# Nokia charger...

Discussion in 'General Electronics Chat' started by donskiter, Nov 27, 2006.

1. ### donskiter Thread Starter Member

Nov 17, 2006
29
0
- I know and i really have good understanding about the input ac source, frequency and output voltage..But i dont understand Wheres the 100mA & max 750mA come up? Can u give me some idea & mathematical explanation to come up for 100mA & 750mA.. thanks
- How can i compute the power rating of these charger??

INPUT AC. 120~240
50-60 hz
100mA
Output DC. 4.8-12
max 750mA

Nov 1, 2006
133
0
Hi Don. While I don't know exactly what's inside your [phone?] charger, I think I can answer your questions. First, the 750 ma. max. output current is probably the maximum withstand current of the internal components like the transformer, diodes, voltage regulator [if used], etc. Second, presumably with the output loaded to max., Nokia techs measured the input current & apparently found it to be 100 ma. or less on several chargers.

One thing that puzzles me about the specs, though, is that the applied voltage whereby 100 ma. was observed isn't shown. If the charger operates on a range of 120-240 VAC then I'd expect the 100 ma. to be at 240 V. If the input voltage is selectable then the max. current should be at 120 V. The specs should indicate the operating voltage where the 100 ma. was measured.

To calculae the output power simply multiply the max. output voltage by the max. output current [amps, not ma.]. In this case the power's 9 W. [Input power can't be figured with certainty since the applied voltage where 100 ma. was measured isn't given.] Long answer for simple questions!

Dave

Jan 10, 2006
613
0
Obviously a switchmode plugpack charger (common on Nokia chargers over here anyway).
The output voltage is monitored to vary the operation of the primary circuit providing a constant voltage out, and allowing a wide input voltage...(120 - 240 vac).
Most Switch Mode Power supplies are around 80 - 85% efficient, so if the input wattage is 12 W (100mA 120V) then one would expect output wattage around 9.5 - 10 W.
In this case it works out at 9 watts (750mA 12V).

NB, in the case of 240 v operation, you would most likely find the input current would be further reduced to somewhere around 50 - 60 mA

4. ### donskiter Thread Starter Member

Nov 17, 2006
29
0
Thanks guys...now i understand...

5. ### engr_mariano New Member

Feb 14, 2007
2
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hi guys,can someone send me a schematic diagram of a nokia charger. tanx alot in advance!!!

6. ### Distort10n Active Member

Dec 25, 2006
429
1
I would imagine you could find plenty of phone charge schematics on Google or USENET. I doubt you will find one for a specific Nokia charger. It is like asking for schematics for a cell phone jammer.

Good luck with that.

Jan 10, 2006
613
0
They're not worth repairing if thats what you want to do....

8. ### Electroluxx New Member

Feb 6, 2011
2
0
=============================================

The 100mA refers to the max current the things will draw from the mains at 120-240ac. Presumably at 120vac as this is the lowest input voltage.

The 750ma refers to the maximum current the thing will allow you to draw from it on the DC output side and be 'ok'. So in theory this little baby can deliver up to 12Vdc at 750mA.

Ootherwise known as 8 Watts. On the mains side meanwhile, current drain is not expected to exceed 100mA.

Hope that helps Mr Old THread from a newbie - Electroluxx.

9. ### marshallf3 Well-Known Member

Jul 26, 2010
2,358
201
Darn things are like \$3 shipped from eBay.

The 750 mA refers to the max it can put out into an almost dead battery. Pretty hefty charger but it won't be regulated.

10. ### debe Well-Known Member

Sep 21, 2010
929
178
Just for the curious pic of a typical plug pack. They are definitly not worth reparing as the 8pin PWM chip costs more than a new plug pack.

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