multiple 220V to 5v, 2A ac to dc adapters connected to the same input terminals of input voltage 220v
is it safe to join output in series to replace 10v /15v/25v adapters etc. ?
edit : and in parallel to get 5v, 4amps out of identical (5v , 2amp max ) adapters?
I've hooked 2 12V industrial units in series to replace a 24V after a burnout, worked fine for a few days until a 24 was delivered, just test carefully and thoroughly before hooking up anything valuable.
Hi,
Yes, this works.. I have also used two 12V adapters connected to supply + and - 12V for analog circuits.
If you connect separate supplies in series you should ideally have a reverse diode across each supply output to
prevent back-driving on overload.
MarkT:
If you connect separate supplies in series you should ideally have a reverse diode across each supply output to
prevent back-driving on overload.
Could you explain exactly how that occurs
MarkT:
If you connect separate supplies in series you should ideally have a reverse diode across each supply output to
prevent back-driving on overload.
whats is meant by "back-driving"?
ive got a bunch of 5v , 2amp adapters
could they be stacked in parallel to get 5v, 4amps out of identical (same model) (5v , 2amp max ) adapters?
if the adapters are ac output voltage only they need to be connected in phase with one another or you will not get the addition voltage easiest seen with an oscilloscope or in parallel to get more current i.e. two 10vac in phase = 20vac but out of phase = 0vac as they oppose each other
jackrae:
Could you explain exactly how that occurs
The load fails (short circuit or over-current), one of the supplies gives up before the other, then
one supply back-drives the other. Same thing happens with cells in a battery, or cells in a PV-panel.
Generally a bad idea - its not necessarily a condition the supply is protected against.
If you just need 10V supply, do not buy 2 5V supplies. If you need +/-5V, then its normally OK
to stack two 5V supplies because fault currents flow to ground (ie 0V), not directly from +5V to -5V.
Connecting voltage supplies in parallel however is not going to work like you think, can even blow
everything up. Never attempt it without isolating diodes.
Since I don't have access to the internal control circuits, the only way to share and add the output currents is with what is called "droop sharing". Basically, a small resistance in series with each output gives the inevitable small voltage differences somewhere to go. This decreases the available output voltage by Ohm's Law, but that is the cost of bending single-output designs into a shared output environment. I also can use a diode (one per adapter) as the droop device, basically diode-ORing them together into the load. With ideal diodes, the adapter with the highest output (even by a few millivolts) will supply 100% of the load until its output sags down to the level of the next highest output. then that adapter's diode will conduct, and the two will share the load current until their outputs sag down to the level of the third-highest output. then that one joins the party, etc. Of course with real-world diodes the transitions are much softer, but that's the overall idea.
SumitAich:
Since I don't have access to the internal control circuits, the only way to share and add the output currents is with what is called "droop sharing". Basically, a small resistance in series with each output gives the inevitable small voltage differences somewhere to go. This decreases the available output voltage by Ohm's Law, but that is the cost of bending single-output designs into a shared output environment. I also can use a diode (one per adapter) as the droop device, basically diode-ORing them together into the load. With ideal diodes, the adapter with the highest output (even by a few millivolts) will supply 100% of the load until its output sags down to the level of the next highest output. then that adapter's diode will conduct, and the two will share the load current until their outputs sag down to the level of the third-highest output. then that one joins the party, etc. Of course with real-world diodes the transitions are much softer, but that's the overall idea.
That could work if the power supply units are closely matched so they share the load more-or-less equally.
Even if you have two identical power supply units you need to consider what happens when one is powered-up and the other is not. Use of diodes would prevent the power from one power supply being applied to the output of the power supply unit that is not switched on. However, the power supply that is switched on may be overloaded.
I would consider powering part of the circuit from one power supply unit and the other part of the circuit from the other power supply unit. You would still need to consider carefully the interface between the two circuits when one power supply is on and the other is not.
Adopters can be parallel or series connected. A chain will be weaker than the weakest link; so power rating. It is very important to check an adopter's output electrolytic capacitor voltage and PIV of diodes used.
kesirajus:
Adopters can be parallel or series connected. A chain will be weaker than the weakest link; so power rating. It is very important to check an adopter's output electrolytic capacitor voltage and PIV of diodes used.
what is meant by an adapter's output electrolytic capacitor voltage
kesirajus:
Adopters can be parallel or series connected. A chain will be weaker than the weakest link; so power rating. It is very important to check an adopter's output electrolytic capacitor voltage and PIV of diodes used.
Ignore this rather bogus advice. Its all covered above.