Wireless power transmission device and operating method of wireless power transmitter

1 . A wireless power transmission device for supplying wireless power to a wireless power reception device, the wireless power transmission device comprising:

a converter circuit configured to generate a test signal based on an input current generated directly from a power source, the test signal having a test frequency;

a resonant tank configured to transmit wireless power in response to the test signal;

a current sensing circuit connected to the power source, the current sensing circuit configured to directly sense the input current when the wireless power is transmitted; and

a controller configured to control the converter circuit to generate the test signal, calculate a quality factor of the resonant tank based on the input current directly sensed by the current sensing circuit, compare the quality factor with a reference quality factor, and control the converter circuit to reset the test frequency or transmit a digital ping signal to the wireless power reception device according to a result of comparing the quality factor with the reference quality factor.

2 . The wireless power transmission device of claim 1 , wherein the controller is configured to:

control the converter circuit to sequentially generate a signal having a frequency in a stored frequency range as the test signal,

sequentially store sensed values corresponding to input currents as signals are sequentially generated,

set an input current corresponding to a greatest value among the stored sensed values as a greatest input current,

set the frequency as a test resonance frequency when the greatest input current is sensed,

calculate at least one cut-off frequency based on the stored sensed values and the greatest input current, and

calculate the quality factor based on the test resonance frequency and the at least one cut-off frequency.

3 . The wireless power transmission device of claim 2 , wherein

the test signal is a square wave having a test duty ratio in a stored duty ratio range, and

the controller is configured to set the frequency as the at least one cut-off frequency in response to sensing at least one input current corresponding to at least one sensed value that is 3 dB less than the greatest value among the stored sensed values.

4 . The wireless power transmission device of claim 1 , wherein the controller is configured to:

control the converter circuit to generate a signal having a stored initial frequency as the test signal,

store a sensed value corresponding to a specified input current sensed as the signal is generated,

calculate an amount of change per unit time of the specified input current using the sensed value,

determine whether a sign of the amount of change per unit time has changed, and

calculate a frequency step in the initial frequency and reset the calculated frequency step to the test frequency when the sign is constant.

5 . The wireless power transmission device of claim 4 , wherein, when the sign is changed, the controller is configured to:

set, as a greatest input current, an input current corresponding to the sensed value stored when the sign is changed,

set a frequency as a test resonance frequency when the greatest input current is sensed,

calculate one cut-off frequency based on the stored sensed values and the greatest input current, and

calculate the quality factor based on the test resonance frequency and the one cut-off frequency.

6 . The wireless power transmission device of claim 1 , wherein the controller is configured to:

control the converter circuit to generate, as the test signal, a first signal having a specified resonant tank resonance frequency,

store a first sensed value corresponding to an input current sensed as the first signal is generated,

calculate a cut-off frequency greater than the specified resonant tank resonance frequency based on a stored bandwidth and the specified resonant tank resonance frequency,

control the converter circuit to generate a second signal having the cut-off frequency as the test signal,

store a second sensed value corresponding to an input current sensed as the second signal is generated, and

compare the first sensed value with the second sensed value, and reset the test frequency when the first sensed value is less than the second sensed value.

7 . The wireless power transmission device of claim 6 , wherein the controller, when the first sensed value is greater than or equal to the second sensed value, is configured to:

subtract a frequency step of a stored positive number in the cut-off frequency,

control the converter circuit to generate a signal having a subtracted frequency as the test frequency,

store a sensed value corresponding to an input current sensed as the signal is generated,

calculate an amount of change of the sensed input current per unit time using the sensed value,

determine whether a sign of the amount of change is changed, and

subtract the frequency step from the subtracted frequency according to a determination result or calculate the quality factor based on the subtracted frequency and the sensed value.

8 . The wireless power transmission device of claim 7 , wherein, if the sign is constant, the controller is configured to:

subtract the frequency step from the subtracted frequency,

when the sign is changed, set, as a greatest input current, an input current corresponding to the sensed value stored when the sign is changed,

set a frequency as a test resonance frequency when the greatest input current is sensed,

calculate one cut-off frequency based on the stored sensed value and the greatest input current, and

calculate the quality factor based on the test resonance frequency and the one cut-off frequency.

9 . A wireless power transmission device for supplying power to a wireless power reception device, the wireless power transmission device comprising:

a power source connected between a first node and ground;

a current sensing circuit connected between the first node and a second node;

a converter circuit including a first transistor connected between the second node and a third node, a second transistor connected between the second node and a fourth node, a third transistor connected between the third node and the ground, and a fourth transistor connected between the fourth node and the ground;

a resonant tank connected between the third node and the fourth node; and

a controller connected to an output terminal of the current sensing circuit, the controller connected to a gate electrode of each of the first to fourth transistors, and the controller configured to output a first switching signal to the gate electrode of the first transistor, output a second switching signal to the gate electrode of the second transistor, output a third switching signal to the gate electrode of the third transistor, and output a fourth switching signal to the gate electrode of the fourth transistor,

wherein at least one signal group of a first signal group including the first and third switching signals and a second signal group including the second and fourth switching signals is a square wave having a test frequency and a test duty ratio, and

wherein a phase difference between two switching signals included in the at least one signal group is 180 degrees.

10 . The wireless power transmission device of claim 9 , wherein

the first signal group is the square wave, and

one of the second and fourth switching signals has a turn-on level for turning on a transistor, and another one of the second and fourth switching signals has a turn-off level.

11 . The wireless power transmission device of claim 10 , wherein

a first voltage applied to the fourth node is a voltage level of the ground, and

a second voltage applied to the third node is a square wave having the test frequency.

12 . The wireless power transmission device of claim 11 , wherein,

when a voltage level of the first switching signal is a turn-on level, a voltage level of the second switching signal is a turn-off level, a voltage level of the third switching signal is a turn-off level, and a voltage level of the fourth switching signal is a turn-on level, the voltage level of the first voltage is lower than the voltage level of the second voltage, and

when the voltage level of the first switching signal is a turn-off level, the voltage level of the second switching signal is a turn-off level, the voltage level of the third switching signal is a turn-on level, and the voltage level of the fourth switching signal is a turn-on level, the voltage level of the first voltage is the same as the voltage level of the second voltage.

13 . The wireless power transmission device of claim 9 , wherein

the first signal group and the second signal group are the square wave,

a phase difference between the first switching signal and the fourth switching signal is 0 degrees or 360 degrees, and

a phase difference between the second switching signal and the third switching signal is 0 degrees or 360 degrees.

14 . The wireless power transmission device of claim 13 , wherein

a first voltage applied to the fourth node and a second voltage applied to the third node are square waves having the test frequency, and

a phase difference between the first voltage and the second voltage is 180 degrees.

15 . The wireless power transmission device of claim 14 , wherein,

when voltage levels of the first switching signal and the fourth switching signal are turn-off levels and voltage levels of the second switching signal and the third switching signal are turn-on levels, the voltage level of the first voltage is higher than the voltage level of the second voltage, and

when voltage levels of the first switching signal and the fourth switching signal are turn-on levels and voltage levels of the second switching signal and the third switching signal are turn-off levels, the voltage level of the first voltage is lower than the voltage level of the second voltage.

16 . An operating method of a wireless power transmitter for controlling a resonant tank, the method comprising:

setting a test frequency of a test signal applied to the resonant tank;

applying the test signal to the resonant tank to transmit wireless power;

sensing an input current generated directly from a power source, in response to the transmitted wireless power;

calculating a quality factor of the resonant tank based on the directly sensed input current;

comparing the quality factor with a reference quality factor; and

resetting the test frequency or performing an operation of wirelessly transmitting power according to a result of comparing the quality factor with the reference quality factor.

17 . The method of claim 16 , wherein

the setting of the test frequency comprises setting a frequency included in a stored frequency range as the test frequency, and

the calculating of the quality factor of the resonant tank comprises:

sequentially applying a signal having the frequency as the test signal to the resonant tank, sequentially sensing input currents generated from the power source, and sequentially storing sensed values corresponding to the input currents;

setting a specified input current corresponding to a greatest value among the stored sensed values as a greatest input current, and setting the frequency as a test resonance frequency when the greatest input current is sensed;

calculating a bandwidth based on a cut-off frequency in response to sensing at least one input current corresponding to at least one sensed value 3 dB less than the greatest value among the stored sensed values; and

calculating the quality factor using the test resonance frequency and the bandwidth.

18 . The method of claim 16 , wherein

the setting of the test frequency comprises setting a stored initial frequency as the test frequency, and

wherein the calculating of the quality factor of the resonant tank comprises:

applying a signal having the initial frequency as the test signal to the resonant tank, sensing a specified input current generated from the power source, and storing a sensed value corresponding to the specified input current;

calculating a change amount of the specified input current per unit time using the sensed value;

determining whether a sign of the change amount is changed;

repeating changing the initial frequency to store the sensed value and calculating the change amount until the sign is changed;

setting an input current corresponding to the stored sensed value as a greatest input current when the sign is changed, and setting a frequency as a test resonance frequency when the greatest input current is sensed;

calculating a bandwidth based on a cut-off frequency in response to sensing an input current corresponding to a sensed value 3 dB less than the stored sensed value, when the sign of the stored sensed values is changed; and

calculating the quality factor using the test resonance frequency and the bandwidth.

19 . The method of claim 16 , wherein

the setting of the test frequency comprises setting a specified resonance frequency as a first test frequency, and

wherein the calculating of the quality factor of the resonant tank comprises:

applying a first test signal to the resonant tank, sensing a first input current generated from the power source, and storing a first sensed value corresponding to the first input current;

calculating a first cut-off frequency greater than the specified resonance frequency using a stored first bandwidth and the specified resonance frequency, and setting the first cut-off frequency as a second test frequency;

storing a second sensed value corresponding to a second input current sensed by applying a second test signal to the resonant tank;

comparing the first sensed value with the second sensed value; and

repeating setting the test frequency, storing the first sensed value, setting the second test frequency and storing the second sensed value until the first sensed value is greater than or equal to the second sensed value.

20 . The method of claim 19 , wherein the calculating of the quality factor of the resonant tank comprises:

subtracting a frequency step of a stored positive number from a frequency when the first sensed value is greater than or equal to the second sensed value;

storing a sensed value corresponding to the sensed input current by applying a signal having a subtracted frequency to the resonant tank as the test frequency;

calculating a change amount of the sensed input current per unit time using the sensed value;

determining whether a sign of the change amount is changed;

repeating subtracting a positive frequency step, storing the sensed value, and calculating the change amount until the sign is changed;

setting an input current corresponding to the stored sensed values as a greatest input current when the sign is changed, and setting a frequency as a test resonance frequency when the greatest input current is sensed;

calculating a second bandwidth based on a second cut-off frequency in response to sensing an input current corresponding to a sensed value 3 dB less than the stored sensed value, when the sign of the stored sensed values is changed; and

calculating the quality factor using the test resonance frequency and the second bandwidth.