Wireless power transfer system and driving method thereof

1. A wireless power transmission system, comprising:

a primary coil provided at a primary side of the wireless power transmission system;

a secondary coil provided at a secondary side of the wireless power transmission system;

a capacitor and a control switch electrically coupled in series between lateral ends of the secondary coil;

a regulation controller configured to generate a control signal corresponding to a sensed secondary-side current that flows through the secondary coil, and to control a switching operation of the control switch according to a result of a comparison between the control signal and a feedback signal corresponding to an output voltage of the wireless power transmission system;

an error amplifier configured to output a result of a comparison between the output voltage of the wireless power transmission system and a predetermined reference voltage; and

a compensator coupled between an output terminal of the error amplifier and an inverse terminal of the error amplifier and configured to generate an error voltage as the feedback signal by compensating an output of the error amplifier.

2. The wireless power transmission system of claim 1 , wherein the regulation controller is configured to generate the control signal by rectifying a sense voltage that corresponds to the secondary-side current.

3. The wireless power transmission system of claim 1 , wherein an impedance at the secondary side is changed according to the switching operation of the control switch.

4. The wireless power transmission system of claim 1 , further comprising:

a current sensor configured to sense the secondary-side current and to generate a sense voltage corresponding to the sensed secondary-side current,

wherein the regulation controller comprises:

a rectifier configured to generate the control signal by rectifying the sense voltage;

a comparator configured to compare the control signal with the feedback signal; and

a gate driver configured to generate a gate voltage of the control switch according to an output of the comparator.

5. The wireless power transmission system of claim 1 , further comprising a first resonance capacitor including a first electrode coupled to a first end of the secondary coil,

wherein the capacitor and the control switch are coupled in series between a second electrode of the first resonance capacitor and a second end of the secondary coil.

6. A driving method of a wireless power transmission system, comprising:

generating a primary-side current that flows to a primary coil at a primary side of the wireless transmission system;

magnetically coupling the primary coil to a secondary coil at a secondary side of the wireless power transmission system to generate a secondary-side current that flows through the secondary coil and has a same frequency as the primary-side current;

sensing the secondary-side current to generate a sense voltage that corresponds to the secondary-side current;

generating a control signal from the sense voltage;

generating a feedback signal corresponding to an output of the wireless power transmission system;

comparing the control signal to the feedback signal; and

controlling an impedance at the secondary side according to a result of comparing the control signal to the feedback signal,

wherein the wireless power transmission system comprises an error amplifier and a compensator coupled between an output terminal of the error amplifier and an inverse terminal of the error amplifier, and generating the feedback signal comprises:

comparing, using the error amplifier, the output voltage of the wireless power transmission system to a predetermined reference voltage; and

generating, using the compensator, an error voltage as the feedback signal by compensating an output of the error amplifier.

7. The driving method of the wireless power transmission system of claim 6 , wherein the wireless power transmission system further comprises a capacitor and a control switch electrically coupled in series between lateral ends of the secondary coil, and controlling the impedance at the secondary side comprises controlling a switching operation of the control switch according to a result of comparing the control signal to the feedback signal.

8. The driving method of the wireless power transmission system of claim 6 , wherein generating the control signal comprises:

generating the control signal by rectifying the sense voltage.

9. A wireless power transmission system comprising:

an inverter that is configured to generate a primary-side current at a primary side of the wireless power transmission system;

a primary coil to which the primary-side current flows at the primary side;

a secondary coil at a secondary side of the wireless power transmission system, the secondary coil being magnetically coupled to the primary coil;

a control switch across the secondary coil;

a first rectifier that is configured to generate a rectified voltage by rectifying a sense voltage that corresponds to a secondary-side current that flows through the secondary coil and has a same frequency as the primary-side current;

a second rectifier that is configured to rectify a voltage across the secondary side to generate an output voltage of the power transmission system;

an error amplifier configured to output a result of a comparison between the output voltage of the power transmission system and a predetermined reference voltage;

a compensator coupled between an output terminal of the error amplifier and an inverse terminal of the error amplifier and configured to generate an error voltage as a feedback signal by compensating an output of the error amplifier; and

a regulation controller that is configured to control a switching operation of the control switch based on a result of comparing the rectified voltage to the feedback signal.

10. The wireless power transmission system of claim 9 , wherein the regulation controller further comprises a capacitor that is in series with the control switch.

11. The wireless power transmission system of claim 10 , wherein the capacitor and the control switch are across lateral ends of the secondary coil.