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This paper presents the interleaved four-phase buck-based current source in continuous conduction mode with proposed isolated energy-recovery scheme for electrical discharge machining (EDM). EDM requires a pulse current with high slew rate in the output current of the current source. The interleaving technique allows the output slew rate of the buck-based current source to be improved due to the existence of the paralleled inductors at the start of discharge. The proposed isolated energy-recovery scheme provides a major path for the inductor to release its stored energy, thus avoiding high voltage stress in the output terminal when the gap reverts to the high-impedance state. The energy stored in the inductor is recycled to the input capacitor and can be reused for machining. The experimental results validate that the output current slew rate is high and that the energy is recovered when the gap is in the high-impedance state. Index Terms--Buck-based, current source, EDM, energy-recovery, interleaving.

This paper presents a comprehensive study of a current-fed full-bridge boost dc-dc converter with zero-current switching (ZCS), based on the constant on-time control for high-voltage applications. The current-fed full-bridge boost converter can achieve ZCS by utilizing the leakage inductance and parasitic capacitance as the resonant tank. In order to achieve ZCS under a wide load range and with various input voltages, the turn-on time of the boost converter is kept constant, and the output voltage is regulated via frequency modulation. The steady-state analysis and the ZCS operation conditions under various load and input-voltage conditions are discussed. Finally, a laboratory prototype converter with a 22-27-V input voltage and 1-kV/1-kW output is implemented to verify the performance. The experimental results show that the converter can achieve high output voltage gains, and the highest efficiency of the converter is 92 % at full-load condition with an input voltage of 27 V. Index Terms--Current fed, high voltage, zero-current switching (ZCS).

This paper presents the piezoelectric transformer (PT)-based continuous-conduction-mode (CCM) current source (CS) charge-pump (CP) power-factor-correction (PFC) electronic ballast. The main drawbacks of the PT-based dc-side discontinuous-conduction-mode (DCM) CS CP-PFC electronic ballast include high di/dt, high current stress and high switching losses. In order to solve these problems that are caused by DCM operation, and to reduce the components count, the PT-based bridgeless CCM CS CP-PFC electronic ballast is proposed in this paper. The experimental results show that the electronic ballast proposed in this paper not only can achieve high power factor and low total harmonic distortion, but also the switches can operate under a zero-voltage-switching condition without requiring a series inductor in front of the employed PT. Index Terms--Charge-pump (CP), continuous-conduction-mode (CCM), current source (CS), discontinuous-conduction-mode (DCM), piezoelectric transformer (PT), power factor (PF), power-factor-correction (PFC), total harmonic distortion (THD), zero-voltage-switching (ZVS).

This paper presents the design and implementation of the 2.65-MHz self-oscillating complementary electronic ballast with a constant-lamp-current control for a metal halide lamp. In order to avoid the inherent acoustic-resonance problem of metal halide lamps, the ballast's switching-frequency level was selected to be 2.65 MHz, which satisfies higher magnitudes of maximum electromagnetic interference (EMI) limitation at frequencies of between 2.5 to 3.0 MHz, within the EMI/electromagnetic compatibility frequency range 'chimney' for RF lighting systems. With the constant-lamp-current control scheme, the lamp current can be regulated to be less dependent on the input ac voltage. Finally, a 20-W prototype ballast is implemented to demonstrate the ability to avoid the acoustic-resonance and to provide constant levels of lamp current. Index Terms--Acoustic resonance, ballast, complimentary, electromagnetic interference (EMI) chimney, high intensity discharge (HID), lighting, self-oscillating, 2.65 MHz.

This paper presents a constant power control circuit for a three-stage high-intensity discharge (HID) electronic ballast. The three-stage electronic ballast is composed of a boost pre-regulator to achieve a high power factor, a DC/DC buck converter to regulate lamp current with constant lamp power, and a full-bridge inverter to drive the HID lamp with a low-frequency ac squarewave current. The buck converter operating in current mode utilizes current sense level-shift technique to achieve constant power output. The proposed constant power control circuit is easily designed and implemented for the three-stage HID electronic ballast. Finally, a laboratory prototype of a 70 W HID electronic ballast is implemented. The measured results show that the proposed ballast can be applied for various HID lamps with low lamp power variation (less than 0.6%). Index Terms--Acoustic resonance, constant power, electronic ballast, HID lamps, low-frequency squarewave.

This paper presents the 2.65-MHz self-oscillating electronic ballast with constant-lamp-current control for metal halide (MH) lamps. To avoid the inherent acoustic-resonance problem of MH lamps, the switching frequency is chosen to be above 1 MHz. Furthermore, in order to satisfy higher magnitudes of maximum electromagnetic interference limitation at frequencies of between 2.5 to 3.0 MHz, the ballast's switching-frequency level was selected to be 2.65 MHz, which falls within the frequency range 'chimney,' for radio-frequency lighting systems, such as electrode-less fluorescent lamps. The conventional self-oscillating electronic ballast is disadvantageous because the lamp current varies according to the input voltage. This difference in lamp current causes poor color rendering index for the lamp. In order to solve this issue for the self-oscillating electronic ballast, the constant-lamp-current control circuit is proposed to provide constant lamp current. Finally, a 20 W self-oscillating ballast with the proposed constant-lamp-current control for MH lamps is implemented in order to demonstrate the ability to avoid acoustic resonance and to provide constant levels of lamp current. Index Terms--Color rendering index (CRI), electromagnetic interference (EMI), metal halide (MH), radio-frequency (RF).

This paper presents active current-equalization (CE) techniques for equalizing the lamp currents of multi-lamp electronic ballasts. Multi-lamp products, such as the backlighting for liquid crystal display (LCD) panels, have to be capable of equalizing luminance. Due to the deviations of lamps and ballasts, the currents flowing through the lamps are not equal, which causes poor-quality backlight sources for LCD panels. Additionally, since the size of thin-film transistor LCD (TFT-LCD) monitors is becoming larger, a multi-lamp drive system must provide higher levels of voltage and current and more power for longer length lamps and more lamps. Since the number of lamps that can be driven by one inverter is limited, distributed multi-ballast drive systems are becoming popular. In order to achieve current equalization for distributed multi-ballast drive systems, the active CE technique is proposed to equalize every output current of the ballast. In this paper, the three-ballast drive system, for distributed single-lamp inverters, is implemented with the active CE technique. In addition, the CE ability in dimming range is demonstrated by experiments in order to verify the performance of the proposed active CE circuit scheme. Index Terms--Liquid crystal display (LCD) panels, thin-film transistor (TFT).

This paper proposes a bridgeless-type ac-side continuous-conduction-mode (CCM) current-source (CS) charge-pump (CP) power-factor-correction (PFC) electronic ballast. The drawbacks of conventional dc-side discontinuous-conduction-mode (DCM) electronic ballasts include high di/dt, high current stress, and high switching losses. As a result, conventional dc-side DCM CS-CP-PFC electronic ballasts have low efficiency, due to the DCM operation, and the ballasts require a large input electromagnetic interference filter. Conventional dc-side CCM CS-CP-PFC electronic ballasts are able to solve these problems, but still require a higher component count. To efficiently reduce the cost of electronic components, a bridgeless-type ac-side CCM CS-CP-PFC electronic ballast is proposed. A 32-W rated power electronic ballast prototype circuit is designed and implemented. Experimental results verify that the input-current harmonics meet the IEC 61000-3-2 Class-C Standard, and the CP capacitor helps the PFC inductor current to achieve CCM and high power factor. Index Terms--Charge-pump (CP), continuous-conduction-mode (CCM), current-source (CS), discontinuous-conduction-mode (DCM), electromagnetic interference (EMI), power-factor-correction (PFC).

This paper proposes a novel push-pull Class-E series-parallel resonant power amplifier (PA), which parallels two basic one-inductor, one-capacitor Class-E high-efficiency switching-mode tuned PA (Sokal, 1981) circuits. This proposed topology utilizes a push-pull scheme to realize sinusoidal output voltage. The previously published Class-E circuits (Sokal, 1981) can be implemented in a very simplified circuit. However, the simplified circuit is only appropriate for applications in which the harmonic content of output is not an important criterion. The proposed amplifier with two series-parallel resonant load networks will allow sinusoidal output voltage to be achieved by associating with the positive and negative quasi-sinusoidal waveforms. The complementarily activated configuration will provide continuous high-ripple-frequency input-current waveforms; this approach significantly reduces electromagnetic interference and requires very little filtering. With the symmetry of the push-pull Class-E circuit, there is the additional benefit that the even harmonics are suppressed at the load, and thus there are fewer harmonic distortions. However, each switch is symmetrically driven with a duty ratio of less than 0.5 to meet the nominal Class-E operating conditions, which leads to a narrower operating frequency variation. A prototype of the proposed PA shows over 95 % efficiency at 48-V input, with 18-W output and an operating frequency of 900 kHz. Index Terms--Class-E power amplifier (PA), harmonic distortion (HD), high-efficiency amplifier, push-pull amplifier, switching PA, zero-voltage switching (ZVS).

This paper proposes a phase-locked loop (PLL) control scheme for the electronic ballast employing a parallel-serial resonant tank (PSRT), in which the resonant frequency of the circuit is continuously tracked, in order to drive the fluorescent lamps even with low equivalent resistance at steady-state. Compared with the conventional PLL control of the electronic ballasts for cold cathode fluorescent lamps, the proposed PLL control scheme, by sensing the phase signals at the both ends of the resonant inductor, is able to have resonant frequency tracked for the electronic ballasts, where the equivalent resistance of the fluorescent lamps is even equal to hundreds of ohms or lower at steady-state. By employing the current regulator circuit, the proposed PLL controller regulates the values of the lamp's current by adjusting the operating frequency from the resonant frequency as a reference frequency point, the lamp's current is accurately controlled. The analysis of the proposed PLL control scheme will be presented in this paper. Finally, the implementation of a prototype circuit is provided to demonstrate the performance of the proposed PLL control scheme by associating with a current regulator circuit. Index Terms--Parallel-serial resonant tank (PSRT), phase-locked loop (PLL).

Because of the traction power load characteristics of mass rapid transit (MRT) systems, a significant difference exists between the peak and valley of the traction power load curve. Furthermore, an extremely high traction power peak occurs if numerous trains are accelerating simultaneously. Careful train scheduling can avoid the simultaneous acceleration of too many trains, thus reducing maximum traction power. This paper employs genetic algorithms to optimize train scheduling and uses the Kaohsiung MRT system as an example. Simulation results show that the proposed method can significantly reduce the maximum traction power. Index Terms--Genetic algorithms (GAs), mass rapid transit, traction power, train schedule.

This paper proposes a circuit model for the transient period of inrush current in a transformer. The magnetizing inrush model is developed from the structural parameters of the transformer. In the analysis of the magnetization curve, the relationship between the magnetic flux density and magnetic field intensity differs from the ordinary B-H curve; this paper interchanges the B and the H and characterizes the B-H of the magnetic core as a simple tangent function in the H-B planes. Furthermore, the concept of inrush equivalent inductance [1] is also used in the magnetizing inrush model. Using the magnetizing inrush model, an inrush current value can be estimated before the transformer is manufactured. Moreover, in the future, this model can provide the power system with a more thorough transient analysis. During this research, the inrush currents are simulated using the circuit model from ICAP/4. Fourteen actual transformers, each with a different winding structure, are used for demonstration. Experiments and simulations are carried out to examine the proposed method. Index Terms--Inrush current, inrush equivalent inductance, magnetizing inrush model, transformer.

This paper proposes a novel self-oscillating, boost-derived (SOBD) dc-dc converter with load regulation. This proposed topology utilizes saturable cores (SCs) to offer self-oscillating and output regulation capabilities. Conventionally, the self-oscillating dc transformer (SODT) type of scheme can be implemented in a very cost-effective manner. The ideal dc transformer provides both input and output currents as pure, ripple-free dc quantities. However, the structure of an SODT-type converter will not provide regulation, and its oscillating frequency will change in accordance with the load. The proposed converter with SCs will allow output-voltage regulation to be accomplished by varying only the control current between the transformers, as occurs in a pulse-width modulation (PWM) converter. A control network that combines PWM schemes with a regenerative function is used for this converter. The optimum duty cycle is implemented to achieve low levels of input- and output-current ripples, which are characteristic of an ideal dc transformer. The oscillating frequency will spontaneously be kept near-constant, regardless of the load, without adding any auxiliary or compensation circuits. The typical voltage waveforms of the transistors are found to be close to quasisquare. The switching surges are well suppressed, and the voltage stress of the component is well clamped. The turn-on/turn-off of the switch is zero-voltage switching (ZVS), and its resonant transition can occur over a wide range of load current levels. A prototype circuit of an SOBD converter shows 86% efficiency at 48-V input, with 12-V, 100-W output, and presents an operating frequency of 100 kHz. Index Terms--Pulse-width modulation (PWM) converter, saturable cores (SCs), self-oscillating boost-derived (SOBD), self-oscillating dc transformer (SODT), switching-mode power supplies (SMPSs), zero-voltage switching (ZVS).