34
User’s Manual
PMX_MULTI
Basic Functions
CV Power Supply and CC Power Supply
The PMX has functions that makes it possible to function as a constant-voltage source and constant-cur-
rent source even when the load is changed. The constant-voltage source operation is referred to as con-
stant-voltage (CV) mode. The constant-current source operation is referred to as constant-current (CC)
mode. The operation mode is determined by the following three values.
• Output voltage setting (Vs)
• Output current setting (Is)
• Load resistance (R
L
)
The operation modes are described below.
The above figure shows the product’s operation modes. The load resistance is denoted as R
L
. The resis-
tance, which is denoted as Rc, is calculated from the set voltage and current (Rc = Vs/Is). The power sup-
ply is designed so that it operates in CV mode in area
and CC mode in area
. The boundary is the
line defined by R
L
= Rc. This line represents the load at which the output voltage and the set voltage are
equal and the output current and the set current are equal. If load resistance RL is greater than resistance
Rc, the operating point is in area
, and the PMX operates in CV mode (point p). In this case, the set cur-
rent Is equals the current limit.
When the product is operating in CV mode, the output voltage is maintained at the set voltage. Output cur-
rent I is determined by the equation I = Vs/RL and is a current that is less than current limit Is. The actual
current that flows is not necessarily equal to the specified value.
For loads in which transient overcurrent flows, current limit Is must be set higher than the overcurrent
value.
Conversely, if load resistance R
L
is less than resistance Rc, the operating point is in area
, and the prod-
uct operates in CC mode (point q). In this case, set voltage Vs equals the voltage limit.
When the product is operating in CC mode, the output current is maintained at the set current. Output volt-
age V is determined by the equation V = Is x R
L
and is a voltage that is less than voltage limit Vs. The
actual voltage that is applied is not necessarily equal to the specified value.
For loads that generate transient overvoltage, voltage limit Vs must be set higher than the over.
Crossover point
The product switches automatically between CV mode and CC mode according to the changes in the
load. A crossover point is the point at which the mode switches.
For example, when operating in CV mode, if the load changes and the output current reaches the current
limit, the PMX automatically switches to CC mode to protect the load. Likewise, when operating in CC
mode, if the output voltage reaches the voltage limit, the PMX switches to CV mode.
Output current Iout
Output voltage V
out
Crossover point
A = CV mode area
B = CC mode area
Vs = Set voltage
Is = Set current
Rc = Vs/Is (Ohm
ʼ
s Law)
RL = Load resistance
Vmax = Maximum settable voltage
Imax = Maximum settable current
R
L
= R c
R
L
> R c
R
L
< R c
V m a x
V s
I m a x
I s
0
p
q
A
B
A
B
A
B
