Low-heat wireless power receiving device and method

1. A low-heat wireless power receiving device comprising:

a power receiving coil configured to receive a wireless power signal;

an impedance matching/rectifying unit configured to match impedance so that the power receiving coil can resonate with the wireless power signal and to rectify the wireless power signal to convert it to a DC power;

a charging power supply unit including a low-heat transforming unit and a high-heat transforming unit connected in parallel with each other and supplying an output power of the impedance matching/rectifying unit to a power receiving unit as a charging power;

a current detecting unit configured to detect a current level of a power stored in the power receiving unit; and

a control unit configured to control an impedance matching of the impedance matching/rectifying unit, to determine a charging load state of the power receiving unit in accordance with a time-lapse of charging the power receiving unit and the current level detected by the current detecting unit, and to selectively turn on the low-heat transforming unit and the high-heat transforming unit in accordance with the determined charging load state.

2. The low-heat wireless power receiving device of claim 1 , wherein the control unit determines an initial light load state to turn off the low-heat transforming unit and to turn on the high-heat transforming unit when the power receiving unit starts to be charged, and determines a middle load state to turn on the low-heat transforming unit and to tum off the high-heat transforming unit when a predetermined initial charging time has passed.

3. The low-heat wireless power receiving device of claim 2 , wherein the control unit turns on both the low-heat transforming unit and the high-heat transforming unit for a predetermined time when the control unit determines a middle load, and

the control unit maintains the low-heat transforming unit being turned on and turns off the high-heat transforming unit when the predetermined time has passed.

4. The low-heat wireless power receiving device of claim 1 , wherein the control unit determines a light load state to turn off the low-heat transforming unit and turns on the high-heat transforming unit when a detection current level of the current detecting unit enters a predetermined range of a first level.

5. The low-heat wireless power receiving device of claim 4 , wherein the control unit turns on both the low-heat transforming unit and the high-heat transforming unit for a predetermined time when the control unit determines the light load state, and

the control unit turns off the low-heat transforming unit and turns on the high-heat transforming unit when the predetermined time has passed.

6. The low-heat wireless power receiving device of claim 1 , wherein the control unit turns off both the low-heat transforming unit and the high-heat transforming unit when the control unit determines that the power receiving unit has been charged up on the basis of a detection current of the current detecting unit.

7. The low-heat wireless power receiving device of claim 1 , wherein the low-heat transforming unit is a transforming unit using an FET as a switching element and the high-heat transforming unit is an LDO.

8. A low-heat wireless power receiving method comprising:

matching impedance by controlling an impedance matching/controlling unit by means of a control unit when a wireless power signal is received by a power receiving coil;

determining a charging load state of a power receiving unit in accordance with a time-lapse of charging the power receiving unit and a current level detected by a current detecting unit by means of the control unit; and

charging the power receiving unit with a charging power based on the wireless power signal by selectively turning on a low-heat transforming unit and a high-heat transforming unit in accordance with the determined charging load state by means of the control unit.

9. The method of claim 8 , wherein the determining of a charging load state of the power receiving unit in accordance with a time-lapse of charging the power receiving unit and a current level detected by a current detecting unit by means of the control unit, includes:

determining the charging load state of the power receiving unit as an initial light load state at an initial stage where the power receiving unit starts to be charged and determining a middle load state when a predetermined initial charging time has passed.

10. The method of claim 9 , wherein the charging of the power receiving unit with a charging power based on the wireless power signal by selectively turning on the low-heat transforming unit and the high-heat transforming unit in accordance with the determined charging load state by means of the control unit, includes:

turning off the low-heat transforming unit and turning on the high-heat transforming unit in the initial light load state; and

turning on the low-heat transforming unit and turning off the high-heat transforming unit when the middle load is determined.

11. The method of claim 10 , wherein the turning-on of the low-heat transforming unit and turning-off of the high-heat transforming unit when the middle load is determined, includes:

turning on both the low-heat transforming unit and the high-heat transforming unit for a predetermined time; and

turning on the low-heat transforming unit and turning off the high-heat transforming unit when the predetermined time has passed.

12. The method of claim 8 , wherein the determining of a charging load state of the power receiving unit in accordance with a time-lapse of charging the power receiving unit and a current level detected by a current detecting unit by means of the control unit, includes:

determining a light load state when a detection current level of the current detecting unit enters a predetermined range of a first level; and

determining that the power receiving unit has been charged up when the detection current level of the current detecting unit is equal to or less than a second level set lower than the first level.

13. The method of claim 12 , wherein the determining of a light load state when a detection current level of the current detecting unit enters a predetermined range of a first level includes:

turning off the low-heat transforming unit and turning on the high-heat transforming unit by means of the control unit.

14. The method of claim 13 , wherein the turning-off of the low-heat transforming unit and turning-on of the high-heat transforming unit by means of the control unit, includes:

turning on both the low-heat transforming unit and the high-heat transforming for a predetermined time by means of the control unit; and

turning off the low-heat transforming unit and keeping the high-heat transforming unit being turned on by means of the control unit when the predetermined time has passed.

15. The method of claim 12 , wherein the determining that the power receiving unit has been charged up when the detection current level of the current detecting unit is equal to or less than a second level set lower than the first level includes:

turning off both the low-heat transforming unit and the high-heat transforming unit by means of the control unit.