[Motorola Droid RAZR] Ohmster:
LOL! Dude, we don't "argue",

we have discussions

. :)

I don't believe that they pack an SMPS into a typical phone charger, image with scale attached. I have never opened one as they are not repairable, burn out the primary of the tiny transformer, and are then garbage. No screws to open, no parts to replace. I do not want to smash a good charger to find out if there is a tiny SMPS inside, but if it comes to it, I will find one that I do not use, break it open, and show you the inside. Who knows, maybe I'm wrong? :p

The few tiny wall chargers that I have cracked open in an attempt to fix them contain one tiny laminated core iron transformer, a bridge rectifier, and one or two electrolytic filter capacitors, that's it. They cannot be fixed because in almost all cases, the tiny primary winding of the transformer (Thickness of light sewing thread) burns out from a wall surge and cannot be fixed. The transformer is shot and it is very difficult to find a replacement transformer and glue it back together. Easier to pay $10 for a new one. :)

I have been working on SMPS power supplies all my life. I hated them when they came out. Diodes, filter capacitor, and a tapped laminated core transformer, piece of cake. Now circuits, feeback loops, miniature parts, and it has to be troubleshot like any other circuit. Break the feedback loop or lose a component in it, say a resistor or opto-coupler, and the whole thing goes up in smoke. The most common failure in these things is a very small electrolytic capacitor that "drys out" and it ESR or "equivalent series resistance" goes so high the power supply "thinks" it is underpowered and cranks up the voltage, or vice-versa, depending on the design. The powder core transformer is about the size of 4 bouillon cubes although I have seen "mini standby supplies" with smaller transformers.

Your math is flawed. We either use the input voltage times the input current to determine the power draw on the AC outlet, OR we use the output voltage times the output current to determine the power being generated and consumed by the device.

E=IR Ohm's Law

P=IE Power

That is 5 volts x .7 amps, NOT the input AC voltage of 110VAC!

5V x .7A = 3.58 Watts

, NOT 74 watts! Since a typical night light is a 7 watt bulb and does not get very warm, I seriously doubt that a miniature power supply would "melt plastic" at 3.5 watts. And that little powdered core transformer and the circuit components could not fit into a very small plastic box used for phone chargers. The small brick on monitors and laptops, yes, they use an SMPS all the time. Mini phone chargers do not. To complicated, too expensive, and too big.

You want to measure power consumption of the charger then use AC wall voltage of 110VAC and multiply it by the current consumed by the charger in AC milliwatts from the wall socket and change those milliwatts to a very small decimal figure of actual current drawn from the wall socket in amperes. E.G.: 100mA or .1A x 110V = 11W

(This is an estimated guess based on experience. I did not get out my DVM and calculator for this but I could. C'mon, give me a break. It is a little late to open up the workbench for this post. Wall current drawn from small chargers is in the milliamp range, not Amperes.)

Capice? I have been doing this for over 30 years my friend. Now, ...how does that go? ..."Doh!" ;)

But, feel free to research it and find a snappy comeback. :laugh:

Here are some good URLs to help you figure it out my friend.

Ohm's Law Calculator

Electric Power

BTW: I only explain things in the technical manor in which I know how. I attach neither hostility nor friendship in an explanation so no insult should be taken. If you prove me wrong, I will be the first to say "you're right, my bad". :cowboy: