4.4.8 Output ON/OFF Control
4.4.7 Foldback Protection
The ON/OFF circuit has two controls; a front panel pushbutton and a rear panel connection. priority is
given to the rear panel connection.
1. Foldback protection will shut down the power supply output if the load current exceeds the current
limit setting level. This protection is useful when the load circuitry is sensitive to over current
condition.
2. Toarm the Foldback protection, the FOLD pushbutton should be pressed so the FOLD LED
illuminates. At this condition transition from Constant Voltage to Constant Current mode will activate
the Foldback protection.
3. Activation of the Foldback protection disables the power supply’s output, turns on the ALM (alarm)
LED and flashes the FOLD LED.
4. There are 2 modes of releasing an activated Foldback protection.
1. Short press on FOLD pushbutton enables the output and re-arms the protection circuit. If the load
is smaller than the current limit level, the power supply will restore normal operation. If the load is
greater than the current limit level, the output will be disabled again and Foldback indicators will
be on.
2. Long press (approx. 3sec) on FOLD pushbutton will disable the Foldback protection circuit and
enable the output. The power supply will restore operation to Constant Voltage or Constant
Current mode depending on the load characteristics and power supply setting.
1. Rear panel ON/OFF Control
2. Front panel ON/OFF Control
Contacts 9, 10 at the rear panel External Control connector (fig. 4-2, item 4) serve as ON/OFF
terminals. Either short circuit or TTL ‘0’ level enables the power supply output and open circuit or TTL ‘1’
level disables the power supply’s output. An open collector transistor can be used for the ON/OFF
control as shown in fig. 4-3, with sink current ability of more than 2.5mA. Please note that pin 10 (COM)
is internally connected to the - Sense potential, therefore for floating ON/OFF Control a photocoupler
should be used as shown in Fig. 4-4.
The Front Panel ON/OFF is controlled by the OUT pushbutton. Toenable the output, OUT pushbutton
should be pressed so that OUT LED illuminates. The operation of OUT pushbutton is enabled only if
the rear panel ON/OFF is configured to ‘ON’.
Fig. 4-3: ON/OFF Control, references to - Sense.
(ZUP rear panel view)
Fig. 4-4: Floating ON/OFF Control
(ZUP rear panel view)
2
2
- LS
- LS
- S
- S
+LS
+LS
+S
+S
On/Off
On/Off
2.5mA
ON
ON
OFF
OFF
COM
COM
P
P
VRFV
VRFV
VCVP
VCVP
VRFI
VRFI
VCCP
VCCP
RCVP
RCVP
RCCP
RCCP
1
1
Output Good
Output Good
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