Led Display Circuit - Toshiba e-STUDIO555 Service Manual

5.4.2

LED display circuit

Method of LED display
Example: Displaying "COPY"
+5.1VA
Current
Low
G
Q3 Q1
COM1
(COPY)
Low
LED10
SG
Q11
OUTP7
5
SG
Fig. 5-6
The transistors (Q3 and Q1) are turned ON when the COM1 signal becomes Low level.
Also, when OUTP7 signal changes to Low level, the current flows from +5.1VA via the transistor (Q1) to
the LED10 (COPY) to turned ON the LED10.
Conditions to turn ON the LED
1. The transistor (Q1) connected to the LED anode is ON.
2. The transistor (Q11) connected to the LED cathode side is ON.
The LED is turned ON when 1) and 2) are satisfied.
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