Systems and methods of reduction of parasitic losses in a wireless power system

• US 9,536,656 B2
• Filed: 05/09/2013
• Issued: 01/03/2017
• Est. Priority Date: 05/21/2012
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Oettinger, Eric Gregory, Muratov, Vladimir Alexander, Patil, Ravindra Krishna, Siddabattula, Kalyan, Waters, William Ford III
• Primary Examiner(s): Barnie, Rexford
• Assistant Examiner(s): Parries, Dru
• Application Number:
  US13/891,168
• Publication Number:
  US 20130307348A1
• Time in Patent Office: 1,335 Days
• Field of Search: 307/104
• US Class Current: 1/1
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/0029 with safety or protection devices or circuits

Abstract

Example embodiments of the systems and methods of reduction of parasitic losses in a wireless power system disclosed herein provide a practical means of accurately estimating parasitic losses in a wireless power transfer system irrespective of coupling. Such systems and methods may be used to generate an equation which predicts parasitic losses in a wireless power system. In an offset case, in which the transmitter and receiver are not directly coupled, losses associated with the recirculating current in the primary LC tank dominate the loss, and the transmitted power may be better estimated by measuring the power inputs, power outputs, and injected losses in a controlled environment; making a mathematical fit to an equation, which from the various power measurements and injected loss, predicts the expected transmitter losses; and then, in an operational environment, using the equation to predict parasitic losses based on the power inputs, power outputs and expected loss equation.

Claims

1. A method comprising:

transferring power from a transmitter to a receiver in a wireless power system;

measuring input power to the transmitter;

receiving a message from the receiver indicating power received at the receiver;

determining an amount of power lost in the transferring to indicate a presence of a parasitic loss in the wireless power system;

determining a portion of the transferred power attributed to parasitic loss in a foreign object;

reducing the power transmitted from the transmitter to a non-zero level so that the portion of transferred power lost in the foreign object does not exceed a predetermined safe level; and

ignoring messages from the receiver requesting a higher level of transmitted power, wherein the presence of a parasitic loss is determined by comparing measured losses to expected losses, the expected losses determined by measuring system characteristics in a controlled environment, by applying a mathematical fit of the system characteristics to an equation for predicting parasitic losses, wherein the equation calculates expected loss as the sum of;

a first constant multiplied by the square of transmitter peak voltage;

a second constant multiplied by the transmitter peak voltage; and

a third constant.

2. The method of claim 1, gradually reducing power transmitted from the transmitter until an acceptable loss threshold is reached.

3. The method of claim 2, further comprising setting the acceptable loss threshold in reference to a value received in a control error packet (CEP) message.

4. The method of claim 3, further comprising ignoring the CEP message and directly controlling based on the parasitic loss.

5. The method of claim 2, further comprising setting a transmit power regulation setpoint at the accepted loss threshold and regulating the transmit power at the transmit power regulation setpoint with a proportional loop.

6. The method of claim 2, wherein the reducing of the power transmitted from the transmitter occurs within a predefined range of parasitic loss.

7. A method comprising:

transferring power from a transmitter to a receiver in a wireless power system;

measuring input power to the transmitter;

receiving a message from the receiver indicating power received at the receiver;

determining an amount of power lost in the transferring to indicate a presence of a parasitic loss in the wireless power system;

determining a portion of the transferred power attributed to parasitic loss in a foreign object;

reducing the power transmitted from the transmitter to a non-zero level so that the portion of transferred power lost in the foreign object does not exceed a predetermined safe level; and

ignoring messages from the receiver requesting a higher level of transmitted power, wherein the presence of a parasitic loss is determined by comparing measured losses to expected losses, the expected losses determined by measuring system characteristics in a controlled environment, by applying a mathematical fit of the system characteristics to an equation for predicting parasitic losses, wherein the equation calculates expected loss as the sum of;

a first constant multiplied by the square of transmitter peak voltage;

a second constant multiplied by the transmitter peak voltage;

a third constant; and

a fourth constant multiplied by input current.

8. A system comprising:

a transmitter in a wireless power system configured to;

transmit power to a receiver;

measuring input power to the transmitter;

receiving a message from the receiver indicating power received at the receiver;

determining the presence of a parasitic loss in the wireless power system;

determining a portion of the transferred power attributed to parasitic loss in a foreign object;

reduce the power transmitted to a non-zero level so that the portion of transferred power lost in the foreign object does not exceed a predetermined safe level; and

ignoring messages from the receiver requesting a higher level of transmitted power, wherein the presence of a parasitic loss is determined by comparing measured losses to expected losses, the expected losses determined by measuring system characteristics in a controlled environment, by applying a mathematical fit of the system characteristics to an equation for predicting parasitic losses, wherein the equation calculates expected loss as the sum of;

a first constant multiplied by the square of transmitter peak voltage;

a second constant multiplied by the transmitter peak voltage;

a third constant; and

a fourth constant multiplied by input current.

9. The system of claim 8, wherein the transmitter is further configured to gradually reduce the power transmitted from the transmitter until an acceptable loss threshold is reached.

10. The system of claim 9, wherein the transmitter is further configured to set the acceptable loss threshold in reference to a value received in a control error packet (CEP) message.

11. The system of claim 10, wherein the transmitter is further configured to ignore the CEP message and directly control the transmitted power based on the parasitic loss.

12. The system of claim 9, wherein the transmitter is further configured to set a transmit power regulation setpoint at the accepted loss threshold and regulate the transmit power at the transmit power regulation setpoint with a proportional loop.

13. The system of claim 9, wherein the transmitter is configured to reduce the power transmitted from the transmitter when the parasitic loss is within a predefined range.

14. A system comprising:

a transmitter in a wireless power system configured to;

transmit power to a receiver;

measuring input power to the transmitter;

receiving a message from the receiver indicating power received at the receiver;

determining the presence of a parasitic loss in the wireless power system;

determining a portion of the transferred power attributed to parasitic loss in a foreign object;

reduce the power transmitted to a non-zero level so that the portion of transferred power lost in the foreign object does not exceed a predetermined safe level; and

ignoring messages from the receiver requesting a higher level of transmitted power, wherein the presence of a parasitic loss is determined by comparing measured losses to expected losses, the expected losses determined by measuring system characteristics in a controlled environment, by applying a mathematical fit of the system characteristics to an equation for predicting parasitic losses wherein the equation calculates expected loss as the sum of;

a first constant multiplied by the square of transmitter peak voltage;

a second constant multiplied by the transmitter peak voltage and the transmitter input current; and

a third constant.

15. A system comprising:

means for transmitting power to a receiver;

means for measuring input power to the transmitter;

means for receiving a message from the receiver indicating power received at the receiver;

means for determining the presence of a parasitic loss in the wireless power system;

means for determining a portion of the transferred power attributed to parasitic loss in a foreign object;

means for reducing the power transmitted to a non-zero level so that the portion of transferred power lost in the foreign object does not exceed a predetermined safe level; and

means for ignoring messages from the receiver requesting a higher level of transmitted power;

further comprising means for determining the presence of a parasitic loss by comparing measured losses to expected losses, the expected losses determined by measuring system characteristics in a controlled environment, by applying a mathematical fit of the system characteristics to an equation for predicting parasitic losses, wherein the equation calculates expected loss as the sum of;

a first constant multiplied by the square of transmitter peak voltage;

a second constant multiplied by the transmitter peak voltage; and

a third constant.