I need to deliver 5V, 1A (5W) of power to a load that's 5+ meters away from the power source, however I'm keen to use small-ish wires and connectors, which I know will result in volt drops through the power lines with that much current.

I thought about increasing the supply voltage (to say, 24V) with a linear regulator stepping the voltage back down to 5V, but what I can't seem to find out is if the current flowing through my power lines gets reduced reduced down to 200mA (ish) @ 24V to match the 5W of load (Accepting there will be some efficency losses)....or if the current flowing through the power lines would still be 1A. Seems like this should be a easy question but I can't find a easy answer!

If this is true (And the current flowing in the power lines gets decreased) then I assume I can just increase the supply voltage to a point where the regulator current (Vin - Vout) * ILoad (?) is within limits of the device/package?


1 Answer 1


If you use a switching regulator to step down the voltage at the load, the input current will be less than the output current, but this is not true of linear regulators. Linear regulators will pull the same current from their input that they provide to the output, simply "burning off" the excess voltage in the regulator itself, causing the regulator to heat up with all the wasted power. A switching converter, instead, pulls more than the load current at some times to charge up its output capacitor, and pulls (ideally) no current the rest of the time, with the output capacitor supplying the load during these periods.

Given your situation, you may want to add some sort of input filter for your converter as well, beyond just the standard input capacitor.

  • \$\begingroup\$ Thanks. While this isn't necessary the answer I was hoping for it makes sense. I was trying to avoid switching power supplies as I've actually got multiple instances of this and I'm concerned about the potential radiated EMC emissions from so many switch mode supplies all running at the same time. I assume your recommendation for input filtering is to smooth the output of a switch mode supply? \$\endgroup\$ Jul 4, 2022 at 23:10
  • 1
    \$\begingroup\$ No, the input filtering is to minimize the current noise on the line. Smoothing the output is the job of output filtering. If you're concerned about emissions, you definitely need input filters. \$\endgroup\$
    – Hearth
    Jul 4, 2022 at 23:13

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