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Usin
g
your Pro
g
rammable Power Supply 5 - 13
5.5.3 Constant volta
g
e or constant current source
Your power supply has been desi
g
ned accordin
g
to the automatic crossover
principle. This means that each output channel will operate in the Constant
Volta
g
e (CV) mode or in the Constant Current CC mode, dependin
g
on:
• the pro
g
rammed output volta
g
e V
set
and current I
set
• the resistance (impedance) of the load R
load
, connected to the output channel
For a
g
iven V
set
and I
set
, an output channel is either:
in the CV mode if or in the CC mode if .
In the CV mode the output is a constant volta
g
e, so the current throu
g
h the load
depends on the load resistance (R
load
).
In the CC mode the output is a constant current, so the volta
g
e across the load
depends on the load resistance (R
load
).
The followin
g
picture shows when the output channel
g
oes into the CV or into the
CC mode of operation, when connected to a variable resistor R
load
.
If R
load
increases (R
load
> R
c
), the output channel
g
oes into the CV mode,
reducin
g
the current throu
g
h the load.
If R
load
decreases (R
load
< R
c
), the output channel
g
oes into the CC mode,
reducin
g
the volta
g
e across the load.
R
load
V
set
I
set
>
R
load
V
set
I
set
<
Rload >Rc
R=
∞ (open circuit)
Voltage
V(set)
Rc=
Vset
Iset
(crossover point)
Rload <Rc
CC
CV
I(set)
Current
ST5848
R=
0
(short circuit)
Fi
g
ure 5.5.7 Power Output Crossover Point