2-11
EMP-9000/8000
SEIKO EPSON Revision:A
2.4. Ballast unit
it is the unit that regulates again the DC power supply (DC240-390V/0.8A) for the ballast that
is supplied from the power supply unit to generates the AC power supply (AC45-200V) for the
UHE lamp.
Figure2-14
Circuit Block
Figure2-15
(1). Process outline
• The sub power supply : The voltage for control circuit (+15V/+20V) inside the ballast unit
is generated.
• Switching circuit : Doing the switch actuation for the regulation again according to
the output signal (BACT) of the main board Assy unit. (The
BACT signal is doing the ON/OFF of the ballast output.) Doing
the modification (the adjustment of the output voltage) of the
switching duty according to the feedback signal from the detec-
tion circuit.
• Regulator circuit : The voltage for the lamp of AC45~200V is generated.
• Detection circuit : Monitoring the regulator circuit and genarates the feedback sig-
nal of the output voltage stabilization and detects of output cur-
rent. When the lamp inner housing becomes consume, the
“LPST“ signal is transmitted to the main board Assy unit.
Regurator circuit
HV
Ballast output
LV
AC45~200V
Detection circuit
Feedback
Sub power supply
+15/+20V
Switching circuit
CP501 (connected to Main
board Assy unit)
CP1 (connected to Power
Supply Unit)
DC input
240~390v
BACT
LPSTC
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