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This paper presents an optimal lowest-voltage-switching technique for boundary mode power factor correction (PFC) converters. The proposed approach minimizes the switching loss of the power MOSFET without additional discrete components. Optimal zero-voltage-switching or valley-switching can be achieved for universal input range. The gate driver delay can also be taken into account. A boundary mode boost PFC converter with the proposed optimal switching technique has been implemented using a 0.5-μm N-well process. Experimental results show that the proposed approach can realize optimal soft switching, and improve the efficiency of the boost PFC converter. The proposed lowest-voltage-switching technique can be applied to other resonant converters as well.

This paper proposes a new variable field wind generator with soft magnetic composite material and the basic theories were presented. Basically, the overlapping of the two magnetic fields is applied to its machine operation. The fundamental theory of the new wind generator is the same as traditional generators. Its bias of magnetic fields and two stator partitions increase iron and copper losses. Soft magnetic composite material technology which can reduce wire length and copper loss improves its efficiency. It has a simple rotor structure and a field winding with adjustable magnetic field on the stator. This new wind generator can reach high speed by reducing its rotor field directly and produce constant output voltage at a wide range of speed by adjusting its magnetic field. Theoretical derivation and simulation results perform its practicability.

This paper presents a novel control method for a current-fed full-bridge inverter actuating an ultrasonic piezoelectric transducer (PT). In the conventional ultrasonic detection system, the PT has maximum transmitting gain at its series resonance frequency while having maximum receiving gain at its parallel resonance frequency. With the proposed approach, the PT could have maximum transmitting gain at the parallel resonance frequency and this frequency can be automatically traced, and hence adapted, to the environmental variation. A prototype circuit was constructed to verify the proposed control method. The experimental results show that the receiving voltage signal could have a maximum value at the parallel resonance frequency, and the traced frequency is 0.04 kHz higher than the parallel resonance frequency.

A feedback network for isolated switch-mode power supplies that automatically reduces the currents flowing through the optocoupler to nearly zero under the no-load condition is presented. This feedback network uses a proposed reverse-type shunt regulator to generate an error signal for optical coupling, and a modified PWM controller is adopted to receive the feedback signal. In comparison to the conventional topology, this proposed one exhibits much lower standby power loss. Besides, light-load efficiency can be improved as well. For implementing the proposed scheme, the PWM controller and the reverse-type shunt regulator are designed and fabricated in VIS 0.5- $\mu$ m 5-V/40-V high-voltage CMOS technology. Experiments reveal that a 12-V/18-W flyback converter prototype which adopts the proposed feedback technique will save a power of at least 27 mW under the no-load condition and improve the system efficiency by 2.2 $\%$ under the 10 $\%$ -load (1.8-W output) condition.

In this paper, we propose a regulated pulse current laser driver with the frequency double approach to synthesize green laser. Experiment results show that green laser synthesis conducted with the regulated pulse current driving (RPCD) technique has an electrical to optical conversion efficiency improvement of up to 78%, as compared to the DC driving technique with mean driving current of 250 mA at room temperature. This driver was fabricated with a 0.5 μm CMOS process and has a modulation frequency range of 300 kHz-700 kHz, a wide range of peak pulse current between 120 mA-900 mA with the average current range between 0 mA-280 mA. This paper not only demonstrated the synthesize procedure of green laser but also proposed driver with the RPCD technique enhances the electrical to optical conversion efficiency of green laser and its implementation in integrated circuit, making it a good match with green laser microchip to create a low cost, compact-sized device ideal for mobile projector applications.

Source switching circuit with low-gate-driving loss in high-voltage buck light emitting diode (LED) driver is proposed in this study. Source switching circuit comprises of a high-voltage power metal-oxide semiconductor field-effect transistor (MOSFET) (HVMOS) and a low-voltage power MOSFET (LVMOS) in series, a capacitor and a Zener diode. By switching the HVMOS by different source voltage and constant gate voltage, it recycles gate charges of HVMOS to reduce gate-driving loss. Gate charges are recycled in the capacitor when LVMOS is turning off, and can be reused when LVMOS is turning on. This circuit also provides a new power feeding route for control chip, and power consumption is relatively low on the proposed route. The power feeding route also improves power efficiency. With a 12 W LED load, the experiment shows that the efficiency of the proposed driving circuit is improved by 3.7% with 156 V input voltage and 4.8% with 326 V input voltage compared with the converter using single HVMOS.

A novel driving technique, called pulse current driving technique for LED driver, is proposed. A complete introduction and analysis of the proposed driving technique and the conventional driving technique will be presented in this paper. The LED driver supply maximum peak current is 220 mA and operating frequency is between 500 kHz and1 MHz. Simulation and experimental results are presented to verify the analytical results. The LED driver is fabricated with CMOS 0.35-μm technology and chip area with pads is 0.89 mm 2. The design of the proposed circuit structure is simple, without additional output capacitance compensation for stability and with small power consumption, and is implemented in integrated circuit. As a result of the above benefits, the proposed approach is believed to be suitable in portable application.

This paper presents a primary side control method for a low power wireless energy transmission system (WETS), with no physical wire connection required between the primary and secondary-side circuits. The primary side control method implemented in the WETS does not require extra space in the secondary side to regulate transmission energy. A charging protection was embedded within the secondary side to monitor the charging current and battery voltage, and to protect the battery against over-charging current or voltage. LLC resonant converter and class-E amplifier structures with zero-voltage switching were utilized to minimize transmission loss due to leakage inductance. In our experiments, the secondary side battery was fed a stable charging current in constant-current mode and low current in constant-voltage mode where the battery voltage reached approximately 4.1 V. The results show that the WETS achieved primary side control in all air-gap conditions. The overall efficiency of the WETS with LLC resonant converter was between 33.5% and 54.1%, and that of the class-E amplifier was between 30% and 66.2% when operating in the constant-current mode.

Analysis and design of a single-stage LLC resonant converter are proposed. A single-stage converter uses only one control signal to drive two power converters, a power factor corrector (PFC) converter and a dc/dc converter, for reducing the cost of the system. However, this simplicity induces power imbalance between two converters, and then, the bus voltage between two converters drifts and becomes unpredictable. To ensure that the bus capacitor voltage can be kept in a tolerable region, the characteristics of a PFC converter and an LLC tank are investigated, and then, a design procedure is proposed correspondingly. Finally, a single-stage LLC resonant converter is implemented to verify the analysis.

This paper proposes a novel single-stage ac-to-dc light-emitting-diode (LED) driver circuit. A buck-boost power factor (PF) corrector is integrated with a flyback converter. A recycling path is built to recover the inductive leakage energy. In this way, the presented circuit can provide not only high PF and low total harmonic distortion but also high conversion efficiency and low switching voltage spikes. Above 0.95 PF and 90% efficiency are obtained from an 8-W LED lamp driver prototype.

This brief presents a high-efficiency current-regulated charge pump for a white light-emitting diode driver. The charge pump incorporates no series current regulator, unlike conventional voltage charge pump circuits. Output current regulation is accomplished by the proposed pumping current control. The experimental system, with two 1-muF flying and load capacitors, delivers a regulated 20-mA current from an input supply voltage of 2.8-4.2 V. The measured variation is less than 0.6% at a pumping frequency of 200 kHz. The active area of the designed chip is 0.43 mm2 in a 0.5-mum CMOS process.

A new zero-voltage-switching (ZVS) control approach is presented for pulsewidth modulation (PWM) buck converters under discontinuous conduction mode (DCM)/continuous conduction mode (CCM) boundary. This proposed technique compensates for control circuit delay, and hence, turns on power MOS at the instant exactly when drain-to-source voltage becomes zero. No complicated timing calculation circuits or additional external components are required. This proposed integrated ZVS control can be applied to other dc-dc converters as well. The corresponding circuit analysis, implementation, and die photograph are presented in this paper. Simulation and experimental results for an example circuit with V IN of 5 V and V OUT of 3.3 V reveal that buck converters with the presented ZVS technique have higher efficiency than conventional ones, especially at higher frequencies. At about 3.6 MHz operation, the measured conversion efficiency of the PWM buck converter under DCM/CCM boundary mode with the proposed ZVS approach is 11% higher.

Driving power MOSFET at high switching frequency may induce significant switching power losses. A gate driver with low energy consumption is proposed for power MOSFET in switching power conversion applications. The proposed gate driver regulates the output gate driving voltage for minimizing the loss of charging and discharging the gate capacitor. No extra off-chip components are required, and hence, the proposed approach can be completely designed on chip. A 40 V/0.5 mum CMOS technology is utilized and experiments on a boost converter are performed. The power dissipation of the proposed gate driver, compared with the conventional gate driver, can be reduced up to 15.5% and 55.4% under 15 V and 30 V supply voltage, respectively.