Our cable boxes are indescribably stupid. It can take 5 minutes for one to get far enough into the reboot process to determine that it has locked up and has to be bounced to restart the boot. Losing 5-10 minutes of a program or film can be very frustrating. I've come close to putting the DVR box on its own UPS.

A while back I noticed a new thing in the small appliance aisle - a digital clock/radio with the banner "Never needs setting!" The design is based on a low-power PIC with a lithium coin cell for backup. A nice idea, but impossible to retrofit into a 30 year old beast with a vacuum fluorescent display that uses the power line for its timebase.

Thanks to DC for the reminder about the transformer. I knew that, and that the output AC source impedance will be relatively high. Exactly how this will affect the operation of the devices is unknown, something to discover along the road. To be clear, I've got a *lot* of transformers to choose from.

And now referencing the original post,

The question was about the facility/futility of using a class D audio amp as a more efficient driver for a sinewave UPS output transformer. So far, no big negatives. Thanks, everyone.

ak

 

Retrofitting the older digital clocks for lithium battery back up is not what I am suggesting, but rather just enough power from a 9 volt battery, or a supercap, to keep the counters and memories alive. 15 seconds slow will not be a big deal, and also there would not be the need to keep the display lit for that time. And yes, for your dumb cable box probably a regular UPS of the lower power rating is a better idea. I don't record stuff and so I have no problems there. Also, at least one box includes a battery backup feature.