# Parallel circuit

What happens if i connect 2 or more similar 12 volt and 5 amperage electrical adapters in parallel to a single load to avoid power outage and continuous power supply.

Volt= 24 or 12 Amp = 5 or 10

So, if there is a substitute such as transfer switch then please suggest the component name and it be available economically.

## 2 Answers

You should never place two voltage sources in parallel. Their voltages are never exactly the same and that combined with a low output impedance gives a very high current from the higher to the lower voltage. The supplies will get very hot and most likely get damaged.

The way to solve this is to put a diode in series with each of them. Then the supply with the higher voltage will supply the power, the diode on the other supply prevents current from the first one from flowing in. Suppose PS1 is 12.5V and PS2 is 12V. Then the connected cathodes of the diodes are at 12.5V - 0.7V = 11.8V. So there's only 200mV across the diode of PS2, too little to let it conduct. If PS1 fails, the voltage drops to 11.3V at which PS2's diode begins conducting and PS2 begins supplying power.

This is never a good idea because they won't be at the same exact voltage; thus, they'll fight each other until one dies first. Some wall adapters are pretty bad. It says 12Vdc, but they'll output anywhere from 11.8V to around 12.4V. You can put a diode in series for one of them.

@echad Power transferred must match both side of the equation, P = P (assuming perfect condition). For example, you have a load that draws 1A. If you have one power supply, then that power supply must supply 1A at that voltage. If you have two, then the load is shared between the power supplies.