Transient protection apparatus and method for wireless power transfer system
A method includes in a switching cycle of a power converter in a wireless power transfer system, finding a time instant corresponding to one fourth of the switching cycle, wherein the power converter is coupled between an input power source and a transmitter coil magnetically coupled to a receiver coil, at the time instant, detecting a current flowing through the transmitter coil, wherein power transferred between the transmitter coil and the receiver coil is proportional to the current flowing through the transmitter coil, comparing the current flowing through the transmitter coil with a plurality of predetermined thresholds to determine whether a transient occurs, and applying a control mechanism to the power converter in response to an occurrence of the transient.
1. An apparatus comprising:
a transmitter coil configured to be magnetically couple to a receiver coil;
a power conversion device coupled to the transmitter coil; and
a controller configured to control a operating variable of the power conversion device in response to a operating condition change, wherein the controller comprises a one-fourth cycle detection block configured to set up a current sensing time instant corresponding to one fourth of a switching cycle of the power conversion device, and wherein at the current sensing time instant, a current flowing through the transmitter coil is detected and compared with a plurality of predetermined thresholds to determine which type of transient occurs.
2. The apparatus of claim 1 , wherein:
the power conversion device is a full-bridge converter.
3. The apparatus of claim 1 , wherein:
the controller is configured to adjust a switching frequency of the power conversion device in response to a transient.
4. The apparatus of claim 3 , wherein:
the transient is a coupling transient, wherein under the coupling transient, the controller is configured to apply a first control mechanism to the power conversion device.
5. The apparatus of claim 4 , wherein:
the transient is a load transient, wherein under the load transient, the controller is configured to apply a second control mechanism to the power conversion device.
6. The apparatus of claim 5 , wherein:
a transient response of the second control mechanism is faster than a transient response the first control mechanism.
7. The apparatus of claim 1 , further comprising:
a current sense block configured to sense an input current flowing into the power conversion device, wherein the sensed input current is used to generate a first threshold for determining whether a coupling transient occurs, and a second threshold for determining whether a load transient occurs.
8. The apparatus of claim 1 , wherein:
at the current sensing time instant, power transferred from the transmitter coil to the receiver coil is proportional to the current flowing through the transmitter coil.
9. A method comprising:
in a switching cycle of a power converter in a wireless power transfer system, finding a time instant corresponding to one fourth of the switching cycle;
at the time instant, detecting a current flowing through a transmitter coil of the wireless power transfer system;
comparing the current flowing through the transmitter coil with a plurality of predetermined thresholds; and
applying a control mechanism to the power converter based on comparing results of the step of comparing the current flowing through the transmitter coil with a plurality of predetermined thresholds.
10. The method of claim 9 , further comprising:
comparing the current flowing through the transmitter coil with a first predetermined threshold indicating a coupling transient; and
comparing the current flowing through the transmitter coil with a second predetermined threshold indicating a load transient.
11. The method of claim 10 , further comprising:
applying a first control mechanism to the power converter when the coupling transient is applied to the wireless power transfer system; and
applying a second control mechanism to the power converter when the load transient is applied to the wireless power transfer system, wherein a transient response of the second control mechanism is faster than a transient response of the first control mechanism.
12. The method of claim 9 , wherein:
at the time instant, power transferred from a transmitter to a receiver of the wireless power transfer system is proportional to the current flowing through the transmitter coil of the wireless power transfer system.
13. The method of claim 9 , further comprising:
detecting an input current of the wireless power transfer system; and
determining the plurality of predetermined thresholds based on the input current.
14. The method of claim 9 , further comprising:
in the switching cycle of the power converter, using a rising edge of a gate drive signal of the power converter as a starting point to start counting until finding the time instant corresponding to one fourth of the switching cycle.
15. A method comprising:
in a switching cycle of a power converter in a wireless power transfer system, finding a time instant corresponding to one fourth of the switching cycle, wherein the power converter is coupled between an input power source and a transmitter coil magnetically coupled to a receiver coil;
at the time instant, detecting a current flowing through the transmitter coil, wherein power transferred between the transmitter coil and the receiver coil is proportional to the current flowing through the transmitter coil;
comparing the current flowing through the transmitter coil with a plurality of predetermined thresholds to determine whether a transient occurs; and
applying a control mechanism to the power converter in response to an occurrence of the transient.
16. The method of claim 15 , further comprising:
comparing the current flowing through the transmitter coil with a first predetermined threshold to determine whether a coupling transient occurs; and
applying a first control mechanism to the power converter in response to an occurrence of the coupling transient.
17. The method of claim 16 , further comprising:
comparing the current flowing through the transmitter coil with a second predetermined threshold to determine whether a load transient occurs; and
applying a second control mechanism to the power converter in response to an occurrence of the load transient.
18. The method of claim 17 , wherein:
a transient response of the second control mechanism is faster than a transient response of the first control mechanism.
19. The method of claim 17 , further comprising:
sensing an input current of the wireless power transfer system; and
determining the first predetermined threshold and the second predetermined threshold based on the input current of the wireless power transfer system.
20. The method of claim 15 , further comprising:
using a rising edge of a gate drive signal of the power converter as a starting point to start counting until finding the time instant corresponding to one fourth of the switching cycle.