Tag Archives: HID ballasts

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.

Powering HID ballasts with Atmel MCUs

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. Specifically, we’ve highlighted 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 fluorescent ballasts, producing warm and inviting light without flickering or humming. And today we are getting up close and personal with the Atmel-side of HID ballasts.

Due to their high light (lumen) output per watt, HID lights work quite well in large indoor and outdoor public areas. They are also being increasingly used for vehicle headlights, projection TVs and displays. However, HID ballasts do require sophisticated wattage control.

Fortunately, the embedded EERPROM on Atmel’s stalwart AT90PWM is capable of storing tube wattages and parameters for accurate wattage detection and parameter adjustment without additional components. Meanwhile, Integrated Power Stage Controllers (PSCs) help reduce electromagnetic interference (EFI), manage lamp power and control voltage in HID lamps.

In addition, Atmel accelerates time to market for engineers with its ATAVRFBKIT light ballast demonstration kit which incorporates a broad range of design features, including universal line input, low harmonic distortion, low stand-by power and aging protection features.

“In short, digital HID ballasts are fast replacing magnetic HID ballasts because of their significant energy and cost savings,” an Atmel engineering rep told Bits & Pieces. “With the Atmel AT90PWM microprocessor family, you can embed up to three Power Stage Controllers (PSCs) to drive your lighting system according your lamp power.”

Interested in learning more about Atmel devices for HID ballasts? Be sure to check out our extensive portfolio here.