High Voltage Down Converter Circuit

[Pat Pending]

Does anyone know of a simple discrete DC/DC down converter from 75V to 12V@20mA?

[mariush]

That would be kind of hard to get one ready made, you have lots of options if you get that down to a maximum of 72v :

http://www.digikey.com/product-detail/en/VWRBS2-D48-S12-SIP/102-1519-ND/1558914
http://www.digikey.com/product-detail/en/VWRAS2-D48-D12-SIP/102-1535-ND/1558930


But you could build one yourself if you don't need it to be the isolated kind, look up the LM500x family of switching regulators. They take up to about 95v DC and regulate down to whatever you want, and they're about 2-3$ in 10-50 pcs quantity:

http://www.digikey.com/product-detail/en/LM5008AMM%2FNOPB/LM5008AMMCT-ND/2075647
http://www.digikey.com/product-detail/en/LM5009MM%2FNOPB/LM5009MMCT-ND/1001314
http://www.digikey.com/product-detail/en/LM5007MM%2FNOPB/LM5007MMCT-ND/599064

Add a couple of dollars in inductor, resistors and capacitors and you're done, cheaper than an isolated dc-dc converter.

[PSR B1257]

If you only need 20mA you might use a linear regulator - like the TL783 - instead.
As every other voltage regulator of that kind, it's programmable with just two resistors.

What kind of 12V/20mA load is this? If the 20mA are constant, you need just a single resistor.

[Pat Pending]

Thanks Everyone

I'd been looking at the MAX5033, but then two issues arose, 1st it's expensive in small quantities and 2nd it's by Maxim
or rather no one carries a large stock whereas the LM500x is carried in the many thousands.

I was hoping for some sort of jelly bean buck converter if one still exists?

[PSR B1257]

What about my questions...

To give you a propper suggestion, we need to know what you intend.