SINGLE STAGE BOOST-ASYMMETRIC LLC

• US 20140268902A1
• Filed: 03/13/2013
• Published: 09/18/2014
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: BUCHERU, Bogdan T.
• Granted Patent: US 9,325,249 B2
• Time in Patent Office: Days
• US Class Current: 363/21.02
• 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 single stage boost-asymmetric LLC AC/DC power switching converter, the converter comprising:

a bridge rectifier, the bridge rectifier receiving an external AC (alternating current) power for conversion into a rectified DC (direct current) power; and

a power stage, the power stage receiving the rectified DC power for conversion into an output DC power, the power stage comprising;

a high frequency magnetic transformer, the high frequency magnetic transformer comprising a primary winding and a secondary winding,

a pair of complementary switches,

a resonant tank, the resonant tank comprising a resonant inductor and a pair of resonant capacitors, and

a high voltage storage capacitor,

wherein the pair of complementary switches, the resonant inductor, and the high voltage storage capacitor are disposed on a primary winding side of the power stage,

wherein the pair of resonant capacitors is disposed on a secondary winding side of the power stage.

2. The converter of claim 1:

wherein the pair of complementary switches is comprised of a first switch and a second switch, the first switch being switched to be opened and closed at a switching frequency with a duty cycle of D, the second switch being switched to be opened and closed at the same switching frequency with a duty cycle of (1-D) so that the second switch is opened when the first switch is closed and the second switch is closed when the first switch is opened,

wherein the duty cycle D cannot be 0 or 1.

3. The converter of claim 2 wherein the converter is operated mostly in an asymmetric mode, wherein the duty cycle D is not equal to 0.5 when operating in the asymmetric mode.

4. The converter of claim 3:

wherein the resonant inductor has a first and a second terminal,

wherein the high voltage storage capacitor has a first and a second terminal,

wherein the first terminal of the resonant inductor is connected to the primary winding,

wherein the first switch is disposed between the second terminal of the resonant inductor and the first terminal of the high voltage storage capacitor, and

wherein the second switch is disposed between the second terminal of the resonant inductor and the second terminal of the high voltage storage capacitor.

5. The converter of claim 4 further comprising a controller for using a feedback loop to adjust the duty cycle D and the switching frequency so that an output voltage of the converter is regulated.

6. The converter of claim 5 wherein a boosted high voltage on the primary winding side of the power stage is controlled by adjusting the duty cycle D and a gain on the secondary winding side of the power stage is controlled by adjusting the switching frequency.

7. The converter of claim 1, wherein the resonant inductor is an independent inductor.

8. The converter of claim 1, wherein the resonant inductor is derived from a leakage inductance of the transformer.

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

10. The 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 side of the power stage,

wherein the output filter capacitor is disposed on the secondary winding side of the power stage.

11. A method for operating a single stage boost-asymmetric LLC AC/DC power switching converter including a bridge rectifier, a pair of complementary switches and a single stage LLC transformer, the method comprising:

processing, with the bridge rectifier, an external AC (alternating current) power into a rectified DC (direct current) power; and

processing, with the pair of complementary switches, the rectified DC power into an internal DC power associated with a boosted high voltage by switching the pair of complementary switches to be opened and closed at a switching frequency with duty cycles of D and (1-D),

processing, with the single stage LLC transformer, the internal DC power into an output DC power with power conditioning and voltage regulation,

wherein the power conditioning is performed by an inductance of the single stage LLC transformer,

wherein the voltage regulation is performed by the single stage LLC transformer by means of frequency modulation operating in resonant mode (LLC).

12. The method of claim 11:

wherein the pair of complementary switches comprises a first switch and a second switch,

wherein the first switch is switched to be opened and closed at the switching frequency with a duty cycle of D, the second switch is switched to be opened and closed at the same switching frequency with a duty cycle of (1-D) so that the second switch is opened when the first switch is closed and the second switch is closed when the first switch is opened,

wherein the duty cycle D cannot be 0 or 1.

13. The method of claim 12:

wherein the single stage LLC transformer is comprised of a high frequency magnetic transformer, the high frequency magnetic transformer comprising;

a primary winding, and

a secondary winding,

wherein the resonant mode (LLC) is provided by the primary winding, a resonant inductor, a first resonant capacitor, and a second resonant capacitor,

wherein the pair of complementary switches and the resonant inductor are disposed on the primary winding side of the transformer,

wherein the first resonant capacitor and the second resonant capacitor are disposed on the secondary winding side of the transformer.

14. The method of claim 13, wherein the AC/DC power switching converter is operated mostly in an asymmetric mode, wherein the duty cycle D is not equal to 0.5 when operating in the asymmetric mode.

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

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

16. The method of claim 15, wherein the boosted high voltage is controlled by adjusting the duty cycle D and a gain on the secondary winding side of the transformer is controlled by adjusting the switching frequency.

17. A single stage boost-asymmetric LLC AC/DC power switching converter, the converter comprising:

a bridge rectifier, the bridge rectifier comprising a first, a second, a third, and a fourth terminal, the first terminal and the second terminal connected to an external AC (alternating current) power source;

a high frequency magnetic transformer, the high frequency magnetic transformer comprising;

a primary winding, the primary winding comprising of a first and a second terminal, the first terminal connected to the third terminal of the bridge rectifier, and

a secondary winding, the secondary winding comprising of a first and a second terminal;

a resonant tank, the resonant tank comprising;

a resonant inductor, the resonant inductor comprising of a first and a second terminal, the first terminal connected to the second terminal of the primary winding,

a first resonant capacitor, the first resonant capacitor comprising of a first and a second terminal, the first terminal of the first resonant capacitor connected to the first terminal of the secondary winding, and

a second resonant capacitor, the second resonant capacitor comprising of a first and a second terminal, the first terminal of the second resonant capacitor connected to the first terminal of the secondary winding;

a pair of complementary switches, the pair of complementary switches comprising;

a first switch, the first switch comprising of a first and a second terminal, the first terminal connected to the second terminal of the resonant inductor, and

a second switch, the second switch comprising of a first and a second terminal, the first terminal connected to the second terminal of the resonant inductor,

wherein the first switch is switched to be opened and closed at a switching frequency with a duty cycle of D, the second switch is switched to be opened and closed at the same switching frequency with a duty cycle of (1-D) so that the second switch is opened when the first switch is closed and the second switch is closed when the first switch is opened, wherein the duty cycle D cannot be 0 or 1;

a high voltage storage capacitor, the high voltage storage capacitor comprising of a first and a second terminal, the first terminal of the high voltage storage capacitor connected to the fourth terminal of the bridge rectifier and the second terminal of the first switch, the second terminal of the high voltage storage capacitor connected to the second terminal of the second switch;

an input filter capacitor, the input filter capacitor comprising of a first and a second terminal, the first terminal of the input filter capacitor connected to the third terminal of the bridge rectifier and the first terminal of the primary winding, the second terminal of the input filter capacitor connected to the fourth terminal of the bridge rectifier; and

an output filter capacitor, the output filter capacitor comprising of a first and a second terminal, the first terminal of the output filter capacitor connected to the second terminal of the first resonant capacitor, the second terminal of the output filter capacitor connected to the second terminal of the second resonant capacitor.

18. The converter of claim 17, wherein the resonant inductor is an independent inductor.

19. The converter of claim 17, wherein the resonant inductor is derived from a leakage inductance of the high frequency magnetic transformer.

20. The converter of claim 17, wherein the first and the second switches are high frequency MOSFET (metal-oxide-semiconductor field-effect transistor) switches.