Chien-Yeh Ho

A Novel ZVS-PWM Single-Phase Inverter Using a Voltage Clamp ZVS Boost DC Link

A novel zero-voltage-switching pulse-width-modulation (ZVS-PWM) single-phase inverter using a voltage clamp ZVS boost dc link is proposed in this paper. The proposed voltage clamp ZVS boost dc link not only provides the switches in the section of conventional PWM buck inverter operate at ZVS, but it has a boost input voltage function and the switches in itself also operate at ZVS. Thus, except for the switch in the section of ZVS-PWM commutation cell, all power semiconductor devices in proposed inverter operate at ZVS turn on and turn off. The switch in the section of ZVS-PWM commutation cell operates at zero-current-switching (ZCS) turn-on and turn-off. Besides operating at constant frequency, the proposed inverter has no voltage stress and current stress on the main switch compared to the hard switching inverter counterpart. Auxiliary components rated at very small current are used. The principle of operation, theoretical analysis, and experimental results of the new ZVS-PWM single-phase inverter, rated 1kW and operated at 80 kHz, are provided in this paper to verify the performance.

Design and implementation of four-phase PWM dimming control for backlight inverter

This paper proposes a novel control scheme which possesses four-phase PWM dimming control loop for backlight inverter. We adopt four-phase PWM dimming control circuit to control the brightness of twelve lamps. Each phase can control four or two lamps. Circuit architecture is full bridge phase-shift circuit which can improve the total efficiency of the driving circuit. From the experimental results, we verify the performance that four-phase PWM dimming control will be better than the conventional single phase one. It can uniform lamp current, brightness and luminance.

Design of Class E Backlight Module With Optimal Operating Frequency Tracking Mechanism

This paper proposes a new control approach for tracking the optimal operating frequency of a backlight inverter. First, a class E backlight module is introduced to simplify the backlight circuit and to raise the system efficiency. A piezoelectric transformer (PT) is used to drive the cold cathode fluorescent lamp (CCFL) to eliminate the drawbacks of a conventional transformer and to reduce the dimension of the backlight module. Next, phase-locked loop (PLL) technique is embedded in the backlight system, as a feedback mechanism, to track the optimal operating frequency of the PT so that the PTs temperature effect is removed and, hence, the system efficiency and stability is improved. The feedback variable proposed is a phase difference rather than lamp current amplitude traditionally used. The complete analysis and design considerations are detailed.

Design and analysis for backlight inverter with six-phase PWM dimming control circuit

This paper proposes a novel dimming control scheme which possesses six-phase PWM dimming control for backlight inverter. We adopt six-phase PWM dimming control circuit to control the brightness of twelve lamps. Each phase driving circuit can control two lamps. Circuit architecture is full bridge circuit which can improve the total efficiency of driving circuit. Due to single-phase PWM dimming consumes large input current Iin(A) Iin(A) than six -phase PWM dimming at the same PDIM. So, it causes that single-phase dimming presents larger percent error range (-6.36 ~ +9.8%) and six-phase dimming presents smaller percent error range(-1.26~+1.98%)in average lamp current Ioavg (mA) comparing with lamp currents Io(mA). Hence the six-phase dimming achieves uniform output lamp currents which is called current equalization. From the experimental results, We verify that six-phase dimming is better than conventional single-phase dimming in the performance and in power efficiency η. We use twelve CCFLs(300-mm/2.4-mm) inside of a 24 inch LCDTV.

Design rule and system parameters compare between multi-phase and multi-lamp PWM dimming control for backlight inverter

This paper proposes a novel multi-phase PWM dimming control scheme which possesses two-phase, four-phase, six-phase, and eight-phase for backlight inverter. Each phase driving circuit can control the lamp current of two ccfls at least. From the experimental results for four-phase and six-phase PWM dimming control, we got a conclusion which power efficiency η (%) is directly proportional to No. of phases and lamp current error E (%) is inversely proportional to No. of phases. Hence higher phases dimming will achieve uniform output lamp currents which is called current equalization. We develop a design rule which compare system parameters in multi-phase dimming control for backlight inverter. We conclude that the experimental results also can apply for two-phase and eight-phase PWM dimming control.

Zero-current-transition current-fed full-bridge PWM converter

This paper analyses and designs a zero-current transition current-fed full-bridge transformer-isolated PWM converter. The proposed converter combines the conventional pulse-width-modulation technique and soft commutation technique to promote the circuit performance. Comparison with conventional current-fed full-bridge transformer-isolated PWM converter, the proposed converter own double voltage function at output port without additional voltage and current stresses on main switches. A zero-current-switching auxiliary circuit is configured in the presented rectifier to provide the soft-switching function on main switches and auxiliary switches and improve the problem of switching losses and EMI. A prototype has been implemented in laboratory to verify circuit theory.

High voltage driving circuit with negative pulse feature for tubular field emission lamp

A high voltage driving circuit having pulse mode is proposed for driving tubular field emission lamp (FEL). The employed main circuit topology, which is a flyback converter operated in discontinuous conduction mode (DCM), will not only provide a low cost negative pulse feature, but also eliminate the arcing phenomenon caused by traditional DC driving so as to improve the system efficiency and the lamp lifespan. In this paper, an equivalent model of the FEL is constructed to exhibit its capacitive characteristics. Moreover, each operation mode in a switching cycle is also described. And then a complete design considerations and mathematical model are detailed. All the experimental results agree with the computer simulations to verify the theoretical predictions.

Interleaved resonant converter with flying capacitor

This paper presents a new DC/DC converter for high input voltage and high load current applications. In order to adopt low voltage rating power devices in high voltage applications, two split capacitors with four active switches are used in the primary side to reduce the voltage stress of power switches at Vin/2. Two flying capacitances are used in order to automatically balance two split capacitor voltages in every switching cycle. The proposed converter includes two resonant circuits to share the load current and to reduce the current stress of passive components. If the switching frequency is less than the series resonant frequency, power switches can be turned on under zero voltage switching and rectifier diodes can be turned off under zero current switching. Therefore, the switching losses on power semiconductors are reduced. The interleaved pulse-width modulation is adopted to further reduce the ripple current at output side. Thus, the output filter inductances can be reduced. Finally, experiments with a 1.2kW prototype are provided to verify the effectiveness of the proposed converter.

A ZCS-PWM interleaved forward converter

This paper proposed a zero-current- switching pulsewidth-modulation (ZCS-PWM) interleaved forward dc/dc converter. The proposed ZCS-PWM interleaved forward converter combines the conventional pulse-width-modulation technique and soft commutation technique. The main switch and auxiliary switch operate at zero-current-switching turn on and turn off, and the all passive semiconductor devices in the proposed converter operate at zero-voltage-switching (ZVS) turn on and turn off. The proposed converter uses two ZCS-PWM interleaved forward converter with interleaved operation to increase the output power and reduce the output ripple. Besides operating at constant frequency and reducing commutation losses, the proposed converter has no additional current stress and conduction loss in the main switch in comparison to the conventional hard switching forward converter counterpart. The power transformer can self-reset without the conventional reset winding. The principle of operation, theoretical analysis, and experimental results of the proposed ZCS-PWM interleaved forward converter, rated 500W and operating at 40 kHz, are provided in this paper to verify the performance of the proposed converter.

System parameters comparison between six-phase and tweleve-phase PWM dimming control by design rule for backlight inverter

This paper proposes a novel twelve-phase PWM dimming control for backlight inverter. We adopt twelve-phase or six-phase PWM dimming to control the brightness of twelve lamps. Each phase can control one or two lamps. Circuit architecture is full bridge phase-shift circuit which can improve the total efficiency of the driving circuit. From the experimental results for four-phase and six-phase PWM dimming control, we got a conclusion which power efficiency η (%) is directly proportional to No. of phases and lamp current error E (%) whose range is inversely proportional to No. of phases. By the design rule, we compare system parameters between twelve-phase and six-phase dimming control for backlight inverter. Hence higher phases dimming will achieve uniform output lamp currents which is called current equalization. Higher phases dimming possesses higher power efficiency η (%). We develop the design rule that it also can apply for twelve-phase PWM dimming control.