Very noob question, I know wattage is voltage x amperage, but does this mean the wattage of a power source will always be the same? For example, if you have a 120 watt solar panel which is 12 volts and 10 amps, and you use a converter to lower the output to 5 volts, does that mean the amperage is now 24 amps? I'm just messing around with charging a 5v 2a portable phone battery that I can use to run a Raspberry Pi off of.
Does changing the voltage of a power source change the amperage?
- Thread starter CBiard
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Roswell Bob
Solar Enthusiast
If you use a switcher you will see that type of response. A buck converter will get the voltage down to 5v for you. Because it is switching you will observe large spikes on the input side of the buck regulator that the panel will not know what to do with. The fix is a LC filter on the input side of buck regulator.
If I wasn't so lazy I would go simulate it for you and post pics.
If I wasn't so lazy I would go simulate it for you and post pics.
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Roswell Bob
Solar Enthusiast
A bit of useless trivia follows: A switching power supply acts like a negative resistance. For a steady output power as the input voltage rises the input current goes down.
Roswell Bob
Solar Enthusiast
Here is simulation. Notice the nasty input current waveform. A solar panel wouldn't be able to keep up with this. The solution is a large LC filter or LCLC filter on the input side. If you notice the sparks you get when you connect a mppt charger to a panel or battery array it is this LC filter that is charging. Input is 12v with Iavg=14A. Output is 5v with I=24A
Roswell Bob
Solar Enthusiast
Sorry - seems I didn't answer your question. The output load impedance will determine the power. In this case I used 0.21 ohm. There should be some agreement between input VxA and output VxA according to converter efficiency.
Thank you for your answer! I found this on amazon and ordered it, but I'm not sure what it is or if it's actually the right thing for my system. If I used this with a 100w 12v solar panel (I know that's over kill but as a hypothetical) that's about 8.3 amps. That converter is 3 amps, so what would happen to the other 5.3 amps? I assume the converter would give them off as heat or something.
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