A LED driver circuit, including a LED module, a bias circuit, a first switch, an inductor, a regulator, a controller, a second switch, and a current-to-voltage converter, is used to provide a load current for the LED module, wherein the bias circuit is biased by a first bias current and the regulator is biased by a second bias current, and the first bias current and the second bias current are drawn from the load current. Besides, the controller can be implemented with a low voltage controller.