83-517-000 Rev.
A
45
5.5
FOLDBACK PROTECTION
FOLD
back protection will shut down the power supply output if the load current exceeds the Output current limit
setting level. This protection is useful when the load circuitry is sensitive to an overcurrent condition.
Setting the FOLDback Protection
5.5.1
To arm the
FOLD
back protection, the
FOLD
button should be pressed so that the
FOLD LED
illuminates. In this
condition, a transition from Constant-Voltage to Constant-Current mode will activate the
FOLD
back protection.
Activation of the
FOLD
back protection disables the power supply output,
displays “
Fb
” on the
VOLTAGE
meter
and causes the
ALARM LED
to blink.
Resetting Activated Foldback Protection
5.5.2
There are four methods to reset an activated Foldback protection.
1. Press the
OUT
button. The power supply output is then enabled and the Output voltage and current will
return to their last setting. In this method, the
FOLD
back protection remains armed, therefore if the load
current is higher than the Output current limit setting, the
FOLD
back protection will be activated again.
2. Press the
FOLD
button to cancel the
FOLD
back protection. The power supply output will be disabled and
the
VOLTAGE
meter will display
“
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
FOLD
back protection remains armed, therefore if the load current is higher than the Output current limit
setting, the
FOLD
back protection will be activated.
4. Turn the power supply
OFF
using the AC
ON/OFF
power switch, wait until the front panel display turns
OFF
,
then turn the unit back
ON
using the AC
ON/OFF power switch
. The power supply output is then enabled
and the Output voltage and Output current will return to their last settings. In this method, the
FOLD
back
protection remains armed, therefore if the load current is higher than the Output current limit setting, the
FOLD
back protection will be activated 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 input power. The Output
ON/OFF
can be
activated from the front panel using the
OUT
button or from the rear panel J1 connector
SO
or Enable/Disable
pins. The front panel
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 Output current fall to zero and the
VOLTAGE
meter
displays
“
OFF
”.
5.7
OUTPUT SHUT-OFF (SO) CONTROL VIA REAR PANEL J1 CONNECTOR
Contacts J1-2, -3 and -15 (Figure 4-3, Item 5) serve as Output Shut-Off (
SO
) terminals. The
SO
terminals accept
a 2.5V to 15V signal or Open-Short contact to Enable or Disable the power supply output
The
SO
function is 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 input power; even if the
SO
is
OFF
(as no transition from ON to OFF occurred). After an
ON
to
OFF
transition it is detected, the
SO
will enable
or disable the power supply output according to the signal level or the short/open applied to J1.
This function is useful for connecting power supp
lies in a “Daisy-chain” (refer to Section 5.16). The SO control
can also be used to reset the OVP and
FOLD
back Protection (refer to Section 5.3 and 5.5 for details). When the
unit is shut-
off by a J1 signal, the VOLTAGE display will show “SO” to indicate the unit state. J1 contact 15 is the
SO signal input and contacts 2 and 3, IF_COM, are the signal return (connected internally).
Contacts J1-2, -3 and -15 are optically isolated from the power supply output.
The SO control logic can be selected by the rear panel SW1 Setup switch. Refer to Table 5-2 for SW1 setting
and SO control logic.
SW1-5 Setting
SO signal level
J1-2 (3), J1-15
Power Supply
Output
Display
DOWN
(default)
2 - 15V or Open
0 - 0.6V or Short
ON
OFF
Voltage/Current
“
SO
”
UP
2 - 15V or Open
0 - 0.6V or Short
OFF
ON
“
SO
”
Voltage/Current
Table 5-2: Shut-Off (SO) Logic Selection
