38 PMC-A
Fig. 4-1 illustrates the operating modes for the PMC-A. RL
stands for the load resistance value, and RC stands for the resis-
tance value calculated from the current and the voltage setup
value (R
C = VS/IS). The regulated power supply is designed as
operating in CV mode when the operating point is in the
range, and in CC mode when the operating point is in the
range. The straight line (RL = RC) is a line between CV mode
and CC mode. This line shows loads for which the output volt
-
age and the setup voltage are equalized, or which the output
current and the setup current are equalized. If load resistance
R
L is greater than load resistance RC, the power supply operates
in CV mode because the operating point is within the
range.
At this time, the current setup value IS becomes the current
limit value.
When operating in CV mode, the output voltage is maintained
at the voltage setup value. The output current is determined by
the relation I=V
S/RL, and is reduced to a value below the cur-
rent limit value IS. Note that the current of the setup value does
not flow at this time.
For the loads to allow transient peak current flow, the current
limit value must be set so that the peak current does not reach
the limit value.
Conversely, if load resistance RC is greater than load resistance
R
L, the power supply operates in CC mode because the operat-
ing point is within the range. At this time, the voltage setup
value IS becomes the voltage limit value.
When operating in CC mode, the output current is maintained
at an established current value. The output voltage is deter
-
mined by the relation V=IS × RL, and is reduced to a value
below the current limit value V
S. Note that the voltage of the
setup value is not applied at this time.
For the loads in which transitory surge voltage arises, the volt-
age limit value must be set so that the surge voltage does not
reach the voltage limit value.
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