Search Results - fred lee

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Matrix Transformer and the Winding Structure
A novel matrix transformer structure along with its winding structure are proposed. 4 transformers are integrated in 1 core and flux cancellation is employed to reduce the flux density in the top and bottom plates of the magnetic core. The primary windings are arranged to fully utilize the copper in the PCB. SR and output are part of the secondary ...
Published: 2/8/2017   |   Inventor(s): Chao Fei, Fred Lee, Qiang Li
Keywords(s):  
Category(s): Electrical
Multiphase Coupled and Integrated with PCB winding for PFC Converters
In this invention, the inductors of multiphase PFC converters are coupled and integrated into one magnetic core. The coupling can improve converter efficiency. With a novel structure, the inductors can be built with PCB winding with similar loss as traditional litz wire inductors. In addition, balance technique is applied to reduce common mode EMI ...
Published: 2/6/2017   |   Inventor(s): Yuchen Yang, Mingkai Mu, Fred Lee, Qiang Li
Keywords(s):  
Category(s): Electrical
Soft-Switching Techniques for Three-Phase AC/DC Converters
This invention provides a modulation for three-phase AC/DC converter. This modulation can achieve soft switching and thus improve converter efficiency, especially for high-density-driven high frequency operation. In spite of variable switching frequency operation, this modulation has narrow switching frequency variation range, which reduces switchi...
Published: 8/26/2016   |   Inventor(s): Zhengrong Huang, Zhengyang Liu, Fred Lee, Qiang Li, Furong Xiao
Keywords(s):  
Category(s): Electrical
Universal System Structure for Low Power Adapters
This innovation presents a novel system structure for low power adapters both for the power level below and above 75W. The system is consisted two-stage, namely ac-dc rectifier and unregulated isolated dc-dc converter. The second stage operates at fixed switching frequency to achieve high efficiency as well as easy feedback control and SR driving s...
Published: 4/11/2016   |   Inventor(s): Fred Lee, Xiucheng Huang, Qiang Li
Keywords(s):  
Category(s): Electrical, Energy, Engineering
A Method of Capacitor Voltage Ripple Reduction by Controlling Modulation Index Together with 2nd Order Current Injection for Modular Multilevel Converter
In this invention, a method of capacitor voltage ripple reduction for modular multilevel converter is proposed. In conventional control of MMC, capacitor voltage ripples consist of fundamental component and 2nd order component. That is because the module input power contains fundamental power and 2nd order power. With power flow analysis, the physi...
Published: 4/11/2016   |   Inventor(s): Yadong Lyu, Yi-Hsun Hsieh, Fred Lee, Qiang Li
Keywords(s):  
Category(s): Electrical, Engineering, Transportation
Adaptive SR Driving Scheme for Resonant Converter
In this invention, adaptive SR driving for resonant converter using ripple counter concept is proposed. With the proposed method, SR drain to source voltage Vds is sensed to detect the body diode conduction and SR is well tuned to eliminate the body diode conduction within all operation regions of resonant converter in different applications. Tow c...
Published: 3/30/2015   |   Inventor(s): Chao Fei, Fred Lee, Weiyi Feng, Qiang Li
Keywords(s):  
Category(s): Electrical, Energy, Engineering
A Novel Driving Scheme for Synchronous Rectifier in CRM Flyback
Synchronous rectifier (SR) is widely adopted in flyback converter to reduce the conduction loss. However, the conventional SR driving method based on direct current or voltage sensing is sensitive to the parasitic ring, which may cause SR early turn off and therefore decrease the converter efficiency. This innovation presents a novel SR driving met...
Published: 2/27/2015   |   Inventor(s): Xiucheng Huang, Fred Lee, Qiang Li
Keywords(s):  
Category(s): Electrical, Energy, Engineering
Multi-Step Simplified Optimal Trajectory Control (SOTC) Based on Only VO and ILoad
In this invention, multi-step Simplified Optimal Trajectory Control (SOTC) based on only VO and ILoad is proposed to solve the challenges in the control of resonant converter. The main concept involved in this invention is that adaptive multi-step SOTC based on controller's performance is employed to settle resonant tank. The proposed method has a ...
Published: 2/27/2015   |   Inventor(s): Chao Fei, Fred Lee, Weiyi Feng, Qiang Li
Keywords(s):  
Category(s): Electrical, Energy, Engineering
Improved Current-Mode Control with Single-Step Load Transient
Non-linear single-step load transient improvement structures are proposed for current mode controlled converters. Two popular variable-frequency current mode controls are Constant On-Time (COT) and Ramp Pulse Modulation (RPM) due to their fast transient response. However, conventional COT and RPM both need multiple steps to increase inductor curren...
Published: 2/27/2015   |   Inventor(s): Virginia Li, Pei-Hsin Liu, Qiang Li, Fred Lee
Keywords(s):  
Category(s): Electrical, Energy, Engineering
Coupled Inductor for Interleaved Three-level DC-DC Converters and Its Integrated Designs
This disclosure investigates and evaluates coupled inductor in interleaved multiphase three-level DC-DC converters. If non-coupled inductor is used and maintaining the inductance of inductor, multiphase three-level DC-DC converters interleaving operation will increase the inductor current ripple, although the overall current ripple and Common Mode...
Published: 12/22/2014   |   Inventor(s): Mingkai Mu, Sizhao Lu, Yang Jiao, Fred Lee
Keywords(s):  
Category(s): Electrical, Energy, Engineering
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