Getting a regulated 12V DC supply can be extremely simple with something like a LM7812. However, I am trying to get a regulated 12V output with a supply that can range from 10V to 18V. My thought is to regulate down to 9V and then back up using a step-up regulator. Is this the simplest solution available?
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\$\begingroup\$ Consider switching inverting voltage regulators. Linear Inverting Regulators. Definitely the "simplest solution" if you feel okay reading the schematic upside down. \$\endgroup\$– jonkMar 11, 2018 at 8:57
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\$\begingroup\$ Depending upon how much current you need for the output 12V and whether this is for a small volume hobby project you may want to check on Amazon/eBAY for "buck boost regulator". You can get modules ready made in the 10USD range. \$\endgroup\$– Michael KarasMar 11, 2018 at 9:08
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2 Answers
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You need a buck-boost regulator. Linear Technology makes a wide range of them.
answered Mar 11, 2018 at 8:19
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2\$\begingroup\$ I have used LT buck-boost regulators for several projects. The OP should be aware that, for a given load on the regulated output, the current load on the source supply will not be a smooth monotonic function as the input voltage is swept through the operating range. My experience is that the current from the source will have quite a dynamic shift at the point that the regulator is changing over between the buck or boost modes of operation. This can be an important factor to consider when calculating battery life when the source is a battery supply. \$\endgroup\$ Mar 11, 2018 at 8:49
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1\$\begingroup\$ And here I was going to suggest using a -5 V zener so that there'd be enough headroom for the LM7812. ;) \$\endgroup\$– jonkMar 11, 2018 at 8:51
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\$\begingroup\$ jonk, great humor :) @MichaelKaras, to mitigate the switchover point dynamics, there's architectures like SEPIC, though they tend to be a little more complicated to build. \$\endgroup\$ Mar 11, 2018 at 11:36
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You could make a buck - boost converter with wires, inductors and an controller IC. And then make a PCB. That takes design effort and some skill as noise (especially ground loops) can be problematic. There is also the issue of low output voltage regulation. Some switching circuits will output literally twice the nominal output voltage at very low /zero loads. So if this is important to you, a more complex circuit is required.
Or you can buy this for £55:-
It's just one module and does exactly what you want. This is the data sheet. It doesn't require any additional components most of the time. My philosophy is to only build what you can't reasonably buy. And TRACOPOWER will be able to make much better volts that most hobbyists.
If you can tolerate a 10% minimum load, then you can use a variant of these that's ~£40. I've use both and they're excellent (and I don't work for TRACOPOWER before you ask). You can always add a minimum load with a power resistor /on indicator lamp, but that kinda detracts from the otherwise high conversion efficiency (87%).
answered Mar 11, 2018 at 14:08