Dimming DC-DC LED Drivers: Luminous Efficiency, Power Losses, & Best-in-Class

Light Emitting Diodes (LEDs) have become pervasive in modern lighting and automotive applications. LED drivers regulate LED current which sets their luminous output, where dimming is an important attribute. Dimming techniques fall in one of two categories: "analog" or "duty-cycled" (pulse-width-modulated), and duty-cycled (PWM) dimming decomposes into three further classes: shutdown, shunt- and series-switched. However, a comprehensive analysis of dimming techniques, corresponding power losses, and their dimming capabilities is lacking in the literature. This paper explains and quantifies those in the context of a switched inductor (SL) DC-DC converter. Presented analysis incorporates SL conversion efficiency and models luminous flux, dimming range, and luminous efficiency. This paper reveals and verifies that analog dimming is up to 57% more efficient with the widest dimming range.