Is a charger the same as a power supply.

[bumpy]

I need a 5 volt power supply for one of my bits of kit.

When I search I see, on sale, power supplies and chargers that cover 5volts, but are they the same thing?

If I plug in a 5 volt charger surely it must have the ability to wack in enough voltage to charge a 5v battery so will this overload my device.

Thanks

[Pharos]

A power supply is defined as having the required voltage output and the necessary current capability for whatever device it was designed for.

A charger has a specific design need. It has to overcome the internal resistance of the device to be charged, and so generally has a greater output voltage than that of the device to be charged.

A charger with an output voltage of 12V is inadequate for charging a 12V car battery for this reason, and they usually have an output of up to around 17 to 20V to overcome the internal resistance of the battery.

So for your bit of kit, if it needs 5V, then a power supply of 5V with enough current capacity will suit.

[struth]

yeah, chargers produce more of a constant current profile while psu's are more of a constant voltage(up to required current)

[bumpy]

Thanks guys

Given that the USB port on a computer can be used both as a power supply and charger, what is happening there?

[Firebottle]

If using USB as a charger there is always an embedded charger in the connected device.

[bumpy]

If using USB as a charger there is always an embedded charger in the connected device.

That makes perfect sense. Its been concerning me for years :)

[struth]

yeah pc usb lines in general make very poor chargers.. usb2 only has max of 500ma and its not smart.. much less if its a bus usb.

[Pharos]

Many power supplies, typically so of wall warts, have a voltage higher than that specified and it is not critical, so the 'over voltage' can be used to charge or to power a device without any harm, especially when small currents are involved.