Research On Resonant Multi-output LED Driver

In recent years, the situation of energy shortage make people increasingly aware of energy conservation’s importance. As a new light source? the LED possesses many merits such as long life, energy conservation and environment friendly. It has been widely used in road lighting, tunnel lighting and other high-power lighting applications. And the efficient and reliable LED drive power is the key to ensuring the LED stable work.Firstly, this paper introduces the structure of LED driver and key techniques of the LED driver such as constant current driver, multi-channel with current balancing and dimming. Then, analyze circuit characteristics of the LCL-T resonant converter and passive current balancing methods based on the capacitance or series transformers. According to the above analysis, a high-power LED driver composed by the LCL-T resonant converter and multioutput with passive current balancing is proposed in this paper, the working principle and its characteristics is discussed in detail.Secondly, in allusion to the LCL-T resonant converter using in high-power LED applications, an multi-phase parallel LCL-T resonant converter suitable for high-power LED driver is proposed, and the working principle of the circuit is analyzed, then deduced constant exchange equivalent AC circuit and the constant current characteristic, a detailed analysis of the circuit affected by the various circuit parameters, and the design of the circuit parameters and the implementation of the circuit is given, the simulation and the experiment verification of the feasibility of the constant current output program. Based on the multi-phase parallel LCL-T resonant converter, a new phase-shift dimming control strategy is proposed, through phase-shifting control realized with LED’s dimming control, a detailed analysis of the working principle of the dimming strategy, and the relationship between the phase angle of the output current’s rms is deduced, and the experimental results show that the dimming solution has advantages of high accuracy dimming, enabling full-range dimming and so on.By analyse multioutput passive current balancing method now exist? a new passive current-sharing method based on multi-phase parallel LCL-T resonant converter is proposed in this paper, this method use series transformers and capacitors combination to receive current balance of 2N outputs, and it is simple, precise balance and low requirement for series transformer. The balancing scheme and working process of a 4-outputs LCL-T circuit using this method is detail analysed, the voltage characteristics of the balancing capacitor are discussed, simulation and experiment show the correctness of the analysis.Finally, a 200W LED driver experimental prototype using dsPIC33FJ16GS502 singlechip as the main controller with four outputs and dimming function is developed, and the experiment results verify the feasibility of the proposed program.