LED lighting has been more and more important in the world,LED driver has been described according to the character of LED.The principle of valley-filled YFC and flyback circuit has been analyzed and discussed.A novel and improved valley-filled YFC circuit is proposed with simulation result.For the application of high lighteness LED,the flyback and current-sensing and feedback circuits more suitable for LED lighting have been further studied.A LED driver has been designed according to the theory and works well and stably for a long time.