Pondering a high-level system design question here, thinking out loud.
I am designing a product that needs to deliver 3~5 Watts of audio power to an 8/4 Ohm speaker load.
The product runs from 24 VDC, the audio source is from a 3.3 V MCU via DAC or PWM.
The MCU requires 300 mW at 3.3 V supply.
Cost / physical size are the main design drivers here.
Option #1 - Use a switch mode regulator to create a +5V supply capable of delivering ~ 1 amp, with a small linear regulator to get 3.3V for the MCU.
Use a class-D amplifier to drive the speaker.
This idea seems like it would be efficient, but expensive.
Advantages-
a) Lowest power dissipation heatsink-less design.
b) No big Electrolytic coupling caps required.
c) Energy efficiency.
Disadvantages-
a) High BOM cost.
Option #2 - Use a tiny 3.3V switching regulator for the MCU, run a linear audio amp from the +24V
This option seems cheapest but very inefficient, heat sink problems might negate the savings?
Advantages-
a) Lower BOM cost
b) Simplicity?
Disadvantages-
a) Custom heat sink- hard to realize with SMD parts.
b) Poor efficiency.
c) Big DC blocking cap for half-bridge amplifier configuration.
What would you do?
EDIT- this is a high volume product concept- think chip level solutions.
I am designing a product that needs to deliver 3~5 Watts of audio power to an 8/4 Ohm speaker load.
The product runs from 24 VDC, the audio source is from a 3.3 V MCU via DAC or PWM.
The MCU requires 300 mW at 3.3 V supply.
Cost / physical size are the main design drivers here.
Option #1 - Use a switch mode regulator to create a +5V supply capable of delivering ~ 1 amp, with a small linear regulator to get 3.3V for the MCU.
Use a class-D amplifier to drive the speaker.
This idea seems like it would be efficient, but expensive.
Advantages-
a) Lowest power dissipation heatsink-less design.
b) No big Electrolytic coupling caps required.
c) Energy efficiency.
Disadvantages-
a) High BOM cost.
Option #2 - Use a tiny 3.3V switching regulator for the MCU, run a linear audio amp from the +24V
This option seems cheapest but very inefficient, heat sink problems might negate the savings?
Advantages-
a) Lower BOM cost
b) Simplicity?
Disadvantages-
a) Custom heat sink- hard to realize with SMD parts.
b) Poor efficiency.
c) Big DC blocking cap for half-bridge amplifier configuration.
What would you do?
EDIT- this is a high volume product concept- think chip level solutions.
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