iWatt Debuts Industry’s First Driver to Power 32 Strings of LEDs for Direct & Segment-Edge Backlighting in Ultra-Thin LED TVs

iWatt, Inc., has expanded its family of DC/DC LED backlight drivers with its iW7032 which can power up to 32 parallel strings of LEDs. Like its iW7040 sibling, which powers up to 64 parallel strings of LEDs, the iW7032 is a mixed-signal IC that features iWatt’s digital adaptive switching technology with integrated MOSFETs. Adaptive switching reduces thermal overhead and power consumption, while the integrated MOSFETs reduce component count, form factors and costs for dynamic backlighting. The 32-channel iW7032 targets mainstream direct or segment-edge-dimmed TVs, while iWatt’s existing 64-channel iW7040 is suited for high-end, direct-dimmed TVs. Both drivers are designed to enable real cost savings in dynamic backlighting, as well as easy integration into ultra-thin LED TVs.

With high voltage support (up to 56V) and adaptive switching to overcome thermal problems, the iW7032 is capable of driving more parallel strings of LEDs from a single IC than existing solutions, reducing component count for TV manufacturers. Typical ICs can drive eight, 12 or at most 16 strings of LEDs, while the iW7032 can drive up to 32 parallel strings, numbering 15 LEDs per string, to power 480 total LEDs from one IC. iWatt’s high-voltage support also saves the cost of any additional protection MOSFETs required by ICs with lower string voltages.

iWatt’s proprietary digital adaptive switching technology solves the thermal problems of driving a large number of parallel strings of LEDs, where a significant amount of wasted power typically heats the inside of the TV and increases the chance of thermal-stress-related LED failures. iWatt’s adaptive switching technology senses the mismatch of the varying forward voltages (Vf) of the multiple strings of LEDs and adjusts appropriately for each string. This reduces the wasted power by up to 90 percent (iWatt projects it saves 2-5W per IC), minimizes the heat generated, and enables a single iWatt IC to drive many multiples of LED strings.

The iW7032 features an integrated MOSFET for each string of LEDs to save component count and reduce form factors for easy integration into ultra-thin LED TVs. The company projects this can reduce driver printed-circuit-board (PCB) form factors by up to 50% compared to solutions relying on external MOSFETS.

With the ability to drive more LEDs with fewer ICs, and by integrating the MOSFETs, iWatt projects LED TV manufacturers can save $1 to $3 in bill-of-material (BOM) costs for each iW7032 used. A typical 46” direct-lit LED TV might use two to four iW7032 drivers, saving the manufacturer up to $12.

Gyan Tiwary, senior vice president and general manager of the DC/DC group at iWatt said that TV makers can now offer the picture quality of a direct or segment-edge-lit TV, for the price of an edge-lit one. “By overcoming the thermal problems of driving large numbers of LEDs together, our engineers have made a large contribution towards cutting costs for the dynamic backlighting industry,” he said. A graph comparing LED TV backlighting options (direct, segment edge and edge dimming) is available: Graph_Comparing_LEDTV_Backlighting_Options_iWatt_June, 2011

The mixed-signal iW7032 driver supports three programmable pulse-width modulation (PWM) schemes, adding center-shift PWM output alignment capabilities to the industry’s traditional head-shift or tail-shift only modes. The 10-bit PWM can be used for brightness control on a per channel basis ranging from 1% to 99.9% with10-bit resolution.

The iW7032 provides three real-time dimming control modes. Local dimming mode (120mA) turns the backlight off in dark areas leading to deeper black levels and improved contrast ratio. Scanning mode (240mA) minimizes flicker and ghosting problems to reduce motion blur. Finally, the 3D mode (480mA) delivers the current and brightness required for 3D images.

Comprehensive safety features include: LED-failure (open and short circuit) and over-temperature protection while operating, and LED open and over-temperature protection at startup. Once the driver observes and validates a fault, it can turn off the whole IC or just the string associated with the fault. The IC enables LED TV makers to meet the stringent power requirements of Energy Star and other efficiency standards worldwide.

iWatt confirms that a large global LED TV brand has chosen the iW7032 for their new, high-performance platform with models just now hitting the market.