An LED driver having an input to receive AC power from an AC power source, a semiconductor switch and an inductor controlled to produce a sinusoidal current drawn from the AC power source, and a large non-electrolytic (e.g. film) capacitor energy storage component. The semiconductor switch operates with a varying pulse-width-modulation frequency to regulate the voltage across the non-electrolytic capacitor energy storage component in such a way that a ripple current through the inductor is substantially smaller than a pulse-width-modulation cycle average current through the inductor. A DC-to-DC converter couples the energy from the non-electrolytic energy-storage capacitor to an LED string. A feedback loop allows the LED string to be regulated in either constant current mode or constant power mode and information for the feedback regulation is fed back across a high-voltage boundary using a low-cost signal transformer.