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CN-121984353-A - Resonant power conversion circuit and driving method thereof

CN121984353ACN 121984353 ACN121984353 ACN 121984353ACN-121984353-A

Abstract

The application provides a resonant power conversion circuit and a driving method thereof, the resonant power conversion circuit comprises a resonant capacitor, a transformer, an upper bridge transistor, a lower bridge transistor and a control circuit. The resonance capacitor is coupled between the resonance node and the ground terminal. The transformer includes a primary coil coupled between a switching node and a resonant node. The upper bridge transistor provides an input voltage to the switching node, and the lower bridge transistor couples the switching node to ground. When the control circuit judges that the driving frequency of the upper bridge transistor or the lower bridge transistor enters the frequency range, the control circuit simultaneously turns off the upper bridge transistor and the lower bridge transistor for delay time so as to move the driving frequency out of the frequency range.

Inventors

  • YANG DAYONG
  • LIU GUOJI
  • LIN ZICHENG

Assignees

  • 立锜科技股份有限公司

Dates

Publication Date
20260505
Application Date
20250722
Priority Date
20250613

Claims (20)

  1. 1. A resonant power conversion circuit for converting an input voltage to an output voltage, comprising: the resonance capacitor is coupled between a resonance node and a grounding end; A transformer including a primary coil and a secondary coil, wherein the primary coil is coupled between a switching node and the resonant node; an upper bridge transistor for providing the input voltage to the switching node based on an upper bridge driving signal; A lower bridge transistor for coupling the switching node to the ground terminal based on a lower bridge driving signal, and The control circuit generates the upper bridge driving signal and the lower bridge driving signal based on the output voltage; When the control circuit judges that a driving frequency of the upper bridge driving signal or the lower bridge driving signal enters a frequency range, the control circuit simultaneously turns off the upper bridge transistor and the lower bridge transistor for a delay time so as to move the driving frequency out of the frequency range.
  2. 2. The resonant power conversion circuit of claim 1, further comprising: A feedback circuit for generating a feedback voltage based on the output voltage; Wherein the control circuit comprises: A compensation circuit for generating a compensation voltage based on the feedback voltage and subtracting a sawtooth wave from the compensation voltage to generate a compensation signal; wherein when the feedback voltage is less than a feedback threshold voltage, the compensation voltage is equal to the feedback threshold voltage; And when the feedback voltage is not smaller than the feedback threshold voltage, the compensation voltage is equal to the feedback voltage.
  3. 3. The resonant power conversion circuit of claim 2, wherein the compensation circuit comprises: The first amplifier comprises a first positive input end, a first negative input end and a first output end, wherein the first positive input end receives the feedback voltage, and the first negative input end is coupled to the first output end; The second amplifier comprises a second positive input end, a second negative input end and a second output end, wherein the second positive input end receives the feedback threshold voltage, and the second output end generates the compensation voltage; a resistor coupled between the second negative input terminal and the first output terminal and generating a differential current; An N-type transistor including a gate terminal, a drain terminal and a source terminal, wherein the gate terminal is coupled to the second output terminal, and the source terminal is coupled to the second negative input terminal; A digital circuit for extracting a circulating current from the drain terminal; a current mirror for mapping the sum of the differential current and the circulating current to a mapped current, and And a summation circuit for subtracting the sawtooth wave from the compensation voltage to generate the compensation signal.
  4. 4. The resonant power conversion circuit of claim 2, further comprising: A first current detection circuit for detecting the current flowing through the resonant capacitor to generate a current detection signal; An integrator for integrating the current detection signal to generate an integrated signal; a full-wave rectifying device for full-wave rectifying the integrated signal generated by the integrator to generate a rectified signal, and The rectification circuit is coupled with the secondary coil and converts the current flowing through the secondary coil into the output voltage; Wherein the control circuit generates the upper bridge drive signal and the lower bridge drive signal based on a relationship of the compensation signal and the rectified signal.
  5. 5. The resonant power conversion circuit of claim 2, wherein the control circuit further comprises: An output voltage detection circuit for judging whether the feedback voltage is smaller than a low power threshold voltage to generate a pre-burst signal; Wherein when the feedback voltage is less than the low power threshold voltage, the output voltage detection circuit enables the pre-burst signal; When the feedback voltage is not smaller than the low power threshold voltage, the output voltage detection circuit disables the pre-burst signal.
  6. 6. The resonant power conversion circuit of claim 5, wherein the control circuit disables the upper bridge drive signal and the lower bridge drive signal based on the pre-burst signal being enabled to reduce the drive frequency; The control circuit enables the upper bridge driving signal and the lower bridge driving signal respectively based on the disabled pre-burst signal.
  7. 7. The resonant power conversion circuit of claim 5, wherein the output voltage detection circuit further determines whether the driving frequency enters the frequency range when the feedback voltage is less than the low power threshold voltage; Wherein when the driving frequency enters the frequency range, the control circuit enables a cyclic signal to simultaneously turn off the upper bridge transistor and the lower bridge transistor for an audio delay time; Wherein after the audio delay time, the control circuit enables the upper bridge drive signal and the lower bridge drive signal, respectively, at least once.
  8. 8. The resonant power conversion circuit of claim 7, wherein the frequency range is an audio range; wherein the audio delay time is not less than a maximum value of an audio reciprocal.
  9. 9. The resonant power conversion circuit of claim 7, wherein the compensation circuit generates a mapping voltage based on the difference between the feedback threshold voltage and the feedback voltage; The output voltage detection circuit determines that the driving frequency of the resonant power conversion circuit enters the frequency range based on the mapping voltage being between a first audio voltage and a second audio voltage; The mapping voltage is used for determining the enabled time length of the pre-burst signal.
  10. 10. The resonant power conversion circuit of claim 9, wherein the compensation circuit increases the mapping voltage based on a number of times the cyclic signal is enabled to extend a length of time the pre-burst signal is enabled.
  11. 11. A driving method for driving a resonant power conversion circuit, the driving method comprising: Based on the voltage across a resonant capacitor and an output voltage of the resonant power conversion circuit, driving an upper bridge transistor and a lower bridge transistor of the resonant power conversion circuit; Judging whether the output voltage of the resonant power conversion circuit is too high; when the output voltage is judged to be too high, a burst mode is entered; judging whether a driving frequency of the resonant power conversion circuit is in an audio frequency range or not, and And when the driving frequency is judged to enter the audio frequency range, prolonging the time length of the burst mode.
  12. 12. The driving method of claim 11, wherein the resonant power conversion circuit comprises the resonant capacitor coupled between a resonant node and a ground, a transformer comprising a primary winding and a secondary winding, the upper bridge transistor providing an input voltage to a switching node, and the lower bridge transistor coupling the switching node to the ground; wherein the primary coil is coupled between the switching node and the resonant node.
  13. 13. The driving method of claim 11, wherein the step of driving the upper bridge transistor and the lower bridge transistor of the resonant power conversion circuit based on a voltage across the resonant capacitor of the resonant power conversion circuit and the output voltage comprises: full-wave rectifying the voltage across the resonant capacitor to generate a rectified signal; Generating a compensation voltage based on the feedback voltage; subtracting a sawtooth wave from the compensation voltage to generate a compensation signal, and Comparing the rectified signal with the compensation signal to drive the upper bridge transistor and the lower bridge transistor; wherein when the feedback voltage is less than a feedback threshold voltage, the compensation voltage is equal to the feedback threshold voltage; And when the feedback voltage is not smaller than the feedback threshold voltage, the compensation voltage is equal to the feedback voltage.
  14. 14. The driving method of claim 13, wherein the step of full-wave rectifying a voltage across the resonance capacitor to generate the rectified signal comprises: Detecting the current flowing through the resonant capacitor to generate a current detection signal; integrating the current detection signal to generate an integrated signal, and Full wave rectifying the integrated signal to produce the rectified signal.
  15. 15. The driving method of claim 13, wherein the step of determining whether the output voltage is too high comprises: Judging whether the feedback voltage is smaller than a low-power threshold voltage or not; entering the burst mode when the feedback voltage is less than the low power threshold voltage, and When the feedback voltage is not smaller than the low power threshold voltage, the burst mode is not entered; wherein in the burst mode, the upper bridge transistor and the lower bridge transistor are turned off simultaneously.
  16. 16. The driving method of claim 13, wherein the step of determining whether the driving frequency of the resonant power conversion circuit enters the audio range further comprises: generating a mapping voltage based on the feedback voltage; Judging whether the mapping voltage is between a first audio voltage and a second audio voltage; When the mapping voltage is between the first audio voltage and the second audio voltage, judging that the driving frequency of the resonant power conversion circuit enters the audio frequency range, and When the mapping voltage is located outside the first audio voltage and the second audio voltage, the driving frequency of the resonant power conversion circuit is judged not to enter the audio range.
  17. 17. The driving method of claim 16, wherein the step of generating the mapping voltage based on the feedback voltage comprises: generating a differential current based on the difference between the feedback threshold voltage and the feedback voltage; Mapping the differential current into a mapped current by a current mirror, and The mapping current flows through a resistor to generate the mapping voltage.
  18. 18. The driving method as claimed in claim 16, wherein the time length of the burst mode is extended to an audio delay time when it is determined that the driving frequency of the resonant power conversion circuit enters the audio range; wherein after the audio delay time, the upper bridge drive signal and the lower bridge drive signal are respectively enabled at least once based on an enabled one-cycle signal.
  19. 19. The driving method as claimed in claim 18, wherein the audio delay time is not less than a maximum value of audio inverse.
  20. 20. The driving method as recited in claim 18, further comprising: Determining the burst mode and the number of times the cyclic signal is enabled based on the length of time a pre-burst signal is enabled; Counting the number of times the cycling signal is enabled; And extending the length of time that the pre-burst signal is enabled based on the number of times the cyclic signal is enabled.

Description

Resonant power conversion circuit and driving method thereof Technical Field The present invention relates to a resonant power conversion circuit and a driving method thereof, and more particularly to a resonant power conversion circuit for eliminating audio noise and a driving method thereof. Background With the continuous development of portable electronic devices, the development trend of power conversion circuits is as same as most power products, and the development trend is toward high efficiency, high power density, high reliability and low cost. Since resonant power conversion circuits (including LLC resonant power conversion circuits and the like) have the advantages of achieving zero voltage switching (zero-voltage switching, ZVS) on the primary side and zero current switching (zero-current switching, ZCS) of the secondary side rectifier diode in the full load range, enabling the duty cycles of the upper bridge transistor and the lower bridge transistor to be 50% by adopting frequency control, reducing cost and improving efficiency by adopting transistors with lower voltage on the secondary side without an output inductor, and the like, the resonant power conversion circuits are increasingly applied to dc voltage converters in recent years. When the resonant power conversion circuit operates in a low load state, the resonant power conversion circuit often enters a burst mode (burst mode) to reduce power consumption in the low load state. However, when the resonant power conversion circuit is operated in the burst mode, the switching frequency of the driving upper bridge transistor and the driving lower bridge transistor may fall into the audio frequency range, thereby generating noise. Therefore, there is a need for improvements in burst mode for resonant power conversion circuits. Disclosure of Invention The invention provides a resonant power conversion circuit and a driving method thereof, wherein whether the burst frequency of the resonant power conversion circuit enters an audio frequency range is judged by monitoring a mapping voltage related to a feedback voltage. When the burst frequency of the resonant power conversion circuit is judged to enter the audio frequency range, the time for which the upper bridge transistor and the lower bridge transistor are both turned off is prolonged, so that the driving frequency leaves the audio frequency range, and noise generated by the resonant power conversion circuit is eliminated. In view of the above, the present invention provides a resonant power conversion circuit for converting an input voltage to an output voltage. The resonant power conversion circuit comprises a resonant capacitor, a transformer, an upper bridge transistor, a lower bridge transistor and a control circuit. The resonant capacitor is coupled between a resonant node and a ground terminal. The transformer comprises a primary coil and a secondary coil, wherein the primary coil is coupled between a switching node and the resonance node. The upper bridge transistor provides the input voltage to the switching node based on an upper bridge driving signal. The lower bridge transistor couples the switching node to the ground based on a lower bridge driving signal. The control circuit generates the upper bridge drive signal and the lower bridge drive signal based on the output voltage. When the control circuit judges that a driving frequency of the upper bridge driving signal or the lower bridge driving signal enters a frequency range, the control circuit simultaneously turns off the upper bridge transistor and the lower bridge transistor for a delay time so as to move the driving frequency out of the frequency range. According to an embodiment of the present invention, the resonant power conversion circuit further includes a feedback circuit. The feedback circuit generates a feedback voltage based on the output voltage. The control circuit further comprises a compensation circuit. The compensation circuit is used for generating a compensation voltage based on the feedback voltage and subtracting a sawtooth wave from the compensation voltage to generate a compensation signal. When the feedback voltage is smaller than a feedback threshold voltage, the compensation voltage is equal to the feedback threshold voltage. When the feedback voltage is not less than the feedback threshold voltage, the compensation voltage is equal to the feedback voltage. According to an embodiment of the present invention, the compensation circuit further includes a first amplifier, a second amplifier, a resistor, an N-type transistor, a digital circuit, a current mirror, and a summation circuit. The first amplifier includes a first positive input terminal, a first negative input terminal, and a first output terminal, wherein the first positive input terminal receives the feedback voltage, and the first negative input terminal is coupled to the first output terminal. The second amplifier includes a second positiv