LED Driver ICs & Constant-Current Control on Embedded Systems Development

Constant-Current LED Drivers

Mon, 01 Jan 0001 00:00:00 +0000

Constant-Current LED Drivers#

LEDs are current-driven devices — their brightness is proportional to the current flowing through them, and their forward voltage is a consequence of that current, not a control parameter. Driving an LED from a voltage source with just a resistor works for basic applications, but the brightness varies with supply voltage, temperature, and the LED’s own forward voltage tolerance. Constant-current driver ICs eliminate this variability by regulating the current through each LED string regardless of supply voltage fluctuations, LED forward voltage variation, or temperature drift.

PWM Controllers

Mon, 01 Jan 0001 00:00:00 +0000

PWM Controllers#

Pulse-width modulation is the universal technique for dimming LEDs. Rather than reducing the current (which shifts the LED’s color), PWM switches the LED fully on and fully off at a frequency high enough that the eye perceives an average brightness proportional to the duty cycle. A 50% duty cycle at 1kHz looks like half brightness — the LED flickers 1000 times per second, far faster than the eye can track. Dedicated PWM controller ICs generate these signals precisely, freeing the MCU from timing-critical output tasks.

Multiplexing & Charlieplexing

Mon, 01 Jan 0001 00:00:00 +0000

Multiplexing & Charlieplexing#

Driving a large number of individual LEDs — not addressable strip LEDs, but discrete LEDs in a custom matrix or indicator array — quickly exhausts available GPIO pins. Multiplexing exploits persistence of vision to drive N×M LEDs from N+M pins by scanning through rows (or columns) fast enough that the eye perceives all LEDs as simultaneously lit. Charlieplexing pushes this further, exploiting the tri-state capability of GPIO pins to drive N×(N−1) LEDs from just N pins.