Electronics > Beginners

Best way to step up a voltage?

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Sudo_apt-get_install_yum:
Hey all!

This is a simple question but I guess it’s got a lot of answers!

What is the best way to step up a voltage from 3.3v to 12v? The max current draw is only 7mA.
 
I was thinking of using a capacitive charge pump driven by a PWM pin on my micro but I’m not sure if it’s the best practice for low power applications.

Since the current draw is so small id want to avoid using a boost converter. There are some for low current applications but they cost ~5$.

Any suggestions or design tips would be awesome!

***EDIT***
They datasheet says VCC-MAX = 12.5V but later says that VCC-MAX is 15V, so I guess I could use a voltage doubler and get 13.2V and still be within specs.
The datasheet doesn’t specify max noise so I’m not really sure. The IC is a SSD1306.

stmdude:
How clean your want your 12V to be would be relevant

Sudo_apt-get_install_yum:
I’m not 100% sure but a few mV should be within tolerance I think. Not crazy amount like 100mV!

Ian.M:
If your MCU's PWM can be gated by an on-chip comparator, you can implement the control loop of a boost converter in hardware inside your MCU, only needing an external inductor, N-MOSFET, Schottky diode, smoothing cap and a potential divider for feedback.  The feedback disables the PWM on a cycle by cycle basis if the output voltage is over the threshold thus regulating it.

Set the on time so the inductor doesn't saturate starting fron zero flux and the off time slightly greater than the on time, to avoid flux walking during startup.   If you need more output current, you can run a software control loop to reduce the off time in proportion to the output voltage.

Excessive ripple is likely to cause display flicker so you'll probably need a LC filter or a capacitance multiplier after the point the feedback divider taps from.

pieroc91:
On a project i needed 12v from 7.2v, i just bought a kit based on a mt3608 that are less than $5 , tested to see how much stress could handle and overdrived an 12v motor from 3.3v, the motor suffered more than the booster, really happy on how easy to use it was

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