Resonant power converter, output voltage control method, and signal-processing circuit thereof

Abstract

A resonant power converter, an output voltage control method, and a signal processing circuit thereof are disclosed. The output voltage control method includes: generating a target switching frequency signal based on a feedback signal and a reference signal; generating a switching frequency control signal and a dead time control signal corresponding to the target switching frequency signal; and outputting a switching control signal to a primary-side switching circuit of the resonant power converter based on the switching frequency control signal and the dead time control signal.

Claims

1. A resonant power converter, comprising: A primary-side switching circuit; a secondary-side switching circuit; A resonant tank circuit is coupled between the primary-side switching circuit and the secondary-side switching circuit; a feedback circuit is coupled to an output terminal of the secondary-side switching circuit and configured to provide a feedback signal indicating an output voltage at the output terminal; A signal processing circuit coupled to the feedback circuit includes: a proportional-integral controller configured to generate a target switching frequency signal based on the feedback signal and a reference signal; and a dead-time controller coupled to the proportional-integral controller configured to receive the target switching frequency signal and correspondingly generate a switching frequency control signal and a dead-time control signal, such that it has a pulse frequency modulation mode, an equivalent frequency modulation mode, and a burst mode; and a switch drive circuit coupled to the signal processing circuit and the primary-side switch circuit, configured to output a switch control signal pair to the primary-side switch circuit based on the switching frequency control signal and the dead-time control signal; wherein, in the pulse frequency modulation mode, a switching operating frequency of the switch control signal pair is between a lower operating frequency limit and an upper operating frequency limit, and a dead time of the switch control signal pair is maintained at a lower dead-time limit; In the equivalent frequency modulation mode, the switching operation frequency of the switch control signal pair is maintained at the upper limit of the operating frequency, and the dead time of the switch control signal pair is between the lower limit of the dead time and the upper limit of the dead time. In the burst mode, the switch control signal pair is output intermittently, and when the switch control signal pair is in the output state, its switching operation frequency is maintained at the upper limit of the operating frequency, and its dead time is maintained at the upper limit of the dead time.

2. The resonant power converter as claimed in claim 1, wherein the dead-time controller is configured to operate in the pulse frequency modulation mode in response to a target frequency indicated by the target switching frequency signal being between the lower limit and the upper limit of the operating frequency.

3. The resonant power converter as claimed in claim 1, wherein the dead-time controller is configured to, in response to a target frequency indicated by the target switching frequency signal being above the upper limit of the operating frequency, determine a dead-time increment corresponding to the dead-time control signal based on an excess amount of the target frequency exceeding the upper limit of the operating frequency, and operate in the equivalent frequency modulation mode in response to the determined dead time being between the lower limit of the dead time and the upper limit of the dead time.

4. The resonant power converter as claimed in claim 1, wherein the dead-time controller is configured to, in response to a target frequency indicated by the target switching frequency signal exceeding an upper limit of the operating frequency, determine a dead-time increment corresponding to the dead-time control signal based on an excess amount of the target switching frequency signal exceeding the upper limit of the operating frequency, and operate in the burst mode in response to the determined dead-time reaching the upper limit of the dead-time; wherein in the burst mode, in response to the feedback signal reaching an upper limit trigger voltage, the switching control signal pair remains low; and in response to the feedback signal reaching a lower limit trigger voltage, the switching control signal pair resumes output.

5. The resonant power converter as claimed in claim 1, wherein a duty cycle of the switching control signal pair is the same in the pulse frequency modulation mode, the equivalent frequency modulation mode, and the burst mode.

6. An output voltage control method, suitable for a resonant power converter, comprising: A feedback signal is acquired from a feedback circuit, the feedback signal indicating an output voltage of the resonant power converter; a target switching frequency signal is generated based on the feedback signal and a reference signal; a switching frequency control signal and a dead time control signal are generated correspondingly based on the target switching frequency signal; and a switching control signal pair is output to a primary-side switching circuit of the resonant power converter based on the switching frequency control signal and the dead time control signal; wherein, in a pulse frequency modulation mode, a switching operating frequency of the switching control signal pair is between a lower operating frequency limit and an upper operating frequency limit, and a dead time of the switching control signal pair is maintained at a lower dead time limit; wherein, in an equivalent frequency modulation mode, the switching operating frequency of the switching control signal pair is maintained at the upper operating frequency limit, and the dead time of the switching control signal pair is between a lower dead time limit and an upper dead time limit; In a burst mode, the switch control signal pair is output intermittently, wherein when the switch control signal pair is in the output state, its switch operation frequency is maintained at the upper limit of the operation frequency, and its dead time is maintained at the upper limit of the dead time.

7. The output voltage control method as described in claim 6, wherein the steps of generating the switching frequency control signal and the dead time control signal according to the target switching frequency signal include: The pulse frequency modulation mode is operated in response to a target frequency indicated by the target switching frequency signal being between the lower limit and the upper limit of the operating frequency.

8. The output voltage control method as described in claim 6, wherein the steps of generating the switching frequency control signal and the dead time control signal according to the target switching frequency signal include: In response to a target frequency indicated by the target switching frequency signal being above the upper limit of the operating frequency, a dead time increase amount corresponding to the dead time control signal is determined based on an excess amount of the target switching frequency signal exceeding the upper limit of the operating frequency; and in response to the determined dead time being between the lower limit of the dead time and the upper limit of the dead time, operation is performed in the equivalent frequency modulation mode.

9. The output voltage control method as described in claim 6, wherein the steps of generating the switching frequency control signal and the dead time control signal according to the target switching frequency signal include: In response to a target frequency indicated by the target switching frequency signal exceeding the upper limit of the operating frequency, a dead-time increase amount corresponding to the dead-time control signal is determined based on the amount by which the target frequency exceeds the upper limit of the operating frequency; and in response to the determined dead-time reaching the upper limit of the dead-time, the system operates in the burst mode; wherein, in the burst mode, in response to the feedback signal reaching an upper limit trigger voltage, the switching control signal pair remains low; and in response to the feedback signal reaching a lower limit trigger voltage, the switching control signal pair resumes output.

10. A signal processing circuit that performs the output voltage control method as described in any one of claims 6 to 9.

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