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INTRODUCTION
l How LED
Driver IC supports high Grayscale and Refresh-Rate performance on LED Panel
LED is driven by constant current and we can
use the PWM method (Constant Current Pulse Width Modulation) to achieve the
brightness control of LED. Therefore, if we bypass the detail design of the LED
Panel Control System, simply focus on the driving speed requirement of the LED
Panel. The panel Refresh-Rate is decided by the time of address searching
(Tacc) and the Min. Constant Current Pulse Width which mainly depends on the
current(I) driving speed capability of the LED Driver IC. For
example, if a outdoor full color LED Panel with 768 pixel address, it can be
simply figured out that the (Tacc) time is associated with system CLK Freq. For
CLK Freq. 10Mhz->768*0.1us=76.8us, the (Tacc) is 76.8us, and 30Mhz->768*0.033us=25.6us. The (Tacc) time will
achieve 3 times reduction if the CLK Freq. speeds up from 10Mhz to 30Mhz. To
upgrade the Grayscale of LED Panel, the current(I) driving speed capability
(generally defined as the Spec. of Min. OE Response Time ) of the LED Driver IC
is mainly affected. The Min. OE response time of traditional LED driver IC in
the market is about 250ns. For 8 bits grayscale applied on LED Panel, it means
that the R/G/B can individually present 256 grayscale and totally present 256*256*256=16777216 A. Tradition Driver IC (Support 250ns Min. OE Response Time) Set the weight as 1/64,1/32…1,2…2048 Tfr=25.6*(6+4095)+5*4=1786.4(us) Fr=559.7 Hz B. GrayscaleBoostTM Driver IC (Support 25ns Min. OE Response Time) Set the weight as 1/1024,1/32…1,2…128 Tfr=25.6*(10+255)+9*4=146.6
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integrated circuit
