Shann-Chyi Mou

A High-Efficiency Dimmable LED Driver for Low-Power Lighting Applications

This paper presents a dimmable light-emitting diode (LED) driver with adaptive feedback control for low-power lighting applications. An improved pulsewidth modulation dimming technique is studied for regulating the LED current and brightness. Under universal input voltage operation, high efficiency and high power factor can be achieved by a coupled inductor single-ended primary inductance converter power factor correction (PFC) converter with a simple commercial transition-mode PFC controller. The operation principles and design considerations of the studied LED driver are analyzed and discussed. A laboratory prototype is also designed and tested to verify the feasibility.

A Single-Stage Soft-Switching Flyback Converter for Power-Factor-Correction Applications

This letter presents a single-stage soft-switching Flyback converter for power-factor-correction (PFC) applications. High power factor and high conversion efficiency can be achieved by a simple single-stage circuit with soft-switching features. The operation principles and design criteria for the studied PFC converter are analyzed and discussed. A laboratory prototype is also built and tested. Finally, the experimental waveforms for this prototype circuit are shown to verify the feasibility of the proposed scheme.

Design of an RGB LED Backlight Circuit for Liquid Crystal Display Panels

This paper presents a red, green, and blue (RGB) light-emitting diode (LED) backlight circuit for liquid crystal display (LCD) panels. Some studies have been conducted to devise dimming methods that regulate the RGB LED currents. In this paper, design considerations for the RGB LED backlight are presented. A laboratory prototype for 20-in panels is implemented and tested. The color gamut of an LCD panel with the designed RGB LED backlight is measured and discussed. The experimental results of the laboratory prototype are also shown to verify feasibility of the findings.

A single-stage high efficiency high power factor LED driver

In this paper, we study the feasibility of a single-stage LED driver. The operating principles and design considerations for the LED driver in this study are analyzed and discussed in detail. A laboratory prototype has been built and tested. Using the prototype, high efficiency, high power factor and LED current control were achieved using a wide AC input voltage range from 90V to 270V.

A battery charger with maximum power point tracking function for low-power photovoltaic system applications

A battery charger with MPPT function for low-power PV system applications is presented in this study. For effective miniaturization, the battery charger is designed with high frequency operation. Some current-sensing techniques are studied, and their MPPT implementation is compared. A pulse charging method is also designed to prolong battery lifetime. The operation principles and design considerations of the proposed PV charger are analyzed and discussed in detail. A laboratory prototype is implemented and tested to verify the feasibility of the proposed scheme. Experimental results show that high MPPT accuracy and conversion efficiency can be simultaneously achieved under high frequency operation.

A single-stage dimmable electronic ballast with high power factor

A novel fixed frequency electronic ballast that consists of a single-stage asymmetrical half-bridge inverter, a load resonant tank and a switched-capacitor dimming control circuit is proposed for driving fluorescent lamps. High efficiency and unity power factor are achieved by the proposed single-stage topology. The switched-capacitor dimming control technique in the studied high frequency electronic ballast provides better EMI features. The steady-state operating principle and design procedure for the proposed single-stage dimmable electronic ballast are analyzed and discussed in detail. A ballast prototype was implemented at the laboratory. The experimental results verify the feasibility of the proposed method.

Single-Stage Voltage Source Charge Pump Electronic Ballast with Switched-Capacitor Dimmer for Multiple Fluorescent Lamps

This paper presents a single-stage electronic ballast for driving multiple fluorescent lamps in which a dimming control scheme is proposed to regulate the lamp current. A laboratory prototype is built and tested, and it is found that unity power factor can remain under individual lamp brightness control. The experimental results are therefore shown to verify the feasibility of the proposed method.

A single-stage soft-switching flyback converter for power-factor-correction applications

This paper presents a single-stage soft-switching Flyback converter for power-factor-correction (PFC) applications. High power factor and high conversion efficiency can be achieved by a simple single-stage circuit with soft-switching features. The operation principles and design criteria for the studied PFC converter are analyzed and discussed. A laboratory prototype is also built and tested. Finally, the experimental waveforms for this prototype circuit are shown to verify the feasibility of the proposed scheme.

Current and white-balance controls of an RGB LED backlight power supply system

This paper presents an RGB LED backlight circuit for liquid crystal display (LCD) panels. Some studies have been conducted to devise dimming methods that regulate the RGB LED currents. In this paper, design considerations for the RGB LED backlight are presented. A laboratory prototype for 20-inch panels is implemented and tested. Color gamut and white-balance features of an LCD panel with the designed RGB LED backlight is measured and discussed. The experimental results of the laboratory prototype are also shown to verify feasibility of the findings.

Dual Mode Control Multiphase DC/DC Converter for CPU Power

High performance voltage-regulator-modules (VRMs) for the new generation of microprocessors have many strict and challenging specifications that include high power-density, high output-current capability, low output-voltage deviation and fast transient-response. In this paper, a dual mode control multiphase DC/DC converter is presented. The proposed scheme combines voltage and hysteretic control modes and has the merits of high efficiency, simple control and fast transient response. It can be also used for single-phase and built in integrated circuit without additional cost and space. The operating principles and design considerations are analyzed and discussed in detail. A 1.3 V/80 A four-phase laboratory prototype was simulated and implemented to verify the feasibility of the proposed scheme. The results are satisfactory