Zaohong Yang

US Patent:

8363439, Jan 29, 2013

Filed:

Apr 22, 2008

Appl. No.:

12/107321

Inventors:

Zaohong Yang - Richardson TX, US

Assignee:

Flextronics AP, LLC - Broomfield CO

International Classification:

H02M 5/42
H02M 7/04
H02M 7/68

US Classification:

363 89

Abstract:

An power converter that is operable to convert AC power into DC power that may be delivered to a load. The power converter includes a transformer and a controllable switch. The switching frequency of the power converter is configured to be dependent on the level of the AC voltage of an AC power source. The switching frequency may be proportional to the AC voltage to provide a constant magnetic flux density swing for the transformer in the power converter. The switching frequency may be controlled by using a circuit that converts the AC voltage from the AC power source into a frequency signal that is proportional to the AC voltage.

US Patent:

8520414, Aug 27, 2013

Filed:

Jan 19, 2010

Appl. No.:

12/689771

Inventors:

Paul Garrity - Rockwall TX, US
Zaohong Yang - Richardson TX, US

Assignee:

Power Systems Technologies, Ltd. - Ebene

International Classification:

H02M 3/335

US Classification:

363 2114

Abstract:

A controller for a power converter having a transformer T with a primary winding coupled to a power switch SW and a secondary winding coupled to a synchronous rectifier switch SR. In one embodiment, the controller includes a first controller configured to control a conductivity of the power switch SW, and a first delay circuit configured to delay an initiation of the conductivity of the power switch SW. The controller also includes a second controller configured to control a conductivity of the synchronous rectifier switch SR as a function of a voltage difference between two terminals thereof, and a second delay circuit configured to delay an initiation of the conductivity of the synchronous rectifier switch SR. The controller still further includes a shutdown circuit configured to substantially disable conductivity of the synchronous rectifier switch SR before the initiation of conductivity of the power switch SW.

US Patent:

20090257256, Oct 15, 2009

Filed:

Apr 11, 2008

Appl. No.:

12/101353

Inventors:

Paul Garrity - Rockwall TX, US
Zaohong Yang - Richardson TX, US

Assignee:

FLEXTRONICS AP, LLC - Broomfield CO

International Classification:

H02M 7/04

US Classification:

363 61

Abstract:

A high efficient input current shaping AC to DC converter with PFC front end that reduces input current harmonics is provided. In one embodiment, an AC to DC converter connectable with an alternating current source and operable to output a direct current comprises a PFC front end followed by a DC/DC converter. The PFC front end reduces harmonic components present in an input current waveform received by the PFC front end from the alternating current source and includes current steering circuitry and, optionally, valley filling circuitry. The DC/DC converter comprises one that presents pure resistive input impedance to the PFC front end. The DC/DC converter outputs the direct current to a load connected thereto.

US Patent:

20100188876, Jul 29, 2010

Filed:

Jan 19, 2010

Appl. No.:

12/689881

Inventors:

Paul Garrity - Rockwall TX, US
Zaohong Yang - Richardson TX, US

International Classification:

H02M 7/217

US Classification:

363127

Abstract:

A controller for a power converter and method of operating the same employable with a bridge rectifier having first and second synchronous rectifier switches. In one embodiment, the controller includes an amplifier configured to enable a turn-on delay for the first synchronous rectifier switch SR. The controller also includes a discharge switch Q having first and second switched terminals coupled to gate and source terminals, respectively, of the first synchronous rectifier switch SR and configured to discharge a gate-to-source capacitance of the first synchronous rectifier switch SR to enable a turn off thereof.

US Patent:

20100315839, Dec 16, 2010

Filed:

May 7, 2010

Appl. No.:

12/776249

Inventors:

Zaohong Yang - Richardson TX, US
Paul Garrity - Rockwall TX, US

International Classification:

H02M 3/335

US Classification:

363 17

Abstract:

An energy recovery snubber circuit for use in switching power converters. The power converters may include a switch network coupled to a primary winding of an isolation transformer, and rectification circuitry coupled to a secondary winding of the isolation transformer. The energy recovery snubber circuit may include clamping circuitry that is operative to clamp voltage spikes and/or ringing at the rectification circuitry. The clamped voltages may be captured by an energy capture module, such as a capacitor. Further, the energy recovery snubber circuitry may include control circuitry operative to return the energy captured by the energy capture module to the input of the power converter. To maintain electrical isolation between a primary side and a secondary side of the isolation transformer, a second isolation transformer may be provided to return the captured energy back to the input of the power converter.

US Patent:

20170346406, Nov 30, 2017

Filed:

Nov 17, 2016

Appl. No.:

15/354705

Inventors:

- Cupertino CA, US
Zaohong Yang - Plano TX, US

International Classification:

H02M 3/335

Abstract:

This disclosure describes an AC/DC power converter that produces multiple output voltage levels. The AC/DC power converter may include a gain adjustment circuit. The gain adjustment circuit may adjust the gain of a feedback signal of the converter in accordance with the converter's output voltage level. The gain adjustment circuit provides sufficient gain and phase margins to the converter and thus enhances the converter's stability.

US Patent:

20170093289, Mar 30, 2017

Filed:

Jun 9, 2016

Appl. No.:

15/177998

Inventors:

- Cupertino CA, US
Zaohong Yang - Plano TX, US

International Classification:

H02M 3/335
H02M 1/08

Abstract:

This disclosure relates to flyback transformer-based power converters that are capable of providing multiple output voltage levels. With respect to USB-PD adapter design, the flyback converter's output may be changed from 12V to 20V—based on the charging device's request. By using a bias circuit that monitors an output voltage level of the flyback converter, a bias voltage for the bias circuit may be determined to improve efficiency of the flyback converter. Embodiments include a comparator, microcontroller or switches to compare output voltage levels and provide bias voltages to the bias circuit.

US Patent:

20160094130, Mar 31, 2016

Filed:

Sep 26, 2014

Appl. No.:

14/498578

Inventors:

- Cupertino CA, US
Zaohong Yang - Plano TX, US

International Classification:

H02M 3/335

Abstract:

The disclosed embodiments present a flyback voltage converter that reduces switching losses in a primary-side switching transistor. This flyback converter includes a primary current path that feeds from an input power source into a voltage input of the flyback converter, then through a primary winding of a transformer and a primary transistor to a primary ground. It also includes a secondary current path that feeds from a secondary ground through a secondary winding of the transformer and a diode to a voltage output. During operation, the flyback converter toggles the primary transistor on and off to cause current to flow in an alternating fashion through the primary and secondary current paths. During this toggling process, before the primary transistor is turned on, a parasitic capacitance from the primary transistor is discharged into a reservoir capacitor. This charge is subsequently used to facilitate power efficiency in the flyback converter.