Method and Circuit for LED Driver Dimming

摘要

An LED driver includes a transformer, current control loop and current adjustment circuit. The primary side of the transformer transfers energy to the secondary side of the transformer responsive to an input signal. The secondary side delivers output current to one or more LEDs at a magnitude corresponding to the amount of energy transferred to the secondary side. The current control loop controls current in the primary side so that the output current equals a reference current signal. The current adjustment circuit injects a current adjustment signal into the current control loop responsive to a phase-cut signal which removes a portion of the input signal. The current control loop also decreases the current in the primary side responsive to the current adjustment signal so that a brightness of each LED connected to the secondary side is decreased by an amount corresponding to the magnitude of the current adjustment signal.

主权项

1. An LED driver, comprising:
a transformer having a primary side and a secondary side, the primary side operable to transfer energy to the secondary side responsive to an input signal and the secondary side operable to deliver output current to one or more LEDs at a magnitude corresponding to the amount of energy transferred to the secondary side; a current control loop operable to control current in the primary side so that the output current equals a reference current signal; a current adjustment circuit operable to inject a current adjustment signal into the current control loop responsive to a phase-cut signal which removes a portion of the input signal; and wherein the current control loop is further operable to decrease the current in the primary side responsive to the current adjustment signal so that a brightness of each LED connected to the secondary side is decreased by an amount corresponding to the magnitude of the current adjustment signal.