Ekkachai Mujjalinvimut

An Improved Asymmetrical Half-Bridge Converter With Self-Driven Synchronous Rectifier for Dimmable LED Lighting

This paper proposes an adaptive feedback gain compensation technique and adaptive feedforward loop control based on analog design for an asymmetrical half-bridge converter without electrolytic capacitor to improve the system dynamic response and the system performance (i.e., low flickering and low ripple) for dimmable high-brightness light-emitting diode (LED) applications. In addition, an improved driving circuit of self-driven synchronous rectification (SR) is proposed for switching loss reduction at the secondary of the transformer. The control circuit is designed such that the SR metal-oxide-semiconductor field-effect transistor switch operates under zero-voltage switching (ZVS) mode while the driving signals are maintained within the acceptable voltage limits under duty cycle variations of the LED dimming applications. Simulation and experimental results obtained from a 60-W hardware prototype have confirmed the validity of the proposed method, where the settling time of the output current has been improved by 90% and the ripple of the output current has been reduced to less than 4% under rated current. The SR switches operate under ZVS condition throughout all operating regions where the maximum efficiency at 96.4% has been achieved.

Load monitoring and output voltage control for SP topology IPT system using a single-side controller without any output measurement

This paper presents the method to estimate load value and output voltage of the inductive power transfer (IPT) system with series-parallel (SP) compensation topology. This technique uses primary side measured variables without the need of secondary side measurement and communication devices between the circuits. In addition, the magnitude of the output voltage has been controlled by using only a single-side controller located in the primary circuit. The Phase shift (PS) control of the full-bridge inverter is used instead of the primary side DC-DC converter to regulate the output voltage. This lowers the overall system cost, size, complexity and loss compared to the conventional IPT dual-side controllers. The proposed estimation technique has been investigated through phasor analysis of the mutual inductance coupling model and also verified by the computer simulation. Performance of the proposed primary side single controller against the step change in output voltage reference and load value is shown in the simulation results. Experimental results of the output voltage control against load variation validating the viability of the proposed single-side controller.

Asymmetrical half-bridge converter with adaptive feedback compensation for dimmable LED lighting applications

This paper proposes an adaptive feedback gain compensation technique and simple PI control for an asymmetrical half-bridge (AHB) converter to solve slow system response problem due to the fact that the DC gain of the AHB converter depends on the duty cycle. The focus is on dimmable high brightness light-emitting diode (LED) applications subjected to disturbances or an immediate change of the reference output current from a dimming of the LED brightness or the case of a fault in the LED string. The curve fitting method is employed to address the nonlinearity of the adaptive feedback gain compensating parameters in the control loop. The system is implemented based on analog design, using only an additional low-cost operational amplifier. Experimental results obtained from a 60-W converter confirm the validity of the proposed method where the settling time of output current has been improved by 60-70% with the reduced overshoot. In additional, the system dynamic responses and performance are immune to duty cycle variation.

An improved self-driven synchronous rectifier for high efficiency dimmable LED lighting applications

This paper presents an asymmetrical half bridge (AHB) converter for dimming low-voltage high-current LED lighting application. An improved driving circuit of a self-driven (SD) synchronous rectification (SR) is proposed for switching loss reduction at the secondary of the transformer. The control circuit is designed such that the SR MOSFET switch operates under zero-voltage switching (ZVS) mode while the driving signals are always within the acceptable voltage limits under duty cycle variations of the LED dimming applications. Experimental results obtained from a 60-W prototype have shown that the switches operate under ZVS throughout all operating region where the highest efficiency of the AHB converter is at 96.4%.

A design study of ultrasonic motor drive

An ultrasonic motor (USM) has been widely used in a great variety of applications since it exhibits several advantages over the conventional electromagnetic motor such as high torque at low speeds, light weight, quiet operation, no electromagnetic interference (EMI), and high holding torque without supply. In this paper, the basic principle of USM drive is presented using the commercial D6060 driver for USM modeled USR60-E3 as a sample test. Its equivalent circuit model and parameters, and speed control are also explained. The commercial D6060 driver for USM modeled USR60-E3 is also tested and some experimental results are included. The new driving circuit for USM is proposed and the series inductance is designed. This circuit would improve the speed controlling easier and smoother than D6060 driver, using the manually adjusted potentiometer. Some preliminary simulation results are presented to validate the proposed driving circuit with the designed series inductance.