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Optimization part 1

A project log for NE555 buck converter

NE555-spiced buck converter

VedranVedran 01/08/2022 at 20:340 Comments

The circuit kinda works, but it leaves a lot to be desired. There's 3 areas that I'd like to improve:

Baseline; Output (channel 1, top) trying to keep up with 5.1V reference as the input (channel2, bottom) increases from 6.5V to ~12V

Capacitances

I think the part where I can improve the most is tweaking input/output capacitances. So I grabbed all of my capacitors and started playing around.

Currently, my physical circuit features only one 10uF input capacitor and one output 33uF capacitor. So I set input voltage to 13V (well in the region where ripple is high) and started testing different capacitors. Trial an error (table below) gave 47u as the best available option.

Input ripple (VinPP)
Output ripple (VoutPP)Input capacitance (Cin)
3.4V1.4V10u
1.5V0.9V22u
1.7V0.9V33u
1.4V0.9V47u
1.8V0.9V100u

Or graphically

Noise on the output (channel 1, top) as the input voltage (channel 2, bottom) changes from 6.5V to 12V

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