Easy extremely low ripple Variable Voltage supply 0-30 V/max 1 amp. made with only one 2N3055 (demo)
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- čas přidán 26. 08. 2022
- 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 • Change a 500 uA meter ...
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: • Radiofun232 on CZcams... 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.
My books about electronics & analog radio technology are available via the website of "LULU”, search for author “Ko Tilman” there.
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I keep all my YT videos constant actual, so the original video’s with the most recent information are always on CZcams. 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. - Věda a technologie
Excellent project. Excellent schematic with great details and notes. Excellent teaching. All = Thank you! I will be studying on the Miller Effect. I think that you may have cheated yourself, significantly, by measure the ripple with the lid off of the case.
Thanks and your comment is much appreciated. Very sorry that I do react now (8 okt 2023) but I think it had to do with the CVD. I am reading now (8 okt 2023) approx 50-80 comments that were never sent to me during CVD times by Google/CZcams. Perhaps because I was too critical? I don't know why, kind of shame.
You are creating good things, explication is also good. But your quality of work is below any acceptable limit.
I don't think so!
Can I assume that by using a Darlington (2 transistors product gain of about 1K) configuration - the output capacitance would increase proportionally that much further, and so reducing the ripple? I wonder how a power FET would function here? Out comes my components box again :)
Thanks Michael and yes, with a Darlington (say a BD 139 and a 2N3055) you can get somewhat better results in terms of ripple rejection. Reason, like you know, that we may multiply the capacitor at the base of the Darlington (say 100 uF) by the amplification factor of the Darlington. Say 150 (BD 139) x 70 (2N3055) = 10500. So a 1 uF cap is "changed" (only effective...., what the circuit connected to the emitter of the 2N3055 "sees") to a 10500 uF capacitor. That means an enormous ripple rejection with a very small capacitor, that also (extreme ripple rejection) will be the case with high output currents. The circuit published here is in a kind of way a "middle of the road circuit", with the smallest amount of components. And it is a good idea to make this circuit with a power MOSFET, driven by (say) a BD 139 (or not..., using it solo). When the circuit with a power MOSFET starts to oscillate, a 100 N capacitor between the gate and the ground or the source can prevent that. 28 Aug. 2022.
@@radiofun232 Comprehensive reply - cheers Ko.
Thank you for a low ripple variable voltage supply 0 -30 V. How did you calculate the value of the fuse on the primary coil of the transformer? Should that the fuse be fast or slow type?
Should be a slow type. The value of this fuse is related to the situation where there is a pure shortcut on the the secundary winding. In that case it must burn out. That also depends on the voltage where the transformer works: 110 V or 230 V AC. A 110 V transformer takes more current on the primary when, on the secondary winding, an output of 24 Volt at 1 Amp is given. Has also to do how much current is taken in the first split second when the E.M. field in the transformer is built up (inrush current, reason for the slow type). And that depends on the load that is present at the secundary winding. So a lot of parameters. For small transformers (20-30 Watt) in general a fuse of 1 Ampère is a good choice, in the 230 V AC situation. Try, test, experiment. A good test can be done with a set of automotive lamps, voltmeter and ampère meter. Test, in that case, the transformer on the nominal voltage and current.
Hello! I am obliged for your reply. I calculated that if the voltage of the primary winding is 240VAC, the current of the primary winding is (1 A x 30 V) / 240 V = 1/8 Amp that is 125 mA. So the fuse on the primary coil of the transformer ought to be at least 125 mA (5 x 20 mm glass fuse 250 Vt type). Hopefully 130 mA or 170 mA slow fuse would be fine. If 1 Amp is the maximum output current for 0 - 30 Volt variable voltage supply, then 1 Amp or little more, let's say 1.25 ... 1.50 Amp fuse on secondary coil of the transformer is good. Actually 24 VAC voltage on the secondary coil of the transformer gives 24 V x square root of 2 which is about 1.4142 = 33.94 Volt. I am using a 21.6 Watt small transformer, which is about to give maximum 1.6 Amp current on the second winding, thus the maximum DC voltage of this variable voltage supply is below than 30 Volt, perhaps only 18 - 20 Volt.
@@perttisalonen850 Thanks for your calculations and reply. I agree with them, they are OK. Issues can/could be: the inrush current and the fact that, with a shortcut on the secondary, the voltage drops to "zero" (not complete, anyway) and the current will go much more higher than the max. 1.6 Amp. Surely the 130 mA primary fluse will burn out. 😁
@@radiofun232 The shortcut of the secondary coil shall increase of the inrush current over 1.6 Amp and of course would blow the fuse. If one is wanting to have an over current protection with the variable voltage supply and also an over heating protection of the transformer, then this simple variable voltage supply would no do at all. On such case one could make a variable 0 - 30 DC power supply using adjustable current, let's say 3 Amp with a L200 regulator, a couple of transistors, an IC, resistors, capacitors, zener diodes, one fixed voltage regulator. As L200 regulator needs minimum 1.25 Volt control voltage, a small negative control voltage circuit, e.g. with 555 timer circuit which start the adjustable voltage from 0 Volt., not from 1.25 Volt. However, it is a complicated variable voltage supply suitable for a laboratory power supply unit.
@@perttisalonen850 I see you know everything, before you asked me. Good idea is to publish such a circuit on your You Tube channel, that at the moment has no content. Everyone can learn from that.🐒
2 september 2022.
can i uae 5200 transistor
The 2SC5200 is a power NPN transistor with a Hfe/Bèta of 50-160. So I think the answer is yes. Measure the Hfe-Bèta.
@@radiofun232 thank u. Always loved all your videos