I'm a power systems guy who usually don't like electronic circuits, but right now only them can save me. I'm finishing my new place where I'll be using a lot (to me) of 12V and 24V power supplies to power lighting. Normally I'd use only a toggle switch to power it on and off as necessary, but since I'm using some zigbee drivers to power it I've to let the PSUs connected or I'd lose the ability to turn on and adjust the drivers/strips. That brings me two problems due to the time they will be on even thought the light is off (95% of the time it will be draining some power to power it's own circuit and the driver) that are higher bills and smaller lifetime to the PSUs.
I've thinking about it for quite some time and yet to understand how can I improve it. For the last days my idea was to use some kind of circuit that, based on the current drained by the driver, it switches between a bigger and a smaller DC source. If the current is under some threshold it's powering only the driver and maybe a much dimmed strip, being possible to power it with only an AC DC power module of 5W or less. But if it's draining more power it switch to a bigger one, with enough power to use the lights in full power.
That's the best way to do that? There is some kind of circuitry that I could use? Or this is just a really dumb idea?

 

IMO, more points of failure with little actual gain. Get a correctly sized power supply with low idle current and high efficiency at the rated load. If you have a always on, low power requirement for wireless or controllers, then a seperate power supply dedicated for that might be a good idea.

 

So, that's just an dumb idea. Thank you for your response.

 

So, that's just an dumb idea. Thank you for your response.

It's not a dumb idea, just IMO, impractical for your simple application. I've seen staged power supplies for some applications and even several on the same object like large magnets that have a large supply coil for the bulk current and a smaller supply coil for fine tuning the total magnetic flux using hall sensor magnetic feedback to lock to a setpoint for the smaller supply.

 

No, not a dumb idea, actually an interesting concept. But I would size the smaller supply to be just enough to support all of the memory, and just let it help out a bit when the high power supply was required. Only half the switching and switch logic required.
Really, if the high current supply did not draw current when connected to a load but not powered, and with suitable adjustment, the big supply could be rigged to switch on when the voltage dropped a slight bit as a load was supplied. Or be triggered to start up when the current from the memory supply went above some threshold.

So really it could be a quite handy scheme with a bit of different control logic. AND it certainly could be a great improvement in efficiency. Just a bit of a different control scheme. Not a dumb idea at all.