal is lower than the compensation signal, the determining element generates a start signal; a mode selection element, configured for receiving the input voltage and the output voltage, wherein when a voltage difference between the input voltage and the output voltage is less than or equal to a predefined voltage, the mode selection element generates a buck-boost mode; a first controller, coupled to the determining element and the mode selection element, configured for generating a first signal with high level for a first predefined time according to the start signal in the buck-boost mode, and generating the first signal with low level after the first predefined time; a second controller, coupled to the determining element and the mode selection element, configured for generating a second signal with high level for a second predefined time according to the start signal in the buck-boost mode, and generating the second signal with low level after the second predefined time, wherein the first predefined time is more than the second predefined time; and a driving element, coupled to the mode selection element, the first controller, and the second controller, configured for turning on the first switch according to the first signal with high level and turning off the first switch according to the first signal with low level in the buck-boost mode, and configured for turning on the third switch according to the second signal with high level and turning off the third switch according to the second signal with low level in the buck-boost mode, wherein the first switch and the second switch are reversely switched, and the third switch and the fourth switch are reversely switched.