K
N
D
0
0
0
----
,
I
0
I N T
8
Load
Figure
6
The power supply output voltage can be modulated by an external low power
signal. This mode of operation is initially intended to give a possibility to
add a variable amount of ripple to the output voltage. This is useful for
example, when a circuit has been developed using a practically ripple free
regulated power supply as power source, and is intended to be operated from
a simple rectifier. The amount of ripple which the actual circuit can stand,
is easily examined by varying the ripple modulation amplitude from the
laboratory regulated power supply. When this low amplitude modulation
(less than 2
V
p-p) is used, the upper frequen�y limit (-3 dB) is approxima
tely 25 Hz with 20-100
%
load.
Above this frequency limit the amplitude-frequency curve falls 6 dB per
octave. At frequencies over 50 Hz the amplitude is limited by the slew-rate
capability.
MODEL
SLEW-RATE at
1
A
150-600
w
32
v
1000
w
32
v
150-600
w
60
v
1000
w
60
v
200
V
/sec
100
V
/sec
300
V
/sec
150
V
/sec
The slmv-rates as specified above apply for a mm1mum current of 1 A and
1 A bebw the value the current limit is set to.
The slew-rate is proportional to the smallest of:
1)
DC output current
2) Difference between current limit and DC output current
Example: Model B32-5R with a 3A DC load and current set at 5A.
How much is the slew-rate?
1) DC output current is 3 A.
2) Difference between the current limit and DC output current is:
5 A - 3 A
=
2 A.
2 A is the lowest of the two. Slew-rate at
1
A is 200
V
/sec.
So the slew-rate in this example amounts to 2 x 200
=
400
V
/sec.
Figure
7
illustrates the slew-rate limitation as a function of output DC cur
rent for the eight models of RACPAC, each having its current limit control
set at maximum.
12
