Hi,
I want to build a bluetooth audio system with an ESP32 + DAC + Class D amplifier. This is the first draft of the project and I would like to discuss it with you before starting real tests, in order to optimize the schematics.
What I would like to discuss in particular is the power supply. The entire assembly will be powered from a 12V voltage source, obviously an SMPS. This voltage goes directly into the power amplifier. Then, the ESP32 module and the DAC must also be powered from the main 12V. And here's the interesting part. I started the power supply chain through a bidirectional LC filter, which must filter in particular the ripple generated by the 5V DC converter on the input, so that it doesn't go into the amplifier. On the converter side, I added dumping with an RC snubber for stability, and on the amplifier side, the dumping is introduced by the amplifier's filter capacitors that have an ESR of 2 x 260mR. The converter drops the voltage from 12V to 4.5V. Then comes another LC filter cell similar to the one on the input, with dumping included. This attenuates by 48 dB at 400kHz (the coverter frequency). From here, it goes into an LDO that powers the ESP32 with 3.3V... And it also goes to the DAC, through an RC filter (since we have low consumption), which increases the attenuation to 83dB, and through a 3.3V LDO that further increases the attenuation to 123 dB ! This is my first attempt at designing LC filters and DC converters, so I need to check it with someone who really knows about this...
What do yoy think ? Is this enough to have a quiet amplifier, without switching interference in the audio band ?
I want to build a bluetooth audio system with an ESP32 + DAC + Class D amplifier. This is the first draft of the project and I would like to discuss it with you before starting real tests, in order to optimize the schematics.
What I would like to discuss in particular is the power supply. The entire assembly will be powered from a 12V voltage source, obviously an SMPS. This voltage goes directly into the power amplifier. Then, the ESP32 module and the DAC must also be powered from the main 12V. And here's the interesting part. I started the power supply chain through a bidirectional LC filter, which must filter in particular the ripple generated by the 5V DC converter on the input, so that it doesn't go into the amplifier. On the converter side, I added dumping with an RC snubber for stability, and on the amplifier side, the dumping is introduced by the amplifier's filter capacitors that have an ESR of 2 x 260mR. The converter drops the voltage from 12V to 4.5V. Then comes another LC filter cell similar to the one on the input, with dumping included. This attenuates by 48 dB at 400kHz (the coverter frequency). From here, it goes into an LDO that powers the ESP32 with 3.3V... And it also goes to the DAC, through an RC filter (since we have low consumption), which increases the attenuation to 83dB, and through a 3.3V LDO that further increases the attenuation to 123 dB ! This is my first attempt at designing LC filters and DC converters, so I need to check it with someone who really knows about this...
What do yoy think ? Is this enough to have a quiet amplifier, without switching interference in the audio band ?
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