S.-Y. Tseng

A single-stage fast regulator with PFC based on an asymmetrical half-bridge topology

This work presents single-stage regulators with power-factor correction (PFC) based on an asymmetrical half-bridge topology. The proposed regulator is formed from a boost converter with two coupled inductors and an asymmetrical half-bridge converter with the synchronous switch technique, and it is controlled with pulsewidth modulation to achieve zero-voltage switching (ZVS). The boost converter is operated in discontinues conduction mode to achieve PFC. With the coupled inductors, input current ripple and power factor can be improved significantly. The proposed regulator has the features of constant-frequency operation, ZVS, and low voltage stress imposed on the active switches. Moreover, the regulator can achieve high power factor, high power density, high efficiency, low switching loss, and low component count, which makes its applications at medium-power levels feasible. Experimental results have verified the discussed features of the proposed regulator.

Interleaved buck converters with a single-capacitor turn-off snubber

This paper proposes interleaved buck converters with a single-capacitor snubber to smooth out switch turn-off transition. The single-capacitor snubber is used to limit rising rate of drain-source voltage of the metal-oxide-semiconductor field-effect transistor (MOSFET) switch in the converters to reduce turn-off loss. In addition, the converters are operated at the boundary of continuous and discontinuous conduction modes (CCM), (DCM) to reduce turn-on loss, and in an interleaving fashion to reduce output current ripple. As compared with the counterparts of conventional converter topologies, the proposed converters have the merits of less component count, higher efficiency over a certain load range, smaller size, and they are easier to implement. Hardware measurements obtained from experimental prototypes have verified these merits.

Generation of pulsed electric fields for processing microbes

This paper first reviews viable microbe processing mechanism and then presents generation of pulsed electric fields for processing microbes. Microbe processing includes food sterilization, waste treatment, pollution control, and medical diagnostics and treatment. To generate pulsed electric fields for achieving sterilization, a generated high dc output voltage is chopped into pulsed waveforms, in which their pulse-width varies from tens of nanoseconds to hundreds of microseconds, period changes from 0.1 to 1 ms, and electric field intensity is from tens to hundreds of kV/cm. In this study, we propose wide pulses stacked with narrow pulses to prevent undesired air breakdown and reduce power consumption. Modified half-bridge series resonant converters are used to generate high dc voltages. They are operated at high frequency, in discontinuous conduction mode and with a PWM control; therefore, its weight and size can be reduced significantly and its efficiency can be correspondingly improved.

LED backlight power system with auto-tuning regulation voltage for LCD panels

This paper proposes a light emitting diode (LED) backlight power system for liquid crystal display (LCD) panels. The proposed power system is regulated by error quantities of feedback circuit from which variation value of the voltage across LED driving IC in each driving LED channel is attained due to changes of temperature on LEDs. With this compensation algorithm, the proposed LED backlight power supply can regulate its output voltage with auto-tuning to compensate a forward drop voltage of multi-LED-string and to maintain a constant voltage across each driving IC when temperature on LEDs is changed Compared with the conventional LED backlight power system, the proposed power system can reduce the temperature on LEDs about 6degC~8degC under driving IC operated in a safety of area. As a result, the proposed power system can reduce the temperature on LED driving IC to increase life cycle of components and reduce color shift significantly. Hardware measurement obtained from experimental prototype has been verified its feasibility.

Wide Pulse Combined With Narrow-Pulse Generator for Food Sterilization

This paper proposes a wide pulse combined with a narrow-pulse generator for solid-food sterilization. The proposed generator is composed of a full-bridge converter in phase-shift control to generate a high dc-link voltage and a full-bridge inverter associated with an L-C network and a transformer to generate wide pulses combined with narrow pulses. These combined pulses can prevent undesired strong air arcing in free space, reduce power consumption, and save power components, while sterilizing food effectively. The converter and inverter can be operated at high frequencies and with pulse width-modulation control; thus, its weight and size can be reduced significantly, and its efficiency can correspondingly be improved. Experimental results obtained from a prototype with plusmn10-kV wide pulses combined with plusmn10-kV narrow pulses and with 10- to 50-kW peak output power, depending on pulsewidth of the output pulses, have demonstrated its feasibility.

A Novel Turn-On/Off Snubber for Interleaved Boost Converters

This paper proposes an interleaved boost converter with a novel L-C-D snubber to reduce turn-on and turn-off switching losses. The proposed L-C-D snubber is composed of a single capacitor to form turn-off snubber, and an inductor and a diode connected in parallel to form a turn-on snubber. In this circuit structure, the turn-off snubber is used to limit rising rate of voltage across switch of the proposed converter and to reduce turn-off switching loss. While, the turn-on ones are used to smooth out current through switch of the proposed one and to reduce turn-on switching loss. Furthermore, the proposed converter is operated in an interleaved fashion to reduce output current ripple. Compared with the counterparts of conventional converter topologies, the proposed converter has merits of less component count, higher efficiency, smaller size, and they are easier to implement. Hardware measurement obtained from experimental prototype has been verified these merits.

Buck-Boost Combined with Active Clamp Flyback Converter for PV Power System

This paper presents an LED lighting system with PV sources. The circuit of the proposed system adopts buck-boost converter associated with flyback converter to charge battery and to drive an LED lighting system. In this research, buck-boost converter is used as a charger for charging battery, and flyback converter with active clamp circuit is adopted to drive the LED lighting. To simplify the circuit structure, switches of two converters are integrated with a synchronous switch technique. With this approach, the proposed system has several merits, which are a less component count, lighter weight, smaller size and higher conversion efficiency. Compared with the conventional converter with hard-switching circuit, the proposed one can improve conversion efficiency of 5% and achieve efficiency about 83% under full load at driving the LED lighting. Experimental results obtained from a prototype with output voltage of 10 V and output power of 20 W have verified its feasibility.

Bipolar Narrow-Pulse Generator With Energy-Recovery Feature for Liquid-Food Sterilization

This paper presents a bipolar narrow-pulse generator with energy-recovery feature for liquid-food sterilization. The generator is formed from a bidirectional flyback converter and active-clamp circuits which are further simplified to the proposed topology with the synchronous-switch technique. In the converter, the leakage inductance of the transformer will resonate with the active-clamp capacitors to recover the trapped energy and to reduce switching loss, improving efficiency by about 13%. In addition, the capacitors can reduce voltage stress significantly. Experimental results obtained from a prototype with the output of plusmn6-20 kV, depending on loads, and the peak power of 1.2 MW has confirmed these discussions.

A single-Capacitor Turn-off Snubber for Interleaved Boost Converter with Coupled Inductor

This paper proposes an interleaved boost converter associated with a coupled inductor with a single-capacitor turn-off snubber to reduce the switching loss at turn-off transition. The proposed turn-off snubber is also used to limit rising rate of voltages across switches for reducing spike voltage. In this circuit structure, the proposed converter is operated in an interleaved fashion to reduce output current ripple and with a coupled inductor to increase step-up voltage ratio. As compared with the counterparts of conventional converter topologies, the proposed converter has the merits of less component count, higher efficiency, smaller size, and they are easier to implement. Hardware measurement obtained from experimental prototype have been verified these merits.

Active Clamp Interleaved Flyback Converter with Single-Capacitor Turn-off Snubber for Stunning Poultry Applications

The paper proposes an active clamp interleaved flyback converter with a single-capacitor turn-off snubber associated with a full-bridge inverter for stunning poultry applications. The proposed converter can use active clamp circuit to recover the energy of transformer and to achieve zero-voltage switching at turn-on transition. In addition, the proposed one adopts a single-capacitor snubber not only to smooth out switch turn-off transient for reducing turn-off loss but to reduce the ringing voltage of diodes in secondary winding of transformer when switch of the proposed one is operated at turn-on transition. Compared with the counterparts of the conventional converter topologies, the proposed converter has the merits of less component counts, higher efficiency, smaller size, and they are easier to implement. Performance measurements from a prototype have verified feasibility of the overall system design. This designed system has contributed a lot of humane slaughter and has attracted much attention.