2-17
Filter circuit
The DC input (+24V) from CN6 (when IM-403 is not con-
nected) or CN9 (when IM-403 is connected) is supplied to
the +24V DC control circuit and the +5V control circuit the
filter circuit.
+5V DC control circuit
The +5V regulator circuit switches the input +24V and
converts it to +5V. The switching regulator IC (U9) switches
the input +24V, smooths it via L18, D13, and C49, and
outputs +5V.
+24V DC control circuit
The +24V DC voltage that drives the printer mechanism is
supplied via a FET (Q33) (circuit signal: I24PSW). The
output state (+24V output on/off) of the FET (Q33) is
controlled by an IC (U8A). The SW24V signal is supplied
from the P60 terminal (pin 9) of the CPU (U12) to the A
terminal input (pin 1) of the IC (U8A). The SW24V signal is
the +24V system circuit protection signal. This signal turns
off the FET output when overcurrent is detected in the
power supplied to the printer mechanism and when an error
is detected by the CPU.
Note that the +24V output is also turned off during a system
reset.
Figure 2-40. Power Supply Circuit
CONFIDENTIAL
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