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LED backlight driver promises better TV screen

Posted: 11 Jul 2013     Print Version  Bookmark and Share

Keywords:iWatt  LED backlight driver  iW7019  LCD TV  BroadLED 

iWatt Inc. has announced its 8-channel LED backlight driver aimed to deliver better screen performance and lower cost in next-generation 2D and 3D LCD TVs. According to the company, the iW7019 gives designers a rich set of integrated features to improve picture quality and render a more lifelike viewer experience. These include both head and tail-mode PWM dimming to reduce motion blur, and high-resolution, 12bit local dimming to improve contrast ratio.

The iW7019 integrates a DC-to-DC boost controller with 10V gate drive, high-voltage current sinks and iWatt’s patented BroadLED digital current regulation technology that eliminates the need for costly LED binning, indicated the firm.

iWatt said the features of the iW7019 make it an ideal choice for edge-lit, direct-lit and segment-edge-lit LED LCD TV designs. It drives up to eight parallel LED strings at 85V (maximum) per channel and can sink up to 200mA per string for 2D and 450mA per string for 3D TV applications. A wide, 9-28V input supply voltage range makes the iW7019 compatible with existing TV power systems, so there is no added expense for a separate voltage rail, indicated iWatt. Comprehensive dimming modes provide maximum flexibility to support both patterned retarder and shutter glass 3D TV technologies, as well as 2D TV with just one IC.

iWatt’s BroadLED digital technology claims to lower system costs by reducing the voltage offset (Vf) between mismatched LED strings. Backlight driver ICs need to drive multiple strings of LEDs, however, each LED has a different forward voltage. This voltage offset has traditionally been managed by “binning,” where LEDs are sorted for similar forward voltages, but this adds significant cost. BroadLED technology senses the voltage mismatch between the multiple LED strings and adjusts each string’s Vf as needed, enabling the use of loosely binned LEDs to reduce system costs. The difference in string voltages also produces higher power dissipation. BroadLED technology eliminates up to 90 per cent of this wasted power, while maintaining ±2 per cent current matching.

In addition to BroadLED technology, the iW7019 incorporates a number of additional features to reduce system costs. The integrated DC-to-DC boost controller provides a 10V gate drive, enabling the use of lower-cost power FETs, while the integrated, high-voltage current sinks eliminate the added cost of external high-voltage FETs. An on-chip frequency synthesizer lowers cost by relaxing the timing accuracy requirements on the video system timing controller. The digital control engine in the iW7019 generates the PWM wave form, manages all fault readouts and reports faults, removing the need for expensive MCUs. Additional savings come from the 85V capability on drain sensing, which eliminates external diodes usually required for LED short-circuit fault management, as well as cascodes or zener clamps typically required for protection.

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