Electrical – PIC Pin 3V to 12V Boost Circuit

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I need to voltage boost my battery voltage 3V to 12V DC to power cheap RF module transmitter. The boost voltage will last until I transmit 3 or 4 bytes of serial data. Roughly 5ms time.

I read this wonderful article by olin lathrop & trying to understand it.

I need 3V to boost upto 12V. 50mA current is more than enough.
Supply battery is CR123 3V Cell.

I have some questions…!

1) Where is the boosted output voltage calculation? How to calculate it?

2) What component values need to change in the attached diagram to get 12V/50mA?

schematic

simulate this circuit – Schematic created using CircuitLab

Best Answer

The schematics you see is a basic PWM controlled boost converter, with no feedback loop: this is extremely dangerous. The 12V at the output is not guaranteed.

The math behind how you calculate these values is fairly complex. See: https://en.wikipedia.org/wiki/Boost_converter or this paper by TI: http://www.ti.com/lit/an/slva372c/slva372c.pdf Where the switch is your PWM controlled transistor opening and closing at a very high frequency.

As a result, no one designs raw boost converters like that. You should use a dedicated boost converter IC. There are seriously TONS of them. Texas Instruments (again -- no I don't have anything to do with them...) has a fairly good selection of them.