146
PLZ-4WH
Operating Area
How constant current and constant voltage (CC+CV) mode
works
On the PLZ-4WH, you can add constant voltage (CV) mode to constant current (CC) mode.
Constant current and constant voltage mode operation
When the PLZ-4WH is used in constant current and constant voltage mode (CC+CV), it
operates as a constant-current load and a constant-voltage load (shunt regulator) as shown
in the figure below. Operating as a constant-current load, the PLZ-4WH sinks the specified
current (I) regardless of the output voltage V
M
of the constant-voltage power supply. When
V
M
is greater than V, the PLZ-4WH 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-4WH 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-4WH 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.
The battery voltage is V
M
. In constant current (CC) mode, if the current is increased
(I
M1
→
I
M2
→
I
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.
PLZ-4WH Series
Battery
I
V
R
1
The voltage is constant even
when the current varies.
The current is constant even
when the voltage varies.
VM
Current I
Voltage
V
0
CC operation
CV operation
CC setting
CV
Setting
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
M
1
M
2
P
N
P
N1
Constant current line
(constant current settings: I
M1
, I
M2
, and I
N
)
I
M1
I
M2