Designing a non-isolated flyback LED driver

Overview

Flyback LED drivers are relatively versatile because the structure can be used with input voltages higher or lower than the required output voltage. In addition, when the flyback circuit operates in discontinuous inductor current mode, it can keep the LED current constant without the need for additional control loops. The circuit described in this application note is based on the highly integrated MAX16802 PWM LED driver IC.

application

LED track lighting
general LED lighting equipment

characteristic

• 10.8V to 24V input voltage range

• Powers a single 3.3V LED, providing 350mA (typical) current (for other LED configuration structures, please follow the design steps)

• 29V (typ) maximum open circuit voltage from anode to ground

• 262kHz switching frequency

• Cycle-by-cycle throttling

• On/off control input

• Allows the use of low frequency PWM signals to adjust brightness

• Circuit can be adjusted to accommodate various series and parallel LED configurations