Tag Archives: fluorescent

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.

tvtopologieschart

“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.

Atmel’s lighting tech is in the television space

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.

We’ve also talked about how Atmel MCUs are used to light up both fluorescent and HID ballasts. And today? How Atmel tech helps drive television direct backlights.

“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.

Atmel brightens LED ballasts

Earlier this month, Bits & Pieces discussed how Atmel MCUs (microcontrollers) can be used to light up fluorescent ballasts, producing warm and inviting light without flickering or humming. Today, we want to talk about the role Atmel MCUs have to play in brightening LED ballasts.

The unique, low-power, non-flickering, directional output capabilities of LEDs make them perfect for indoor lighting under counters and in hallways and staircases, with concentrated arrays typically used for room lighting. Rugged and damage-resistant, LEDs are also a cost-effective solution for outdoor applications such as garden walkways and decorative features.

So what advantages do Atmel MCUs offer engineers designing LED ballast solutions? Well, on example is Atmel’s AVR AT90PWM microcontroller. The AT90PWM supports the DALI standard, which is used to network multiple ballasts to a centralized system for tighter light level control and significant energy savings.

In addition, Atmel solutions allow developers to build fluorescent lighting solutions based on, for example, a full-featured single-chip AVR especially designed for wireless applications, or a general microcontroller (MCU) with a range of standard-compliant transceiver options.

In addition, Atmel helps accelerate time-to-market for lighting engineers by providing development packages with evaluation and debug tools, as well as ballast demo kits with complete, updatable C code to implement advanced control and protection algorithms in a microprocessor’s memory.

“To sum it up, LED ballasts must provide LEDs with a constant source of current,” and Atmel engineering rep told Bits & Pieces. “And that is why built-in hardware modulator, a high current LED driver and interrupt options makes Atmel’s AT90PWM microcontroller well suited for LED applications.”

Want to learn more about Atmel’s extensive portfolio of MCUs that can be used for LED ballasts? Be sure to check out this link here.