Voltage regulator + current amplifier?

[autir]

I have read that voltage regulators dispose of surplus power by dissipating it as heat.
I have an idea, most probably something is wrong but I would like to ask you. What if the regulator supplied just a small amount (~10mA) of current to a current amplifier which would provide the "real" current for the rest of the cirquit? Thus we would not have wasted energy and big heatsinks and fans.
What is your opinion on the subject?

 

[Alun]

Well for a start a current amplifier supplied with a small constant current cource would form a current regulator and not a voltage regulator. Voltage regulators normally work by using a voltage amplifier with lots of negative feedback to amplify a small reference voltage.

When an amplifier amplifies a small signal or voltage it dissipates or wastes energy as heat. So for example if a DC power amplifier powered of a 12V battery with a gain (multiplication factor) of 2 had a 1.5 volt input signal the output would be 3V. Now if this was powering a 6 ohm load the output current would be 3/6 = 0.5 Amps and the power in the load would be 0.5*3 = 6W. The amplifier would still have to drop the 12V power supply down to 3V

 

[audioguru2]

Hi Autir,
Only linear voltage regulators heat-up because of the power they must dissipate due to the voltage across them and the current through them (P = V X I). Switching voltage regulators heat much less. Look at the high efficiency of the switching regulators in your computer, delivering hundreds of Watts of power with only about 10% heating.
The input power to the regulator isn't surplus, extra power must be provided (and dissipated) to a linear regulator because its input voltage is excessive and fluctuating.

I don't think a current amplifier would work because its input voltage and load current are changing, besides it would probably also need a regulated supply voltage anyway.

 

[Kevin Weddle]

A current amplifier won't regulate because there is no feedback. A changing load would cause voltage fluctuation. What you could do is add feedback and that of course leaves you with the original concept. A voltage regulator with an external pass transistor.

By the way it is funny how that circuit works. The input to the regulator is on the output side and the output of the regulator is on the input side. It works backwards from conventional thinking. And the regulator with a pass transistor is a little artificial in design which means it is not the best regulator you could have.

 

[Malorisov]

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