QTD20.241
Q-Series
24V,
20A,
DC
I
NPUT
21.
A
PPLICATION
N
OTES
21.1.
R
EPETITIVE
P
ULSE
L
OADING
Typically, a load current is not constant and varies over time. This DC/DC converter is designed to support loads with a
higher short-term power demand (=BonusPower
®
). The short-term duration is hardware controlled by an output
power manager and is available on a repeated basis. If the BonusPower
®
load lasts longer than the hardware
controller allows it, the output voltage will dip and the next BonusPower
®
is available after the BonusPower
®
recovery
time (see chapter 5) has elapsed.
To avoid this, the following rules must be met:
a)
The power demand of the pulse must be below 125% of the nominal output power.
b)
The duration of the pulse power must be shorter than the allowed BonusPower
®
time. (see output section)
c)
The average (R.M.S.) output current must be below the specified continuous output current.
If the R.M.S. current is higher, the unit will respond with a thermal shut-down after a period of time. Use the
maximum duty cycle curve (Fig. 21-2) to check if the average output current is below the nominal current.
d)
The duty cycle must be below 0.75.
Fig. 21-1
Repetitive pulse loads, definitions
Fig. 21-2
Max. duty cycle curve
100%
P
PEAK
T
PEAK
P
0
T
0
max.
125%
125%
100
0
0.2
0.4
0.6
0.75
Duty Cycle
105
110
115
120
P
PEAK
P
0
= 10%
P
0
= 50%
P
0
= 75%
P
0
= 100%
P
0
Base load (W)
P
PEAK
Pulse load (above 100%)
T
0
Duration between pulses (s)
T
PEAK
Pulse duration (s)
D
uty
C
ycle
T
0
=
T
peak
-
(D
uty
C
ycle
x T
peak
)
T
peak +
T
0
T
peak
D
uty
C
ycle
=
Example:
A load is powered continuously with 240W (= 50% of the rated output load). From time to time a peak
power of 600W (= 125% of the rated output load) is needed for 1 second.
The question is: How often can this pulse be supplied without overloading the DC/DC converter?
- Make a vertical line at P
PEAK
= 125% and a horizontal line where the vertical line crosses the P
0
= 50%
curve. Read the max. duty cycle from the duty cycle-axis (= 0.37)
-
Calculate the required pause (base load) length T
0
:
21/27
-
Result: The required pause length = 1.7s
-
Max. repetition rate = pulse +pause length =
2.7s
More examples for pulse load compatibility:
P
PEAK
P
0
T
PEAK
T
0
P
PEAK
P
0
T
PEAK
T
0
600W 480W
1s >25s
600W 240W
0.1s >0.16s
600W 0W 1s >1.3s
600W 240W
1s >1.6s
540W 240W
1s >
0.75s
600W 240W
3s >4.9s
D
uty
C
ycle
T
0
=
T
peak
-
(D
uty
C
ycle
x T
peak
)
0.37
1s
-
(0.37 x 1s)
=
= 1.7s
Oct. 2016 / Rev. 2.0 DS-QTD20.241-EN
All parameters are specified at 24V, 20A, 600Vdc input, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
www.pulspower.com Phone +49 89 9278 0 Germany