One light emitting diode display circuit

Light-emitting diodes can be used DC, AC and pulse and other drivers, resistance typical buck LED display circuit as shown in Figure 13-1.
One light emitting diode display circuit - schematic

LED tubes reported the string loop current limiting resistor R can calculate the following formula; O DC drive [see Figure 13-1 (a), (b)] when R = EU, P 21FR formula R- limiting resistor , KN; E power supply voltage, V; UF-emitting diode forward voltage drop (as 1.7-2V), V; IF-emitting diode current, generally the maximum operating current IFm for 1 / 3-1 / 5, mA; resistor power Pr selected, the actual power consumption is Wei R, in order to prevent overheating of the resistance, to be more than sufficient quantity, w. AC drives [see Figure 13-1 (c), (d)] when R = 0 45U-UF IF formula U- RMS AC voltage, V. Diode VD is used to protect the light emitting diode AC negative half weeks when the breakdown is not, the choice 1N4007,1A / 1000V. pulse drive when there [see (e)] R = E two (UCEs + UF) fF formula B a power supply voltage, V; U. . . - Tube voltage drop transistor saturated conduction time (about 0. 3V), V.

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