Power Supply on a separate PCB

Community PCB Design
1

Hi,

I was doing a product teardown of a smoke detector and I noticed something about the PCB setup. The power supply circuit was on a different board than the rest of the PCB setup. Is there a benefit to doing it this way? Or was it just a design choice. I am looking to design my own pcb and am looking for some advice.

Thanks

2

Perhaps if the PCB fails then it can be replaced, or perhaps different psu board’s can be used for different voltages/countries.

3

Maybe for high voltage separation if it’s powered from the mains. It might also facilitate using the board in multiple products to make it easier to conform to power standards in different countries.

4

And of course, sometimes a circuit is split into two (or more) PCBs in order due to mechanical constraints in the housing.

Examples:

  • - Two boards stacked one on top of the other (with spacers) in to fit in a housing that is small but deep.

  • - A power supply board that mounts to a transformer or chassis-mount power connector. A heavy transformer mounted to a board, with the board in turn mounted to the housing, can cause stress cracks during shipping. Mounting the transformer to the housing, and the board to the transformer can get around this problem, if the board is relatively lightweight. If the circuit board is large, though, that could cause stress on the transformer terminals the board is mounted to. So putting just the supply-specific portion of the circuit on a small board that mounts to the transformer, and the rest of the circuit on a second board mounted to the chassis eliminates the problem.
  • - If one part of the circuit has front panel controls, and another part has i/o, power connectors, or a heat sink that go on the back panel, splitting the circuit into two boards, one mounted to the front panel and the other mounted to the rear housing, with a cable in between, allows pcb-mounted controls and connectors to be used, reducing the amount of hand wiring to be done.
    • 5

    Of course it has some advantages;

    Some countries use different voltages rating such as 110 and 230 VAC. so separate power supply boards might be of help in such situation. Although, currently that has been solved by the introduction of ICs that has a voltage rating of between 110 and the 230 VAC.

    Also, the separate boards might be introduced for easy replacement in case of the mechanical failure.