A power supply with dynamic control of resonant mode, comprising:
- a boost active power factor correction (PFC) circuit configured to convert an alternative-current (AC) voltage provided by AC mains into a direct-current (DC) voltage and then convert the DC voltage into a pulse DC voltage, and comprising:
- a boost inductor configured to store or discharge energy of the DC voltage, and comprising:
- a first end coupled to the DC voltage;
- and
- a second end;
- a power switch configured to control the boost inductor to store and discharge the energy of the DC voltage according to a first control signal, and comprising:
- a first end coupled to the second end of the boost inductor;
- a second end coupled to a first ground level;
- and
- a control end for receiving the first control signal which periodically switches between a first enable level and a first disable level;
- a resonant converting circuit configured to convert the pulse DC voltage into an output voltage, and comprising:
- a transformer configured to transfer energy of the pulse DC voltage from a first primary side to a first secondary side for supplying the output voltage, and comprising:
- a primary winding disposed on the first primary side and including a first dotted terminal and a first undotted terminal;
- a first secondary winding disposed on the first secondary side and including a second dotted terminal and a second undotted terminal;
- and
- a second secondary winding disposed on the first secondary side and including a third dotted terminal and a third undotted terminal, wherein the second undotted terminal is coupled to the third dotted terminal;
- a first resonant switch configured to control an operation of the resonant converting circuit according to a second control signal, and comprising:
- a first end coupled to the pulse DC voltage;
- a second end;
- and
- a control end for receiving the second control signal which periodically switches between a second enable level and a second disable level;
- a second resonant switch configured to control the operation of the resonant converting circuit according to a third control signal, and comprising:
- a first end coupled to the first dotted terminal;
- a second end coupled to the first ground level;
- and
- a control end for receiving the third control signal which periodically switches between a third enable level and a third disable level;
- and
- a resonant tank coupled to the first resonant switch, the second resonant switch and the primary winding, and configured to selectively operate in a multi-element resonant mode or in a single-element resonant mode according to a fourth control signal;
- a zero-current detecting circuit configured to:
- detect a boost inductor current flowing through the boost inductor;
- output the fourth control signal having a fourth enable level for controlling the resonant tank to operate in the single-element resonant mode when determining that the boost inductor current is in a zero-current state;
- output the fourth control signal having a fourth disable level for controlling the resonant tank to operate in the multi-element resonant mode when determining that the boost inductor current is not in the zero-current state;
- detect a status of the output voltage;
- and
- output a logic signal having a second level when determining that the boost inductor current is in the zero-current state and the output voltage is at a first level, wherein the zero-current detecting circuit comprises:
- a zero-current detecting unit configured to transfer energy of the boost inductor current from a second primary side to a second secondary side for supplying a sensing voltage, and comprising:
- a magnetizing winding disposed on the second primary side, wherein a first end of the magnetizing winding is coupled to the first end of the boost inductor and a second end of the magnetizing winding is coupled to the second end of the boost inductor;
- and
- a sensing winding disposed on the second secondary side, wherein a first end of the sensing winding is for providing the sensing voltage and a second end of the sensing winding is coupled to the first ground level;
- an error amplifier configured to selectively provide the fourth control signal having a fourth enable level or a fourth disable level based on a level of the sensing voltage, and including:
- a first input end coupled to the first end of the sensing winding for receiving the sensing voltage;
- a second input end coupled to the first ground level;
- and
- an output end for outputting the fourth control signal;
- and
- a logic circuit configured to selectively provide the logic signal having the second level based on a level of the fourth control signal and a level of the output voltage, and including:
- a first input end coupled to the output end of the error amplifier for receiving the fourth control signal;
- a second input end for receiving the output voltage;
- and
- an output end for outputting the logic signal;
- a voltage-stabilizing feedback compensation circuit configured to selectively provide a feedback voltage associated with the pulse DC voltage according to a fifth control signal;
- and
- a control circuit configured to:
- provide the first control signal, the second control signal, the third control signal and the fifth control signal;
- control a duty cycle of the first control signal according to the feedback voltage;
- receive the logic signal;
- output the fifth control signal having a fifth disable level for deactivating the voltage-stabilizing feedback compensation circuit when determining that the logic signal is at the second level;
- and
- output the fifth control signal having a fifth enable level for activating the voltage-stabilizing feedback compensation circuit when determining that the logic signal is not at the second level.