Huang-Jen Chiu

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 bidirectional DC–DC converter for fuel cell electric vehicle driving system

This paper presents a power converter for a fuel cell electric vehicle driving system. A new bidirectional, isolated topology is proposed in consideration of the differing fuel cell characteristics from traditional chemical-power battery and safety requirements. The studied converter has the advantages of high efficiency, simple circuit, and low cost. The detailed design and operating principles are analyzed and described. The simulation and experimental waveforms for the proposed converter are shown to verify its feasibility.

LED Backlight Driving System for Large-Scale LCD Panels

This paper presents an LED backlight driving system for large-scale liquid crystal display panels. High efficiency, high power factor, circuit simplicity, and low cost can be achieved by using a single-stage charge-pump asymmetrical half-bridge converter. To regulate the LED current and brightness for the LED backlight system, some current sharing methods are presented and compared. The requirements for the current sharing and luminance balance among paralleled LED arrays can be satisfied while current ripple is eliminated significantly. Because of the addition of bypass diodes, an alternative current path can be offered when a single LED fails. The LED array will not be extinguished. Reliability of the LED backlight system can thus be improved effectively. A laboratory prototype has been built and tested. The simulation and experimental results are shown to verify the feasibility of the proposed method.

Design and Implementation of RGB LED Drivers for LCD Backlight Modules

In this paper, a backlight module driver driving high-power red, green, and blue light-emitting diodes (RGB LEDs) for a 19-in liquid crystal display is proposed. The DC-DC series resonant converters (SRCs) with zero-voltage switching and constant-output-current control are implemented to drive the RGB LED arrays. Phase-shifted pulsewidth modulation dimming control is adopted to effectively narrow the load variations and improve the output voltage regulations of the SRCs. A DSP-based hysteresis control algorithm is performed to track the white-color point and the specified backlight luminance. Analysis and design considerations of the proposed drivers are presented in detail. Experimental results agree well with the theoretical predictions and confirm the validity of the proposed approach.

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.

Eliminating the Temperature Effect of Piezoelectric Transformer in Backlight Electronic Ballast by Applying the Digital Phase-Locked-Loop Technique

A new controller for eliminating the temperature effect of a piezoelectric transformer (PT) in a backlight electronic ballast is proposed in this paper. First, a class-D backlight inverter is employed to simplify the circuit configuration and to raise system efficiency. Next, to reduce the dimensions of the backlight module for satisfying the thin-shaped design trend and to overcome the drawbacks of a conventional transformer, a PT is incorporated instead. Then, a digital phase-locked-loop (DPLL) controller is embedded into the backlight system as a feedback control mechanism to track the optimal operating frequency of the PT, so that the PTs temperature effect is removed; hence, system efficiency and stability is improved. The design considerations are detailed, and the experimental results confirm the validity of the proposed control strategy

A multiple-input DC/DC converter for renewable energy systems

This paper presents a multiple-input DC/DC converter for renewable energy systems. The proposed DC/DC converter can be used to obtain well-regulated output voltage from several power sources, such as wind turbines, photovoltaic arrays, fuel cells, etc. The energy provided by these power sources can be simultaneously transferred into the load. The proposed multiple-input DC/DC converter has the advantages of simple configuration, fewer components, lower cost and high efficiency. The operating principle, theoretical analysis, and design criteria are provided in this paper. A laboratory prototype with two different power sources was successfully implemented and tested. The simulation and experimental results are given to verify the feasibility of the proposed scheme

A module-integrated isolated solar microinverter

This paper presents a module-integrated isolated solar microinverter with pseudo-dc link. The studied grid-tied microinverters can individually extract the maximum solar power from each photovoltaic panel and transfer to the ac utility system. High conversion efficiency and high maximum power point tracking accuracy can be achieved with the studied pseudo-dc link topology. The operation principles and design considerations of the studied solar inverter are analyzed and discussed. A laboratory prototype is implemented and tested to verify its feasibility.

Analysis and elimination of voltage imbalance between the split capacitors in half-bridge boost rectifiers

The voltage imbalance between the split capacitors in a halfbridge boost rectifier is reviewed in this letter. It can be proven that the optimal compensation strategy is to add only a DC component in the source current. The adverse effects of the imbalance elimination control loop to the input power factor are studied. The analytical results are verified through experiments.

A high-efficiency soft-switched AC/DC converter with current-doubler synchronous rectification

An improved ac/dc converter based on asymmetrical half-bridge topology is proposed in this paper. To substantially enhance the efficiency for low-voltage/high-current output applications, a current-doubler synchronous rectifier is combined with a modified asymmetrical half-bridge converter that retains the inherent zero-voltage-switching property. The power losses in the secondary rectification stage and the primary switches can be significantly reduced. The proposed architecture exhibits extreme simplicity and lower cost while providing unity power factor, well-regulated output, and high power density. The detailed operating principles and design procedures for the proposed converter are described in this paper. Simulation and experimental results for a laboratory prototype are discussed to verify the feasibility.