128
PLZ-4WL
Operating Area
How constant resistance and constant voltage (CR+CV)
mode works
On the PLZ-4WL, you can add constant voltage (CV) mode to constant resistance (CR)
mode.
Constant resistance and constant voltage mode operation
When the PLZ-4WL is used in constant resistance and constant voltage mode (CR+CV), it
operates as a constant-resistive load and a constant-voltage load (shunt regulator) as shown
in the figure below. When the PLZ-4WL operates as a constant-resistive load and the voltage
V
M
of the constant-voltage power supply varies, the PLZ-4WL sinks current to maintain I = V/
R, with the specified resistance value R fixed. When V
M
is greater than V, the PLZ-4WL
operates as a constant-voltage load and keeps input voltage V constant even when the input
current I varies. Current does not flow when V
M
is less than or equal to V.
The PLZ-4WL switches between the two modes automatically. In the figure below, R
1
is the
internal resistance of the constant-voltage power supply. In constant-voltage (CV) mode, the
PLZ-4WL may operate unstably if R
1
is low.
Transition of the operating point: overpower protection (OPP)
In this example, we will assume that the discharge characteristic of a battery is being
measured.
When the overcurrent protection (OCP) setting I
OCP
is greater than current I
N
at point N, the
voltage of the battery is V
M
. In constant resistance (CR) mode, if the resistance is reduced
(R
M1
R
M2
R
N
) so that the input current (load current) increases, the operating point
moves along segment MN (M
1
M
2
N).
When the overpower protection (OPP) setting is P
N
, OPP is activated when point N is
reached.
At this point, one of two types of operations occurs, depending on the protection action
setting for OPP. If the protection action is set to LOAD OFF, the load turns off. If the protection
action is set to LIMIT, the PLZ-4WL sinks current as a constant-power load at point N. Even if
you attempt to decrease the resistance to increase the current, the current will not increase
beyond point N. If you increase the resistance to decrease the current, overpower protection
I
V
PLZ-4WL Series
Battery
V
M
R
1
Current I
Voltage
V
0
CV
Setting
The voltage is constant even
when the current varies.
The resistance is constant even
when the voltage and current vary.
CR operation
CV operation
Input current [A]
Input voltage [V]
Logarithmic scale
V
M
V
Q
Q
S
Constant power line
(constant voltage setting)
Constant voltage line
Operating area
OPP activation point
(OPP setting)
M
N
I
N
I
OCP
M
1
M
2
P
N
P
N1
R
M1
R
M2
R
N
Constant resistance line
(constant resistance settings: R
M1
, R
M2
, and R
N
)