Dimming circuit and method

A Light Emitting Diode (LED) driver circuit for driving an LED string comprising:

• an input voltage source;
• a switch-mode power supply for supplying regulated current to the LED string, the switch-mode power supply having a first terminal coupled to the input voltage source, a second terminal coupled to the LED string, and a third terminal coupled to a pulse width modulated input adapted to enable and to disable the switch-mode power supply repetitively at a low frequency rate;
• a zero current detector for detecting output current of the switch-mode power supply becoming substantially zero, the zero current detector coupled to the second terminal of the switch-mode power supply;
• a control circuit having a first terminal coupled to the pulse width modulated input and a second terminal coupled to the zero current detector;
• a disconnect switch coupled to a third terminal of the control circuit and the LED string;
• and
• an output filter capacitor having a first terminal coupled to the LED string and the switch mode power supply and a second terminal coupled to the disconnect switch.