Switch mode power supply system with dual ramp compensation associated controller and method

摘要

A switch mode power supply system has a constant on-time signal generator, a logic circuit, a feedback circuit, a first ramp signal generator, a second ramp signal generator, a switch circuit having a power switch, and a comparator. A feedback signal from the feedback circuit is compensated by the first ramp signal generator, and a reference signal is compensated by the second ramp signal generator. The comparator compares the compensated feedback signal with the compensated reference signal to indicate an off time of the power switch while the constant on-time signal generator decides the on-time of the power switch.

主权项

1. A controller for controlling a switch mode power supply system, wherein the switch mode power supply system comprises a switch circuit that comprises a power switch, and wherein the controller comprises:
a feedback circuit, coupled to an output of the switch mode power supply system, configured to generate a feedback signal that is based on an output signal of the switch mode power supply system; a first ramp signal generator, coupled to the switch circuit, configured to generate a first ramp signal, the first ramp signal generator compensating the feedback signal with the first ramp signal to generate a compensated feedback signal; a comparator, having an inverting terminal receiving the compensated feedback signal, and a non-inverting terminal coupled to a reference signal, and an output terminal generating a comparative result; a constant on-time signal generator, generating a constant on-time signal; a logic circuit, coupled to the constant on-time signal generator and the output terminal of the comparator, configured to generate a control signal to control the power switch turning ON and OFF; and a second ramp signal generator, configured to generate a second ramp signal according to the control signal, wherein the reference signal is compensated by the second ramp signal before provided to the comparator, so as to make an average value of the compensated feedback signal be equal to the reference signal.