[SOLVED] What is the maximum current we can obtain from a 5V DC supply..??

[ramshkrish]

Hi guys:-D i got my 5V 700mA modem adapter repaired and went to purchase a new one with same current rating.. But the vendor gave me an adapter of 1200mA instead of 700 mA and said its better than 700mA.. But to my surprise it worked fine.. So, now i am confused what my actual modem rating will be..:?::?:

---------- Post added at 20:33 ---------- Previous post was at 20:31 ----------

If higher current rating works then what is the use of manufacturing those 700mA adapters..

 

[Sckoarn]

ramshkrish,
The 700 mA version is less costly to make because it probably uses a smaller transformer. Other components may be cheeper as well because of the lower current rating. The 1200 mA adapter works because the modem will only take what it needs. As long as the voltage output is the same, the current rating can be higher than required. I would bet that the 700 mA adapter is over rated for the modem by at least 200mA. That is good design.

Sckoarn

 

[ramshkrish]

Thanks for the reply... Ok what if i give an current rating of 2000mA. Wont the circuit get damaged..?????

 

[Sckoarn]

ramshkrish,
The modem should only "take" the power it needs, providing a power supply that is "able" to supply more, should never hurt anything. The rating of the supply is to let you know what it's maximum power output "can" be.

Sckoarn

 

[alexan_e]

You can't "GIVE" current to a circuit, you can only apply a voltage to it and the circuit will get the amount of current it needs as long as your power supply is able to provide it.
So for a device with a rating of 5v/0.5A you need a power supply that can provide at least 0.5A,
even if it the power supply is a 5v/5A when you connect the load with a rating of 5v/0.5A it will still draw only 0.5A.
The circuit will only draw more current if a wrong voltage is applied that is above the actual device rating and
even in that case it depends on the device kind, if it has any internal regulation or protection etc.

You can't force more current into device unless you provide more voltage to it (above rated voltage for the device) and this is something that you should avoid.

Alex

 

[KJ6EAD]

Ramshkrish, if the power supply were responsible for the amount of current drawn as you previously thought, we would all have to change the power supply in our P.C. each time we plugged in a USB device.

 

[ramshkrish]

Thank you so much guys... Problem solved...