1. A controller that controls one or more light-emitting diodes (LEDs), wherein the controller is configured to:receive an output voltage from a secondary transformer winding of a transformer;
receive first information across a galvanic isolation barrier, wherein the first information comprises a desired LED brightness;
receive second information across the galvanic isolation barrier, wherein the second information comprises an output voltage of an auxiliary transformer winding; and
control the one or more LEDs based on the first information;
control the output voltage of a secondary transformer winding and the output voltage of the auxiliary transformer winding based on the first information and the second information.