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Let say I have non-inductive Load and it is rated as follow:

  • 0.2A @ 1V applied
  • 2A @ 5V applied

Which is powered by a DC battery and is rated as follow:

  • 5V output
  • 1A max current supply

I am going to divide the supply voltage by switching it with PWM, say 20% duty cycle and as a result we can simulate a 1V voltage is applying onto the Load. In this case, may I know how much current will the Load draw? As it is a non-inductive Load, does it mean that it would (tend to) draw 2A current for every high state in PWM (because high state is 5V)? However, the battery can provide only 1A at maximum, so it may not work properly.

OR... Should I just treat it as 1V applied and so that the current drawn by the Load should be only 0.2A?

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A simple solution might be to place a large capacitance capacitor between the battery and the switch, so that it provides the short current pulse under load.
I would start with at least 1000uF, low ESR type. It depends on your frequency or the time on vs. time off.

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  • \$\begingroup\$ So did you mean the Load would draw 2A in the above case? \$\endgroup\$
    – mannok
    Apr 15 '20 at 9:43
  • \$\begingroup\$ Yes, there is no going around it. But only during the time on. The AVERAGE current will be the maximum current times the duty cycle. The only other way is to provide a sufficient inductor to convert the higher voltage pulses into a lower voltage smooth current, but then you would need a diode and a capacitor at the output, basically making a buck converter. \$\endgroup\$ Apr 15 '20 at 9:48
  • \$\begingroup\$ How about if the Load is inductive? e.g. motor. Will the case be different? as inductive Load store some energy like what capacitor does. \$\endgroup\$
    – mannok
    Apr 15 '20 at 9:50
  • \$\begingroup\$ The current through an inductive load will depend on the frequency and the pulse width, and on the inductance value, of course. You would have to have more details and do some quick calculations. The Internet is full of examples, you just need to be specific enough and know what you want. \$\endgroup\$ Apr 15 '20 at 10:02

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