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I need a cheeap solution for 900-1000V to 12V buck converter. Output power is 1W. Is there any monolithic power ic for this? If not what do you suggest ?
I don't recall seeing any ICs past 600-700V (you
can look at Power Integrations, IXYS, etc.). My off
the cuff suggestion is for a push-pull scheme where
transformer can do the down conversion, and some
power switch like IGBT (low freq high current) or SiC
(see 1600V power devices now, push-pull uses low
side FETs only on the primary which is good since SiC
gate voltage requirements are unhelpful and flying
high side drivers, few).
- - - Updated - - -
There are some outfits that do HV modules but I only
recall seeing them go the other way (5-12V to kV).
Still maybe Pico has something for you.
Cheap, and kV, however do not usually go together.
Actual maxiumum voltage is around 800VDC. I found ST viper16 buck converter but it has 800V mosfet. Also found FSL4110LR flyback controller with 1000V mosfet but with reflected voltage and spikes in flyback voltage can go above 1000V i guess. It's look i have to use external mosfet. For buck converter duty cycle will be too low do you know any buck controller can work with these conditions? Or i have to use multi stage converter?
I can first divide dc voltage by two with two series cap(also 2 series resistor for be sure voltage is divided equally) then use 600-800V integrated mosfet buck controller to make 12V(such as st viper06). Then put ldo to make 5V from 12V.
You better model the voltage divider you are planning. I think you will find your balancing resistors will waste as much power as a dropping resistor and a zener.
Push pull requires switches 2x the bus voltage + margin.
Buck requires a 12v/1000v duty cycle as Mr Kluas reports - not likely.
I've used Sanyo 1500v parts on 1000v flyback supplies. They consistantly failed well over 1500v on the bus Not sure if those fets are still available.
I have also used 2 800v fets in series. That is rather tricky. Power Integrations may have a patent on this design and may be able to provide an app note on it.
Look at flyback or forward converter while paying attention to the reset voltages.
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