GW Instek PSU-Series User Manual - Manual (Page 23)

GETTING STARTED
23
CC and CV Mode
CC and CV mode
Description When the power supply is operating in
constant current mode (CC) a constant current
will be supplied to the load. When in constant
current mode the voltage output can vary,
whilst the current remains constant. When the
load resistance increases to the point where the
set current limit (I
SET
) can no longer be
sustained the power supply switches to CV
mode. The point where the power supply
switches modes is the crossover point.
When the power supply is operating in CV
mode, a constant voltage will be supplied to
the load, whilst the current will vary as the
load varies. At the point that the load
resistance is too low to maintain a constant
voltage, the power supply will switch to CC
mode and maintain the set current limit.
The conditions that determine whether the
power supply operates in CC or CV mode
depends on the set current (I
SET
), the set voltage
(V
SET
), the load resistance (R
L
) and the critical
resistance (R
C
). The critical resistance is
determined by V
SET
/I
SET
. The power supply
will operate in CV mode when the load
resistance is greater than the critical resistance.
This means that the voltage output will be
equal to the V
SET
voltage but the current will be
less than I
SET
. If the load resistance is reduced
to the point that the current output reaches the
I
SET
level, the power supply switches to CC
mode.