Meanwell Power Supply
Intro
I needed a 5v, 3A power supply that could power the RPi by stepping down the 12v car power supply. I needed the power supply to be switched off when the car was off:
- When the Pico is on, but maintaining an OFF state, this power supply should be off
- When the Pico was also off (because there’s nothing powering it), this power supply shouldn’t also turn on.
Schematic
The main trick I used here was to have a 120 ohm pull-down resistor on the control line from the Pico to the power supply. When the Pico is sending a logic high, this resistor is large enough so that the logic high isn’t pulled too low, allowing the power supply to turn on.
When the Pico is grounding the control line, the resistor doesn’t do anything.
When the Pico is dead (it’s off too because the LIN transceiver’s power supply is switched off due to a lack of bus traffic), then the power supply would be on (based on it’s schematic), but this 120 ohm resistor pulls the control line low.
It’s not ideal, because there’s still some current draw to do this, but in ~1 year of daily driving the car with this installed, I haven’t had a dead battery yet.
Meanwell Power Supply KiCad Project
Breadboard
PCB
