Synchronous rectifier controller and control method used for adjusting a voltage of a control terminal of a rectifier switch

A synchronous rectifier controller for controlling a rectifier switch, the rectifier switch comprising a control terminal, the synchronous rectifier controller comprising:

• a voltage regulator comprising an output terminal configured to provide a control voltage to the control terminal of the rectifier switch, the voltage regulator further comprising:
• a comparator configured to receive a channel voltage of the rectifier switch and compare the channel voltage with a threshold voltage to output a comparison result signal, wherein the comparison result signal has a first logic value when the channel voltage is higher than the threshold voltage, and the comparison result signal has a second logic value different from the first logic value when the channel voltage is lower than the threshold voltage;
• a first inverter configured to receive the comparison result signal and invert the comparison result signal to generate an inverted comparison result signal complementary to the comparison result signal;
• a waveform slope detection circuit configured to receive the channel voltage of the rectifier switch, and generate a waveform slope signal accordingly, wherein the waveform slope signal has a third logic value when a waveform of the channel voltage is rising, and the waveform slope signal has a fourth logic value when the waveform of the channel voltage is falling;
• a second inverter configured to receive the waveform slope signal and invert the waveform slope signal to generate an inverted waveform slope signal complementary to the waveform slope signal;
• a main pull-up power supply coupled to the output terminal of the voltage regulator and configured to pull up the control voltage;
• a main pull-down power supply coupled to the output terminal of the voltage regulator and configured to pull down the control voltage;
• an auxiliary pull-up power supply coupled to the output terminal of the voltage regulator and configured to simultaneously pull up the control voltage with the main pull-up power supply;
• and
• an auxiliary pull-down power supply coupled to the output terminal of the voltage regulator and configured to simultaneously pull down the control voltage with the main pull-down power supply;
• wherein one of the comparison result signal and the inverted comparison result signal is used to enable the main pull-up power supply, the other one of the comparison result signal and the inverted comparison result signal is used to enable the main pull-down power supply, one of the waveform slope signal and the inverted waveform slope signal is used to enable the auxiliary pull-up power supply, and the other one of the waveform slope signal and the inverted waveform slope signal is used to enable the auxiliary pull-down power supply.

A control method of a synchronous rectifier controller, the synchronous rectifier controller comprising a voltage regulator, the voltage regulator providing a control voltage to a control terminal of a rectifier switch to control the rectifier switch, the control method comprising:

• comparing a channel voltage of the rectifier switch with a threshold voltage to output a comparison result signal, wherein the comparison result signal has a first logic value when the channel voltage is higher than the threshold voltage, and the comparison result signal has a second logic value different from the first logic value when the channel voltage is lower than the threshold voltage;
• generating an inverted comparison result signal according to the comparison result signal, wherein the inverted comparison result signal is complementary to the comparison result signal;
• enabling a pull-up power supply by using the inverted comparison result signal to pull up the control voltage when the channel voltage is lower than the threshold voltage;
• and
• enabling a pull-down power supply by using the comparison result signal to pull down the control voltage when the channel voltage is higher than the threshold voltage.

A control method of a synchronous rectifier controller, the synchronous rectifier controller comprising a voltage regulator, the voltage regulator providing a control voltage through an output terminal, the control voltage being provided to a control terminal of a rectifier switch to control the rectifier switch, the control method comprising:

• comparing a channel voltage of the rectifier switch with a threshold voltage to output a comparison result signal, wherein the comparison result signal has a first logic value when the channel voltage is higher than the threshold voltage, and the comparison result signal has a second logic value different from the first logic value when the channel voltage is lower than the threshold voltage;
• generating an inverted comparison result signal according to the comparison result signal, wherein the inverted comparison result signal is complementary to the comparison result signal;
• outputting a waveform slope signal according to the channel voltage of the rectifier switch, wherein the waveform slope signal has a third logic value when a waveform of the channel voltage is rising, and the waveform slope signal has a fourth logic value when the waveform of the channel voltage is falling;
• generating an inverted waveform slope signal according to the waveform slope signal, wherein the inverted waveform slope signal is complementary to the waveform slope signal;
• selectively enabling a main pull-up power supply by using one of the comparison result signal and the inverted comparison result signal to pull up the control voltage, and selectively enabling a main pull-down power supply by using the other one of the comparison result signal and the inverted comparison result signal to pull down the control voltage;
• and
• selectively enabling an auxiliary pull-up power supply by using one of the waveform slope signal and the inverted waveform slope signal to simultaneously pull up the control voltage with the main pull-up power supply, and selectively enabling an auxiliary pull-down power supply by using the other one of the waveform slope signal and the inverted waveform slope signal to simultaneously pull down the control voltage with the main pull-down power supply.