Over-Current/Over-Voltage/Overload Protection; Safety Interruption; Table 1-4 Low Voltage Power Supply Dc Power Specifications - HP LASERJET ENTERPRISE M725dn Troubleshooting Manual

Table 1-4
DC voltage
+24V
+5V
+3.3V

Over-current/over-voltage/overload protection

The over-current/over-voltage protection automatically stops the DC voltage to the product components
whenever an excessive current or abnormal voltage is detected. The overload protection automatically
stops the DC voltage to the product components whenever the temperature of the low-voltage power
supply PCA rises to a specified temperature.
The low-voltage power supply has a protective circuit against over-current, over-voltage, and overload
to prevent failures in the power supply circuit. If DC voltage is not being supplied from the low-voltage
power supply, the protective function might be running. In this case, turn the power off, and then
unplug the power cord. Do not turn the product switch on until the root cause is found and corrected.
The DC controller determines a low-voltage power supply failure and notifies the formatter when the
protective function runs.
In addition, the low-voltage power supply has three fuses to protect against over-current. If over-current
flows into the AC line, the fuse blows to stop AC power.

Safety interruption

For user and service technician safety, the product interrupts the power supply of +24V by turning off
the interlock switch. The DC power to the following components is interrupted:
High-voltage power supply
●
Fuser motor
●
The remote switch control-circuit turns on or off the product so that the ac power flows even if the power
switch is turned off. Be sure to unplug the power cord before disassembling the product.
12 Chapter 1 Theory of operation
Low voltage power supply DC power specifications
Behavior
+24VB Off during Sleep mode (sleep level1, active off and inactive off)
+24VC Off during Sleep mode (sleep level1, active off and inactive off), interrupted when the left door
opens
+24VD Off during Sleep mode (sleep level1, active off and inactive off), interrupted when the left door or
the cartridge door opens
+5V Off during Sleep mode (sleep level1, active off and inactive off)
+3.3VA Constantly supplied
+3.3VB Off during Sleep mode (inactive off)
+3.3VC Off during Sleep mode (active off and inactive off)
+3.3VD Off during Sleep mode (sleep level1, active off and inactive off)
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