Wireless power transmitter
A wireless power transmitter includes: a converter including switching elements forming a bridge circuit and configured to output an alternating current (AC) voltage in response to control signals; a resonator including a resonant capacitor and a resonant coil, and configured to receive the AC voltage to transmit power wirelessly; and a controller configured to set a dead time at which a magnitude of the AC voltage is substantially zero in response to a signal received from a wireless power receiver.
1. A wireless power transmitter comprising:
a converter comprising switching elements forming a bridge circuit, and configured to output an alternating current (AC) voltage in response to control signals;
a resonator comprising a resonant capacitor and a resonant coil, and configured to receive the AC voltage to transmit power wirelessly; and
a controller configured to set a dead time at which a magnitude of the AC voltage is substantially zero, in response to a signal received from a wireless power receiver.
2. The wireless power transmitter of claim 1 , wherein the switching elements are configured to be respectively turned on or off in response to a corresponding signal among the control signals, an amplitude of the AC voltage is determined according to an operating duty cycle of one of the switching elements, and a frequency of the AC voltage is determined according to an operating frequency of the switching signals.
3. The wireless power transmitter of claim 1 , wherein the converter further comprises
a first switching element connected between a first node, an end of the resonator, and a second node,
a second switching element connected between the first node and a ground,
a third switching element connected between a third node, another end of the resonator, and the second node,
a fourth switching element connected between the third node and the ground,
a coil connected between the first node and a terminal to which an input voltage is applied externally, and
a capacitor connected between the second node and the ground.
4. The wireless power transmitter of claim 1 , wherein the controller is further configured to vary a frequency of the control signals in response to an amount of power required by the wireless power receiver being equal to or greater than a reference value, and to vary the dead time in response to the amount of power required by the wireless power receiver being equal to or lower than the reference value.
5. The wireless power transmitter of claim 4 , wherein the varying of the frequency of the control signals comprises varying the frequency of the control signals within a range of a frequency equal to or greater than a first reference frequency to a frequency equal to or less than a second reference frequency, and the frequency of the control signals is fixed at the second reference frequency when the dead time is varied.
6. The wireless power transmitter of claim 5 , wherein the controller is further configured to fix the frequency of the control signals to the second reference frequency, and to vary a duty cycle of one of the control signals.
7. The wireless power transmitter of claim 5 , wherein the controller is configured to fix the frequency of the control signals to the first reference frequency, and to vary a duty cycle of one of the control signals.
8. The wireless power transmitter of claim 1 , wherein
the bridge circuit comprises a full bridge circuit comprising a first leg and a second leg, and
the controller is further configured to output the control signals such that an on-duty cycle of a low side switching element of the first leg and an on-duty cycle of a high side switching element of the second leg are different from each other.
9. A wireless power transmitter comprising:
a converter comprising switching elements forming a bridge circuit, and configured to output an alternating current (AC) voltage in response to control signals;
a resonator comprising a resonant capacitor and a resonant coil, and configured to receive the AC voltage to transmit power wirelessly; and
a controller configured to perform a first mode operation in which an operating duty cycle of one of the control signals is fixed and a frequency of the control signals is varied and output, and a second mode operation in which a duty cycle and the frequency of the control signals are fixed and a phase difference between two of the control signals is varied and output.
10. The wireless power transmitter of claim 9 , wherein the switching elements are respectively turned on or off in response to a corresponding signal among the control signals, an amplitude of the AC voltage is determined according to an operating duty cycle of one of the switching elements, and a frequency of the AC voltage is determined according to an operating frequency of the switching elements.
11. The wireless power transmitter of claim 10 , wherein the converter further comprises
a first switching element connected between a first node, an end of the resonator, and a second node,
a second switching element connected between the first node and a ground,
a third switching element connected between a third node, another end of the resonator, and the second node,
a fourth switching element connected between the third node and the ground,
a coil connected between the first node and a terminal to which an input voltage is applied externally, and
a capacitor connected between the second node and the ground.
12. The wireless power transmitter of claim 9 , wherein the controller is further configured to perform the first mode operation in response to an amount of power required by a wireless power receiver being equal to or greater than a reference value, and to perform the second mode operation in response to the amount of power required by the wireless power receiver being equal to or lower than the reference value.
13. The wireless power transmitter of claim 9 , wherein the controller is further configured to set a detection duty cycle while determining whether a wireless power receiver is present, to fix a duty cycle of one of the control signals to the detection duty cycle in the first mode operation and the second mode operation, and to output the control signals.
14. The wireless power transmitter of claim 13 , wherein the controller is further configured to output the control signals such that the frequency of the control signals is varied within a range of a frequency equal to or greater than a first reference frequency to a frequency equal to or less than a second reference frequency, when the first mode operation is performed, and to fix the frequency of the control signals to the second reference frequency and to output the control signals by varying the phase difference, when the second mode operation is performed.
15. The wireless power transmitter of claim 9 , wherein
the bridge circuit comprises a full bridge circuit comprising a first leg and a second leg, and
the controller is further configured to output the control signals such that an on-duty cycle of a low side switching element of the first leg and an on-duty cycle of a high side switching element of the second leg are different from each other.
16. The wireless power transmitter of claim 15 , wherein
the low side switching element of the first leg and a high side switching element of the first leg are configured to be turned on or off alternately with respect to each other,
a low side switching element of the second leg and the high side switching element of the second leg are configured to be turned on or off alternately with each other, and
the controller is further configured to vary and output a phase difference between control signals, among the control signals, controlling switching elements of the first leg and control signals, among the control signals, controlling switching elements of the second leg, in the second mode operation.
17. A wireless power transmitter comprising:
a converter comprising a bridge circuit comprising switching elements;
a controller configured to
output control signals controlling the switching elements to cause the converter to output an alternating current (AC) voltage, and
vary a phase difference between two of the control signals, independently of operating duty cycles of the two of the control signals, to adjust the AC voltage; and
a resonator configured to receive the AC voltage to transmit power.
18. The wireless power transmitter of claim 17 , wherein the controller is further configured to
fix an operating duty cycle of one of the control signals and vary a frequency of the control signals, in a first mode operation, and
fix an operating duty cycle and the frequency of the control signals, and vary the phase difference between the two of the control signals, in a second mode operation.
19. The wireless power transmitter of claim 18 , wherein the controller is further configured to
vary the frequency of the control signals within a range of a frequency equal to or greater than a first reference frequency to a frequency equal to or less than a second reference frequency, in the first mode operation, and
fix the frequency of the control signals to the second reference frequency, in the second mode operation.
20. The wireless power transmitter of claim 18 , wherein the controller is further configured to perform one of the first mode operation and the second mode operation based on an amount of power required by a receiver receiving the transmitted power.