I have this toy I am making for my toddler that includes Arduino Micro and Raspberry Pi Zero (plus 10 APA-102 RGB LEDs and audio amplifier that feeds a 3W speaker.
This all is powered through a 5V USB power bank. It serves nicely for a battery, also when the power bank itself is changing via the supply cable. The problem is that when the power bank supply cable is disconnected from the supply (usually a power adapter in wall socket), there's a brief power loss to the output sockets that causes reboot for both Arduino and Zero.
I am looking for a reliable solution to keep the devices powered for that brief moment. Something connected in parallel to the power bank output. Perhaps a reasonably large capacitor would do? I am afraid if the capacitor would discharge too quickly and damage the devices. A small rechargeable 5V battery could do, but that seems to be an overkill.