Research On Protection And Constant Current Driver Of High Power Light Emitting Diode In Illumination Use

LED is used more and more widely with the characteristics of energy conservation, environment protection and so on. But in its promotion process, there are still problems to be solved in LED tunnel light, street light, etc. The problems of open circuit protection and temperature protection limit the number of LED series, which can increase the number of LED constant current driver. According to this issue, a protection chip is researched to improve the number of LED series, which can realize LED over-voltage, open circuit and temperature protection. Besides, LC series resonant circuit is used to design the LED open-loop constant-current driver, which can be used to provide constant current for verifying the chip protection functionFirstly, a LED electro-optical model is established, and the effect of the drive current on LED luminous efficiency is researched in simulation,which can be used to guide the design of LED protection and LED driver. According to the LED volt-ampere characteristic curve and the LED forward current and the relative luminous efficiency curve, each curve expression can be obtained by using the curve fitting method. With the expressions, LED electro-optical model is designed. Through simulation the effect of five kinds of drive current on LED luminous efficiency is studied and analyzed. And the experiment is designed and experiment results prove the validity of the simulation model.Then, a chip which can achieve LED over-voltage, open circuit and temperature protection is reaserched which can increase the number of LED series and reduce the number of constant current driver. The chip principle is analyzed, according to which a protection chip is designed. By analyzing the protection chip, the design method and basis are obtained. The simulation results prove that the circuit can achieved LED over-voltage, open circuit and temperature protection. Discrete components are used to build analog circuits for experiment. And the experiment results show the validity of the protection circuit.Finally, the LC series resonant circuit is used to design LED open-loop constant-current driver which was used in distributed DC bus structure and can improve the reliability of driver. The open-loop constant-current theory is analyzed and the design basis for the switching frequency, resonant inductor and capacitor, transformer turns ratio is given. Resonant inductor and transformer are calculated in theory. According to the basis, simulation and experiment are designed, and the experiment results are accordance with the simulation results, which prove the validity of the analysis and design.