Reverse protection of Multicomp pro DC/DC converters MP-K78xx?

Hi,

There is a partial answer that is relevant, in the datasheet:

4. Converter cannot be used for hot swap and with output in parallel;

Even with any alternative (more expensive) product that is more fully specified, it's unlikely to allow multiple sources to be connected together in this way. Usually some 'OR' circuit is needed, perhaps with diodes, or MOSFETs. In your example, perhaps the USB source could be connected to the input of the DC-DC converter instead (via a Schottky diode). It might be slightly out-of-spec since USB power isn't exactly 5.0V, and may even go out of spec with different loads too, but maybe such a cut-down method is acceptable for some applications.

Are there USB connectors that have an Earth switch in them like DC Barrel Jacks - when a USB cable is plugged in it disconnects an Earth turning an alternate power source off?

Are there USB connectors that have an Earth switch in them like DC Barrel Jacks - when a USB cable is plugged in it disconnects an Earth turning an alternate power source off?

Hi Andrew,

Neat idea! I've not seen one, but if it exists, it would be a useful part. I once used a normal switch (microswitch) positioned such that the user couldn't physically insert the USB connector, without pushing the microswitch lever down first. Since 3D printers are so popular, maybe a sliding door for a USB connector and switch could be designed.

I suppose there are alternate physical approaches: need to make sure that the alternate power source becomes un-powered.

I doubt using such nice-but-unheard-of USB connector would be practically useful for transparent power source switching as activating that mechanical switch would not be timely and instant enough to both prevent the two sources be active at the same time and therefore collide and at the same time not to cause power drop because of time gap between one source gets disconnected to the other getting connected. Or?

They aren't designed for instantaneous power changeover, no.  They would disconnect the Earth before connecting the power so they wouldn't both be active at the same time but there would be a time where nothing was powered.  Basically, your approach should be what Shabaz and I have mentioned - you may also need to consider common grounding as well.