Resonant power converter with half bridge and full bridge operations and method for control thereof
A resonant power converter with half bridge and full bridge operations and a method for control thereof are provided. The resonant power converter includes a full bridge circuit, a control circuit and a PFC circuit. The full bridge circuit switches a power transformer in response to switching signals. The control circuit coupled to receive a feedback signal and an input signal generates switching signals. The feedback signal is correlated to the output of the power converter and the input signal is correlated to the input voltage of the full bridge circuit, where the full bridge circuit is operated as a full bridge switching when the input signal is lower than a threshold, and the full bridge circuit is operated as a half bridge switching when the input signal is higher than the threshold. The PFC circuit generates the input voltage of the full bridge circuit.
1. A resonant power converter comprising:
a full bridge circuit for switching a power transformer in response to switching signals;
a control circuit coupled to receive a feedback signal and also coupled to the full bridge circuit to receive an input signal for generating switching signals; in which the feedback signal is correlated to the output of the resonant power converter and the input signal is correlated to the input voltage of the full bridge circuit,
wherein the full bridge circuit is operated as a full bridge switching when the input signal is lower than a threshold; and the full bridge circuit is operated as a half bridge switching when the input signal is higher than the threshold.
2. The resonant power converter as claimed in claim 1 , in which the control circuit is further coupled to receive a line-voltage signal; wherein the full bridge circuit is operated as a full bridge switching when the line-voltage signal is lower than a second threshold; and the full bridge circuit is operated as a half bridge switching when the line-voltage signal is higher than the second threshold; the line-voltage signal is correlated to a line input voltage of the resonant power converter, and the line-voltage signal is generated by the line input voltage.
3. The resonant power converter as claimed in claim 2 , further comprising:
a PFC circuit generating the input voltage of the full bridge circuit;
wherein the PFC circuit generates a first input voltage when the line-voltage signal is lower than the second threshold; and the PFC circuit generates a second input voltage when the line-voltage signal is higher than the second threshold; the second input voltage is higher than the first input voltage.
4. The resonant power converter as claimed in claim 1 , in which the control circuit comprising:
a switching circuit generating switching signals in response to the feedback signal and the input signal; in which switching signals comprises a first signal, a second signal, a third signal and a fourth signal;
wherein the frequency of switching signals is varied in response to the feedback signal; switching signals are switching alternatively for the full bridge switching; the third signal is off, the fourth signal is on, and the first signal and the second signal are switching for the half bridge switching.
5. A method for the control of a resonant power converter comprising:
generating switching signals to drive a full bridge circuit in response to a feedback signal and an input signal, wherein the input signal is received through coupling to the full bridge circuit;
full bridge switching a power transformer in response to switching signals when an input signal is lower than a threshold;
half bridge switching the power transformer in response to switching signals when the input signal is higher than the threshold;
wherein the feedback signal is correlated to the output of the resonant power converter and the input signal is correlated to the input voltage of the full bridge circuit.
6. The method as claimed in claim 5 , further comprising:
generating switching signals in response to a line-voltage signal;
full bridge switching a power transformer in response to the switching signals when the line-voltage signal is lower than a second threshold;
half bridge switching the power transformer in response to the switching signals when the line-voltage signal higher than the second threshold;
wherein the line-voltage signal is correlated to the line input voltage of the resonant power converter, and the line-voltage signal is generated by the line input voltage.
7. The method as claimed in claim 6 , further comprising:
generating the input voltage of the full bridge circuit by a PFC circuit;
wherein the PFC circuit generates a first input voltage when the line-voltage signal is lower than the second threshold; and the PFC circuit generates a second input voltage when the line-voltage signal is higher than the second threshold; the second input voltage is higher than the first input voltage.
8. The method as claimed in claim 5 , in which the switching signals comprising:
a first signal, a second signal, a third signal and a fourth signal;
wherein the frequency of switching signals is varied in response to the feedback signal; the switching signals are switching alternatively for the full bridge switching; for the half bridge switching, the third signal is off, the fourth signal is on, and the first signal and the second signal are switching.