Intermec EasyCoder PX4i Service Manual page 141

Power Factor Control
Forward Converter
Connections
Overheating Protection
EasyCoder PX4i and PX6i Service Manual
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The power factor control transforms the AC input voltage to 385 VDC
by sensing the shape of the curve of the input voltage and chopping it to
short pulses, where the pulse amplitude follows the shape of the curve. The
booster is protected by two 7A fuses.
The forward converter transforms 385 VDC to 24 VDC 0-17A. The 24
VDC is the bulk voltage. Other voltages needed for internal devices are
converted from 24 VDC by the driver board and the CPU board.
P2 24 VDC to driver board.
P3 Temperature and power fail signals to driver board
X1 Input voltage 90 to 265 VAC, 45 to 65Hz
The power supply unit is fi tted with a sensor that will shut down the unit
in case of overheating (Power Fail Interrupt or PFI) and another sensor
that will warn the main CPU if the power supply is getting hot (Notify).
A Power Fail Interrupt (PFI) signal will warn the logics so valuable data
can be saved before power is lost. Before a print operation is executed,
the Notify signal is checked. If the Notify signal is activated, a warning is
shown in the display and the main CPU will reduce the power consump-
tion to avoid shutdown by detaining the printing until the Notify signal is
deactivated.
Primary switched power supplies are generally diffi cult to repair. If one
component fails due to aging or overload, a number of other compo-
nents will also break as a consequence. They are hard to troubleshoot,
because the PSU often is "dead" or the fuses blow immediately. It is
also impossible to guarantee the life of a repaired PSU, because com-
ponents may still work but be on the verge of failing. Thus, if a fuse
blows, do not attempt repairing the PSU, but replace the entire unit!
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Chapter 13 — Power Supply
131