High voltage edge-lit TV topologies with Atmel

Bits & Pieces has been getting up close and personal with Atmel’s versatile lighting (MCU) portfolio in recent weeks. First, we took a look at the role Atmel MCUs (microcontrollers) have to play in brightening LED ballasts, highlighting the AVR AT90PWM microcontroller which supports the DALI standard and is used to network multiple ballasts to a centralized system for tighter light level control and significant energy savings.

We’ve also talked about how Atmel MCUs are used to light up both fluorescent and HID ballasts, as well as drive television direct backlights. And today we’ll be discussing high voltage edge-lit TV topologies. Specifically, edge-lit configurations use external power supplies and NFETs to allow voltage power supplies to drive a larger number of LEDs (72 LEDs) per string and can sink up 1A (determined by NFET ratings).

“Atmel LED drivers are capable of driving up to 16 parallel strings of LEDs, all while offering fault detection and management of open-circuit and short-circuit LEDs,” an Atmel engineering rep told Bits & Pieces.

“These devices address the edge-lit and high-brightness LEDs which require higher power while enabling dimming via external pulse width modulation (PWM) signals or analog current control with an internal digital-to-analog converter (DAC).”

In addition, the engineering rep noted that edge-lit topologies are the most popular backlight architectures in current LCD television applications because they are less expensive (requires fewer LEDs) compared to direct-backlight topologies.

“Edge-lit designs are also capable of offering zone (regional) dimming but are limited to larger tiles (coarse zones) and require expensive diffusers which use light guides to distribute light to desired zones,” the engineering rep continued.

“Edge-lit applications require an external DC-to-DC supply to boost the supply up to 250V to allow 72 LEDs per string. Television manufactures also implement LED string phase shift to reduce the overall RMS power requirements and minimize EMI noise by effectively driving one LED string at a time within a frame time period.”

Interested in learning more about high voltage edge-lit TV topologies with Atmel? Be sure to check out our official device breakdown page here.