Research On Passive Current Balancing Method Of Multi-output LED Driver Based On Resonant Converter Topology

As a new generation of semiconductor solid state lighting, LED lighting has become one of the highlights of modern technology. Mean whiles, the application of LED lighting is conductive to the development of low-carbon economy. On one hand, in order to achieve the desired output power and brightness, it’s necessary to put LED strings in series-parallel structure, which will involve the problems of multi-output current balancing. One the other hand, comparing with the PWM converter, resonant converter has the advantage of the high switching frequency, small switching losses, high efficiency, small size etc. The research on passive current balancing method of multi-output LED driver based on resonant converter topology in this paper is based on this background. The primary research is as follows:Firstly, the paper summarizes the current application of high brightness LED and the existing current balancing strategy of multi-output LED driver. Besides, briefly introduces the different features and applications about active and passive current balancing methods. Meanwhiles introduces LED electrical characteristics and LED driver topologies which are commonly used.Secondly, basing on the resonant converter topology and the passive current balancing strategy, the paper introduces three passive current balancing scheme about multi-output LED based on different resonant topologies.The first strategy is multi-output LED current balancing circuit based on non-isolated SRC resonant converter. The basic operation principle of non-isolated SRC resonant converter and the mechanism of capacitance passive current balancing are analyzed. The second strategy is multi-output LED current balancing circuit based on LLC resonant converter. The operation principle and the design consideration of the key parameters is described in detail. And then theoretically deduced the effect on LLC resonant circuit, which causes by the blocking capacitor. In addition in order to improve the adaptability when the LED is failure, subsitutes full-bridge rectifier for half-wave rectifier. The third strategy is multi-output hybrid passive current balancing circuit based on LLC resonant converter. The principle of hybrid passive current balancing method which uses coupled inductor and blocking capacitor is studied and summarized in detail in this section. Though the theoretical analysis, it can find that the strategy has better current sharing ability and higher efficiency.Finally, simulates the circuit under PSIM, and a prototype was proposed to test in the laboratory. The result is individually verify the feasibility and rationality of the three strategies.