[SOLVED] Split 2 Difference Voltage

[Help]

Dear All,



Can we share 2 difference voltage source to Load with added a Inductor or Resistor in between 2 source?

The intention of connecting the Inductor/Resistor in between 2 source is either source will supply the voltage to Load A or Load B when either Regulator no output. Is it practical in this design?

I have experience, if Regulator-A supply the voltage without a Inductor/Resistor in series and no output supply from Regulator-B then the Regulator-B will get overheat.

Thank you.

 

[goldsmith]

2source.jpg

Can we share 2 difference voltage source to Load with added a Inductor or Resistor in between 2 source?

Hi Help !!
I saw your diagram . before anything a question why you are attempting to use an inductor or perhaps a resistor between those supplies ?
And your answer is simply no you can't because 4.5 vol PSU will be considered as a load for 5 volt PSU so you'll see just dissipation an perhaps destruction !
I have a better idea . what if you tell what do you want to do exactly so i help lead you through the better way ?

Best Wishes
Goldsmith

 

[kam1787]

a diode in series between Va and La and another between Vb and Lb

 

[shatruddha]

with proper placement of diodes it should work, basically thats what is done in UPS and other power backup systems

 

[Venkadesh_M]

yeah a diode in output of each source will do this (without feeding into any sources)......

 

[Help]

Hello Goldsmith, kam1787, shatruddha and Venkadesh_M,

Thanks for you all reply.

Actually i have few board which is build in regulator but some of the board without power regulator. So, i would like to common up all the Vcc. That's why i'm thinking of using inductor or resistor as bridge to join supply. Ya, i was thinking to place the diode or Schottky diode but the voltage will drop around 0.2~0.7 Volt and will generate the heat when current goes up.

Any advice?

Thanks for sharing...

 

[kripacharya]

I think the diode-at-output-of-supply is the simplist and best option. Schottky power diodes should be used. If the diode can be inserted inside the voltage control loop, then you will see so diode voltage loss at the output.

With this method, only the higher voltage supply will provide all the power to all your boards. In your case the 5v supply. Only when the 5v supply fails/ falls below 4v, will the 4.5v supply takeover.

Without the diodes you would need to switch on/ off a supply based on monitoring the rail voltage. Thats a tricky business at best.

In case you were thinking of using these supplies in parallel to simultaneously provide power, then a more complex scheme is required which balances the voltage from both supplies.

In all cases, any actual transition or switchover could cause a glitch in the power rail which might affect your boards functioning. So plenty of caps are advised.

 

[kam1787]

.....transition or switchover could cause a glitch in the power rail which might affect your boards functioning. So plenty of caps are advised.

I would think that a single [large] cap on the board side of the circuit would suffice.

 

[kripacharya]

I would think that a single [large] cap on the board side of the circuit would suffice.

LoL !! yeah i guess. What i meant was for plenty of uF worth of caps.

 

[Help]

Ya, thanks all of you. I think that's the only where we can do. I will use the diode. ;-)

 

[Jibby Benjamen]

As long as both sources are at same output voltage use simply 2 diodes of appropriate rating in series with the anodes for each and then connect the common cathode to the load.

 

[kripacharya]

As long as both sources are at same output voltage use simply 2 diodes of appropriate rating in series with the anodes for each and then connect the common cathode to the load.

I don't think the outputs have to be the same voltage. However if they are different, then the higher supply will carry the load, thats all. On failure, the lower voltage source will takeover.