Output Current Balance Research Articles

LLC Converter for Multi-Output LED for Output Current Balancing in case of LED Module Failure

LLC Converter for Multi-Output LED for Output Current Balancing in case of LED Module Failure

Current and power quality multi-objective control of virtual synchronous generators under unbalanced grid conditions

In recent years, with the large-scale application of distributed power sources in the power grid, the power grid is moving toward low inertia and low damping. The virtual synchronous generator (VSG) has become a hot topic for scholars since it can simulate the moment of inertia, damping and frequency modulation of synchronous generators. Due to its unbalanced load distribution and the random variation of power loads, grid voltage is asymmetrical. Under grid voltage asymmetry, a VSG experiences output current imbalance and power oscillation. The grid current imbalance further reduces the transformer’s three-phase voltage, which makes it unequal, cyclic, and very easy to cause electricity accidents. Aiming at this problem, this paper proposes three modes of current balance, reactive power balance and active power balance without changing the characteristics of VSGs. The output current balance and power are constant when the grid voltage is asymmetrical. The effectiveness and feasibility of the control strategy are verified by simulation and experimental results, which provides an effective scheme for balanced and stable operation of the grid.

Light‐emitting diode driver with a combined energy transfer inductor for current balancing control

This study proposes a two-channel light-emitting diode (LED) backlight driver specifically for liquid crystal display monitor application that utilises an integrated magnetic component: a combined energy transfer inductor for current balancing. The integrated magnetic component has two functions: as a boost inductor and as a differential-mode current balance transformer. Under proper design and arrangement, all of the windings are wound on a single UU-core. This scheme uses leakage inductance as boost inductor for energy transfer and mutual inductance as differential mode transformer for output current balancing. By introducing the magnetic component, power density is increased whereas the overall cost and volume of the magnetic components are reduced in comparison with those values under conventional topology. The operating principles and design considerations of the proposed LED driver were analysed. A 10 W prototype converter with a two-channel LED string was developed to verify the feasibility of the proposed driver. Experimental results show that the proposed LED driver provides an equal current for a two-channel LED string.

An LED Driver With Dynamic High-Frequency Sinusoidal Bus Voltage Regulation for Multistring Applications

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.