Switching controller with burst mode management circuit to reduce power loss and acoustic noise of power converter

1. A switching controller of power converter, comprising:

an oscillator generating a feedback signal and a pulse signal in response to an output of the power converter;

a PWM circuit receiving the pulse signal to generate a PWM signal;

a burst-mode management circuit receiving the feedback signal and the PWM signal to generate a switching signal and a current-limit signal, the switching signal generating a switching current and regulating the output of the power converter; and

a current-limit comparator coupled to the burst-mode management circuit and a current-sense device for limiting the switching current to decrease a switching frequency or stop switching of the power converter in response to the current-limit signal and a current signal, the current signal being correlated to the switching current.

2. The switching controller of power converter as claimed in claim 1 , further comprising a feedback circuit providing a voltage signal to the oscillator for generating the feedback signal in response to a feedback voltage, the feedback voltage being correlated to the output of the power converter.

3. The switching controller of power converter as claimed in claim 2 , wherein the oscillator comprises:

a feedback converter converting the voltage signal into the feedback signal; and

a pulse signal generator generating the pulse signal in response to the voltage signal.

4. The switching controller of power converter as claimed in claim 1 , wherein the burst-mode management circuit comprises:

a skip circuit generating an acoustic signal in response to the feedback signal;

a logic circuit receiving the PWM signal and the acoustic signal to generate the switching signal;

a timing circuit generating a control signal in response to the acoustic signal; and

a current-limit circuit generating the current-limit signal in response to the control signal.

5. The switching controller of power converter as claimed in claim 4 , wherein the acoustic signal is disabled when the feedback signal is lower than a light-load threshold for turning off the switching signal.

6. The switching controller of power converter as claimed in claim 4 , wherein the control signal is enabled when the acoustic signal is disabled, the current-limit signal is decreased to limit the switching current when the control signal is enabled.

7. The switching controller of power converter as claimed in claim 6 , wherein the current-limit signal is increased gradually when the control signal is disabled.

8. The switching controller of power converter as claimed in claim 4 , wherein the current-limit circuit comprises:

a soft-start capacitor;

a charging current charging the soft-start capacitor;

a first amplifier discharging the soft-start capacitor;

a switch coupled between the soft-start capacitor and the first amplifier and controlled by the control signal; and

a second amplifier coupled to the soft-start capacitor for generating the current-limit signal in response to an output of the soft-start capacitor.

9. The switching controller of power converter as claimed in claim 8 , wherein the first amplifier has a limit signal, the current-limit signal is decreased to the limit signal for limiting the switching current when the control signal is enabled.

10. The switching controller of power converter as claimed in claim 1 , wherein the PWM circuit turns off the PWM signal in response to the current signal and a maximum threshold or the output of the power converter.