Universal LED drivers and wide-range inductive power transfer systems by variable switched capacitance

Abstract

hence, high efficient and long lifetime operations can be realized without high switching frequency operation devices. On the other hands, the variable switched capacitance is utilized to a 100W IPT system for load power regulation under wide-range distance variation between the transmitter (Tx) and receiver (Rx). Wide-range ubiquitous IPT technologies, i.e.,Wi-power zone, where any electric devices can be charged by 3D-omnidirectional wireless charging, are newly proposed for the next wireless power generation. In Chapter 1, versatile LED drivers compatible with various electronic ballasts are proposed, which adopt the variable switched capacitance by controlling the switching duty cycle for LED power regulation. By controlling the switching duty cycle, the resonant frequency of an LC resonant tank of electronic ballasts can be controlled, and the LED power can be appropriately modulated. This resonant-frequency-adjustment characteristic makes the proposed LED driver versatile for most electronic ballasts available in markets. The validity of the proposed LED driver is verified by experiments, showing fair compatibility with three types of eight conventional electronic ballasts in markets and a successful LED power over a wide range of source voltage variation. In Chapters 2-3, TRIAC dimming LED drivers that can control the brightness of LED arrays for a wide range of source voltage variation are proposed. Unlike conventional PWM LED drivers, the proposed TRIAC dimming LED drivers adopt a TRIAC switch, which inherently guarantees zero current switching and has been proven to be quite reliable over its long lifetime. Different from conventional TRIAC LED drivers, the proposed LED drivers utilize the variable switched capacitance, which is modulated by the TRIAC turn-on timing. Thus, the LED power regulation and the dimming control, which can be implemented by a volume resistor in the same way as the conventional TRIAC dimmers of lamps, can be simultaneously performed by a TRIAC control circuit. In Chapter 4, static regulated multi-stage semi-active LED drivers with high power efficiency that regulate the LED power statically against source voltage variation, are proposed. Multi-stage switching circuits are adopted to select the number of operating LED strings in series so that the LED power is appropriately controlled for static LED power regulation. Contrary to the switch-mode-power-supply (SMPS) LED drivers, the proposed LED drivers use switching devices in the multi-stage switching circuits for slow turn-on operation of LED lamps

hence, the resonant frequency of the LC tank in the Rx circuit is controlled and the load power is regulated. The validity of the proposed IPT is verified by simulations and experiments, showing a complete load power regulation over the wide-range distance variation. In Chapters 7-8, wide-range ubiquitous IPT technologies, i.e., Wi-power zone, which can provide an evenly distributed magnetic field over 3D space, are newly proposed. In this ubiquitous IPT zone, any electric devices can be freely charged with 3D omnidirectional wireless charging, i.e., so called six degrees of freedom (6-DoF), anytime and anywhere. Direct and quadrature (DQ) Tx coils having orthogonal phase difference of DQ currents are adopted to generate a DQ rotating magnetic field

hence, a plane Rx coil including vertical and horizontal coil windings is able to receive load power from either vertical or horizontal Rx coil winding. One of ubiquitous IPT can be installed in the ceiling of room by copper wire-type DQ Tx coils, whereas the other one can be installed in the bottom of room by modularized DQ Tx coils. Optimum baseline design procedures of the proposed ubiquitous IPT are established and verified by experimental prototypes for high magnetic field uniformity, 6-DoF characteristic, and simultaneous wireless charging of multiple Rx coils.

Universal LED drivers for high efficient and long life-time operations, variable switched capacitance based inductive power transfer (IPT) technology for load power control, and wide-range ubiquitous IPT technologies are widely researched throughout this dissertation. The variable switched capacitance, which can modulate the resonant frequency of an LC resonant tank by controlling the switching duty cycle, is introduced and utilized to various LED drivers and IPT technology. Versatile LED drivers compatible with various electronic ballasts by the variable switched capacitance are newly proposed and verified for high efficiency, versatile compatibility without malfunctions, and load power regulation. For LED dimming control and load power regulation with high efficient and long lifetime operations of LED drivers, TRIAC dimming LED drivers, which adopt the variable switched capacitance by TRIAC and DIAC devices, are newly proposed. Besides the LED drivers utilizing the variable switched capacitance, two passive-type LED drivers are also introduced, which are contrary to conventional LED drivers adopting pulse-width-modulation (PWM) switching techniques

hence, degradation of the lifetime of switching devices in the proposed LED drivers thus can be mitigated by a non-PWM technique. The validity of the proposed LED drivers was verified by experiments, which show successful static LED power regulation with high power efficiency, meeting PF and THD standards over a wide range of source voltage. In Chapter 5, compact passive LC3 LED drivers that achieve low THD and high PF by using LC parallel resonance are proposed. An optimum number of LED array in series is appropriately selected such that the LED power becomes temperature-robust. The proposed LED drivers are analyzed by the powerful phasor transformation techniques, which are applied to the non-linear switching case for the first time in this chapter. Experimental verification of the phasor transformation for the proposed LED drivers showed good agreements with simulations and designs. In Chapter 6, an adaptively controlled variable switched capacitance is firstly applied to a dipole-coil-based loosely-coupled IPT system with a Tx reflector, which can regulate load power under wide-range distance variation. The equivalent circuit of the proposed IPT can be represented as an LC parallel resonant circuit, and the equivalent capacitance of the variable switched capacitance can be appropriately modulated