一种原边反馈反激式数字化LED驱动电路

为了减少LED的频闪现象,设计了一款原边反馈反激式数字化恒流控制驱动电路.推导了该电路的软启动/恒流切换依据,给出了恒流控制原理,构建了数字控制器的内部结构.软启动/恒流切换模块的设置可以有效抑制浪涌电流,确保Flyback变换器平稳进入恒流状态;基于恒流控制原理设计了去磁时间采样及计数器调制模块,与控制信号生成模块协同工作,达到了自动调节开关导通信号的目的.采用ModelSim与Simulink软件联合仿真,验证了设计方案的可行性.结果表明,Flyback变换器运行在恒流状态时去磁时间与开关周期的比值恒定,输出恒流约为320 mA,电流纹波0.38%,驱动电路可以稳定可靠地工作.

A digital LED driving circuit with the primary side feedback control flyback converter

In order to reduce flickering of the LED, a driving circuit with the primary side feedback control flyback converter is specifically designed on the basis of the digital technology. The principle of soft-start and the controlling flow of constant current output is deduced, the constant current control principle is given, and the internal structure of the digital controller is constructed. The setting of soft-start/constant current switching module can effectively suppress the surge current of the flyback converter and ensure that the flyback converter enters the constant current state smoothly. Based on the principle of constant current control, the demagnetization time sampling module and counter modulation module are designed, which works in coordination with the control signal generation module to automatically switching signal. Finally, the feasibility of the presented scheme is verified by the united simulation technique based on ModelSim and Simulink. The results show that the ratio of demagnetization time to switching period is constant when the flyback converter operates in constant current state, with the output constant current of about 320 mA and the current ripple of 0.38%. Consequently, the drive circuit investigated in this paper can work stably and reliably.