Overload Alarm; Power Supply - Fujitsu DL7600 Maintenance Manual

5.3.7.9 Overload Alarm

A Low voltage alarm occurs if:
When the power-supply voltage decreases besides the print.

5.3.8. Power Supply

The power supply circuit consists of the components shown in the block diagram in Figure 5.3.21
AC input filter
Direct rectifying and smoothing circuit (including surge current preventive circuit)
+5V/+34V switching regulator
This section explains the +5V/+34V switching regulator and surge current preventive circuit according to
the block diagram in Figure 5.3.21.
5.3.8.1 +5 V Switching Regulator
This circuit consists of a one-stone ringing choke converter (RCC) using a hybrid regulator. Two types of power,
+5 and +40 V, are output from one transformer.
The circuit has the following functions:
Self-excitation switching control
When AC power is input, the circuit automatically starts oscillation.
It thus cannot be controlled from the outside.
② Over current control (automatic drooping characteristics)
If a short circuit occurs at the +5 V circuit load, the output voltage automatically droops to prevent damage to
the power supply.
③ Over voltage control
If the 3-terminal switching regulator malfunctions in short mode, over voltage may occur at the +5V output.
The detection section on the secondary side of this circuit detects the over voltage to prevent abnormal voltage
from being output to the +5 V output.
5.3.8.2 +40V Switching Regulator
This circuit consists of a one-stone forward choke converter using a switching control IC. It has the following functions:
+40V ON/OFF control
The *POWST signal can be used to turn off the +40 V and +5 V circuits.
(When *POWST is low, the +40 V outputs are turned on. When *POWST is high, the +40 V outputs are turned off.)
- Over current control (automatic drooping characteristics)
If a short circuit occurs at the +40 circuit load, the +40 V switching circuit is stopped intermittently to
prevent damage to the power supply.
- Over voltage control
If the voltage detection circuit malfunctions and over voltage occurs at the +40 V output, the over voltage
detection circuit detects the over voltage and stops the +40 V switching circuit under +40 V OFF control.
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