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In order to obtain sufficient luminance and achieve high reliability, light-emitting diodes (LEDs) are usually arranged in parallel strings in many high-power applications. Since current imbalance should be avoided among the parallel LED strings, a multichannel constant current LED driver with dynamic high-frequency sinusoidal voltage regulation is proposed in this paper. The proposed driver is composed of one resonant inverter and several LCL-T resonant rectifiers. The number of the rectifiers equals to that of the LED strings. The rectifier whose output current is sensed and closed-loop controlled is called master rectifier and all the others slave rectifiers. The resonant inverter is used to convert dc voltage into high-frequency sinusoidal bus voltage and the LCL-T resonant rectifiers are included to drive LED strings with constant current. The amplitude of the high-frequency sinusoidal bus voltage is dynamically regulated to ensure the output current of the master resonant rectifier to be constant by a closed-loop controller. Since the output current of the slave rectifier is linear with the amplitude of the bus voltage as the master rectifier, there are not any auxiliary circuits included in the slave rectifier while the output current balancing is achieved. Finally, a 200-W prototype with one master and fifteen slave rectifiers is built to verify the performance of the proposed driver.

To obtain sufficient luminance and achieve higher reliability, light-emitting diodes (LEDs) are usually arranged in parallel strings in many high-power applications. Since current imbalance should be avoided among the parallel LED strings, a multi-channel constant current LED driver based on high-frequency AC bus is proposed in this study. The proposed driver is composed of one resonant inverter followed by passive resonant rectifiers according to the number of LED strings. The amplitude of the high-frequency AC bus voltage is regulated by the resonant inverter and each LED string is individually powered with constant current by its corresponding passive resonant rectifier. The proposed driver is characterised by low cost and high efficiency. Finally, a prototype is built to verify the performance of the proposed driver.

In this paper, a direct current control method based on a one-cycle controller (DCOCC) for double frequency buck converters (DF buck) is proposed. This control method can make the average current through the high frequency and low frequency inductors of a DF buck converter equal. This is similar to the average current control method. However, the design of the loop compensator is much easier when compared with the average current control. Since the average current though the high frequency and low frequency inductors is equivalent, the current stress of the high frequency switches and the switch losses are minimized. Therefore, the efficiency of the DF buck converter is improved. Firstly, the operation principle of DCOCC is described, then the small signal models of a one cycle controller and a DF buck converter are presented based on the state space average method. Eventually, a system block diagram of the DCOCC controlled DF buck is established and the compensator is designed. Finally, simulation and experiment results are given to verify the correction of the theory analysis.

With the significant development in the manufacturing process of LEDs, LEDs are promising for various lighting applications. In order to achieve better performance and higher reliability, the multiple LED strings structure is adopted in many applications, such as street lighting and tunnel lighting. This paper is aimed to describe a multi-channel constant current LED driver which is composed of a master AC source and some slave passive constant current sources according to the number of LED strings. The high frequency resonant inverter is controlled to operate as the master AC source, whose output forms the high frequency AC bus, each LED string is individually powered by its corresponding salve passive constant current source driven by the high frequency AC bus. By employing the LED's u-i model instead of the constant resistive load, the performance and characteristics of the driver are analyzed in detail and the experimental results are provided to verify the concept.