LED display driver circuit a
Posted on Mar 28, 2007 8941
As shown in Figure is a large high-brightness LED driver circuit for a sufficient drive current, integrated circuits using a 7447A or 74247. Digital display tube has eight ligh
t-emitting diodes, seven for digital display, a decimal point for displaying. Driver integrated circuits and light emitting diode equivalent circuit as shown in (a), in the display state. 5v power supply by light-emitting diodes and current limiting resistor R connected to the collector of the driving transistor pole. For the safety circuit, the current to the light emitting diode is selected according to the desired current limiting resistor, the maximum current of the light emitting diode 35 mA, each having some margin is set to 30 mA, the light emitting diode drop removing 2V, and the driving transistor drop 0.V guide escape when current limiting resistor voltage drop of about 2.7 V, R V // 2.7 V/30 mA. R 90 0, and thus the election of La 100 Q.