Method and apparatus of providing synchronous regulation circuit for offline power converter

A synchronous regulation circuit for offline power converter, comprising:

• a secondary-side switching circuit coupled to the output of the power converter to generate a pulse signal and a synchronous signal in response to a feedback signal;
• a primary-side switching circuit generating a switching signal coupled to switch a transformer in response to the synchronous signal;
• a power switch set coupled from the transformer to the output of the power converter;
• a control circuit coupled to receives the pulse signal for turning on or off the power switch, wherein the feedback signal is correlated to the output of the power converter, the pulse signal is a first differential signal and coupled to control the power switch set for rectifying and regulating the power converter, the synchronous signal is also a second differential signal coupled from the secondary-side switching circuit to the primary-side switching circuit through an isolation device to generate the switching signal.

A synchronous regulation method, comprising:

• generating a synchronous signal and a pulse signal in response to a feedback signal and an oscillation signal;
• transferring the synchronous signal through an isolation barrier;
• generating a switching signal to switch a transformer in response to the synchronous signal;
• transferring the pulse signal to a latch;
• setting or resetting the latch in response to the polarity of the pulse signal;
• and
• turning on or off a power switch set in accordance with the status of the latch, wherein the feedback signal is correlated to the output of the power converter, and the power switch set is coupled between the transformer and the output of the power converter for rectifying and the regulation.