Boosted output inverter for electronic devices

• US 10,389,274 B2
• Filed: 12/01/2017
• Issued: 08/20/2019
• Est. Priority Date: 04/07/2017
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Qiu, Weihong, Dayal, Rohan, Moussaoui, Zaki
• Primary Examiner(s): Berhane, Adolf D
• Application Number:
  US15/829,610
• Publication Number:
  US 20180294742A1
• Time in Patent Office: 627 Days
• Field of Search: 363 2102, 363123, 363131, 363132, 323273, 323282, 323283
• 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: H02M 7/4815 Resonant converters H02M7/4811 and H02M7/4826 take precedence
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• 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

A power converter can be implemented with a boosted-output inverter, which integrates the functionality of a voltage converter (e.g., boost converter) and a voltage inverter. In particular, a boosted-output inverter includes a primary tank inductor coupled in series with a secondary tank inductor at a central node. The boosted-output inverter also includes two voltage-controlled switches that respectively define a charging phase and a discharging phase of the primary tank inductor. While the primary tank inductor is charging, the secondary tank inductor is inverted to ground. In this manner, current though the secondary tank inductor alternates at a voltage boosted by the fly-back voltage of the primary tank inductor exhibited when the primary tank inductor transitions from the charging mode to the discharging mode. In many cases, the secondary tank inductor is a transmit coil of a transmitter of a wireless power transfer system.

Claims

1. A power converter comprising:

a primary tank inductor comprising;

a first input lead to receive regulated direct current from a power source; and

a first output lead;

a first switch comprising;

a source lead coupled to the first output lead of the primary tank inductor; and

a first drain lead;

an output capacitor coupling the first drain lead of the first switch to ground;

a second switch, comprising a second drain lead coupled to the first output lead of the primary tank inductor; and

a secondary tank inductor comprising;

a second input lead coupled directly to the first output lead of the primary tank inductor; and

a second output lead coupled through a resonant capacitor to ground.

2. The power converter of claim 1, wherein:

the source lead of the first switch is a first source lead; and

the second switch comprises a second source lead coupled to ground.

3. The power converter of claim 1, further comprising a third switch coupled in series with the secondary tank inductor, interposing the resonant capacitor and ground, the third switch configured to selectively enable or disable the secondary tank inductor.

4. The power converter of claim 1, wherein:

the secondary tank inductor is a first secondary tank inductor; and

the power converter further comprises a set of secondary tank inductors comprising the first secondary tank inductor, each secondary tank inductor of the set of secondary tank inductors directly coupled to the first output lead of the primary tank inductor.

5. The power converter of claim 4, further comprising a set of selection switches, each selection switch in series with a respective one secondary tank inductor of the set of secondary tank inductors.

6. The power converter of claim 4, further comprising a set of secondary output capacitors, each secondary output capacitor coupling a respective one secondary tank inductor of the set of secondary tank inductors to ground.

7. The power converter of claim 1, wherein the secondary tank inductor is a transmit coil of a transformer of a wireless power transfer system.

8. The power converter of claim 7, wherein the transformer is an air gap transformer.

9. A power converter comprising:

an output capacitor coupled to ground;

a half-bridge comprising;

a high-side switch coupled to ground via the output capacitor;

a low-side switch coupled to ground directly; and

a central node between a source of the high-side switch and a drain of the low-side switch;

a boost inductor coupled to the central node;

a resonant circuit comprising a secondary tank inductor directly coupled to the central node; and

a processor coupled to the half-bridge and configured to drive the high-side switch and low-side switch at substantially opposite duty cycles and at a resonant frequency of the resonant circuit.

10. The power converter of claim 9, wherein the resonant circuit comprises a resonant capacitor coupling an output node of the secondary tank inductor to ground.

11. The power converter of claim 9, wherein the processor is configured to increase a duty cycle of the high-side switch to increase current in the resonant circuit.

12. The power converter of claim 9, wherein the processor is configured to transition the high-side switch from a closed state to an open state when voltage across the high-side switch is substantially equal to zero volts.

13. The power converter of claim 9, wherein:

the resonant circuit is a first resonant circuit; and

the power converter further comprises a second resonant circuit parallel to the first resonant circuit.

14. The power converter of claim 9, wherein the processor is configured to limit a duty cycle of the high-side switch based on a maximum threshold voltage of the central node.

15. The power converter of claim 9, wherein the boost inductor receives regulated direct current from a regulated direct current source.

16. A method of converting low-voltage direct current to a higher-voltage alternating current, the method comprising:

at a selectable duty cycle;

enabling a low-side MOSFET of a power converter to connect a primary tank inductor to ground; and

disabling the low-side MOSFET and enabling a high-side MOSFET to connect an output of the primary tank inductor to an input lead of a secondary tank inductor and parallel to an output capacitor; and

adjusting the selectable duty cycle to change current through the secondary tank inductor.

17. The method of claim 16, further comprising enabling a selector MOSFET to couple the secondary tank inductor to a central node between the high-side MOSFET and the low-side MOSFET.

18. The method of claim 16, wherein:

the secondary tank inductor is a first secondary tank inductor;

the selector MOSFET is a first selector MOSFET; and

the method further comprises;

enabling a second selector MOSFET to couple a second secondary tank inductor to the central node.

19. The method of claim 17, further comprising modifying the selectable duty cycle based on a maximum threshold voltage of the low-side MOSFET.