Can we connect Schottky diode between buck converter (20A, 25 to 12V) and Battery source device (12V)?

Thread Starter

caroline_01

Joined Aug 17, 2022
7
Hi, I am working on project making connection between buck converter and a IOT device which has small battery inside. The problem is the battery inside IOT device giving back current to the buck converter which stops working of buck converter. I need buck converter giving power to IOT device but also need to stop coming reverse current from IOT device to buck converter.
I found some solutions using reverse protection circuit between both. As I know various solutions like PN junction diode, Schottky diode, P-channel MOSFET and N-channel MOSFET. How to know which one is good fit to solve this problem?

And can Schottky diode (20V, 3A) solve this issue?
 

DickCappels

Joined Aug 21, 2008
9,078
If the IOT device can work ok with the small voltage drop of a Schottky diode, that should be fine. I have to admit that I would be more certain if I saw a sketch of your connections, but I can say that a Schottky diode is one of the classic ways of connecting an alternate power source. It is the world's simplest switch.
 

Thread Starter

caroline_01

Joined Aug 17, 2022
7
If the IOT device can work ok with the small voltage drop of a Schottky diode, that should be fine. I have to admit that I would be more certain if I saw a sketch of your connections, but I can say that a Schottky diode is one of the classic ways of connecting an alternate power source. It is the world's simplest switch.
I don't have the complete circuit diagram of buck connector and Iot device. Because I am using both as products. Here are the links: which devices I am using to make connection.
https://www.iridium.com/products/blue-sky-network-skylink-5100-iot/
https://www.ase-supply.com/Sure_Power_21020C10_DC_DC_Converter_p/sp-21020c10.htm
There is small battery inside IOT device which makes problem.
 

crutschow

Joined Mar 14, 2008
30,438
If current is being fed back to the converter from the battery, then the battery voltage is higher than the converter voltage, which means the battery will discharge before the converter can apply power to the device.
Normally the converter voltage is slightly larger than the battery voltage so this backfeed does not happen.

Where exactly would you put the diode?
 

Thread Starter

caroline_01

Joined Aug 17, 2022
7
If current is being fed back to the converter from the battery, then the battery voltage is higher than the converter voltage, which means the battery will discharge before the converter can apply power to the device.
Normally the converter voltage is slightly larger than the battery voltage so this backfeed does not happen.

Where exactly would you put the diode?
These are the two devices. Their links are below. I am using both as products, as I don't have complete circuit.
https://www.iridium.com/products/blue-sky-network-skylink-5100-iot/
https://www.ase-supply.com/Sure_Power_21020C10_DC_DC_Converter_p/sp-21020c10.htm
I am thinking to put the diode between both device. The positive side of diode connected to the output of the buck converter and the negative side to the input of the IOT device. So, The current can flow through the diode from buck converter to IOT and also stops coming from IOT to buck.
I don't know what exactly voltage of battery in IOT. But, It discharges for 5 minutes after power off.
In the practical field, When both were connected. It was found that Both were showing working for more than hours even the power was turn off. Then I found ohh there is battery inside IOT device.
Then after research on google, I found need to add protection circuit between both. So, I found Schottky diode solution.
I am not sure is it the right solution? If you ever have such kind of experience, any help would be appreciated.
 

Thread Starter

caroline_01

Joined Aug 17, 2022
7
The correct connection depends upon whether you want to charge the battery from the converter.
The converter gives 12v to IOT device. That's what I need. It works well when the power turns on. It creates problem when power is off. I don't know how small and how big is this battery and why it is inside or maybe there is capacitor which discharges.
If I connect diode between them, so the converter is doing their job. There is bit voltage drop which is fine. Atleast the IOT device is still getting between 11 to 11.7v, Enough for running. When power off, I am hoping this diode stop the reverse current (so, buck converter should not behave like boost).
I don't want to charge battery/capacitor, I think it is inside to make bright flash of led. They get charges when we give power to the device.
Maybe I am wrong but I am stuck here.
 

MrChips

Joined Oct 2, 2009
26,790
A picture is worth a thousand words.

Here is a classic automatic power switch over circuit. For low power applications (under 1A) you can use a Schottky diode such as 1N5817.

1660844631306.png
 
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