Buck-boost PFC converters
View Patent ↗A buck-boost PFC converter is provided and includes an inductor, first and second transistors, a first diode, and a control circuit. The inductor has a first terminal and a second terminal. The first transistor is coupled to a positive-power rail and the first terminal of the inductor. The second transistor is coupled to the second terminal of the inductor and a negative-power rail. The first diode is connected from the second terminal of the inductor to an output of the buck-boost PFC converter. The control circuit generates a first signal and a second signal coupled to control the first transistor and the second transistor respectively. The first signal is utilized to turn on the first transistor for conducting the positive-power rail to the inductor. The second signal is utilized to turn on the second transistor for conducting the inductor to the negative-power rail.
1. A buck-boost PFC converter comprising:
an inductor having a first winding and a second winding, and the first and second winding having a first terminal and a second terminal, respectively;
a first transistor coupled to a positive-power rail and the first terminal of the first winding of the inductor, wherein a sine wave signal is provided to the positive-power rail;
a second transistor coupled to the second terminal of the first winding of the inductor and a negative-power rail;
a first diode connected from the second terminal of the first winding of the inductor to an output of the buck-boost PFC converter;
a second diode connected from the first terminal of the first winding of the inductor to the negative-power rail; and
a control circuit generating a first signal and a second signal coupled to control the first transistor and the second transistor respectively;
wherein the first signal is utilized to turn on the first transistor for conducting the positive-power rail to the inductor, and the second signal is utilized to turn on the second transistor for conducting the inductor to the negative-power rail.
2. The PFC converter as claimed in claim 1 , in which the first transistor and the second transistor are switched on/off simultaneously.
3. The PFC converter as claimed in claim 1 , wherein the second winding generates a reflected signal coupled to the control circuit, and the control circuit generates the first signal and the second signal in response to the reflected signal.
4. The PFC converter as claimed in claim 1 , in which the maximum on time of the first signal and the second signal are limited by the control circuit.
5. The PFC converter as claimed in claim 1 , further comprises:
a first resistor coupled between the second transistor and the negative-power rail and generating a current signal; and
a divider coupled to the output of the buck-boost PFC converter and producing a feedback signal,
in which the second winding generates a reflected signal coupled to the control circuit, and the control circuit generates the first signal and the second signal in response to the current signal, the feedback signal, and the reflected signal.
6. The PFC converter as claimed in claim 5 , in which the control circuit comprises:
a flip-flop generating a PWM signal;
a first buffer receiving the PWM signal and generating the first signal; and
a second buffer receiving the PWM signal and generating the second signal;
in which the flip-flop is enabled in response to the reflected signal for generating the PWM signal and reset in response to the feedback signal and the current signal for disabling the PWM signal.
7. A buck-boost PFC converter comprising:
an inductor for the energy transfer, having a first winding and a second winding, and the first and second winding having a first terminal and a second terminal, respectively;
two transistors coupled to an input power rail of the PFC converter to charge the inductor when the transistors are on;
an input diode and an output diode coupled to the inductor to discharge the energy of the inductor to an output of the PFC converter when the transistors are off; and
a control circuit generating switching signals coupled to control the switching of the transistors for regulating an output voltage of the PFC converter and achieving power factor correction;
wherein the output diode is connected from the second terminal of the first winding of the inductor to the output of the PFC converter, the input diode is connected from the first terminal of the first winding of the inductor to the negative-power rail and provides a free-wheeling path for the inductor when the transistors are off, and the output voltage of the PFC converter can be lower or higher than a voltage of the input power rail of the PFC converter.
8. The PFC converter as claimed in claim 7 , in which the transistors are switched on/off simultaneously.
9. The PFC converter as claimed in claim 7 , in which the first winding of the inductor is coupled to the transistors and the second winding of the inductor generates a reflected signal coupled to the control circuit, and the control circuit generates the switching signals in response to the reflected signal.
10. The PFC converter as claimed in claim 7 , in which the maximum on time of the switching signals is limited by the control circuit.