16Channels Output LED Constant Current Drive Circuit Design

As a result of the existing LED light-emitting different characteristics, the same drivercurrent but makes the imparity brightness of LED screen display.To display the consistency,driven by adjusting the average current gain consistency shows results.The existing constantcurrent dirver unable to output peak current different among the16channel, in order tochange brightness by adjust peak current. In this paper, to design a constant current driver,which can make the output peak current adjustable,for each display point of current peakadjustment, in this way for brightness characteristics of the correction.In this paper, design of constant current drive circuit has a16-channel constant currentoutput, by setting the resistance to set the peak constant current. On the basis of thisbenchmark through internal circuit switch gating selection reference current, make thechannel output current was0.80,0.85,0.90,0.95,1.00,1.05,1.10,1.15, and1.2peak outputratio, etc. Can achieve a brightness control, realizes the8-bit grayscale data input, achieved alevel256grayscale display.Including the bandgap reference circuit module, the internal reference voltage, currentmodule,9reference current generation module,16*9switch array,16output constant currentsource module; Buffer shift register with128-bit, eight binary output counter,8-bit digitalcomparator output, synchronous controller, a delay circuit module, etc. CSMC0.5u BCDtechnology on the SPICE model of key modules in Cadence spectre simulation verify thedesign results on simulation tools. The simulation results show that under the condition of8-bit grayscale data input, each channel can realize constant current output, and can realizethe peak current regulation.