As how I understand it, there are two ways of converting DC. One is by using a voltage regulator (zener diode, feedback combination etc), and the other is by using a buck boost converter. Firstly, if there are other methods, please tell me!
How do lab bench power supplies work? I've heard that buck-boost supplies are noisy (for precise lab requirements) and I know that voltage regulators basically drop the remaining voltage as wasted energy.
Now to my question: I have only seen a single transformer in any lab supply, so obviously the output voltage of it is fixed. If say the bench supply's max voltage output is 24V, then I'm assuming the output of the transformer would be ~24+V.
If this is going (after AC-DC conversion) to a voltage regulator, and say I pick 1V fixed o/p voltage and connect the bench supply to a load that draws 1A current. If I understand it correctly) the lab supply will waste at least (P=VI=[24-1]*1) 23W and have an efficiency of just 4%.
Is this true? If so, the heat output would increase dramatically as selected output voltage is lowered (and current increased). So much energy would be wasted? Not to mention heat sinking etc.
What am I missing? Is there a better way? Or is this a necessary sacrifice for getting a precise power supply?