This question arose from a conversation over the weekend and we tied ourselves in knots trying to get to the bottom of it. I didn’t have time to put a simple circuit together so it would be great to get some expert thoughts on this.
With a 12v supply attached we get the following readings: V1 - 12v A1 - 50mA V2 - 5v
(1) With SW1 open, assuming the buck convertor is 80% efficient, what is the expected value of A2?
(2) With SW1 closed, same question/assumptions.
(4) What is the correct way to talk about the difference between measurements at A1 and A2. Is it correct to say that the excess current (46mA) flows into the negative terminals of the buck converter?
Thanks in advance!
This is a simplified version of a real circuit that promoted some discussion. The original components were as follows:
- Buck converter module: https://www.amazon.co.uk/gp/product/B01MQGMOKI
- The module shorts the In- and Out- terminals internally (making SW1 irrelevant as folks have pointed out).
- Mini Ammeter (A1): https://www.amazon.co.uk/gp/product/B00PGOUX0W
- This module forced me to place the ammeter on the return side of the circuit since it effectively shorts the -ve power and test terminals.