LED 照明开发工具 LM3445EVM-695
The implements a dimming solution using the LM3445 integrated circuit from Texas Instruments. The LM3445 is an adaptive constant off-time AC/DC buck constant current controller with built in phase dimming decoder. Line cycles are analyzed continuously by an internal low power digital controller for shape and symmetry. An analog current reference is then generated and used by the power converter stage to regulate the output current. The analog reference is manipulated using control algorithms developed to optimize dimmer compatibility, power factor and THD. Using constant off-time control the solution achieves low part count, high efficiency and inherently provides variation in the switching frequency. This variation creates an emulated spread spectrum effect easing the converters EMI signature and allowing a smaller input filter.