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SM 12 device on a circuit
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tytower:
I have a circuit with a dc photovoltaic string of about 280 volts feeding into this. The circuit calls for a SM12 chip with I think 4 pins. I guessed it was a voltage regulator of some kind but all the googled datasheets give different devices and none seem to fit this .
Can anyone tell me what it would be and where I would get one?
Its marked Pin 1 is L, Pin 2 is N, Pin 3 is +12 v, Pin 4 is 0 v
I Just noticed in the notes he says " A small Chinese postage stamp sized 12v dc power supply provides power ."
Could these two be the same thing . Its input would be 280 Volts DC so I am at a loss here.
Ian.M:
Yes, it could well be a SMPSU module intended for wide range AC input (e.g 100V to 240V AC) as a SMPSU without input power factor correction will usually run from DC with an input range of 1.4 times its AC rating (so 140V to 340V DC for the example range given).
To decide if a particular SMPSU is suitable, after checking its input range converts to include the DC supply voltage, check the SMPSU's circuit - if (ignoring fuses and NTC inrush current limiters) its AC input goes straight to a bridge rectifier with a 350V or higher electrolytic reservoir cap immediately after it, odds are it will be suitable. Anything with a startup circuit or sensing circuit or similar tapping off the AC before the bridge rectifier will *NOT* be suitable.
N.B. any on-board fuse will *NOT* be DC rated so to avoid a serious fire risk, an external DC rated fuse, with sufficient voltage rating *MUST* be used.
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