Synchronous rectifier control circuits of power converters
View Patent ↗A synchronous rectifying control circuit of a power converter is provided. The synchronous rectifying control circuit comprises a synchronous rectifying driver, a charge pump capacitor, and a capacitor. The synchronous rectifying driver is coupled to a transformer for generating a control signal to switch a transistor. The charge pump capacitor is coupled to a power source for generating a charge pump voltage. The capacitor is coupled to store the charge pump voltage. The transistor is coupled to the transformer and operated as a synchronous rectifier. The charge pump voltage is coupled to guarantee a sufficient driving capability for the control signal.
1. A synchronous rectifying control circuit with charge pump of a power converter, comprising:
a synchronous rectifying driver, coupled to a transformer for generating a control signal to switch a transistor;
a charge pump capacitor, coupled to a power source;
a plurality of switches, when a voltage level of said power source is lower than a threshold, coupled to charge said charge pump capacitor by said power source in a switching manner to generate a charge pump voltage for charge pump; and
a capacitor, coupled to store said charge pump voltage;
wherein said transistor is coupled to said transformer and operated as a synchronous rectifier; and
wherein said charge pump voltage is coupled to guarantee a sufficient driving capability for said control signal.
2. The synchronous rectifying control circuit as claimed in claim 1 further comprising an oscillator generating an oscillation signal for said switching manner.
3. The synchronous rectifying control circuit as claimed in claim 1 further comprising:
a detection circuit, coupled to detect said voltage level of said power source;
wherein said detection circuit generates a detection signal when said voltage level of said power source is higher than said threshold; and
wherein said detection signal is coupled to disable said charge pump and delivering said power source to said capacitor.
4. The synchronous rectifying control circuit as claimed in claim 1 , wherein said control signal is disabled when said charge pump voltage is lower than a low-voltage threshold.
5. The synchronous rectifying control circuit as claimed in claim 1 , wherein said control signal is enabled when said charge pump voltage is higher than a high-voltage threshold.
6. A control circuit for synchronous rectifying of a power converter, comprising:
a synchronous rectifying driver, coupled to a transformer to generate a control signal for switching a transistor;
a boost inductor, coupled to a power source;
a switch; when a voltage level of said power source is lower than a threshold, coupled to switch said boost inductor for a boost switching operation so as to charge said boost inductor by said power source to generate a boosted voltage;
a capacitor, coupled to store said boosted voltage;
wherein said transistor is coupled to said transformer and operated as a synchronous rectifier; and
wherein said boosted voltage is coupled to guarantee a sufficient driving capability for said control signal.
7. The control circuit as claimed in claim 6 further comprising:
a detection circuit, coupled to detect said voltage level of said power source;
wherein said detection circuit generates a detection signal when said voltage level of said power source is higher than said threshold; and
wherein said detection signal is coupled to disable said boost switching operation and delivering said power source to said capacitor.
8. The control circuit as claimed in claim 6 further comprising an oscillator generating an oscillation signal for switching said boost inductor.
9. The control circuit as claimed in claim 6 , wherein said control signal is disabled when said boosted voltage is lower than a low-voltage threshold.
10. The control circuit as claimed in claim 6 , wherein said control signal is enabled when said boosted voltage is higher than a high-voltage threshold.