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Negative Topologie Converter

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sanrodriguez

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Hi all,

I have a power supply that outputs +12V and -12V, both referenced to a ground.

Now I need to convert those voltages into +30V and -30V. Looking to the positive (+12V) voltage its relatively easy to me to find a boost converter and achieve the 30V, but I'm struggling to realize how to use buck/boost converter to achieve the -30V from -12V. Can you please suggest some components or suggest some topologies to do this.


Thanks.
 

You might be able to use the same circuit/module as the +12V line. If it's output is isolated (has a transformer) you can simply reverse the input connections and output connections.

We need to know the current requirements and if isolation is applicable to advise further.

Brian.
 
Hi netwixt, thanks for your answer.

I will not use transformer on the output (not isolation).
The current is about 50mA for +30V and 50mA for -30V.
 

There are chips available that can provide positive and negative boost voltages. Take a look at the ADP5071, which works with up to 15 V input. If you search for a bit more you may find a similar solution that is more economical. The problem is that the majority of boost chips operate from 1.5 - 5 V input, which will require down regulation from your 12 V line.
 

A capacitor-based voltage multiplier may suit, since your power needs are low.

Simple voltage doubler driven by clock pulses of negative polarity (-12V). Output is -21V. It may be possible to create a tripler by adding another stage or two.

neg -12V pulses drive simple doubler -21VDC 600 ohm load.png

- - - Updated - - -

Notice the load is referenced to 0V ground.
 
to convert -12 to -30 you can use the same boost topology as a +12 to +30V but need to use a P-fet and reference every thing to the 0v rail & -12 input

a 555 control ckt is particularly good as the o/p can be referenced to the pos rail (0v) thus driving the P-fet appropriately with its source connected to 0v.

Use a 2nd 555 to invert the gate drive to the P-fet, use level shifting from the -30 Vout to drive a 847 on pin 5 to (-12) to achieve regulation...
 
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