Easy extremely low ripple Variable Voltage supply 0-30 V/max 1 amp. made with only one 2N3055 (demo)



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Please read the description/textbox first. A one transistor (2N3055) very easy to make voltage supply, working between 0 Volt and 30 Volt at maximum 1 Ampère. Ripple rejection is very good (watch the video).

And the circuit has in a kind of way a shortcut protection for say half an hour.

Video where I show (28 Aug 2022) how I made a shunt to make a 500 uA meter usable to indicate 0-1.5 Ampère is here https://youtu.be/RUrNr5KYvSM

This power supply is due to its very low hum/ripple usable for sensitive audio circuits. Thus audio pre-amplifiers working between 6 Volt and 18 Volts and audio end-amplifiers that take (say) 500 mA at 18 Volt, that is in general 6-7 Watt output to the loudspeaker.

In these cases (max. 500 mA) the hum-ripple on the power supply lead is extremely low, say non-existent.

Only on max 1 Ampère (that is kind of shortcut) the ripple/hum goes up to (say) 10 Millivolt. That is normal, given the electronic setup. To make it "better", use a 4700 uF smoothing capacitor. And a 500 uF capacitor (instead of 200 uF) from the base of the 2N3055 transistor to ground. Drawback: the voltage regulation can get a slow reaction, when turning the 22 K potentiometer.

On lower output currents/voltages the (50 Hz or 60 Hz) ripple is not detectable parallel to the power (output) leads. Visible in the video (oscilloscope views).

Circuit was used and tested during (say) 20 years and always worked fine.

The 2N3055 (that does the job, NPN power transistor, in theory for say 60 Watt) has to have a Hfe (Bèta, current amplification) of 50 or more. I used here a 2N3055 that had a Bèta of 70.

You must test that with a transistor tester. When buying (nowadays, 2022) a “package” of 2N3055’s (even from reliable electronics shops) there could be a serious spread in the amplification factors of these 2N3055’s.

I found Bèta’s between 8 and 70 (!) when I ordered them via a reliable electronics website (Reichelt in Germany). I am not bashing that company (Reichelt, Germany) because I order there everytime.

But this/was an experience regarding the 2N3055: completely different Bèta’s, though all new/unused/directly sold via the factory (China?).

More or less everything important is told in the video.

Forgot to tell: the aluminum casing of this power supply is used as a heatsink for the 2N3055. Always cumbersome (!), you must use an “isolation kit”, made with a silicone or mica layer/foil, to avoid that the collector of the 2N3055 gets in contact with the aluminum box, that is on minus (-), ground.

But to avoid that: you can also use a heatsink, isolated from the chassis, via a piece of wood or plastic or whatever material. It must be 10 cm x 20 cm aluminum, 1 mm thick. In that case the 2N3055 can be mounted to that aluminum plate, directly, because its collector is isolated from the chassis that is on minus (-, ground).

The heatsink must be so big because on 1 Ampère out at shortcut, the 2N3055 gets all the load/heat, say 1 Amp x 24 Volt = 24 Watt. The power supply is in that way shortcut protected.

My You Tube channel trailer is here: https://youtu.be/xbgQ8T3oqh4 When you search, search always “NEWEST FIRST” to get the right overview. You can also search via the “looking glass” on my Channel trailer via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in.

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https://www.lulu.com/search?adult_audience_rating=00&page=1&pageSize=10&q=Ko+Tilman

I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube. Search there, and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, etc.

Some persons try to find gold via my circuits. I take distance from all these fake claims. I cannot help that these things happen. Upload 27 August 2022.
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Audio
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