83-507-013 Rev. A
36
5.4 UNDER VOLTAGE LIMIT (UVL)
The UVL prevents adjustment of the Output Voltage below a certain limit. The combination of UVL and
OVP functions, allow the user to create a protection window for sensitive load circuitry.
5.4.1 Setting the UVL level
Setting the UVL can be made when the power supply output is Enabled (On) or Disabled (Off). To set
the UVL level, press the OVP/UVL button TWICE, so that the CURRENT meter shows “UUL”. The
VOLTAGE meter shows the UVL setting level. Rotate the VOLTAGE encoder knob to adjust the UVL
level. The display will show ‘UUL” and the setting value for 5 seconds after the adjustment has been
completed and then will return to its previous state.
UVL setting values are limited at the maximum level to approximately 95% of the Output Voltage setting.
Attempting to adjust the UVL above this limit will result in no response to the adjustment attempt. The
minimum UVL setting is zero.
5.5 FOLDBACK PROTECTION
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 an overcurrent condition.
5.5.1 Setting the Foldback protection
To arm the Foldback protection, the FOLD button should be pressed so that the FOLD LED illuminates.
In this condition, transition from Constant Voltage to Constant Current mode will activate the Foldback
protection. Activation of the Foldback protection disables the power supply output, causes the ALARM
LED to blink and displays “Fb” on the VOLTAGE meter.
5.5.2 Resetting activated Foldback protection
There are four methods to reset an activated Foldback protection.
1. Press the OUT button. The power supply output is enabled and the Output Voltage and Current will
return to their last setting. In this method, the Foldback protection remains armed, therefore if the
load current is higher than the current limit setting, the Foldback protection will be activated again.
2. Press the FOLD button to cancel the Foldback protection. The power supply output will be disabled
and the VOLTAGE display will show “OFF”. Press the OUT button to enable the power supply output.
3. Turn the power supply output Off and then On using the SO control (refer to Section 5.7). In this
method the Foldback protection remains armed, therefore if the load current is higher than the output
current setting, the Foldback protection will be activated.
4. Turn the power supply Off using the AC On/Off switch, wait until the front panel display turns Off,
then turn the unit back ON again. The power supply output is enabled and the Output Voltage and
Current will return to their last setting. In this method, the Foldback protection remains armed, there-
fore if the load current is higher than the output current setting, the Foldback protection will be acti-
vated again.
5.6 OUTPUT ON/OFF CONTROL
The Output On/Off Enables or Disables the power supply output. Use this function to make adjustments
to either the power supply or the load without shutting off the AC power. The Output On/Off can be acti-
vated from the front panel using the OUT button or from the rear panel J1 connector. The OUT button
can be pressed at any time to Enable or Disable the power supply output. When the output is disabled,
the Output Voltage and Current fall to zero and the VOLTAGE display shows “OFF”.
5.7 OUTPUT SHUT-OFF (SO) CONTROL VIA REAR PANEL J1 CONNECTOR
Contacts 2, 3 and 15 of J1 (Fig.4-2, Item 5) serve as Output Shut-Off (SO) terminals. The SO terminals
accept a 2.5V to 15V signal or Open-Short contact to disable or enable the power supply output. The SO
function will be activated only when a transition from On to Off is detected after applying AC power to the
unit. (Thus, in Auto-Restart mode, the output will be Enabled after applying AC power; even if SO is at an
Off level). After an On to Off transition it is detected, the SO will Enable or Disable the power supply out-
put according to the signal level or the short/open applied to J1. This function is useful for connecting
power supplies in a “Daisy-chain” (refer to Section 5.16). The SO control can also be used to reset the
OVP and Fold Protection (refer to Section 5.3 and 5.5 for details).
