CLASS E AMPLIFIER OVERLOAD DETECTION AND PREVENTION

• US 20140252873A1
• Filed: 05/22/2014
• Published: 09/11/2014
• Est. Priority Date: 08/16/2011
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Irish, Linda S., Toncich, Stanley Slavko, Von Novak, William H. III
• Granted Patent: US 9,281,711 B2
• Time in Patent Office: Days
• US Class Current: 307/104
• 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 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02M 1/0058 by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero using an auxiliary actively switched resonant commutation circuit connected to an intermediate DC voltage or between two push-pull branches of an inverter bridge H02M7/4811; in resonant inverters H02M7/4815; in inverters operating from a resonant DC source H02M7/4826
• CPC Class Codes: H02M 7/4815 Resonant converters H02M7/4811 and H02M7/4826 take precedence
• CPC Class Codes: H03F 1/523 for amplifiers using field-effect devices H03F1/526 takes precedence
• CPC Class Codes: H03F 3/2176 Class E amplifiers
• CPC Class Codes: H03F 3/245 with semiconductor devices only
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

Systems, methods and apparatus are disclosed for amplifiers for wireless power transfer. In one aspect a method is provided for controlling operation of an amplifier, such as a class E amplifier. The method may include monitoring an output of the amplifier. The method may further include adjusting a timing of an enabling switch of the amplifier based on the output of the amplifier.

Claims

1. A wireless power transfer apparatus, comprising:

an amplifier circuit operably coupled to a coil configured to wirelessly transfer power to a receiver, the amplifier circuit comprising a switching element; and

a monitoring circuit configured to;

cause the switching element to be in an open position during a first phase,

cause the switching element to be in a closed position during a second phase in response to determining that a value indicative of a voltage across the switching element falls below a threshold value, and

cause the switching element to be in a closed position during a third phase.

2. The apparatus of claim 1, wherein the monitoring circuit is further configured to cause the switching element to be in an open position if the voltage across the switching element is greater than the threshold value during a startup phase and until the amplifier circuit is in a stable condition.

3. The apparatus of claim 1, wherein:

the amplifier circuit is configured to not conduct current across the switching element during the first phase, and

the monitoring circuit is further configured to;

adaptively conduct current across the switching element based on the voltage across the switching element during the second phase, and

conduct current across the switching element during the third phase.

4. The apparatus of claim 1, wherein the monitoring circuit is configured to cause the switching element to be in a closed position during the third phase in response to determining that the switching element was not closed during the second phase.

5. The apparatus of claim 1, wherein the switching element comprises a gate terminal, and wherein the monitoring circuit is further configured to conduct current across the switching element by driving the gate terminal with a first gate voltage.

6. The apparatus of claim 5, wherein the monitoring circuit is further configured to:

drive the gate terminal with a second gate voltage during the first phase,

adaptively drive the gate terminal with the first gate voltage based on the voltage across the switching element during the second phase, and

drive the gate terminal with the second voltage above the gate voltage threshold during the third phase.

7. The apparatus of claim 6, wherein the amplifier circuit further comprises a class E amplifier and the switching element comprises a field effect transistor comprising the gate terminal.

8. The apparatus of claim 1, wherein the threshold value is greater than zero.

9. The apparatus of claim 1, wherein the threshold value is set to a level to cause the switching element to be in a closed position before the voltage across the switching element becomes negative.

10. The apparatus of claim 1, wherein the first phase comprises a first time period, wherein the second phase comprises a second time period after the first time period, and wherein the third phase comprises a third time period after the first time period and the second time period.

11. A method of wireless charging, comprising:

opening a switching element of an amplifier circuit coupled to a coil configured to wirelessly transfer power to a receiver during a first phase;

closing the switching element during a second phase in response to determining that a voltage across the switching element falls below a threshold value; and

closing the switching element during a third phase.

12. The method of claim 11, wherein the opening a switching element comprises not conducting current across the switching element, and the closing the switching element comprises conducting current across the switching element.

13. The method of claim 11, wherein the opening or closing the switching element comprises a field effect transistor having a gate terminal configured to be driven by an input waveform to be in an open position or a closed position.

14. A wireless power transfer apparatus, comprising:

a coil configured to wirelessly transfer power via a wireless field;

a driver circuit operably coupled to the coil, the driver circuit configured to receive an input waveform signal; and

a controller configured to adjust a timing of the input waveform signal based on monitoring characteristics of the driver circuit, the characteristics indicative of reactive variations of a load presented to the driver circuit caused by variations in coupling via the wireless field.

15. The apparatus of claim 14, wherein the controller is further configured to monitor the characteristics based on variations in coupling due to a variable number of receivers configured to couple to the wireless field.

16. The apparatus of claim 14, wherein the timing of the input waveform signal is configured to match an output waveform signal of the driver circuit, the output waveform signal indicative of reactive variations of the load presented to the driver circuit.

17. The apparatus of claim 14, wherein a pulse width of the output waveform signal is configured to match a duty cycle of the driver circuit.

18. The apparatus of claim 14, wherein the driver circuit comprises a class E amplifier circuit comprising a switching element controlled by the input waveform signal.

19. The apparatus of claim 18, wherein the input waveform signal is configured to:

adjust a state of the switching element to cause current to not be conducted through the switching element during a first phase; and

adjust the state of the switching element to cause current to be conducted through the switching element during a second phase after the first phase, and wherein the controller is configured to;

adjust the timing of the input waveform to cause current to be conducted through the switching element during a third phase between the first and second phase in response to determining that a value indicative of a voltage across the switching element falls below a threshold value.

20. The apparatus of claim 19, wherein the threshold is determined to cause current to be conducted through the switching element before the voltage across the switching element becomes negative.