Power supplying circuit and liquid crystal display

A power supplying circuit, comprising a rectifier, a flyback converter, a power factor correction circuit, an LLC resonant converter, a power factor correction (PFC) controller, and a LLC resonant controller, wherein

• an first input terminal, a second terminal, and an output terminal of the power factor correction controller connect to a first output terminal and second terminal of the flyback converter and a first input terminal of the LLC resonant controller, respectively;
• a second input terminal of the LLC resonant controller is connected to a first output terminal of the flyback converter, an output terminal of the LLC resonant controller is coupled to the LLC resonant converter, a collecting terminal of the LLC resonant controller is coupled to an output terminal of the PFC controller;
• the PFC controller is configured to supply a first operating voltage to the PFC circuit;
• the LLC resonant controller is configured to supply a second operating voltage to the LLC resonant converter upon a condition that a voltage applied on the output terminal of the PFC circuit reaches a predetermined voltage;
• wherein the PFC controller comprises a first photo-coupler, a first transistor, a second transistor, a control signal processing circuit, a voltage divider, and a clamping circuit;
• the anode of the first photo-coupler is coupled to the first output terminal of the flyback converter;
• the cathode of the first photo-coupler is coupled to a first terminal of the first transistor;
• a second terminal of the first transistor is grounded;
• a control terminal of the first transistor is coupled to the control signal processing circuit;
• a collector of the first photo-coupler is coupled to a second terminal of the flyback converter;
• an emitter of the first photo-coupler is coupled to a control terminal of the second transistor and the clamping circuit through the voltage divider;
• a first terminal of the second transistor is coupled to the second terminal of the flyback converter;
• a second terminal of the second transistor is coupled to the PFC circuit and the first input terminal of the LLC resonant controller;
• the control signal processing circuit comprises a first resistor, a second resistor, and a first capacitor;
• one terminal of the first resistor is coupled to a control signal source;
• the other terminal of the first resistor is coupled to one terminal of the second resistor, one terminal of the first capacitor, and the control terminal of the first transistor;
• the other terminal of the second resistor and the other terminal of the first capacitor are grounded;
• the voltage divider comprises a third resistor and a fourth resistor;
• one terminal of the third resistor and one terminal of the fourth resistor are coupled to the emitter of the first photo-coupler;
• the other terminal of the third resistor is grounded;
• the other terminal of the fourth resistor is coupled to the control terminal of the second transistor;
• the clamping circuit comprises a Zener diode, a first diode, and a second capacitor;
• one terminal of the Zener diode, one terminal of the second capacitor, and a cathode of the first diode are coupled to the control terminal of the second transistor;
• the other terminal of the Zener diode and the other terminal of the second capacitor are grounded;
• an anode of the first diode is coupled to a second terminal of the second transistor;
• wherein the LLC resonant controller comprises a second photo-coupler, a controllable voltage supplier, a third transistor, and a collecting circuit;
• an anode of the second photo-coupler is coupled to one terminal of a fifth resistor and one terminal of a sixth resistor;
• the other terminal of the fifth resistor is coupled to the PFC controller;
• the other terminal of the sixth resistor is coupled to a cathode of the second photo-coupler and an anode of the controllable voltage supplier;
• a cathode of the controllable voltage supplier is grounded;
• a reference terminal of the controllable voltage supplier is coupled to the voltage output terminal of the PFC circuit;
• the collector of the second photo-coupler is coupled to one terminal of a seventh resistor and one terminal of an eighth resistor;
• the other terminal of the seventh resistor is coupled to the first output terminal of the flyback converter;
• the other terminal of the eighth resistor is coupled to a control terminal of the third transistor;
• an emitter of the second photo-coupler is grounded;
• a first terminal of the third transistor is coupled to one terminal of the ninth resistor;
• the other terminal of the ninth resistor is coupled to the first output terminal of the flyback converter;
• a second terminal of the third transistor is coupled to the LLC resonant converter;
• the collecting circuit is configured to collect the voltage applied on the voltage output terminal of the PFC circuit to the reference terminal of the controllable voltage supplier.