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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 letter proposes a novel current-fed parallel-resonant dc-ac inverter with zero-current switching (ZCS) for cold-cathode fluorescent lamps (CCFLs). The leakage inductance of the transformer is integrated within the resonant tank in order to reduce the voltage spikes across the switches. A laboratory prototype is implemented to drive a 617 mm/7W CCFL. Experimental results indicate that the switches of the proposed resonant inverter are operated under the ZCS condition, and the efficiency is approximately 86.8%. The lamp voltage is about 977 [V.sub.rms] and the lamp current is 7 m[A.sub.rms]. Index Terms--Cold-cathode fluorescent lamp (CCFL), currentfed, resonant inverter, zero-current switching (ZCS).

This paper proposes a novel three-phase ac--dc buckboost converter. The proposed converter uses four active switches, which are driven by only one control signal. This converter is operated in discontinuous conduction mode (DCM) by using the pulsewidth modulation (PWM) technique, and the control scheme very easily and simply achieves purely sinusoidal input current, high power factor, low total harmonic distortion of the input current (TH[D.sub.i]) and step-up/down output voltage. Also, the proposed converter provides a constant average current to the output capacitor and load in each switching period. Thus, the ripple component of sixth times line frequency will not appear in the output voltage. Therefore, a smaller output capacitor can be used in the proposed converter. Moreover, the steady-state analysis of voltage gain and boundary operating condition are presented. Also, the selections of inductor, output capacitor and input filter are depicted. Finally, a prototype circuit with simple control logic is implemented to illustrate the theoretical analysis. Index Terms--Buck-boost converter, discontinuous conduction mode (DCM), pulsewidth modulation (PWM), TH[D.sub.i].

The study and implementation of a single-stage current-fed full-bridge boost converter with power factor correction (PFC) and zero current switching (ZCS) for high voltage application is presented in this paper. The single-stage current-fed full-bridge boost PFC converter can achieve ZCS by utilizing the leakage inductance and parasitic capacitance as the resonant tank. The variable frequency control scheme with ZCS is used to regulate the output voltage and achieve high power factor. The operating principle, steady-state analysis, and control method of this single-stage ac-dc PFC converter are provided. Also, the ZCS operational conditions under various operational conditions are discussed. The design guidelines are given and verified by a laboratory prototype converter with 200 ~ 240 [V.sub.rms] input voltage and a 4 kV/1.2 kW output. In order to reduce the switching losses, the highest switching frequency is constrained at 160 kHz. So, the switching frequency of the prototype converter is 50~160 kHz. The measured power factor is 0.995 and the efficiency is 87.4 at full-load condition with an input voltage of 220 [V.sub.rms]. The laboratory prototype converter can be operated at ZCS under full range by carefully designing the circuit parameters. Index Terms--High-voltage converter, high-voltage transformer, power factor correction (PFC), single-stage, zero current switching (ZCS).

We investigated the electrical and magnetic properties of cobalt-substituted manganese--zinc soft ferrite by using the equivalent lumped elements acquired from the appropriate equivalent electrical circuit of polycrystalline ferrite. We applied the equivalent lumped circuit, combined with equivalent lumped resistances and capacitance, to determine the effect of microstructure on electrical and magnetic properties of cobalt-substituted manganese-zinc ferrites. Both the hysteresis loss and the eddy-current loss of soft ferrites account for a major proportion of iron loss in high-frequency switching mode power supplies. Replacing a small portion of [Fe.sup.2+] with [Co.sup.2+] remarkably increases the bulk resistivity of the MnZn ferrite and decreases the core loss by lowering eddy-current loss. A longer isothermal duration causes grain growth and forms a larger equivalent capacitance, which leads to a reduction in hysteresis loss. However, excess substitution of [Co.sup.2+] for [Fe.sup.2+] is disadvantageous to magnetic permeability and raises core loss. We measured the dc resistivity by the four-probe method on sintered disks with both sides polished and coated with a thin layer of silver paste as a good contact material. We measured the magnetic permeability by an impedance analyzer at room temperature. The total loss of [Mn.sub.0.58] [Zn.sub.0.37] [Co.sub.0.01] [Fe.sub.2.04] [O.sub.4] ferrite core does not exceed 420 mW/[cm.sup.3] at 300 kHz/70 mT. Index Terms--Bulk resistivity, eddy-current loss, equivalent lumped circuit, manganese--zinc soft ferrite.

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 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).

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 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).

One by-product of steel making, granulated blast furnace slag, is often wasted. When it is used, it is used in civil engineering and building engineering and mostly applied to road-building. It will soon have many other environmental uses. The granulated blast furnace slag has similar characteristics to glue, and low resistivity was found. With a cement-hydrate catalyst, it can be used to produce glue and, as such, it should be used as a grounding resistance reduction agent. Adding different proportions of water, cement, and salt, the resistivity and clot strength of the grounding resistance reduction agent was studied to find an optimal combination. This finished product can be used in a grounding resistance reduction agent, within which the grounding bar is buried. Our measurements have shown that this method can effectively reduce grounding resistance. Index Terms--Granulated blast furnace slag, grounding bar, grounding resistance, grounding resistance reduction agent, resistivity.

A single-phase three-wire photovoltaic energy conversion system with single-stage structure using a novel maximum power-point tracking (MPPT) algorithm is presented. An equivalent model of the proposed system is derived to analyze the characteristics of the system and to design the controller. Owing to the linear relation of the PV array parameters versus insolation, the model is easy to analyze. The proposed system employs a three-leg inverter to control the MPPT process, the line current, and neutral line current. A current-controlled MPPT algorithm controls the MPPT. A neutral line-mode controller maintains a utility neutral line current of zero. A line-mode controller controls the line current so as to provide power to the utility with a unity power factor. The proposed system acts as a solar generator on sunny days and functions as an active power filter on rainy days. Computer simulation and experimental results demonstrate the accuracy and the superior performance of the proposed technique. Index Terms--Active power filter, maximum power-point tracking, photovoltaic (PV) energy conversion system, solar generator.