A controller includes: a pulse-width modulation (PWM) circuit; a control loop; and a reference voltage controller. The control loop has: a feedback input adapted to be coupled to an output voltage of a power stage; a control loop output coupled to a PWM control input; and an operational amplifier with a first feedback input, a first reference input, and an amplifier output, the first feedback input connected to the feedback input, and the amplifier output coupled to the PWM control input. The reference voltage controller has a reference voltage output coupled to the first reference input, the reference voltage controller configured to adjust a reference voltage provided to the reference voltage output responsive to a dynamic error estimate based on error in the operational amplifier.