Study On LED Constant-Current Driving Power And Circuit Design

Nowadays the energy crisis and global warming problem is getting worse, energy conservation and environmental protection has become the focus of the concern. LED has the advantages of high efficiency, energy saving, environmental protection, long life, etc. If LED lighting can replace the current traditional low efficiency lighting, undoubtedly it will play a pivotal role to ease the current energy shortage and environmental degradation. Because of LED unique I-V curve and temperature characteristics, the sensitivity of LED on the current is higher than the that on the voltage. This requires the dedicated power supply to drive LED. For the unique electrical properties of LED, this thesis researches and designs an accurate and efficient constant DC LED driving power supply.The thesis applies the Buck converter switching as the main circuit, analyzes its working principle in continuous conduction mode (CCM), researches on state-space averaging method used in the application of switching converter and establishes small-signal model. On this basis, the thesis analyzes the peak current-mode Buck converter working principle. From the modeling and simulation, it can be known that peak current-mode Buck converter has good dynamic characteristics and high degree of stability. However, the inductor current is still relatively large error.In order to meet the demand occasions with AC input, Thesis designs and analyzes the chopper circuit, performance of the circuit is emulated. Against the shortage of peak current control mode and in order to improve the control accuracy and stability, the paper brings forward PID control method and introduces the designing of compensation circuit and control circuit. The thesis establishes small-signal model of peak current converter based on PID control, analyzes the steady-state and derives the transfer function. Finally, the performance of PID control circuit is verified by time-domain and frequency-domain simulation.Principle and operation of driving circuit are analyzed in the thesis. Based on that, constant-current driving power is designed and its performance is tested. The test results indicate that the switching power supply circuit has achieved expectation of the function target and the electrical characteristics. The experimental results have a good agreement with theoretic analysis and simulation results.