ESP32 Forum

Posted: **Sun Mar 03, 2019 5:59 pm**

ESP'ians!

I am developing a product and I'm planning use an Ext 5V power supply for the board. Now there will be situations where I'll need the external 5V power supply (to supply 5V to some other components as well) on the Vin port, as well as USB connected to a device (Laptop). I want to know whether it an Ext 5V power supply on Vin port + USB connection at the same time, is a safe configuration? If not, is there anything I can do to combine the two power sources safely?

Thanks a ton in advance!

Regards,
Deepak

Posted: **Mon Mar 04, 2019 7:05 am**

if you connect EXT 5V and USB VBUS directly, there will be current flowing between EXT 5V and USB, since the voltage levels of these two power supply may be different(e.g. EXT 5V is 5.1V, while USB VBUS is 4.8V). And this current may damage either EXT 5V or USB.
You can add a diode for each the power lines before connecting them together.
Also, you can cut off one power supply using a PMOS transistor when the other power supply plug in.

Posted: **Mon Mar 04, 2019 4:13 pm**

I was thinking of the same, but wanted to check if there's any inbuilt way of achieving this. I'll see what best I can do.

Thanks!
Regards,
Deepak

Posted: **Wed Mar 11, 2020 2:24 pm**

ESP'ians!

I am developing a product and I'm planning use an Ext 5V power supply for the board. Now there will be situations where I'll need the external 5V power supply (to supply 5V to some other components as well) on the Vin port, as well as USB connected to a device (Laptop). I want to know whether it an Ext 5V power supply on Vin port + USB connection at the same time, is a safe configuration? If not, is there anything I can do to combine the two power sources safely?

Hi, Re. above, yes you can cannot ext 5V whilst usb power active.
If you look at the schematic you will see a diode ( BAT760 ) which will block reverse currents!
Email me if you want a pic of the part of the schematic I refer too.

Posted: **Thu May 20, 2021 6:32 pm**

if you connect EXT 5V and USB VBUS directly, there will be current flowing between EXT 5V and USB, since the voltage levels of these two power supply may be different(e.g. EXT 5V is 5.1V, while USB VBUS is 4.8V). And this current may damage either EXT 5V or USB.
You can add a diode for each the power lines before connecting them together.
Also, you can cut off one power supply using a PMOS transistor when the other power supply plug in.

Hello, noob question here. What do you mean when you say

"You can add a diode for each the power lines before connecting them together."

I´m making a project using esp32, WS2812B led strip and 5v 5amp PS, i need the usb plugged-in sometimes and sometimes unplugged, should i place the Diode between the PS and the Vin pin, right? should i place it anywhere else?

Thanks a lot for your time!

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