High efficiency bridgeless PFC power converter

1. A bridgeless PFC power converter comprising:

a first inductor, coupled from a first input-terminal to a first transistor;

a second inductor, coupled from a second input-terminal to a second transistor;

a first diode, coupled from the first transistor to an output capacitor;

a second diode, coupled from the second transistor to the output capacitor, in which the first transistor, the second transistor and the output capacitor are further coupled to a ground terminal;

a first capacitor, coupled from the first input-terminal to the ground terminal through a third transistor;

a second capacitor, coupled from the second input-terminal to the ground terminal through a fourth transistor; and

a control circuit, coupled to the output capacitor to receive a feedback signal, the control circuit coupled to the first input-terminal and the second-input terminal to receive a first-input signal and a second-input signal, the control circuit coupled to the first transistor and the second transistor for detecting a first-current signal and a second-current signal;

wherein the control circuit generates a first-switching signal and a second-switching signal to control the first transistor and the second transistor in response to the feedback signal, the first-input signal, the second-input signal, the first-current signal and the second-current signal, the second-switching signal will turn on the second transistor when the first-switching signal switches the first transistor, the first-switching signal will turn on the first transistor when the second-switching signal switches the second transistor; the control circuit further generates a light-load signal to turn off the third transistor and the fourth transistor during a light-load of the PFC power converter.

2. The bridgeless PFC power converter as claimed in claim 1 , wherein the control circuit generates an error signal in response to the feedback signal and a reference signal, the light-load signal is generated in response to the error signal and a threshold signal.

3. The bridgeless PFC power converter as claimed in claim 2 , wherein the control circuit generates an input signal in response to the first-input signal and the second-input signal.

4. The bridgeless PFC power converter as claimed in claim 3 , wherein the threshold signal is programmed by the input signal.

5. The bridgeless PFC power converter as claimed in claim 1 , wherein the control circuit comprises an arbiter circuit to generate a first-enable signal when the first-input signal is higher than a first threshold, the arbiter circuit generates a second-enable signal once the second-input signal is higher than a second threshold, the first-enable signal and the second-enable signal are exclusive, the first-enable signal and the second-enable signal are utilized for generating the first-switching signal and the second-switching signal.

6. The bridgeless PFC power converter as claimed in claim 1 , wherein the control circuit comprises a differential amplifier to generate a current signal for controlling the first-switching signal and the second-switching signal in response to the first-current signal and the second-current signal, the polarity of the differential amplifier is controlled by a first-enable signal and a second-enable signal.

7. The bridgeless PFC power converter as claimed in claim 1 , wherein the control circuit generates a switching signal in accordance with an error signal, a current signal and an input signal; the first-switching signal and the second-switching signal are generated in response to the switching signal, a first-enable signal and a second-enable signal.

8. The bridgeless PFC power converter as claimed in claim 7 , wherein the control circuit generates an over-current signal by comparing the current signal with a programmable signal, the programmable signal is determined by a current source and a resistor, the over-current signal is coupled to disable the switching signal.

9. The bridgeless PFC power converter as claimed in claim 7 , wherein the first-switching signal switches the first transistor in response to the switching signal and the second-switching signal will turn on the second transistor, the second-switching signal switches the second transistor in response to the switching signal and the first-switching signal will turn on the first transistor.

10. A bridgeless PFC power converter comprising:

a first inductor, coupled from a first input-terminal to a first-sense transistor;

a second inductor, coupled from a second input-terminal to a second-sense transistor;

a first diode, coupled from the first-sense transistor to an output capacitor;

a second diode, coupled from the second-sense transistor to the output capacitor, in which the first-sense transistor, the second-sense transistor and the output capacitor are further coupled to a ground terminal;

a control circuit, coupled to the output capacitor to receive a feedback signal, the control circuit coupled to the first input-terminal and the second input-terminal to receive a first-input signal and a second-input signal, the control circuit coupled to the first-sense transistor and the second-sense transistor for detecting a first-current signal and a second-current signal;

a first capacitor, coupled from the first input-terminal to the ground terminal through a third transistor; and

a second capacitor, coupled from the second input-terminal to the ground terminal through a fourth transistor;

wherein the control circuit generates a first-switching signal and a second-switching signal to control the first-sense transistor and the second-sense transistor in response to the feedback signal, the first-input signal, the second-input signal, the first-current signal and the second-current signal, the first-sense transistor has a sense-terminal to output the first-current signal, the second-sense transistor has a sense-terminal to output the second-current signal, the magnitude of the first-current signal is correlated to a current flowed through the first-sense transistor, the magnitude of the second-current signal is correlated to a current flowed through the second-sense transistor, the second-switching signal will turn on the second-sense transistor when the first-switching signal switches the first-sense transistor, the first-switching signal will turn on the first-sense transistor when the second-switching signal switches the second-sense transistor; the control circuit further generates a light-load signal to turn off the third transistor and the fourth transistor during a light-load of the PFC power converter.

11. The bridgeless PFC power converter as claimed in claim 10 , wherein the control circuit generates an error signal in response to the feedback signal and a reference signal, the light-load signal is generated in response to the error signal and a threshold signal, the control circuit further generates an input signal in response to the first-input signal and the second-input signal, the threshold signal is programmed by the input signal.

12. A bridgeless PFC power converter comprising:

a first inductor, coupled from a first input-terminal to a first-sense transistor;

a second inductor, coupled from a second input-terminal to a second-sense transistor;

a first diode, coupled from the first-sense transistor to an output capacitor;

a second diode, coupled from the second-sense transistor to the output capacitor, in which the first-sense transistor, the second-sense transistor and the output capacitor are further coupled to a ground terminal; and

a control circuit, coupled to the output capacitor to receive a feedback signal, the control circuit coupled to the first input-terminal and the second input-terminal to receive a first-input signal and a second-input signal, the control circuit coupled to the first-sense transistor and the second-sense transistor for detecting a first-current signal and a second-current signal;

wherein the control circuit generates a first-switching signal and a second-switching signal to control the first-sense transistor and the second-sense transistor in response to the feedback signal, the first-input signal, the second-input signal, the first-current signal and the second-current signal, the first-sense transistor has a sense-terminal to output the first-current signal, the second-sense transistor has a sense-terminal to output the second-current signal, the magnitude of the first-current signal is correlated to a current flowed through the first-sense transistor, the magnitude of the second-current signal is correlated to a current flowed through the second-sense transistor, the second-switching signal will turn on the second-sense transistor when the first-switching signal switches the first-sense transistor, the first-switching signal will turn on the first-sense transistor when the second-switching signal switches the second-sense transistor;

wherein the control circuit comprises an arbiter circuit to generate a first-enable signal when the first-input signal is higher than a first threshold, the arbiter circuit generates a second-enable signal once the second-input signal is higher than a second threshold, the first-enable signal and the second-enable signal are exclusive, the first-enable signal and the second-enable signal are utilized for generating the first-switching signal and the second-switching signal.

13. A bridgeless PFC power converter comprising:

a first inductor, coupled from a first input-terminal to a first-sense transistor;

a second inductor, coupled from a second input-terminal to a second-sense transistor;

a first diode, coupled from the first-sense transistor to an output capacitor;

a second diode, coupled from the second-sense transistor to the output capacitor, in which the first-sense transistor, the second-sense transistor and the output capacitor are further coupled to a ground terminal; and

a control circuit, coupled to the output capacitor to receive a feedback signal, the control circuit coupled to the first input-terminal and the second input-terminal to receive a first-input signal and a second-input signal, the control circuit coupled to the first-sense transistor and the second-sense transistor for detecting a first-current signal and a second-current signal;

wherein the control circuit generates a first-switching signal and a second-switching signal to control the first-sense transistor and the second-sense transistor in response to the feedback signal, the first-input signal, the second-input signal, the first-current signal and the second-current signal, the first-sense transistor has a sense-terminal to output the first-current signal, the second-sense transistor has a sense-terminal to output the second-current signal, the magnitude of the first-current signal is correlated to a current flowed through the first-sense transistor, the magnitude of the second-current signal is correlated to a current flowed through the second-sense transistor, the second-switching signal will turn on the second-sense transistor when the first-switching signal switches the first-sense transistor, the first-switching signal will turn on the first-sense transistor when the second-switching signal switches the second-sense transistor;

wherein the control circuit comprises a differential amplifier to generate a current signal for controlling the first-switching signal and the second-switching signal in response to the first-current signal and the second-current signal, the polarity of the differential amplifier is controlled by a first-enable signal and a second-enable signal.

14. A bridgeless PFC power converter comprising:

a first inductor, coupled from a first input-terminal to a first-sense transistor;

a second inductor, coupled from a second input-terminal to a second-sense transistor;

a first diode, coupled from the first-sense transistor to an output capacitor;

a second diode, coupled from the second-sense transistor to the output capacitor, in which the first-sense transistor, the second-sense transistor and the output capacitor are further coupled to a ground terminal; and

a control circuit, coupled to the output capacitor to receive a feedback signal, the control circuit coupled to the first input-terminal and the second input-terminal to receive a first-input signal and a second-input signal, the control circuit coupled to the first-sense transistor and the second-sense transistor for detecting a first-current signal and a second-current signal;

wherein the control circuit generates a first-switching signal and a second-switching signal to control the first-sense transistor and the second-sense transistor in response to the feedback signal, the first-input signal, the second-input signal, the first-current signal and the second-current signal, the first-sense transistor has a sense-terminal to output the first-current signal, the second-sense transistor has a sense-terminal to output the second-current signal, the magnitude of the first-current signal is correlated to a current flowed through the first-sense transistor, the magnitude of the second-current signal is correlated to a current flowed through the second-sense transistor, the second-switching signal will turn on the second-sense transistor when the first-switching signal switches the first-sense transistor, the first-switching signal will turn on the first-sense transistor when the second-switching signal switches the second-sense transistor;

wherein the control circuit generates a third switching signal in accordance with an error signal, a current signal and an input signal, the first-switching signal and the second-switching signal are generated in response to a first-enable signal, a second-enable signal and the third switching signal.

15. The bridgeless PFC power converter as claimed in claim 14 , wherein the control circuit generates an over-current signal by comparing the current signal with a programmable signal, the programmable signal is determined by a current source and a resistor, the over-current signal is coupled to disable the third switching signal.

16. The bridgeless PFC power converter as claimed in claim 14 , wherein the first-switching signal switches the first-sense transistor in response to the third switching signal and the second-switching signal will turn on the second-sense transistor, the second-switching signal switches the second-sense transistor in response to the third switching signal and the first-switching signal will turn on the first-sense transistor.

17. A bridgeless PFC power converter comprising:

a first inductor, coupled from a first input-terminal to a first-sense transistor;

a second inductor, coupled from a second input-terminal to a second-sense transistor;

a first diode, coupled from the first-sense transistor to an output capacitor;

a second diode, coupled from the second-sense transistor to the output capacitor, in which the first-sense transistor, the second-sense transistor and the output capacitor are further coupled to a ground terminal; and

a control circuit, coupled to the output capacitor to receive a feedback signal, the control circuit coupled to the first input-terminal and the second input-terminal to receive a first-input signal and a second-input signal, the control circuit coupled to the first-sense transistor and the second-sense transistor for detecting a first-current signal and a second-current signal;

wherein the control circuit generates a first-switching signal and a second-switching signal to control the first-sense transistor and the second-sense transistor in response to the feedback signal, the first-input signal, the second-input signal, the first-current signal and the second-current signal, the first-sense transistor has a sense-terminal to output the first-current signal, the second-sense transistor has a sense-terminal to output the second-current signal, the magnitude of the first-current signal is correlated to a current flowed through the first-sense transistor, the magnitude of the second-current signal is correlated to a current flowed through the second-sense transistor, the second-switching signal will turn on the second-sense transistor when the first-switching signal switches the first-sense transistor, the first-switching signal will turn on the first-sense transistor when the second-switching signal switches the second-sense transistor;

each sense transistor comprises:

a first transistor, coupled to the first inductor or the second inductor;

a second transistor, coupled to the first transistor and the control circuit; and

a resistor, coupled between the first transistor and the second transistor;

wherein the sense-terminal is a joint of the second transistor and the resistor to sense the current flowed through the first transistor of the sense transistor and output the first-current signal or the second-current signal, the magnitude of the first-current signal or the second-current signal is correlated to the current flowed through the first transistor of the sense transistor.