Research On LED Constant Current Driver

With the growing global energy shortage, governments around the world are promoting energy conversation、low-carbon life vigorously. Under this background, LED lighting has been developed rapidly because of its high efficiency、environmental friendly、long life、safety and reliability. The LED driver as a key part of LED lighting has also become a research focus. In this dissertation, a two-stage resonant LED driver is discussed.The constant on-time control strategy of TEA1713is analyzed firstly, the design method of the main parameters and control circuit is discussed in detail, a PFC prototype is tested at the end of the chapater. The principle of LLC is discussed detailedly in chapter III. The voltage gain formula of LLC circuit is derived based on the fundamental harmonic approximation (FHA), in order to design a constant current LED driver, the constant current gain formula is derived by transforming the voltage gain formula. According to the formula, the constant current gain curve is made by Mathcad, and the resonant parameters is derived according to the curve, and LLC circuit is simulated by Saber. Finally, a prototype is worked out and tested based on TEA1713, experimental results are shown by testing a wide range voltage input(90-264V)、0.7A/90-120V output LED driver. The testing results are consistent with the theoretical calculations, indicating that the LED driver was designed reasonably.Another focus of the dessertation is the passive current-sharing techonology. The capacitor current-sharing technology is discussed in the chapater. Then the principle of the capacitor current sharing technology and the selection of the capacitor are analyzed, and the current-sharing circuit is simulated by Saber. Finally, a prototype with two outputs is worked out and tested. The results indicate that current-balancing between two loads can be achieved precisely.