Circuit to create a stiff reference between 390V-400V above ground

[pastro]

Hi all,

I need to build a circuit that has it's normal "ground" terminal ~10V below the high side of the output of a DC-DC converter whose output is 400V above true signal ground. Between the 400V and 390V terminals, the circuit needs to provide a reference voltage that is stiff to load currents flowing between 400V and 390V which can be as high as 0.1mA. Low dissipation in the 10V reference is extremely important--whatever circuit or component I use, it can't dissipate more than 150mW internally--less is better. I've already found that using a voltage divider between 0V and 400V is not stiff enough without dissipating a significant amount of power in the divider chain. A zener and resistor also causes too much power consumption.

Does anyone have a suggestion of how to build such a device? Perhaps there is already a commercial component out there to do such a thing.

(For reference, I want to drive a P-Channel high side MOSFET to switch the 400V. This P channel MOSFET is part of a half bridge (along with a low side N-channel MOSFET) to provide fast on and off rise time switching (~100ns) between 400V and -15V while also allowing for variable on times (out to infinity, which means bootstrapping drivers won't work). The 10V between 400V and 390V will be used to power the P-channel's gate drive circuit.)

Thanks!

 

[Orson Cart]

Power integrations Tiny switch can be set up as a buck converter (or flyback) to generate the 10V below the 400 you require, Regards, Orson Cart.

 

[FvM]

I agree with Orson, that any kind of DC/DC converters is an obvious and often used solution for the problem.

You have been quickly excluding bootstrap methods due to an unlimited duty cycle. For the gate driver problem, it's worth to think about providng the dynamic power demand by a boostrap circuit and the lower static current by a series resistor. A too large static supply current of the driver circuit can thwart this option of course.