Control circuit and method for buck-boost power converter

Abstract

The invention provides a control circuit for a buck-boost power converter. The control circuit is used for providing a control signal so as to drive the buck-boost power level and convert an input voltage into an output voltage. The buck-boost power level includes an inductor and at least two switches connected with the inductor. The control circuit is characterized by comprising a feedback circuit, an error amplifier, a dynamic work cycle generator and a driving circuit, the feedback circuit detects a feedback signal generated by the output voltage, the error amplifier is connected with the feedback circuit and used for amplifying the difference between the feedback circuit and a reference voltage and generating an error signal, the dynamic work cycle generator generates a first signal according to a detection signal after being started, and the driving circuit connects the error amplifier with the dynamic work cycle generator and determines the control signal according to the error signal and the first signal. The control circuit and method for the buck-boost power converter have the advantages that the switching sequence of the switches is optimized, switching loss is reduced, efficacy is improved, and output ripples are reduced.

Description

technical field [0001] The invention relates to a buck-boost power converter, in particular to a control circuit and method for a buck-boost power converter. Background technique [0002] figure 1 A known synchronous buck-boost power converter 10 is shown, which includes a buck-boost power stage 12 and a control circuit 22 that provides signals VA, VB, VC, and VD to switch switches SWA in the buck-boost power stage 12, respectively. , SWB, SWC and SWD to convert the input voltage Vin to the output voltage Vo. In the control circuit 14, the resistors R1 and R2 divide the output voltage Vo to generate the feedback signal VFB, and the error amplifier 24 amplifies the difference between the feedback signal VFB and the reference voltage Vref to generate the signal VCL to the signal generator 22, and the signal generator 22 provides signals VU, VX and VY, wherein the signal VU is related to the signal VCL, the signals VX and VY are sawtooth wave signals, the comparator 18 compar...

AI Technical Summary

Problems solved by technology

In addition, when the signal VU rises or falls and approaches the peak value of the signal VX or the valley value of the signal VY, the duty cycle of the signal VB or VC will be very short, so the switch SWB or SWC may not be fully turned on (turn on) It turns off again, which serves no purpose other than increasing the switching loss

[0004] U.S. Patent No. 7,176,667 also proposes a control circuit for a buck-boost power converter, which uses a pulse width modulation signal that adjusts the pulse width with the output voltage Vo and a signal with a fixed pulse width to determine the switch in the buck-boost mode. Switching of SWA, SWB, SWC and SWD, however, this method of inserting a fixed pulse width signal may cause discontinuous duty cycles during mode conversion, resulting in large output ripples

[0005] Therefore, there are above-mentioned inconveniences and problems in the control circuit of the known buck-boost power converter.

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