High Power Split Rail (375W, +175V, -175V)


New member
Hi all
I am looking for a controller or power converter topology that will allow me to convert 12V to +175V and -175V (Split rail) and will allow for a maximum of 375W to be delivered to the load, the load will be dynamic so the power delivered will vary between no load and full load, but I need the voltage to be constant. Can anyone please provide any directions on how to accomplish this or suggestions or ltspice simulations to work from.

Kind Regards



New member
Hello, are you looking to build this from the ground up? If so, any of the sg3525 or tl494/ka7500b automotive psu circuits all over the web will work, you will just have to the add extra windings to your secondaries and adjust for your required current. Or are you looking for more of an off the shelf solution.


New member
There are lots of supplies out there but finding one that will run off of 12volts with split 175v rails might be a toughie. Might be easier to find two isolated 175v supplies and tie them together or even two 85v split rail supplies and tying the two 85 for 170 and then the two of those together for 170 +/-. But if you wanted to make it yourself I could put a few things together, see how difficult it would be. Making 350 volts rms is not especially difficult or expensive but the diodes will need be quite high voltage. Let me have a look, and I’ll post my thoughts. Does it need to be regulated?


Well-known member
As Easyamp said it is a bit tough and quite challenging for 12v input and such a high output voltage. It would be best to divide it in two supplies, thus the load will be split. If it was all in one piece then the input current may reach 40 amps or so considering a bit of losses.

Your maximum output voltage will need to be around 200-220v each to compensate for voltage drop in inductors and load it self so it can be regulated at the wanted output voltage.

Regulation at that high voltage is also a bit of a problem and has to be tailored carefully.

surge current when charging secondary caps will stress you switching transistors at start up and a good soft start has to compensate for this.

If you are dividing the supply in two smps then a couple of ETD 39 will be sufficient for you working at around 30kHz or so. These are a bit larger than needed so that the windings will sit more comfortably due to the thick wire or copper sheet in the primary winding You can also use toroidial cores instead.

Please tell us the duty cycle of this smps so that we can evaluate a bit more on the average power it needs to deliver
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