Control circuit for reducing touch current of a power converter and operation method thereof

摘要

A control circuit for reducing touch current of a power converter includes an auxiliary pin, a zero-crossing signal generator, a frequency limiting signal generator, and a gate signal generator. The auxiliary pin is used for receiving a voltage generated by an auxiliary winding of the power converter. The zero-crossing signal generator is used for generating a zero-crossing signal according to the voltage generated by the auxiliary winding and a first reference voltage. The frequency limiting signal generator is used for generating a frequency limiting signal according to a gate control signal, a burst mode signal, and the voltage generated by the auxiliary winding. The frequency limiting signal is used for limiting the gate control signal to a predetermined frequency. The gate signal generator is used for generating the gate control signal to a power switch of the power converter according to the frequency limiting signal and the zero-crossing signal.

主权项

1. A control circuit for reducing touch current of a power converter, wherein the power converter is a power factor correction (PFC) power converter, the control circuit comprising:
an auxiliary pin for receiving a voltage generated by an auxiliary winding of the power converter; a zero-crossing signal generator for generating a zero-crossing signal according to the voltage generated by the auxiliary winding and a first reference voltage; a frequency limiting signal generator for generating a frequency limiting signal according to a gate control signal, a burst mode signal, and the voltage generated by the auxiliary winding, wherein the frequency limiting signal is used for limiting the gate control signal to a predetermined frequency; a gate signal generator for generating the gate control signal to a power switch of the power converter according to the frequency limiting signal and the zero-crossing signal; a feedback pin for receiving a feedback voltage corresponding to an output voltage of the power converter, wherein the feedback voltage corresponds to a load coupled to the power converter; a compensation voltage generation unit for generating a compensation voltage according to the feedback voltage and a second reference voltage; and a burst mode signal generation module, comprising:
a first comparator for generating a first comparison result according to the compensation voltage and a burst mode reference voltage; anda signal generation unit for generating the burst mode signal to the gate signal generator according to the first comparison result;wherein the gate signal generator further generates the gate control signal to the power switch according to the burst mode signal and the zero-crossing signal.