This month, Bits & Pieces is taking a closer look at Atmel’s versatile lighting (MCU) portfolio. First, we discussed 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.
“Specifically, an external power supply allows for easy implementation of DC-to-DC boost or SEPTIC power supplies to drive 100mA per string for direct-backlight configurations. Atmel LED Drivers adaptively control the DC-DC/AC-DC converters that power the LED strings, using Atmel Efficiency Optimizer technology, which minimizes power use and maintains LED current accuracy,” an Atmel engineering rep told Bits & Pieces.
“These high-power LED string drivers use internal current control MOSFETs to sink up to 100mA per string, and offer the ability to drive 16 parallel strings of ten white LEDs each, for a total of 160 white LEDs per device. 16 interconnected devices control up to 2560 white LEDs. Each string can be controlled individually to enable area (zone) dimming for highest dynamic range and significantly reduce power usage. These devices address the direct backlight LCD panel and monitor applications.”
In addition, direct backlight topologies offer the most contrast ratio and richest color quality for LCD Television – although direct backlight is not as popular as edge-lit topologies because of the inherent cost and application complexity. Indeed, direct backlight employs a greater number of LEDs and more complex control for zone dimming, allowing for the widest contrast ratio in the market.
“Direct backlight can be accomplished with white LEDs and RGB LEDs. The RGB LEDs offer color control and white point mixing, not offered with white LEDs. Of course, both types of LEDs can be driven by Atmel LED Drivers to offer zone (regional) dimming up to 512 zones (the most zones offered by TV OEMs),” the engineering rep continued.
“[Plus], LED drivers offer internal current sinks that can sink up to 100mA per string, eliminating the need for external NFETs. External DC to DC supplies are commonly used in direct backlight applications – allowing 4 to 8 LED driver ICs to share a power supply, minimizing component cost and board area.”
Interested in learning more about Atmel’s television backlight portfolio? Be sure to check out our official product breakdown page here.