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Use a transformer, bridge and filter capacitor, followed by an integrated regulator, such as the LM317. The 3% accuracy is the norm for power supplies, nothing special there.
The LM317 needs about 2V minimum between the input and output, so make sure the input voltage, at the valley of the line ripple never goes below 8V, even with 180VAC input.
But I cannot get the output within the range. When 180V, loading time, output drops below 5.82V and when input 240V, output exceeds upper limit..more worse when the transfomer's loss increased/heating up.
This adaptor is used for precision equipment. The main problem I facing now is the variation of input voltage. How to fix the output if the supply varied from 180V to 240V and keep fluctuated.
That is the function of the regulator, to keep the output constant while the input varies.
The input voltage variation may seem large, but it's not really that bad. Basically you need a 220V transformer, that has to handle +9%, -18%.
Generally +10% /-15% is the NORMAL variation to be expected, so you only need to go 3% below that. That is not a big difference. You should be able to design a transformer to cover that range.
Make sure the transformer can supply the required current without overheating, and make sure the output voltage, with 180V input, is still enough for the regulator to maintain the output voltage.
Now comes the thing I do not understand: why do you say that the voltage is exceeded when the input is 240V, while at 180 it is not sufficient?
The LM317 I suggested can go up to about 40V input. So if you have 8V minimum at 180V (at ripple valley), with 20% ripple, that is you have about 9VDC, with about 2Vpp ripple, that is the voltage is between 8 and 10V at the input of the regulator. Then at 240VAC, you will have 240/180*9=12VDC, with 20% ripple, that is the voltage will be between 11V and 13V. That is very reasonable. Many linear regulators can deal with input voltage variations MUCH larger than that.
I suspect the transformer you are using is not properly designed. Please review its design or choose a different one.
The easiest way to test what I said and find other possible problems is to power the regulator from a laboratory DC power supply. Load the regulator at 0.3A and vary the input voltage while observing the output. It should remain almost unchanged (within about 1%) for any input between about 7-8V and the maximum allowable for your regulator. If it does change by more than 1%, then you need to look at the regulator, because there is a problem. Otherwise, check the transformer, bridge, filter cap.
Hi wisepi,
I think the right way is to select a precision regulator (better as LM317!) and a trafo with enough output/DC for the regulator (as blastronics sayed it too) even at 180V mains too...
A transformator with max 3W primary is not a real problem to make it self too...
A good regulator can you find from LT/Micrel & NI too.
K.
Added after 6 minutes:
Other possibility (but complexer) is, of course, to built a switcher with a miniature core-E16 or smaller...
Added after 9 minutes:
Hallo soheiliran,
I think you have basically two possibilities:
1,
You takes a trafo 230 to150V & rectifier & buffer capacitors as usual.
2,
You build a switcher too....
3,
in my opinion is a wors way, but not inpossible:
You makes a one way rectifier and select the buffer capacities so that your "Quasi" DC voltage is more or less at ca. 150-170V, but with (to) high ripples:-(... I think for 15A is these solution nothing!
K.
hi,
i recommend you switching regulators.
try using TOPSWITCH-HX from POWER INTEGRATION.
the most significant benefit of these regulators(top switchs) is the software that POWER INTEGERATION supplys i.e : PIExpertSuiteSetup.
you can enter some data about your desired power supply and get the schematic and the amounts.
visit this page if you are interested: powerint.com
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