Power Supply Unit; Construction; Operation Of Dc Output Circuits - Toshiba e-STUDIO350 Service Manual

15. POWER SUPPLY UNIT

15.1 Construction

The power supply unit consists of an AC filter and insulation type DC output circuits.
(1) AC filter
Eliminates noise from the outside and prevents the noise generated by the equipment from leaking
to the outside.
(2) DC output circuits
Converts AC voltage input from outside to DC voltage and supplies it to each electric part. The DC
voltage is divided into the following two lines.
a. Main line
b. Door switch line : Power supply used in the entire equipment during image forming process,

15.2 Operation of DC Output Circuits

(1) Starting line output
When the main switch of the equipment is turned ON, power starts supplying to all the lines only
when two doors (front cover and jam access cover) are closed.
(2) Stopping line output
When the main switch of the equipment is turned OFF, PWR-DN signal is output after the instanta-
neous outage insurance time (20 ms or more) elapses and then the supply of each voltage stops. If
the supply of voltage of the main line (+3.3VA, +5.1VA, +12VA, -12VA) stops earlier than the 24V
line does, it may cause the damage of the electron device on each control circuit. To prevent this,
the supply of these voltages stops after the PWR-DN signal is output and the minimum retaining
time (+3.3VA/+5.1VA: 50 ms or more, +12VA/-12VA: 5 ms or more) elapses.
(3) Output protection
Each output system includes an overcurrent and overvoltage protection circuits (a fuse and internal
protection circuit). This is to prevent the defectives (damage or abnormal operation of the second-
ary circuit) which may be caused by an overcurrent due to a short circuit or an overvoltage due to a
short circuit between different voltages. If the protection circuit is activated (except the case the
fuse is blown out), remove the causes such as short-circuit. Turn ON the power again 1 minute later
to clear the overcurrent protection.
November 2003 © TOSHIBA TEC
: Power supply used in the entire equipment during image forming process.
Five kinds of voltage (+3.3V, +5.1V, +12V, –12V and +24V) are output when
the main switch of the equipment is turned ON.
being supplied via the door switch. Two kinds of voltage (+5.1VD and +24VD)
are output only when the main switch of the equipment is turned ON and two
doors (front cover and jam access cover) are closed.
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