Single stage boost-asymmetric LLC

• US 9,325,249 B2
• Filed: 03/13/2013
• Issued: 04/26/2016
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Bucheru, Bogdan T.
• Primary Examiner(s): Laxton, Gary L
• Assistant Examiner(s): Sprenger, Kevin H
• Application Number:
  US13/802,311
• Publication Number:
  US 20140268902A1
• Time in Patent Office: 1,140 Days
• Field of Search: 363 15- 17, 363/20, 363 2101- 2103, 363/21.12, 363/21.15, 363/21.16, 363/21.18, 363/34, 363/37, 363/39, 363/44, 363/48, 363/74, 363/76, 363/77, 363 80- 82, 363/84, 363 89- 91, 363/123, 363125-127, 363170-173, 323/259, 323/261, 323/282, 323284-288
• US Class Current: 1/1
• 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 1/4258 using a single converter stage both for correction of AC input power factor and generation of a regulated and galvanically isolated DC output voltage H02M1/4241 takes precedence
• CPC Class Codes: H02M 3/3372 of the parallel type
• 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

An AC/DC power converter utilizing a single stage boost-asymmetric LLC topology is disclosed. The converter uses a combined pulse width modulation (PWM) and frequency modulation (FM) to achieve dual control for a single main magnetic element (transformer). The transformer provides an output voltage regulation throughout the primary-secondary isolation operating in resonant mode (LLC) by means of frequency modulation, while at the same time its magnetizing inductance is conditioning the input current and providing a boosted high voltage for energy storage purpose by means of duty cycle control. A single pair of complementary primary switches is used to drive the primary winding of the transformer in order to achieve both voltage regulation and power conditioning. The secondary side capacitors and the resonant inductor, which may be either integrated into the transformer or external to the transformer, achieve the resonant function of the transformer.

Claims

1. A power converter comprising:

a full bridge rectifier configured to receive an alternating current (AC) input for conversion into a rectified direct current (DC) output;

a transformer comprising a primary winding and a secondary winding, wherein a first primary terminal of the primary winding is connected to the full bridge rectifier;

a resonant inductor connected to a second primary terminal of the primary winding;

a storage capacitor and a pair of parallel switches that are disposed on a primary winding side of the transformer such that a current from the full bridge rectifier flows through the primary winding, then the resonant inductor, before flowing through the pair of parallel switches;

a pair of diodes connected to a first secondary terminal of the secondary winding; and

a pair of resonant capacitors connected to a second secondary terminal of the secondary winding.

2. The power converter of claim 1,

wherein the pair of parallel switches is comprised of a first switch and a second switch that is connected in parallel to the first switch.

3. The power converter of claim 2, wherein the storage capacitor is connected in series with the first switch.

4. The power converter of claim 3, further comprising:

output terminals on a secondary winding side of the transformer; and

a controller connected to the pair of parallel switches and the output terminals.

5. The power converter of claim 4, wherein the controller is configured to adjust a duty cycle of the pair of parallel switches and regulate an output voltage at the output terminals of the power converter.

6. The power converter of claim 5, wherein a boosted voltage of the primary winding is controlled by adjusting the duty cycle, and a gain on the secondary winding is controlled by adjusting a switching frequency of the pair of parallel switches.

7. The power converter of claim 5, wherein the pair of resonant capacitors are connected in parallel to the output terminals on the secondary winding side of the transformer.

8. The power converter of claim 1, wherein an inductance value of the resonant inductor is based on a leakage inductance of the transformer.

9. The power converter of claim 1, wherein the pair of parallel switches is comprised of high frequency metal oxide semiconductor field-effect transistor (MOSFET) switches.

10. The power converter of claim 1, further comprising:

an input filter capacitor, and

an output filter capacitor,

wherein the input filter capacitor is disposed on the primary winding, and

the output filter capacitor is disposed on the secondary winding.

11. A method for operating a power converter that includes a full bridge rectifier, a pair of parallel switches, and a transformer, the method comprising:

converting, using the full bridge rectifier, an external alternating current (AC) power into a rectified direct current (DC) power;

converting, using the pair of parallel switches, the rectified DC power into an internal DC power by switching the pair of parallel switches; and

converting the internal DC power into an output DC power using power conditioning and voltage regulation,

wherein the power conditioning is performed by an inductance of the transformer and a resonant inductor that is connected to a primary side of the transformer such that a current from the full bridge rectifier flows through a primary winding of the transformer, then the resonant inductor, before flowing through the pair of parallel switches, and

wherein the voltage regulation is performed by resonant capacitors on a secondary winding side of the transformer, the resonant capacitors configured to resonate with the resonant inductor.

12. The method of claim 11,

wherein the pair of parallel switches comprises a first switch and a second switch that is connected in parallel to the first switch.

13. The method of claim 12,

wherein a resonant mode of the power converter is provided by the primary winding, the resonant inductor, and the resonant capacitors.

14. The method of claim 13, wherein the power converter is operated in an asymmetric mode and a duty cycle of the pair of parallel switches is not equal to 0.5 when operating in the asymmetric mode.

15. The method of claim 14, wherein converting the rectified DC power into the internal DC power and converting the internal DC power into the output DC power comprise:

using a feedback loop, with a controller, to adjust the duty cycle and a switching frequency of the pair of parallel switches so that the output DC power is voltage regulated.

16. The method of claim 15, wherein the internal DC power is controlled by adjusting the duty cycle and a gain on the secondary winding side of the transformer is controlled by adjusting the switching frequency.

17. A power converter comprising:

a full bridge rectifier configured to convert an alternating current (AC) input to a direct current (DC) output, and provide the DC output to a primary side of a transformer of the power converter; and

a resonant tank comprising (i) a resonant inductor connected to the primary side of the transformer and (ii) resonant capacitors connected on a secondary side of the transformer, wherein the resonant capacitors resonate with the resonant inductor in response to a switching operation of parallel switches connected at the primary side of the transformer such that a current from the full bridge rectifier flows through a primary winding of the transformer, then the resonant inductor, before flowing through the parallel switches.

18. The converter of claim 17, wherein the resonant inductor is connected in series with the primary side of the transformer and the parallel switches include at least two switches that are connected in parallel relative to each other.

19. The converter of claim 17, wherein the resonant tank further comprises:

a storage capacitor connected in series with a switch of the parallel switches.

20. The converter of claim 17, wherein the parallel switches operate according to a switching frequency that causes the resonant capacitors to resonate.