PMC-A
39
4
Bas
ic O
p
er
at
io
n
Crossover point
The unit switches between CV mode and CC mode automati-
cally depending on the load. The points where the transition
occurs are called crossover points.
For example, in CV mode, when the load changes and the out-
put current reaches the current limit value, there is an automatic
transition to CC mode in order to protect the load. Similarly, in
CC mode, when the output voltage reaches the voltage limit
value, there is an automatic transition to CV mode.
Example of CV/CC mode operation
The following describes an example of model PMC35-1A.
(rated output voltage 35 V and rated output current 1 A).
Connect an 60
Ω
load resistance (R
L
) to the power supply’s
output terminal and set the output voltage to 20 V and the out-
put current to 0.5 A. In this case, because Rc=20 V/ 0.5 A = 40
Ω
, and 60
Ω
> 40
Ω
(R
L
> Rc), CV mode is activated. When the
voltage rises while still in CV mode, because Vs= 0.5 A × 60
Ω
= 30 V (Vs=I
S
× R
L
), the voltage can go up to 30 V. When the
voltage goes higher than this value, the crossover point is
reached, and there is an automatic transition to CC mode. To
maintain CV mode at rate exceeding 30 V, raise the output cur-
rent setting value (0.5 A).
Next, connect a 25
Ω
load resistor (R
L
) to the power supply’s
output terminal, and establish a 20 V output voltage and a 0.5 A
output current. In this case, CC mode is activated because R
C
=
20V/ 0.5 A = 40
Ω
and 25
Ω
< 40
Ω
(R
L
< R
C
). When the cur-
rent rises while still in CC mode, it is possible that the current
value will rise to a level higher than I
S
= V
S
/ R
L
up to I
S
= 20V/
25
Ω
= 0.8 A. When the current goes higher, it reaches the
crossover point, and there is an automatic transition to CV
mode. To maintain CC mode at rate exceeding 0.8 A, raise the
output voltage setting value (20V).
