Wide range buck converter

[m51]

Dear
I need to design voltage converter having the following characteristics:
Input voltage: 12V to 240V AC / DC
Output voltage: 5V DC
Output current: 150 to 200mA (to powering 5V DC relay and microprocessor).
So far, I don't found buck converter IC with this wide input voltage area.
Can you suggest a cost effective and reliable solution.
Thank you in advance.

 

[ZASto]

I would do it with only one resistor

 

[schmitt trigger]

About a month ago, another poster asked the exact same question.

Never explained exactly why such a wide and conflicting requirements were necessary in the first place (exactly what voltage source will provide either AC or DC over a 20:1 range??).

 

[Orson Cart]

Presumably you need an isolated output? A flyback will do it for you, we have designed a number of these types, easy at the power levels you require.

 

[goldsmith]

Dear
I need to design voltage converter having the following characteristics:
Input voltage: 12V to 240V AC / DC
Output voltage: 5V DC
Output current: 150 to 200mA (to powering 5V DC relay and microprocessor).
So far, I don't found buck converter IC with this wide input voltage area.
Can you suggest a cost effective and reliable solution.
Thank you in advance.

Hi
Is insulation important for you ? or perhaps not ?

By the way , usual buck converters won't handle this easily . you must go for soft switched buck converters .

Best Wishes
Goldsmith

 

[schmitt trigger]

I'm not saying it cannot be done.
But I'm asking why it needs to be done in the first place.

240 volts AC will have a peak voltage of 338 volts. Because of reflected voltage and other voltage peaks, the switching Mosfet will have to withstand at least 600 volt. But with Mosfets, a Rds_on goes hand in hand with withstanding voltage, therefore, this same Mosfet, when operated at 10 volts (12 volts DC minus the bridge rectifier's drop) will have terrible conduction losses.

Same for the transformer...it will have to have a primary wire capable of conducting approximately 30 times the current requirement at maximum AC voltage.

And I haven't touched the start-up circuitry requirements.

The question is: why compromise a design so much? What voltage source exists that will output 12 thru 240 volts, at either AC or DC?

 

[Orson Cart]

The question is: why compromise a design so much? What voltage source exists that will output 12 thru 240 volts, at either AC or DC?

Often this is a requirement for electronic power meters (domestic & industrial) to keep them going even when the incoming mains is low or fluctuating...!

We have designed these from 50Vac to 480Vac operation.

 

[schmitt trigger]

I understand what you say...but that would still be AC only, correct? And your range would be only 9.6to 1, and not 33 to1 from the OP's requirements.
Where does the DC requirement come from?

Perhaps the project requires battery backup. But said battery could not be connected to the same terminals where the AC mains are connected.
If my assumption is correct, what I would do is to is design the flyback 80-260VAC to 5VDC
Have a second powertrain, made from a low cost buck, to regulate from 9-16VDC to 5VDC
Perform the switching between the two at the %VDC side. The transfer circuit could be something as simple as a single diode.