CURRENT LIMIT MODULE AND CONTROL MODULE FOR POWER CONVERTERS AND ASSOCIATED METHOD

摘要

A power converter having a current limit module and a method for controlling the power converter. The power converter converts an input voltage to an output voltage based at least on driving a main switch to switch on and off and regulates the output voltage through regulating a duty cycle of the main switch. The current limit module is configured to compensate a first current limit threshold indicative of a maximum allowable value of a peak value of a switching current of the main switch with a threshold compensation signal indicative of the duty cycle to provide a second current limit threshold. The second current limit threshold is used to limit the maximum value of the peak value, so that a maximum allowable output power of the power converter is substantially uninfluenced by the variation in the duty cycle.

主权项

1. A current limit module for a power converter, wherein the power converter comprises a main switch and is configured to convert an input voltage to an output voltage based on driving the main switch to switch on and off in response to a pulse width modulated signal, and wherein a switching current flows through the main switch, and wherein the percentage of the on time of the main switch in a switching cycle is referred to as a duty cycle, the current limit module comprising:
a threshold compensation circuit having a first compensation input terminal, a second compensation input terminal and a compensation output terminal, wherein the first compensation input terminal is configured to receive a first current limit threshold indicative of a maximum allowable value of a peak value of the switching current, and wherein the second compensation input terminal is configured to receive a threshold compensation signal indicative of the duty cycle, and wherein the threshold compensation circuit is configured to superpose the threshold compensation signal with the first current limit threshold to provide a second current limit threshold at the compensation output terminal; and a current limit comparison circuit having a first comparison input terminal, a second comparison input terminal and a comparison output terminal, wherein the first comparison input terminal is configured to receive a second current sense signal indicative of the switching current with ramp compensation, and wherein the second comparison input terminal is configured to receive the second current limit threshold, and wherein the current limit comparison circuit is configured to compare the second current sense signal with the second current limit threshold to generate a second comparison signal at the comparison output terminal, and wherein the second comparison signal triggers the pulse width modulated signal to turn the main switch off when the second current sense signal exceeds the second current limit threshold.