18
PLZ-4WL
Methods for Ensuring Stable Operation
When you use the PLZ-4WL at a high response speed, it is important to reduce the
inductance of the load wiring and configure the response speed setting appropriately. If the
conditions are not configured appropriately, oscillation and other forms of operational
instability may occur.
Reducing the load wiring inductance
Voltage generated by current changes
The wiring has an inductance of L. If current I changes quickly, a large voltage is induced on
both sides of the wiring. All of this voltage will be applied to the load input terminals of the
electronic load if the impedance of the DUT is low. Voltage E (hereafter referred to as the
generated voltage), which is generated according to the wiring inductance L and the amount
of current change I is expressed as follows:
Generally, a wire’s inductance is approximately 1 µH per meter of wire. If the DUT and the
electronic load are connected using 1 m of wire (total length of the positive and negative
wiring), a change in current of 50 A/µs will generate a voltage of 50 V.
The negative load input terminal provides the reference potential for the external control
signal. The generated voltage may cause the device connected to the external control signal
to malfunction.
When the electronic load is in constant-voltage, constant-resistance, or constant-power
mode, it uses the voltage at the load input terminals to change the load current. So it is easy
for the electronic load to be influenced by the generated voltage.
Large voltage drop caused by current changes during switching
operation
Make the wiring to the DUT as short as possible, and twist it. When the wiring is long or
contains a large loop, its inductance increases, and current changes caused by switching
operations will result in large voltage drops.
If the instantaneous voltage value at the load input terminals drops below the minimum
operating voltage, the recovery response will be delayed significantly. You need to be
especially careful when the slew rate setting is high and when switching operation is
performed at high currents.
EUT
PLZ-4
W
L
E = L × (
ΔI/ΔT)
E: Generated voltage
L: Load wiring inductance
ΔI
: Change in current
ΔT
: Duration of time over which
the current changes
L
I
ΔI/ΔT
E
Load input terminal
+
-
