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Parallel Connecting Two Identical Switching PSUs

W

w_tom

Jan 1, 1970
0
There is no reason why an SMPS needs to be folded back while limiting.

1) It is required quite obviously by specs.
2) It is necessary for safety.
3) It is how computer supplies have been built before there was an
IBM PC.

When can power supplies be used in parallel (ie for redundancy and
longer MTBF)? When each power supply can provide 100% of the load by
itself. That obviously is not the OPs question or intent.

Power supplies designed for parallel (because the load is too large
for one supply) also include a communication circuit between those
supplies - because those unique supplies are specially designed for
parallel applications.
 
L

legg

Jan 1, 1970
0
1) It is required quite obviously by specs.

If it is so written. There are often good reasons not to include this
in an application specification.
2) It is necessary for safety.

This need not be the case. Hardware designed to operate safetly off
high current rails is better designed with source capacity in mind and
suitable protection of reduced trace widths, as appropriate. This
allows for increased redundancy, increased repairability and shorter
down time.
3) It is how computer supplies have been built before there was an
IBM PC.

Foldback limiting was initially required solely to reduce possible
damage to linear regulator elements due to overstess under shorted
load conditions. Switchers need not be thermally or electrically
stressed by a continuous load short - though some lower-power
topologies may be difficult to cheaply configure with constant current
limiting characteristics.
When can power supplies be used in parallel (ie for redundancy and
longer MTBF)? When each power supply can provide 100% of the load by
itself. That obviously is not the OPs question or intent.

No, it was not obviously the OP's intent to introduce redundancy,
however the techniques used to do so are applicable in simple parallel
connections, without redundancy. Few respondents seemed to understand
this at the time.

It would be easier for the OP to parallel switchers that have certain
characteristics, like constant current limiting, adjustable output
voltage and a well defined regulation.
Power supplies designed for parallel (because the load is too large
for one supply) also include a communication circuit between those
supplies - because those unique supplies are specially designed for
parallel applications.

A number of techniques require differing types signal interconnection.
A number of other techniques don't require this interconnection. The
OP may best research this with his specific model of converter in
mind.

RL
 
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