Why do we need a chain of resistors to increase the voltage? [closed]

I did a workshop on SMT today and we made this board attached. However, what I don’t understand completely is the logic: why do we need 3 resistors to increase the voltage (on the boost part)? What do they do exactly?

closed as unclear what you're asking by Edgar Brown, Andy aka, Elliot Alderson, laptop2d, FinbarrJan 1 at 11:40

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• no part number, schematic , shall we guess? From recreation use? – Sunnyskyguy EE75 Dec 30 '18 at 4:46
• why did you not ask the instructor? – jsotola Dec 30 '18 at 5:31
• @DwayneReid this I don’t have. – Dmitry Paranyushkin Dec 30 '18 at 10:08
• @jsotola I did and he explained but I still didn’t get why this particular choice of elements – Dmitry Paranyushkin Dec 30 '18 at 10:08

It's an SMT practice board. ALL of the resistors are 10k, probably because whoever's running the course didn't want to have to stock different values. Therefore, to get a value of 30k, they put three in series.

Sometimes, multiple SMT resistors are put in series for high-voltage circuits because their individual voltage ratings are insufficient. But that isn't an issue in a circuit that outputs 5.5V at most.

BTW, before you reflow the board, you should flip over the resistors that are showing the white side up. It makes no difference functionally, but it makes it easier to inspect the board afterward.

I guess you are on about R4,5,6 on the boost converter ?? if so I would think this is a fed back circuit to make sure the output voltage is always correct.

it hard to say for sure as the as the chip is missing. if you can get the part numbers for the chip you can then google it and find the circuit diagram/manual which will tell you what they are for.

good luck!

• Super thank you! But the question is how exactly do resistors ensure that the output is correct and how is this feedback loop established? Maybe if it’s too long to explain you have a link where I can find it? Thanks! – Dmitry Paranyushkin Dec 30 '18 at 10:10
• no worries, sure I love youtube so I would recommend looking at this vid youtube.com/watch?v=nQFpVKSxGQM otherwise you could google "boost converter feedback circuit explained" and it should come up with some PDF explaining the internal logic of the converter. – Ben Dec 30 '18 at 10:28
• "But the question is how exactly do resistors ensure that the output is correct ..." That's not at all what you asked. If that's what you meant then hit the edit link under your question ... – Transistor Dec 30 '18 at 14:22