ISOLATED SWITCHING CONVERTER WITH SECONDARY SIDE MODULATION AND CONTROL METHOD

摘要

A controller of an isolated switching converter includes an error amplifying circuit, a modulation signal generator, a first comparison circuit, a primary off detection circuit, a secondary logic circuit, an isolation circuit and a primary logic circuit. The error amplifying circuit generates a compensation signal based on the difference between a reference signal and a feedback signal. The first comparison circuit compares the compensation signal with a modulation signal generated by the modulation signal generator and generates a first comparison signal. The primary off detection circuit detects whether the primary switch is off and generates a primary off detection signal. The secondary logic circuit generates a secondary control signal to control the secondary switch based on the first comparison signal and the primary off detection signal. The isolation circuit receives the first comparison signal and generates a synchronous signal electrically isolated from the first comparison signal. The primary logic circuit generates a primary control signal to control the primary switch based on the synchronous signal.

主权项

1. A controller used in an isolated switching converter, wherein the isolated switching converter comprises a transformer having a primary winding and a secondary winding, a primary switch coupled to the primary winding and a secondary switch coupled to the secondary winding, the controller comprises:
an error amplifying circuit configured to receive a reference signal and a feedback signal indicative of an output signal of the isolated switching converter, wherein based on the difference between the reference signal and the feedback signal, the error amplifying circuit generates a compensation signal; a modulation signal generator configured to generate a modulation signal; a first comparison circuit coupled to the error amplifying circuit and the modulation signal generator, wherein the first comparison circuit compares the compensation signal with the modulation signal and generates a first comparison signal; a primary off detection circuit configured to detect whether the primary switch is off and generate a primary off detection signal; a secondary logic circuit coupled to the first comparison circuit and the primary off detection circuit, wherein based on the first comparison signal and the primary off detection signal, the secondary logic circuit generates a secondary control signal to control the secondary switch; an isolation circuit coupled to the first comparison circuit to receive the first comparison signal, wherein based on the first comparison signal, the isolation circuit generates a synchronous signal electrically isolated from the first comparison signal; and a primary logic circuit coupled to the isolation circuit to receive the synchronous signal, wherein based on the synchronous signal, the primary logic circuit generates a primary control signal to control the primary switch.