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Vox Power Limited | Unit 2, Red Cow Interchange Estate, Ballymount, Dublin 22, D22 Y8H2, Ireland | T +353 1 4591161 |
DOC-MN-008-03, VCCS300 User Manual
Output Performance (12V, 24V & 48V Models)
Power Profile
The power profile diagram below is a voltage/current plot that together with the associated table provides details of the main features of the standard output voltages.
Alternative output voltage constructions are available to order, consult your Vox Power Distributer or Vox Power representative for further details.
POWER PROFILE
Model
V
NOM
(V)
I
RATED
(A)
V
OVP
(V)
V
SCP
(V)
I
OCP
(A)
VCCS300(X)-12
12
25A
15
9.6
28.75
VCCS300(X)-24
24
12.5A
30
19.2
14.37
VCCS300(X)-48
48
6.25A
60
38.4
7.18
Over Voltage Protection (OVP)
In the event of an output fault, the unit is protected against excessive output voltages. If the output voltage exceeds the V
OVP
threshold, the output will be disabled,
and the unit will attempt to restart at a minimum of 1 second intervals.
Over Current & Short Circuit Protection (OCP & SCP)
The over current threshold is typically set at 115% of the rated current and has a constant current, straight line characteristic that reduces the output voltage as the
load resistance decreases. If the output voltages falls below the short circuit voltage threshold (V
SCP
) the unit enters short circuit protection mode. In SCP mode, the
output shuts down completely for a minimum of 1 second then attemps to restart. This process repeats until the overload condition is removed, at which point normal
operation resumes.
Reverse Current Protection (RCP)
The output rectifier uses synchronous rectification to achieve high efficiency. Typically synchronously rectified outputs can both source and sink current. The VCCS300
series outputs have internal protection to prevent any reverse current flowing into the unit.
Start-up
The outputs are designed to have a controlled start-up with a rise time of approximately 2ms (0% to 67%) under full load. Start-up into pre-biased loads will not
discharge any external capacitance or cause any damage to the unit.
External capacitance
The outputs can support a large external capacitance as detailed in the table shown.
The capacitances specified ensure reliable start-up with rated load applied.
Larger capacitances can be applied for reduced load currents.
V
OUT
C
EXT_MAX
12
3mF
24
1.5mF
48
0.6mF
Start up into Pre-biased loads
A pre-biased load is a load that already has a voltage present when the power supply is turned on. This can occur if the output capacitors are not loaded and the unit
is turned off and then on again before the capacitors have had a chance to discharge.
In such circumstances there may be a small voltage overshoot of approximately 10% at start up. However, this can be eliminated by adding sufficient external
capacitance.
Shut Down
At shutdown, the outputs enter a high impedance state. Where no external load is present it may take some time for the voltage to decay. When driving inductive
loads, care must be taken to limit the voltage at the output terminals to prevent damage to the unit.
