A novel dimmable light-emitting diode (LED) driver is proposed in this study. The circuit topology uses two active switches. One active switch shared by a buck–boost converter and a buck converter is operated at high-switching frequency while the other one is low-frequency pulse-width modulated to dim high-power LEDs. The buck–boost converter plays the role of a power-factor corrector. It operates at discontinuous-conduction mode to waveshape the line current to be sinusoidal and in phase with the input-line voltage. The buck converter regulates the dc-link voltage to output a low-frequency pulse-width modulation (PWM) voltage to drive high-brightness LEDs. Since only one power-conversion process is required, and the buck converter works only when the low-frequency PWM voltage is at a high level, the proposed LED driver has the advantage of high efficiency. Besides, it achieves unity power factor and low total current harmonic distortion.