Duy T. Nguyen

A Novel Source-Side Monitored Capacitive Power Transfer System for Contactless Mobile Charger Using Class-E Converter

A new source-side monitored capacitive power transfer system (CPTS) for contactless mobile charger using Class-E converter is proposed. Contrary to conventional contactless mobile charger, an exact battery voltage monitoring is achieved without additional cumbersome communication circuits. The proposed CPTS operates in two iterative modes; a main-charging-mode and a sub-battery-monitoring-mode. Not only the battery voltage sensing but also an agile battery charging current control is accomplished with a microprocessor at a transmitting side. The circuit parameters of class-E converter and primary circuit, which consists of the compensating inductors and the capacitive coupled metal plates, are determined for guaranteeing load tolerance. A detail analysis for the battery monitoring operation and design procedures of the proposed CPTS are fully established, and experimentally verified for 4 W prototype of Samsung GALAXY S3 Li-ion battery at the switching frequency of 1.237 MHz.

Versatile LED Drivers for Various Electronic Ballasts by Variable Switched Capacitor

An LED driver compatible with various electronic ballasts that are currently commercially used is newly proposed, which adopts a variable switched capacitor by controlling the switching duty cycle for LED power regulation. The resonant frequency of an LC resonant tank of electronic ballasts can be changed, which makes the proposed LED driver versatile for electronic ballasts for various switching frequencies. In this way, the fluorescent lamp is replaced with an LED lamp, where the electronic ballast in the lighting infrastructure remains unchanged. The zero voltage switching is applied for the variable switched capacitor in the electronic ballast, operating at a frequency of 30-60 kHz. Neither an inductor nor a transformer is introduced in the proposed LED driver, which leads to compact size and high efficiency. Furthermore, no electrolytic capacitor is used, which is beneficial for the long lifetime of LED drivers. A prototype LED driver of 16 W was implemented and verified for the three types of electronic ballasts that are most popular in markets. The LED power was well regulated for a wide range of the source voltage variations between 180 and 270 V, and the power efficiencies of the proposed LED driver were 95.8%, 96.1%, and 94.1% for the instant start, rapid start, and programmed start types of the electronic ballasts, respectively.

LED Driver with TRIAC Dimming Control by Variable Switched Capacitance for Power Regulation

A TRIAC dimming LED driver that can control the brightness of LED arrays for a wide range of source voltage variations is proposed in this paper. Unlike conventional PWM LED drivers, the proposed LED driver adopts a TRIAC switch, which inherently guarantees zero current switching and has been proven to be quite reliable over its long lifetime. Unlike previous TRIAC type LED drivers, the proposed LED driver is composed of an LC input filter and a variable switched capacitance, which is modulated by the TRIAC turn-on timing. Thus, the LED power regulation and dimming control, which are done by a volume resistor in the same way as the conventional TRIAC dimmers, can be simultaneously performed by the TRIAC control circuit. Because the proposed LED driver has high efficiency and a long lifetime with a high power factor (PF) and low total harmonic distortion (THD) characteristics, it is quite adequate for industrial lighting applications such as streets, factories, parking garages, and emergency stairs. A simple step-down capacitive power supply circuit composed of passive components only is also proposed, which is quite useful for providing DC power from an AC source without a bulky and heavy transformer. A prototype 60 W LED driver was implemented by the proposed design procedure and verified by simulation and experimental results, where the efficiency, PF, and THD are 92%, 0.94, and 6.3%, respectively. The LED power variation is well mitigated to below ± 2% for 190 V < Vs < 250 V by using the proposed simple control circuit.

Optimal shaped dipole-coil design and experimental verification of inductive power transfer system for home applications

1m-off long distance and high efficiency inductive power transfer system (IPTS) with optimal shaped dipole-coil structure is proposed for home appliance charging applications. Conductive reflectors for transmitter (Tx) and receiver (Rx) dipole coils are investigated to improve power efficiency and to mitigate electromagnetic field for human safety. By adopting the Tx reflector behind the Tx core, the exposure level of magnetic flux density can be reduced by 94% in average verified by a finite-element method simulation. The optimal switching frequency of 200 kHz was experimentally found for maximum power efficiency, meeting an international guideline of Power Matters Alliance (PMA). It was experimentally verified that 4.2% of power efficiency reduction for the Rx reflector and 7.8% of the power efficiency improvement for the Tx reflector were observed. A prototype of the proposed IPTS for home appliances has achieved 83.1% of high efficiency with 150W of output power transfer.

The analysis of TRIAC dimming LED driver by variable switched capacitor for long life and high power-efficient applications

The analysis of the proposed TRIAC dimming LED driver, which adopts a variable switched capacitor, is proposed in this paper. Because the proposed LED driver adopts a TRIAC switch as the main switch, it is proven to be power-efficient and reliable over long life. Similar to the previous TRIAC dimmers of lamps, turn-on timing of a TRIAC can be controlled by a volume resistor in the proposed LED driver, which modulates the effective capacitance of the variable switched capacitor. Thus, LED power regulation for source voltage change and LED dimming control can be achieved, meeting the standard of power factor (PF) and total harmonic distortion (THD). Because the proposed LED driver has long life and high power efficiency characteristics, it is adequate for industrial lighting applications such as street, factory, parking garage, and emergency stair. The detail analysis of the proposed LED driver is presented in this paper. A prototype of 80 W was fabricated and verified by experiments, which show the efficiency, PF, and THD at Vs = 220 V are 93.8%, 0.95, and 22.5%, respectively, and the LED power variation is well mitigated below 3.75% for 190 V <; Vs <; 250 V.

The LED driver compatible with electronic ballasts by variable switched capacitor

An LED driver compatible with most electronic ballasts commercially used now is newly proposed, which adopts a variable switched capacitor by controlling switching duty cycle for the LED power regulation. The resonant frequency of the LC resonant tank of electronic ballasts can be appropriately controlled, which makes the proposed LED driver be versatile for electronic ballasts for various switching frequencies. In this way, the fluorescent lamp can be replaced with an LED lamp, where the electronic ballast in the lighting infrastructure remains unchanged. The zero voltage switching is applied for the variable switched capacitor in the electronic ballast, operating at the frequency of 30 ~ 60 kHz. Neither an inductor nor a transformer is introduced in the proposed LED driver, which leads to compact size and high efficiency. Furthermore, no electrolytic capacitor is used, which is beneficial for the long lifetime of LED drivers. A prototype LED driver of 16 W was implemented and verified for the three types of electronic ballasts that are most popular in markets. The LED power was well regulated for a wide range of the source voltage variation of 180 ~ 270 V, and the power efficiencies of the proposed LED driver were 95.8%, 96.1%, and 94.1% for the instant start, rapid start, and programmed start types of the electronic ballasts, respectively.

Static Regulated Multistage Semiactive LED Drivers for High-Efficiency Applications

Semiactive light-emitting diode (LED) drivers with high efficiency that regulate LED power statically against source voltage variation are proposed. By adopting multistage switching circuits in the proposed LED driver, the number of operating LED strings in series is appropriately selected according to the source voltage variation, which results in slow regulation of the LED power. A detailed procedure for selecting hysteresis control of the proposed LED driver with an LC3 input filter is fully established. A prototype five-stage LED driver of 100-W class was implemented and verified by experiments, which shows LED power variation of 90-110 W with a very high efficiency of 95.1-97.3% for source voltage variation of 200-253 V, meeting power factor and total harmonic distortion regulations.

A novel passive type LED driver for static LED power regulation by multi-stage switching circuits

A novel passive-type LED driver that can regulate LED power PL statically for the source voltage Vs variation is proposed. Contrary to switch-mode-power-supply (SMPS) type LED drivers, the proposed LED driver is based on passive type LED driver, which does not use pulse-width-modulation (PWM) technique. Thus, the LED power regulation with high power efficiency and a long lifetime of LED operation can be simultaneously performed by multi-stage switching circuits. The LED power can be calculated and controlled by micro controller unit (MCU), which selects the number of operating LEDs in series ns appropriately for the static LED power regulation. A prototype LED driver of 100 W was implemented and verified by experiments, where 90 W <; PL <; 110 W of a small LED power variation with 95.4 % ~ 97.1 % of very high efficiency for 200 V <; Vs <; 245 V was achieved with five stage switching circuits, meeting power factor (PF) and total harmonic distortion (THD) regulation.

Long-Lasting and Highly Efficient TRIAC Dimming LED Driver with a Variable Switched Capacitor

A triode for alternating current (TRIAC) dimming light emitting diode (LED) driver, which adopts a variable switched capacitor for LED dimming and LED power regulation, is proposed in this paper. The proposed LED driver is power efficient, reliable, and long lasting because of the TRIAC switch that serves as its main switch. Similar to previous TRIAC dimmers for lamps, turn-on timing of a TRIAC switch can be controlled by a volume resistor, which modulates the equivalent capacitance of the proposed variable switched capacitor. Thus, LED power regulation against source voltage variation and LED dimming control can be achieved by the proposed LED driver while meeting the global standards for power factor (PF) and total harmonic distortion (THD). The long life and high power efficiency of the proposed LED driver make it appropriate for industrial lighting applications, such as those for streets, factories, parking garages, and emergency stairs. The detailed analysis of the proposed LED driver and its design procedure are presented in this paper. A prototype of 80 W was fabricated and verified by experiments, which showed that the efficiency, PF, and THD at V s = 220 V are 93.8%, 0.95, and 22.5%, respectively; 65 W of LED dimming control was achieved with the volume resistor, and the LED power variation was well mitigated below 3.75% for 190 V s < 250 V.

A compact and high efficient LED driver compatible with electronic ballast by synchronous voltage doubler rectifier

A compact and high efficient LED driver compatible with various electronic ballasts commercially used in markets is newly proposed, which modulates the LED power by controlling a switching duty cycle of a main switch in synchronous voltage doubler rectifier. Thus, the fluorescent lamp can be replaced with the LED lamp without any change of fluorescent lamp fixture. The zero voltage switching (ZVS) is achieved for different switching frequency of electronic ballast, which leads to high efficiency. Furthermore, neither an inductor, a transformer, nor an electrolyte capacitor is used, which makes this LED driver compact size and long lifetime. A prototype of 16 W LED driver was implemented and experimentally verified for 32 W or 36 W electronic ballasts, where high efficiencies of 93.2%, 91.8%, and 92.3% for instant start, rapid start and programmed start ballasts, respectively, were achieved for a wide range of source voltage 180 V <; Vs <; 260 V, adequately meeting high power factor (PF), low total harmonic distortion (THD).