Hi,
I am using a buck converter to obtain a negative voltage, but I have not been successful. I saw a video on YouTube in which the input terminals were interchanged (+ and -), but even after trying that, it still did not work.
Hi Hasham
Most buck converters of the cheaper kind have a common negative or ground. In this case you will not be able to connect the output for a negative voltage.
You will have to find a converter with an isolated negative connection.
Would be an advantage if you quoted the type of converter you are trying to use. Mind reading is not a favourite past time
Cheers Bob
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Hi Bob,
Thanks for your reply. I am using
Yes, you are right checked it has common negative (-In) and ground (-Out).
Two questions
- What sort of load do you need ? e.g. how many amps at what voltage.
- Is the circuit you want to power isolated from everything else… e.g. no common ground needed?
In theory voltages are relative, but how well simple things will work will need to be checked.
e.g. If you take a 0 - 24 Volt and put thew a voltage divider then use the mid point as ground (for the output side), the +24 v now looks like +12V and the ground now looks like -12V… But voltage dividers tend not to be ideal.
e.g. If the Resistor values chosen are two low, you will just be sinking power to ground and wasting it… If the values are too high you may not get enough power to power what you need…
BUT: the real catch is the circuits you connect, are like adding resistance in parallel, thus changing the the “resistance” thus change the voltages.
In some simple circuits it can work, but more compex, not ideal.
The other big catch with this, if your target circuit also connects to something, eg RS232, then the common ground will be connection to 0V on yours which will look like 12V on the other device… not good.
I think I have seen the above referenced as a virtual ground..
On the other hand, Im sure some ready made chips might do it for you… e.g. from a quick google
But you will need to ensure what ever you get meets your needs. I cant recommend an actual product, so this is just an example
Hi Michael
There are lots of supplies where you input a voltage source and get an output of + v, -v and ground in various forms.
Hasham is delightfully vague when it comes to actual requirements, that is entirely non existent.
If hey thinks to provide some information along his requirements he might just get some results
There are several ways to “roll your own” including a “virtual ground” often used in single supply audio applications. As you say the 2 equal value resistor solution can work for µA currents but a few µF is usually required across each resistor. If a few more mA is requires an op amp configured as a unity gain voltage follower can be used to supply the extra ground current. Still limited by the opAmp current limitations but does provide a low impedance ground point which is the better method.
As you go up in current requirements it gets to the use of isolated buck converters, dedicated devices that supply +/- outputs from a single source or a dedicated +/- power source. This could be a transformer with 2 secondary windings with each winding having its own rectifier bridge with electro capacitor which in effect providing 2 power supplies which can be connected in series with the centre being ground and a +/- supply either side.
But with the present state of zero information regarding requirements the expected query result I think could only be nothing. I suppose some clairvoyance might help but I am not in that business.
Cheers Bob
