Research On Control Techniques Of High Power LED

The thesis briefly introduces the characteristics of luminous flux curve and I-V curve of High Power LED (Lighting Emitting Diode) and its driving methods. The operating principles of Buck converter and Boost converter for driving High Power LED are analyzed in detail, the small signal model of their main circuits in continuous conduction mode (CCM) are derived by State-Space Average Method.It can be known from the analysis that peak current mode (PCM) control technique of Buck converter and Boost converter features fast transient response and high stability. But it only controls the forward peak current of LED, not the average current, it can't satisfy the accurate regulation of luminance.In order to control the average current of LED accurately, a new control method, called as I~2 control technique, is proposed by added a new current outer loop into the PCM control technique. It regulates the control voltage by using the integral value of error value between reference voltage and sense voltage to eliminate the steady error of the average current. Small signal model of I~2 control loop is obtained, with which the small signal models of the Buck converter and Boost converter in CCM with I~2 control technique are obtained to analyse the dynamic performance of the systems. The control performance of I~2 control technique is verified by time-domain and frequency-domain simulation finally.A Buck-type LED converter is set up for driving a 350mA, 1W Luxeon? Star. The luminance regulation experiment is taken by using PCM control technique and I~2 control technique respectively. The experimental results have a good agreement with theoretic analysis and simulation results.