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D - 2 Users Manual
This set-up will cause no problem as CH 1 supplies a constant current (CC) of 5A
and CH 2 supplies the additional current needed in constant volta
g
e mode (CV
indicator).
A problem will arise when the current needed by the load decreases below 5A, for
example when the load resistance increases. This is illustrated by fi
g
ure D.2.
Fi
g
ure D.2 Channels connected in parallel to a load. Both channels are in
Constant Volta
g
e mode.
CH 1 will now enter the Constant Volta
g
e (CV) mode, as the current needed by
the load is less than Iset (5A). This implies that the volta
g
e across the load will
chan
g
e to the hi
g
hest Vset (12V). As Vset of CH 2 is 10V, its down pro
g
rammer
will become active, so that CH 1 will supply 3A plus the current the down
pro
g
rammer of CH 2 will sink. So this set-up is not suitable for load currents, which
can be lower than Iset of the Constant Current channel.
For this case there are two solutions. You can set the current of CH 1 to a value
below 3A so that CH 1 will enter the Constant Current mode as indicated in
Fi
g
ure D.1. Or, you can set both channels to the same volta
g
e, so that there will
be a constant volta
g
e across the load. When the volta
g
es are exactly equal, the
down pro
g
rammer will not become active and the current throu
g
h the load will be
equal to the sum of the currents of the individual channels.
Be careful in usin
g
the Standby and Disable modes
Consider the followin
g
case. You have connected two channels in parallel. You
don't need the second channel to supply current, because the first channel can
supply enou
g
h current. You disable the second channel to switch it off. The down
pro
g
rammer of this channel will try to sink its output to 0V. As the first channel still
supplies a volta
g
e, the down pro
g
rammer of the second channel will continuously
sink current. This causes power dissipation inside the case, which must be
prevented as the Power Supply is not desi
g
ned for this use.
Vset = 12V
Iset = 5A
4Ω
12V
3A
CC
3.5A
12V
CH1
Vset = 10V
Iset = 5A
CV
-0.5A
12V
CH2