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ericfont/circuit-20260629-1134.svg

Created June 29, 2026 15:32
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PWM dsm try again, with higher 500kHz sampler
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@ericfont

ericfont commented Jun 29, 2026

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sim

image

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ericfont commented Jun 29, 2026

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Transfer function for feedback, from Leech textbook chapter on "Class D Amplifier":

image

where k = (output PWM peak) / (triangle peak)

In above example, k=1 and fo ~= 160 kHz.

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ericfont commented Jun 29, 2026

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attempt with fo ~= 20kHz (using Cf = 750pF) somehow results in more noise:

image

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ericfont commented Jun 29, 2026

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if use Cf=200pF, then fo ~= 60 kHz:

image

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ericfont commented Jun 29, 2026 •
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if use Cf=10pF, then fo ~= 1.6 MHz

image

Although this is very clean, it isn't really producing a PWM but rather is more just like plain DSM.

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ericfont commented Jun 29, 2026 •
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if use Cf=300pf, then fo = 50kHz

image

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ericfont commented Jun 29, 2026

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Cf=100pF, fo=160kHz, sampling 200kHz

image circuit-20260629-1332

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ericfont commented Jun 29, 2026

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Cf=160pF, fo=100kHz

circuit-20260629-1334 image

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ericfont commented Jun 29, 2026

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no input test

circuit-20260629-1359 image

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ericfont commented Jun 29, 2026

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peaks are every 25kHz:

image

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