Dimming techniques for switch-mode LED drivers

Several techniques that are used to provide dimming control to DC-DC switch-mode LED drivers are described. Exponential growth of LED lighting has ushered in a vast selection of integrated circuit devices to provide controlled power to LEDs. Luminous flux (lumens) is a measure of the useful power emitted by a light source. This metric is a weighted function of the power at each wavelength and is tailored to match the human eye's response across the visible spectrum. Controlling color can also be paramount in many dimming applications. High brightness white LEDs are typically implemented with a blue LED emitter covered by a phosphor coated dome. Color temperature is a metric that describes the color of the light compared to a known reference. Two-Wire PWM dimming is a popular method for automotive interior lighting. These applications were originally used with incandescent loads.