The principle of the LED display driver IC D5026A

D5026A Shanghai times electronics is specifically designed for energy-saving LED display driver IC design, the design thought is energy saving and compatible with the existing schemes, that is to say, can be used for energy saving can be compatible with the traditional. By calculated and tested, made the screen D5026A electricity can be as high as 30% above. The following is a brief introduction of the energy saving principle of D5026A.

figure 1 5026 driver output structure of traditional

figure 2 5026 each unit the principle diagram of the constant current

it is well known that the LED driver is usually driven by constant current source model, figure 1 is the traditional 5026 driver output structure, figure 2 is the principle of constant current each unit. The constant current output current Io = Vr/Rf. In this mode, the output pressure drop on the output voltage Vo by Rf Vr and output pipe pressure drop on the A1 Vds1, namely, V. =Vr+Vds1 。 In the condition of constant current, Vds1 change with load. When a constant output current, there will always be a point when we reduce the Vo Io out constant current state, this point we call it the minimum output voltage Vomin. We will Io = Vr/Rf with V. = Vr + Vds1 together it's not hard to see, when V. - - - - - - Vds1 below Vr output will not be constant current. At this point Vds1 is about 0. 1 v, the minimum output voltage for the Vomin = Vr + 0. 1 ( V) 。

figure 3 D5026A driver output chart

4 D5026A each unit the principle diagram of the constant current

figure 3 is D5026A drive output structure, figure 4 is the principle of constant current each unit. D5026A adopts the working principle of mirror constant current source. Its output current Io fully proportional to the area of the two mirror tube, namely Io (x = Ir Sa1 / Sb1) 。 Sa1 / Sb1 is determined by IC layout design, thus can be a very good consistency.

we contrast figure 2 and figure 4 is very clear that this Vo = Vds, completely omits the feedback resistance Rf on the pressure drop. However, the feedback resistance on the pressure drop is here accounted for a large proportion. This is because, if the feedback resistance pressure drop is set too low it is hard to make up the feedback amplifier disorders caused by the error, it is hard to guarantee consistency of the constant current source. Usually the feedback resistance pressure drop of about 400 mv - 600 mv。 That is to say, D5026A under the same condition than the traditional 5026 lower the minimum output voltage Vomin mv - 400 600mV。

in blue light, for example, we assume that the conduction of blue light voltage of 3. 2 v, without considering factors such as line loss, the traditional 5026 minimum supply voltage Vc = 3. 2 + 0. 4 ( 0. 4 - 0. 6) + 0. 1 = 3. 7V( Even to 3. 9V) 。 While D5026A working in Vc = 3. 2 + 0. 1 = 3. 3V。 The above consideration, of course, is an ideal state, if the examination to the line loss and power fluctuations and other factors, we suggest that the power supply voltage is optional in 3. 6 v - 3. 8V。

we have calculated, if the existing 5 v power supply screen instead of 3. 8 v display, do not need to line, any changes in the structure, control, can be directly power saving 24%. In the past, these are saving electricity are role in 5026, 5026 high working temperature, greatly reduce the reliability of the drive circuit. If use D5026A, drive circuit of power consumption will be greatly reduced, the temperature rise is extremely obvious, saving electric energy and improves the device reliability, reduce structural design at the same time considering the heat dissipation. Under the condition of the same, the 5 v power supply of a certain type of display screen 5026 surface temperature is 73 degrees, use 3. 8 v D5026A surface temperature is 39 degrees, it is obvious that the advantages of using D5026A is self-evident.

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