When using two 0 +V supplies to make a -V 0 +V supply, it can be done under the condition they are floating, so one can connect the +V of one to the 0 of the other.
This precludes using a transformer with a center tap secondary.
This asks for two independent secondaries with independent diodes and cap stuff.
A transformer with two independent secondaries, or two independent transformers.
I know this works, but I suspect there are drawbacks.
Are they dual secondary transformers dedicated to this application that limit unwanted interactions ?
Is using two transformers effectively removes unwanted interactions ? They usually have the primaries in parallel.
What are the drawbacks and appropriate solutions ?
This precludes using a transformer with a center tap secondary.
This asks for two independent secondaries with independent diodes and cap stuff.
A transformer with two independent secondaries, or two independent transformers.
I know this works, but I suspect there are drawbacks.
Are they dual secondary transformers dedicated to this application that limit unwanted interactions ?
Is using two transformers effectively removes unwanted interactions ? They usually have the primaries in parallel.
What are the drawbacks and appropriate solutions ?
So, why most audio equipments use positive and negative regulators ?
A doubt there is a reason of cost. Separate secondaries or center tap is the same cost. Diodes bridges are a marginal cost in the overall system.
I even thing, it is more effective to have twice the same stuff rather than two mirrored stuff. Less parts to source and stock, less development.
A doubt there is a reason of cost. Separate secondaries or center tap is the same cost. Diodes bridges are a marginal cost in the overall system.
I even thing, it is more effective to have twice the same stuff rather than two mirrored stuff. Less parts to source and stock, less development.
As long as complementary pnp and npn transistors are available , 4 more diodes take more space on the pcb.If the voltage is suitable for the Vin max of the regulator i preffer a single regulator with floating ground on low power circuits or circuits that don't need a high dc bias or a very low impedance ground.With the 78xx regulators you can go as high as 35v dc for most regulators except 7824 but there's a fine trick lifting the ground pin of 7805 allowing for a highet Vin/ground voltage than 35v if the output isn't prone to suffer a dead short.
Thus you only need one secondary and one regulator.
Thus you only need one secondary and one regulator.
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If the number of diodes is of concern, there is a way to do it with 4 diodes.
You need independent secondaries which are center tapped.
You cannot use a 4 diodes bridge, you need two diode pairs with common anode ( or common cathode ).
The transformer, uses the same amount of copper wires, it is organised a bit differently.
Here:
3 wires from a center tap secondary deal with a pair of diodes providing a unregulated voltage at a capacitor bank.
Independently, the same is repeated for the second unregulated voltage.
Here the extra cost is only at the transformer with six secondary terminals, instead of four.
Well, as said, it is a mystery why it is not usually done that way.
You need independent secondaries which are center tapped.
You cannot use a 4 diodes bridge, you need two diode pairs with common anode ( or common cathode ).
The transformer, uses the same amount of copper wires, it is organised a bit differently.
Here:
3 wires from a center tap secondary deal with a pair of diodes providing a unregulated voltage at a capacitor bank.
Independently, the same is repeated for the second unregulated voltage.
Here the extra cost is only at the transformer with six secondary terminals, instead of four.
Well, as said, it is a mystery why it is not usually done that way.
There are many things are done not in the very best way. People do something as they are used to do. There must be a strong reason for a person to think about "How we can do it in the best way?". So...
Could there be a drawback to make a dual rail supply with two identical supplies ?
Some hidden issue, some pitfall, I am not aware of.
Some hidden issue, some pitfall, I am not aware of.
You need an opposite diode in paralel with every powersupply to it works safe with any possible transient.
Yes, this is safe.
And this reminds me, the day I used a lab power supply to charge a car battery.
I was stupid enough to hook it reversed.
There was some smoke, when opened I saw this fried diode. It did not survive the battery current, but avoided more damage.
I replaced it, but this power supply does not work as good as before. Well, it is good enough as a battery charger.
And this reminds me, the day I used a lab power supply to charge a car battery.
I was stupid enough to hook it reversed.
There was some smoke, when opened I saw this fried diode. It did not survive the battery current, but avoided more damage.
I replaced it, but this power supply does not work as good as before. Well, it is good enough as a battery charger.
That's what I use. The only drawback I know is that you can't use grounded, centre-tapped transformer windings.