Method for a Current Mode Buck-Boost Converter

摘要

A current mode control buck-boost converter with improved performance utilizes separate buck and boost pulses. The buck-boost converter utilizes a buck/boost decision method with continuous control voltage for buck and boost mode, therefore eliminating transients in the control loop between operation modes and preventing voltage overshoots. If switching in Boost mode and the buck duty cycle is smaller than a set duty cycle, then in the next cycle Buck mode switching will occur. It is possible to track a Buck comparator output and the related duty cycle during Boost mode operation. Thus a mode change decision will only be dependent on a single input. A control loop will incorporate a single loop filter and error amplifier, wherein control voltages for Buck comparator and Boost comparator will be related.

主权项

1. A method to improve performance of buck-boost converters, the method comprising the steps of:
(1) providing a buck-boost regulator configured for current sensing and for generating a slope ramp for a buck-side comparator, comprising an error amplifier, a buck mode comparator, a boost mode comparator, circuitry to generate a control voltage of a boost-side comparator, and circuitry to generate a buck mode duty cycle; (2) utilizing current mode control for the buck-boost converter; (3) using separated buck mode and boost mode pulses; and (4) utilizing a buck-boost mode decision method with a continuous control voltage for both modes.