QS20.241, QS20.241-A1, QS20.241-C1
Q-Series
24V, 20A, SINGLE PHASE INPUT
22. APPLICATION NOTES
22.1. REPETITIVE PULSE LOADING
Typically, a load current is not constant and varies over time. This power supply 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 6) has elapsed.
To avoid this, the following rules must be met:
a) The power demand of the pulse must be below 150% 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. 22-2) to check if the average output current is below the nominal current.
Fig. 22-1 Repetitive pulse loads, definitions
Fig. 22-2 Max. duty cycle curve
DutyCycle
1.0
0.8
0.6
0.4
0.2
0
P0 = 10%
P0 = 50%
P0 = 75%
PPEAK TPEAK
T0
max.
150%
100%
P = 100
%
P0
0
PPEAK
140 150%
100
110
120
130
T
peak
P0
Base load (W)
D
utyCycle =
PPEAK Pulse load (above 100%)
T0 Duration between pulses (s)
TPEAK Pulse duration (s)
T
peak + T0
T
peak
-
(Duty
C
ycle x Tpeak
)
T0
=
D
utyC
ycle
Example: A load is powered continuously with 240W (= 50% of the rated output load). From time to time a peak
power of 720W (= 150% of the rated output load) is needed for 1 second.
The question is: How often can this pulse be supplied without overloading the power supply?
- Make a vertical line at PPEAK = 150% and a horizontal line where the vertical line crosses the P0 = 50%
curve. Read the max. duty cycle from the duty cycle-axis (= 0.37)
- Calculate the required pause (base load) length T0:
Tpeak
-
(Duty
C
ycle x Tpeak
ycle
)
1s
-
(0.37 x 1s)
0.37
- Result: The required pause length = 1.7s
T0=
=
=1.7s
Duty
C
- Max. repetition rate = pulse +pause length = 2.7s
More examples for pulse load compatibility:
PPEAK
P0
480W 1s
0W 1s
240W 1s
TPEAK
T0
PPEAK
P0
TPEAK
T0
720W
720W
600W
>25s
>1.3s
> 0.75s
720W
720W
720W
240W 0.1s
240W 1s
240W 3s
>0.16s
>1.6s
>4.9s
Oct. 2013 / Rev. 2.2 DS-QS20.241-EN
All parameters are specified at 24V, 20A, 230Vac, 25°C ambient and after a 5 minutes run-in time unless otherwise noted.
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