Any ideas for DC power supplly ORing and power source reverse polarity protection

[osvaldor]

Hi all,

For a current project of mine, I have to switch between two voltage sources (wall power supply or battery pack). When an external power source is present it should be used to power the device (with higher than the battery priority). There can be one case, where the wall adapter voltage is 9V and the battery voltage is 12V, but also vice versa. My goal is a device powered from as many power sources as possible (laptop power adapters, etc., for the external power, and different battery power pack configurations). It will be good if there is some protection against connecting the external power source (or the battery) with reverse to the device circuity polarity.
The wall adapter or the battery should power a step-up regulator, where the peak power consumption of the device is around 2W (not all the time, usually the consumption should be less than 1W).

First I tough about using a bridge rectifier on both power source terminals (that would give to my device a protection against reverse polarity, and if it is present a protection to the other power source as well). Unfortunately there is voltage drop across th? diode bridge rectifiers, which I want to avoid for the cases, when the device is running only on battery. Of course I could use Schottky diodes for the diode bridge rectifier, but in that case there is still some voltage drop and there will be small current leakage as well. Also with that simple implementation I cannot guarantee, that with higher priority will be used the external power source and not the battery power pack (attached on the battery terminals).

Please, can anyone suggest a solution, that can cover my requirements.

Thanks in advance for your ideas and thoughts on that problem!

 

[Electro nS]

to solve the problem of reverse polarity , i think you are best to use a bridge diode (schottkey) or simply one diode in series but you said that will not work in your case , so my solution is to use a mosfet to switch you power source and use the internal body diode as protection
check this link out :https://myelectrons.com/mosfet-reversed-protection/

and regarding the switching between power sources why not use a microcontroller ? is this possible , you will have so many options and nice things to introduce to your circuit . if this is not possible , use something like the ones used in Arduino to switch between USB and DC external power , a circuit with very few components try googling and if no luck , tell me .

hope that helps
regards

 

[chuckey]

A standard way is to wire a relay with a diode in series with it across the input power terminals of your device. When the power is of the correct polarity the relay pulls in and passes the power to the device.
Frank