Did a search for current limiting diode:

https://drive.google.com/file/d/1b9hhXX6p7wCrqCKMelPDWgO6h-N3up6U/view?usp=drivesdk

and the first two results didn't seem to be what I was looking for though perhaps I didn't read the datasheet properly (couldn't find the datasheet for the second diode, amazing this stuff is still so obscure)...

According to wikipedia, current limiting diodes are a thing (couldn't find anything within all about circuits)... here's the screenshot:

https://drive.google.com/file/d/1OlpW143bLXy2YXHRrPcGBq4bX5Eg5Ipr/view?usp=drivesdk

I need a diode that will limit the current to 2 or 2.5 amps for charging my phone... Looking everywhere and the only thing I found was a buck converter on ebay that said it would have a maximum output of 2 amps but I don't need to change the voltage...

https://m.ebay.com/itm/Voltage-Regu...=15&_nkw=2A+current+regulator&_from=R40&rt=nc

Anybody know of a common diode I can find on ebay?

 

Welcome to AAC!
The main distributors (e.g. RS, Digikey, Mouser) have many CL diodes to choose from, but most have a low current limit, e.g. 50mA.
Any current-limiting action implies a change in voltage.

 

You could use a two transistor current limiter ( such as below).
The limit is approximately 0.7V/Rsense, so for 2A, Rsense = 0.7/2 = 0.35Ω.
The circuit will have a drop of around 2V when charging.
What is the input voltage?
Depending upon that, T1 is a power transistor and may need to be on a heatsink.
If you need a lower voltage drop there are circuits using a MOSFET that can reduce that.

 

Welcome to AAC!
The main distributors (e.g. RS, Digikey, Mouser) have many CL diodes to choose from, but most have a low current limit, e.g. 50mA.
Any current-limiting action implies a change in voltage.

Ah! So I wasn't confused, yea 50mA isn't enough... It's just at 5V, am I correct in assuming you need to limit the current to the smartphone even if it's at 5V? Seems like that's relevant since there are all of these wall chargers rated at 1 or 2 amps... Would my phone really be fried if I don't add a current limiter? Faster charging would be nice right?

 

You could use a two transistor current limiter ( such as below).
The limit is approximately 0.7V/Rsense, so for 2A, Rsense = 0.7/2 = 0.35Ω.
The circuit will have a drop of around 2V when charging.
What is the input voltage?
Depending upon that, T1 is a power transistor and may need to be on a heatsink.
If you need a lower voltage drop there are circuits using a MOSFET that can reduce that.
View attachment 157912

The source would be just over 5V so I wouldn't want that 2V drop... Would the MOSFET have less than .5V of a drop? Same question I asked Alec, if I don't use a current limiting diode would the phone get fried just connecting directly to the source? Seems bizarre that it would since the current is determined by the load (in this case the phone's battery)... Since I'm already just above 5V I guess I would need to use that buck converter because unless I can find a diode with around .5V drop then anything else will drop the source too far to charge the phone... am I correct?

 

Why do you think you need to limit the current?
Normally you just supply 5V and the phone will limit the current to what it needs.

 

Why do you think you need to limit the current?
Normally you just supply 5V and the phone will limit the current to what it needs.

The reason why I assumed I needed to limit the current is because the current is always limited by those wall USB chargers, otherwise those chargers would just bridge the AC and then reduce the voltage to 5V... Why are there some chargers that supply 1A and others that supply 2A?

 

Why do you think you need to limit the current?
Normally you just supply 5V and the phone will limit the current to what it needs.

Same with car cigarette chargers so I'm assuming the current limiting feature isn't just for protecting against surges off the grid... lol lots of assumptions

 

Why are there some chargers that supply 1A and others that supply 2A?

Cost.
1A chargers are cheaper to make than 2A chargers.
Otherwise there's no reason to buy a 1A charger instead of a 2A, since the load just takes the current it needs.
The current rating is the maximum that the load can safely take from the charger, not how much it will supply to any load.

 

The wall wart power supply that gives 5V to a phone is not a charger circuit, instead it is simply a 5V power supply for the charger circuit inside the phone. The charger circuit inside the phone limits the current.

 

Cost.
1A chargers are cheaper to make than 2A chargers.
Otherwise there's no reason to buy a 1A charger instead of a 2A, since the load just takes the current it needs.
The current rating is the maximum that the load can safely take from the charger, not how much it will supply to any load.

Thanks!

What do you mean by safely take from the charger? As in you can fry your electronics if you do it unsafely?

 

Thanks!

What do you mean by safely take from the charger? As in you can fry your electronics if you do it unsafely?

The power supply current rating is the maximum amount of current you can safely take from it since if your phone draws more than the power supply's maximum allowed current then the power supply will be overloaded and might catch on fire.

 

The power supply current rating is the maximum amount of current you can safely take from it since if your phone draws more than the power supply's maximum allowed current then the power supply will be overloaded and might catch on fire.

Thanks!