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What circuits can be used to provide a voltage supply capable of sinking around 1A of current that will always float 10ish volts below a given supply, that could be from 12 to 200 volts?

I have thought about using negative voltage regulators or buck convertor circuits, but I am unfamiliar with such applications, being more used to absolute offset typologies and positive voltages. I imagine a relative offset will be more challenging to achieve.

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    \$\begingroup\$ It is called an isolated supply. Basically one of the switching converter topologies that uses a transformer instead of an inductor \$\endgroup\$ – DKNguyen Dec 11 '19 at 14:51
  • \$\begingroup\$ It does not need to be isolated, but it does need a very low CC ground bias current for the Vref. Also needs a + LDO with a NPN or Nch source driver and not a Neg LDO \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 11 '19 at 14:55
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    \$\begingroup\$ I suggest that you make a schematic drawing. Perhaps you're asking for an (isolated?) electronic load? \$\endgroup\$ – Bimpelrekkie Dec 11 '19 at 14:56
  • \$\begingroup\$ 10W Zener diode? \$\endgroup\$ – Cristobol Polychronopolis Dec 11 '19 at 15:49
  • \$\begingroup\$ THL 10-2421 \$\endgroup\$ – Andy aka Dec 11 '19 at 16:04
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At the 1A level you’re almost certainly going to want a 10W switching supply, however 12-200V is a very wide range to use that for a power source.

A negative linear regulator would dissipate almost 200W with a 200V supply so that would be very inefficient.

If you have another supply such as 120VAC you could likely hang an isolated AC-DC supply or an isolated DC-DC converter output off the positive rail of the variable supply.

This is not an uncommon arrangement for something like a inverter TIG welder output stage.

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  • \$\begingroup\$ How do you hang a dc-dc converter off of the positive rail? I have been looking FOREVER and never found even a question about it. Is there a DC-DC IC that I can use which has a schematic for the positive rail configuration? I always want it to provide a steady 10v less than the supply. Could you point me to an application note or something? This is essentially like a switching regulator that turns the ground on and off instead of the positive supply, but I have no idea where to find such an IC. An AC source is not an option. \$\endgroup\$ – Hackstaar Dec 12 '19 at 3:50
  • \$\begingroup\$ Say you have a 12VDC:10VDC DC-DC. If the DC-DC output is galvanically isolated (and the isolation is rated appropriately), you connect the + output to the positive rail and then you can draw current from the positive rail to the - output of the DC-DC converter. So you have a -10V rail that can sink current. It can't typically source current. \$\endgroup\$ – Spehro Pefhany Dec 12 '19 at 3:54
  • \$\begingroup\$ Have a gander at @Andyaka's cryptic comment, which is a link to a datasheet for a part that is close to what you are asking for. That DC-DC is spec'd at 1500V isolation, but only for 60s. Probably it would be okay for 200V continuous, but worth looking into the app notes. \$\endgroup\$ – Spehro Pefhany Dec 12 '19 at 3:57

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