Hi all,

I have never been able to figure out how to make a power supply for my circuits that can take (12-250 VDC or 24-250 VAC) input and supply me with 200ma or so of 12VDC power. I see many sensor manufacturers that put this type of power supply into their very small packages. Here is an example of what I am referring to:
Q45VR3DL W/30 | Q45 Series Rugged Rectangle Sensor (bannerengineering.com)

Just checking to see if anybody has an idea what type of circuit they are using.

Thanks

 

The optical switch you linked operates from many voltages. It does not supply you with 12VDC, instead its output is relay contacts that are insulated from the dangerous high voltage that powers it.
It probably uses a series capacitor to reduce the AC input voltage or uses Pulse Width Modulation to reduce the AC or a DC input voltage. Without using a transformer then it is safe because its 12VDC internal voltage cannot be touched by you. Then its simple voltage converter is unsafe (electric shock) to be used by your circuits.

 

The optical switch you linked operates from many voltages. It does not supply you with 12VDC,

He knows that. That is not the question.

He is using this sensor as an example of a commercial product with an exceptional input voltage range, and wants to know how to replicate that power supply function with a regulated 12 V / 200 mA output.

The datasheet does not give the input current range, which would tell us everything we want to know. At the least, it smells like a very wide range buck converter. It could be a simple, transformer-isolated flyback converter such as the sones in any USB wall wart, with different magnetics to handle the wide input range. The power level is half that of a USB wart, so the circuit could be quite small and fit easily in the package shown.

To the TS: You are asking about designing an offline power supply from scratch. I see three options:

1. An isolated linear supply that produces a lot of heat at high input voltages.

2. A non-isolated switching buck regulator. Relatively simple math, but dangerous.

3. An isolated flyback converter. Less dangerous, but much more complicated magnetics design.

There is a fourth option, a non-isolated linear approach using a capacitor as a voltage-dropping element. This type of supply is so dangerous that it used to be banned from discussion. Also, it will not work at all with a DC input.

ak

 

He knows that. That is not the question.

He is using this sensor as an example of a commercial product with an exceptional input voltage range, and wants to know how to replicate that power supply function with a regulated 12 V / 200 mA output.
ak

You are correct AnalogKid. I just put the link to one of the many sensors on the market that can handle this wide input voltage. I realize they are not giving any output. But they are driving the internal processor, LEDs, Relay, Sensor Output and etc. I am just trying to build the front-end power supply portion to use with my own circuit board. 200mA at 12VDC was just a rough starting point.

 

Do you really need such a wide input voltage range, plus AC/DC capability? "Universal input" supplies are everywhere and cheap; input range 85 - 240 Vac - ish.

An alternative is two power supplies, one for low input voltages and one for universal, and internal circuitry (diodes) that automatically switches between them.

ak