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Why does this boost converter circuit not work? Answered

I tried this circuit using a 3.7v supply and instead of a 12v Zener I used a 5v Zener. I also used a 22uH inductor. I get 5v no load but when I add a load the voltage drops a bit and the current is 50ma max. Why is this not working and what could I change to make it work? If this is the wrong circuit altogether, then what discrete circuit would work?
http://www.aaroncake.net/circuits/6-12conv.asp

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Josehf Murchison (author)2015-08-12

Well you should only get 5 volts with a 5 volt Zener and what is the 3.7 volt supply IE a NI battery what MAH?

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user

it's a 3.7v lithium ion battery 2800mah

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user

Battery is small for that booster, the booster draws 2 amps and you have less than 3 amp hours for that booster you need 8 to 10 amp hours battery or the power will just die when you load it. (8000 mah to 10000 mah)

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iceng (author)2015-08-12

The resistance values are all wrong for that low an input voltage.

And the inductor core may be wrong too .

Usually start to make a direct copy to verify you got it wired right and then experiment.

Brake the connect at R6 and see if that Q1, Q2 oscillator is a stable SQ wave as a start.

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Davis Lambert (author)iceng2015-08-12

what do you think the resistor values should be?

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iceng (author)Davis Lambert2015-08-12

Your reducing the voltage by 63%

Try 2.2K => 1.5K .... 4.7K => 3K and see if it oscillates.

BTW change that SQ wave to a narrow pulse wave because of values.

The inductance seems high.

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Davis Lambert (author)iceng2015-08-13

it is oscillating with the original resistor values and the circuit is boosting the voltage to 5v, but if I add a load, the voltage will drop because the current output is so low

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iceng (author)Davis Lambert2015-08-13

Surely you know you said that before.

Ever consider the lower R values may give you the power your wanting.

And the 0.5mm is .019" which is a 24 gauge magnet wire but not enough to calc the real inductance...

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