LIMIT-TO-VALLEY RATIO CIRCUITRY IN POWER CONVERTERS

摘要

A controller for a switched mode power converter includes limit-to-valley ratio circuitry, an on-time generator, and a drive circuit. The limit-to-valley ratio circuitry is coupled to generate a ratio signal in response to sensing a switch current of a switch that regulates an output of the switched mode power converter. The ratio signal is representative of a time ratio between a first length of time that the switch current is at or above a switch current limit and a second length of time that the switch current is at or below a switch current valley that is a portion of the switch current limit. The on-time generator is coupled to vary a switch on-time signal in response to receiving the ratio signal. The drive circuit is coupled to output a drive signal to a control terminal of the switch in response to receiving the switch on-time signal.

主权项

1. A switched mode power converter comprising:
a switch; an energy transfer element coupled to the switch; and a controller coupled to the switch to regulate an output of the switched mode power converter, wherein the controller includes:
limit-to-valley ratio circuitry coupled to generate a ratio signal in response to sensing a switch current of the switch, wherein the ratio signal is representative of a time ratio between a first length of time that the switch current is at or above a switch current limit and a second length of time that the switch current is at or below a switch current valley that is a portion of the switch current limit;an on-time generator coupled to vary a switch on-time signal in response to receiving the ratio signal; anda drive circuit coupled to output a drive signal to a control terminal of the switch in response to receiving the switch on-time signal.