suppose you have a power supply but don't know what is the maximum current
it can deliver. how would you find out what the max current is?
If it is linear, then it may have a current sense/limit circuit, in
which case you would find the value of the appropriate resistor and
consult the datasheet for the regulator. Otherwise, if the CL circuit
relies on turning on a PN junction, then use 0.6V as the limiting
voltage and do the arithmetic. You may need to do a little reverse
engineering if other arrangements are used. Alternatively you could
just keep loading the supply until it droops and hope nothing breaks.
If the supply is a switchmode type, then its absolute maximum rating
would be less than or equal to the rating of the diodes on the
secondary side. I suspect you may be able to estimate the max current
by measuring the switching frequency, allowing for a certain max
ripple, and then calculating the current draw that would produce this
amount of ripple in the output cap.
- Franc Zabkar