A high efficiency driver circuit with fast response is disclosed. Embodiments of the present invention relate to an LED driver that can drive a plural number of LED strings. The driver according to example embodiments includes a voltage converter stage with a feedback loop. The driver can include a speed-up circuit, and/or an adaptive output voltage control circuit, also referred to herein as an overhead control circuit. In at least some embodiments, an input inductor helps to attenuate input current ripple, which could otherwise lead to low high-frequency winding loss in other inductors. The speed-up circuit can provide current regulation of the LED strings and prevent flickering of the LEDs. The overhead control circuit can adjust the output voltage of the driver to an optimum value to improve operating efficiency.