High voltage capable LED driver can drive
32 strings of LEDs
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.
"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"
With high voltage support up to 56V 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 claims iWatt. 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.
With the ability to drive more LEDs with fewer ICs, and
by integrating the MOSFETs, iWatt claims 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 as per iWatt.
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: http://www.iwatt.com/pdf/Graph_Comparing_LEDTV_Backlighting_Options_iWatt_June2011.pdf
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.
Package: 64-pin QFP with an exposed pad.
Availability: Now in samples
Price: each $3.80 in 1K units.
A product brief is available: http://www.iwatt.com/pdf/prod_brief/iW7032_Product_Brief_080.pdf
