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Page 10
U1
2
1
U2
2
1
R9
0
R10
10K
VEE = -34V
S1D13706
X31B-G-012-03
The power supply is configured to generate a voltage (VEE) of -34.0V. This voltage is used
as an input into the temperature compensation circuit shown in Figure 2-3: "Temperature
Compensated VEEY" , which generates VEEY for use by the vertical power supplies.
VDDH
DA204U
3
DA204U
XP4401
Q1A
3
2
R8
0
4
Q2B
XP4501
Figure 2-3: Temperature Compensated VEEY
The brightness reference VEEY must be temperature compensated to ensure the D-TFD
display remains stable over a range of temperatures. The compensation circuit shown in
Figure 2-3: "Temperature Compensated VEEY" uses temperature dependent diode
forward voltage drops to adjust the output level of VEEY. The three serially connected
diodes are connected to VDDH and grounded through resistor R10, which causes them to
be forward biased. At room temperature, the forward voltage of each diode is approxi-
mately 0.7V which sets the base voltage of Q1A at 2.4V. When the temperature changes,
the base voltage changes according to the characteristics of the diodes.
The base voltage at Q1A also appears at the base of Q1B which, along with potentiometers
R1 and R2, determine the current flowing into resistor R7. The current flowing into R7 sets
the output voltage VEEY. Therefore, any change in temperature results in a corresponding
change in the output of VEEY.
Q2A
6
XP4501
R6
22K
1
R5
XP4401
10K
Q1B
1
4
5
6
3
R7
C2
390K
0.047u 50V
3
Epson Research and Development
Vancouver Design Center
R2
33K
R3
2
2
10K POT
R4
15K
VDDH
C3
C4
2.2u 50V
0.1u 16V
VEEY
Connecting to the Epson D-TFD Panels
Issue Date: 01/02/23
VCC
2
R1
50K POT
C1
0.01u 50V
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