Controllers, systems and methods for controlling power of light sources

摘要

A controller for controlling power to an LED light source includes a control terminal and control circuitry coupled to the control terminal. The control terminal provides a control signal to control a transformer. A cycle of the control signal includes a charging period, a discharging period, and an adjusting period. The control circuitry controls a primary winding of the transformer to receive power during the charging period and controls a secondary winding of the transformer to discharge power to the LED light source during the discharging period. The control circuitry further varies a frequency of the control signal periodically by controlling the adjusting period.