Regulated power supply (darlington power) for LM317 10A 1.2..37V

Will it work ??? And which potentiometer is for what and what would I have to change to get better performance?

The circuit is similar to the previous one, with the LM317 circuit you regulate the voltage on the gate, which causes a change in the channel resistance, i.e. without a load, you have the same voltage at the output as at the output from the bridge. When you connect the load, you have a voltage divider in which you change the channel resistance if the gate is properly controlled. The system as well as the previous ones is inefficient and does not control the output voltage, which makes it unstable when the load changes, the output voltage changes. See the applications of the LM317 circuit in the catalog no find a book, eg "integrated circuits in DC voltage stabilizers" A. Borkowski or another one from this subject and you will learn more.

miernik998 wrote:

Will it work ??? And which potentiometer is for what and what would I have to change to get better performance?

What do you think?

I'm afraid this circuit won't work.

Hello

Due to the fact that the topic is not closed, and the interest in this topic, as can be seen over the years, is high, I enclose the revised diagram of a 10A 1.2 ... 37V regulated power supply presented by my colleague Kozak84.
You cannot squeeze 10A on this power supply in any way by installing only one BD911 transistor in place of the control transistor. Any attempts to use the power supply with its parameters will turn out to be a disaster, especially when the output socket is shorted to ground.

In the power supply presented by me in the attached diagram, the current efficiency is realistic at 10A, and shorting the output socket to ground will not damage the power supply in any way.
The 2N3055 transistors must be placed on a large finned heat sink cooled with additional forced air circulation by fans attached to the heat sink. The LM317 stabilizer must also be screwed to the heat sink.

greetings

Added after 1 [minutes]:

Hello

I am returning to the topic, because I introduced significant corrections and minor additions to the previously presented diagram, and for this reason I am enclosing the improved diagram of the power supply. Despite the correctly drawn diagram
I was wondering if the short-circuit protection, and at the same time the maximum current limiter, will work with the given values of the elements? Being more a practitioner than a theorist, I decided to assemble this power supply
, where it turned out that the values of the resistors in the base of the BD911 transistor should be changed. This change significantly increased the reliability of the current limiter actuation. 0.33 Ohm / 5W resistors mounted in the emitters
power transistors have been selected optimally with a current load of up to 10A (they can be 0.33 ... 47 Ohm / 5W).
The NPN power transistors BD249C, 2SC5200 and 2SC3281 worked great in the power supply and I recommend them. The voltage at the output of the power supply with a constant current load of 10A is stable, does not float and maintains its value despite the strongly heated power transistors and the LM317T stabilizer.
In fact, at the maximum load at the ends of the power cables (1.2m long), the output voltage drops from 1.5V to 2V. But I believe that this voltage drop can be reduced with a properly designed PCB
and a properly routed ground path.
As I mentioned before, the power transistors must be placed on a large finned heat sink, additionally cooled by forced air circulation by fans attached to the heat sink. The LM317 stabilizer must also be screwed to the heat sink.
Nevertheless, the power supply, thanks to its simplicity, is worth attention to less demanding electronics.

greetings

Added after 1 [minutes]:

Hello, this power supply does not work for me ... It works in principle, but if I set the voltage of 12v and I will connect the 12v 35w halogen, the voltage drops to 1.5v and the bulb lights up slightly.
I tested earlier on 12v 10w led modules and everything was fine but only lm317 heats up, not 2n3055 ...

I used 2 2n3055 power transistors ...
instead of d22-20-04 I used byp 680 500r.

here is the board, can someone help me ??

Added after 6 [minutes]:

I do not want to throw in the tile diagram

I would like to add that I did not use a bridge because I power the board with a 26V impulse power supply.

Hello

What is the current efficiency of the switching power supply and what voltage does this power supply supply to the board?
The power supply you have built cannot be called a stabilized power supply, but rather a regulated power supply. There will always be some voltage drop at the output of the power supply when loaded with higher currents, but it should not look like what you described. It looks like an electronic fuse has tripped, limiting the current.

The connections on the board seem correct, although I would have done the positioning of the elements and routing the mass differently, because I understand that the black background of the board is mass, and in this power supply it seems to me (I have never set the mass in this way) the mass is badly designed, especially when the power supply is of high current efficiency. Well, it's already done.
If you load the output of the power supply with a 12V / 35W bulb, then at the input of the power supply you must give at least a non-stabilized voltage of +20 ... 22V or a stabilized (rigid) voltage of +16 ... 18V, with a current efficiency of at least 5A.
For starters, connect three power transistors, not two. Check what the result will be. Then, when the voltage under load at the output of the power supply continues to drop, reduce the value of the resistors in the emitters of the power transistors to 0.22 Ohm / 5W. For higher output voltages, use transistors with higher parameters, eg KD502.
I would suggest checking the power supply while supplying the board with the voltage obtained from the mains transformer and the rectifier bridge (or four diodes connected accordingly).
The "-" ground wire, solder directly close to the 6800uF electrolytic capacitors, and the other end to the output socket. Connect the positive wire "+" to the board as planned and its other end to the second output socket.
Desolder the 10uF / 35V capacitor and the 1N4007 diode, which is connected in parallel to the 270 Ohm resistor.

greetings

Hello, thank you for the answer.

So, starting doesn't need that much current, but sometimes it will come in handy for a while.
1.Uses a 26v 13.8A switching power supply as the power source
2. without load I can regulate the voltage from bottom to 24v.
3.These black boxes are mass, I just did not turn on the option to show the mass.
4.When I connect, for example, 2 LED modules 10v 10w each, i.e. about 20w, everything works, it shows me close to 2A.
5. I checked bd911 and 2n3055 and they are fine.
6. short circuit protection works.
7. When I connect this 12v 35w bulb, the voltage from 10v drops to 1.5v and the current also to about 0.4A ??? not sure because i checked in the morning.
8. When connecting this bulb, I can see and hear a spark and nothing happens, the bulb starts to glow slightly after 3 seconds.

Hello

From what I read, you have not yet checked the power supply with three power transistors connected in parallel. Try to do this and you should get a satisfactory result, even though the board is not properly designed.
Then try replacing the resistors in the emitters of the power transistors with smaller values. Only then should you be careful when the output sockets are short-circuited, as the short-circuit current will increase significantly.

greetings

Ok. I will do as you say.

tomorrow I will try to buy 2n3055 and possibly 3 0.22ohm5w resistors

So I bought another 2n3055 transistor, but still the same ...
I followed a bold path on the ground and nothing improved.

Tomorrow I will get these 0.22ohm resistors and we'll see then.

Hello, I did as you said. Still the same ... I don't know what's going on

Added after 53 [minutes]:

It turned out that I have a short circuit on bd911. It's already working like this doll just a question now :)

can I do the current adjustment ???

and which components are responsible for short-circuit protection?

Added after 9 [minutes]:

Hello

In the attached drawing I present a simple power supply with adjustable output voltage in the range of 0V ... 25V with regulation of output current limitation in the range of 1.5 ... 10A and with short-circuit protection.
The PSU is protected against polarity reversal at the PSU output sockets thanks to the D22-20-04 diode (20A / 400V or higher current) connected to the PSU output, e.g. by incorrectly connecting a different voltage source to the output sockets. It's not a perfect solution, but it does the job.
The presented power supply, after correct assembly according to the diagram and commissioning, does not require any adjustment and is immediately ready for operation.

The basic element in the power supply is the LM317T voltage stabilizer in the TO-220 housing, while the stabilizing elements connected in series with the input voltage and the load are five appropriately connected bipolar NPN power transistors BD911 and BD249C.
The BD911 transistor drives four BD249C transistors connected in parallel, thus creating a complex power control transistor operating in the Darlington circuit. The base of the BD911 transistor is connected directly to the Vout pin of the LM317T stabilizer, where the transistor is pre-current controlled. This current is sufficient to drive the power control transistor and therefore it is possible to load the power supply output with a current of up to 10A without any problems.
Changing the voltage at the Vout pin of the LM317T stabilizer from + 1.25V to + 26.25V causes the voltage at the output of the power supply to change from 0V to + 25V, because the combined power control transistor works in the Darlington circuit.

The output voltage is regulated by a 4.7k / A-0.25W linear potentiometer. A 33k resistor connected in parallel to a 4.7k / A potentiometer sets the maximum output voltage of + 25V. By changing the value of this resistor, the upper range of the output voltage can be changed.
The base-emitter junctions of the BD249C transistors, 0.39 Ohm / 5W resistors and the BD911 transistor with a 470 Ohm / A potentiometer are involved in the short-circuit protection and current limit control system.
A 470 Ohm / A-0.25W linear potentiometer is used to adjust the current limitation.
The effectiveness of the minimum and maximum current limiting control depends on the size of the output voltage and, of course, on the setting of the 470 Ohm / A-0.25W potentiometer slider.
At the minimum output voltage, regulation of the output current limitation is performed with a full (100%) turn of the potentiometer knob. On the other hand, at the maximum output voltage, current limiting is performed in the half (50%) of the potentiometer knob turn.
When the potentiometer slider is set at a 47 Ohm resistor, the power supply output can be loaded only with the minimum current, when the potentiometer slider is set at a 4.7 k resistor, the power supply output can be loaded with the maximum current.
If the minimum voltage is set at the output of the power supply, and the load current is maximum, the potentiometer slider should be set at the end of the resistance path, i.e. closer to the 4.7k resistor. If the maximum voltage is set at the output of the power supply and the load current will also be setmaximum, the potentiometer slider should be set in the middle of the potentiometer resistance path.

The BD249C power transistors should be placed on a large ribbed heat sink. The BD911 transistor controlling the BD249C transistors and the LM317T stabilizer should be placed on small separate heat sinks.
BD249C transistors after the heat sink require additional cooling with forced air circulation by means of fans attached to the heat sink.

To reduce the power of losses of BD249C transistors in the power supply, a network transformer with a power of P = 300W with two secondary windings 2 x 13 ... 14VAC / 10A connected in series was used, which are properly switched depending on the voltage that occurs at the output of the power supply, as a result of reducing or they increase the input voltage at the collectors of BD249C transistors.
Remember to use a soft-start system in this power supply.
The power supply uses analog panel meters which, when connected at the output of the power supply, act as an ammeter and voltmeter used to determine changes in current and voltage.

greetings

Added after 1 [hours] 4 [minutes]:

A small addition, the two BD911 transistors used in the power supply should be placed on small separate heat sinks.

Hello. I made the power supply according to the scheme that my colleague gave at the beginning with the difference that I gave 330 ohms instead of 270. Powered by a 36v 5A toroid. It was around 26V at the output. And now I start up and the power supply flashes very nicely.

Except I made a few short circuits by accident and before I figured out where the short was doing this the following happened:
1. After the first short circuit, everything was still normal after the second short circuit, the signaling diode was on and when I wanted to increase the voltage with the potentiometer, it blew up the lm317. After replacement, it did not explode but it was impossible to control and the resistor R = 270 ohm started to burn. What could be the cause?
I've tried everything. I changed the transistor but this resistor is still burning, I can not control the voltage at the output which is always at maximum voltage.
The voltage between the terminals of the r 270 resistor is about 45v

I am asking for feedback and advice on what the problem may be. Thanks in advance and regards

Hello

The voltage of max. + 37V can be supplied to the input of the LM317T stabilizer. The transformer you used (secondary winding ~ 36V / 5V) is not suitable for this power supply, especially for the LM317T stabilizer.
After rectifying the voltage from the secondary winding with a voltage of ~ 36V with the attached filtering capacitor, we get a voltage of U = 50.8V without load (~ 36V x 1.41 = 50.8V). Under load, this voltage may drop to 45V, but the voltage is still too high for this power supply.

The appropriate transformer is a transformer with a secondary winding with a max voltage of ~ 26V with a tap for ~ 15 ... 16V or with two windings 2 x ~ 13V connected in series.
A transformer with a split secondary winding should be used to reduce the voltage drop on the control transistors (2N3055), and thus reduce their power losses, e.g. when the power supply output is set to low voltage (e.g. + 3V) and the output is loaded with maximum current .

You write that using a 330 Ohm resistor (in exchange for 270 Ohm) you got the voltage at the output of the power supply + 26V. Something was already wrong. You should get the voltage at the output of the power supply about + 19V [1.25 x (1 + R2 / R1)] ... After applying + 50.8V to the input of the voltage stabilizer, most likely the internal structure of the stabilizer was partially damaged, and when the stabilizer was short-circuited it was completely damaged.

If the 270 Ohm resistor is "on", the LM317T stabilizer is damaged. The LM317T stabilizer and the BD911 transistor should be placed on separate small finned heat sinks or at least on aluminum sheets with approximate dimensions of 50mm x 70mm x 3mm.
The BD911 transistor and the LM317T stabilizer without heat sinks may be damaged in the event of an extended short circuit.

If the output voltage of the power supply is the same as the input voltage, the 2N3055 control transistors or at best one of these transistors are damaged.

Check the three 2N3055 transistors, the BD911 transistor and the 1N4001 diodes, because I suppose that with the transformer you used, all the transistors and the stabilizer were damaged.

The three resistors in the base of the BD911 transistor should be 10 Ohm.
If the power supply is to have a current efficiency of up to 5A, the resistors in the emitter circuits of the 2N3055 transistors should have the values of 0.56 Ohm / 5W (0.47 ... 0.68 Ohm / 5W to be selected experimentally during maximum load).

Have you used a fuse in the secondary winding of the transformer before the rectifier bridge? In the event of an unfortunate short circuit, it should work, and if it was a 5 ... 6A fuse, it would definitely protect the 2N3055 transistors.

If you had the opportunity, I would suggest replacing the 2N3055 transistors with the KD502 ... 3 transistors. I do not need to remind you that the control transistors must be placed on a large, ribbed radiator cooled with fans.

After repairing the power supply with new components, disconnect the 10uF capacitor before starting it, and then, after checking the power supply, you can connect it.

The power supply must work properly with the use of appropriate elements, and the shorting of the output socket to ground should not last too long.
If you still need help, ask, I will always help in this topic.

thank you very much for your help. I will use it as you advised: I will buy a 24V / 5A transformer or I will connect two 13v transformer windings. But is it sometimes here that this combination does not make another babol? Namely, I have a 1x36V / 5A 1x13V / 5A 1x13V / 1A toroidal transformer. (earlier I connected to 36v and it was exactly as you said the voltage increased to about 50V and at 13v I had about 18V at the output) And now I would like to connect these 2x13V to give 24V only, for example, if I load the power supply with, say, 4 amps, or the winding of this transformer is 13V / 1A will not go with smoke?

Added after 50 [seconds]:



Added after 7 [minutes]:

Hello

You cannot connect two secondary windings in series from two transformers of different power - one with a power of P = 65W (~ 13V x 5A = 65W) and the other with a power of P = 13W (~ 13V x 1A = 13W), and then load so connected in series windings with a current of 4 ... 5A. There will be a large voltage drop on the secondary winding of the transformer with a power of P = 13W and there will be no voltage stabilization at the output of the power supply, and in addition, if such a load is maintained for a longer period of time
the windings of this transformer may be damaged.

If you have options (you know it, you've rewound transformers), a good solution would be to unwind the toroidal transformer you have (~ 36V / 5A - P = 180W) from the secondary winding, about 33w. wire to get the voltage of ~ 25V then making the so-called tapping and re-winding evenly on the core of the unrolled wire.
When unwinding the indicated number of turns from the secondary winding, it is good to check if we have the correct voltage (~ 25V). To do this, scrape off some wire enamel at the point where the tap is to be made, connect the transformer to the mains and measure the voltage with a multimeter connected to the tap and the other end of the wire.
You can also use this transformer differently by making two taps on the secondary winding and thus obtaining two additional voltages ~ 12V and ~ 24V, which are needed to build your power supply.
Assuming rounded up that in the secondary winding of the transformer with the power P = 180W, there is little more than 3w for ~ 1V. wire, and the secondary winding is ~ 36V, the winding should be around 108w. winding wire.
Dividing 108zw by 3 we get the number 36 zw. that is, when we unwind 36 zw. wire and make a tapping, then unwind another 36 loops. and then we will wind the whole wire evenly on the core, we will get three voltages: ~ 12V, ~ 24V, ~ 36V.

However, if you cannot do such a transformation of the transformer, it is best to buy a toroidal transformer with a power of P = 150W with a secondary winding with a voltage of ~ 12V / 12.5A (the cost of a new one is about PLN 80). In such a transformer, the secondary winding is wound bifilarly (simultaneously) with two wires (in toroidal transformers of higher power, the secondary winding is sometimes wound with three or four wires), and the ends of these wires are connected - soldered together to form two leads on the secondary winding (Fig. 1) .
When the two terminals are desoldered, we get four wire ends (fig. 2).
By connecting these four ends of the wire, we get a secondary winding with a voltage of ~ 24V / 6.25A and a tap with a voltage of ~ 12V / 6.25A (Fig. 3)
Such a transformer would be the most suitable for your stabilized power supply with an adjustable output voltage in the range of + 0.6V ... 22.5V with a current load of up to 5A.
I am enclosing a power supply diagram that you can use for your needs.
Following this diagram and taking into account what I wrote previously about the proper assembly of some elements, you will not have problems with starting this power supply.
Power Supplyit has a switch on the secondary winding of the mains transformer that changes the amount of voltage supplied to the rectifier bridge, and thus reduces the voltage drop on the collectors of power transistors and at the same time reduces the power of losses of these transistors at a maximum current load of 5A, when low voltages are set at the output of the power supply.
The rectifier bridge must be attached to a small heat sink.

greetings

Hello

I have assembled such a power supply in a version with output current regulation, the only changes in my version are the 2n3055 power transistors, three, not four, as you can see in the diagram and a potentiometer for current regulation of 500 ohm. The power supply works with voltage regulation ok, but no reaction during current regulation. The power supply was loaded with 3.5A and 7.2A current. What could be the reason why the output current regulation is not working?

Hello
I'm also trying to make this power supply from post 45, also on 2n3055 transistors.
Someone has a circuit board for this.

Ps
I was also interested in the project on this topic, but I do not see the current regulation there

https://www.elektroda.pl/rtvforum/topic2275806-30.html

I join, does any of you have a schematic of the power supply PCB?

The first figure shows a PCB designed by a colleague Błażej85 and adapted to the construction of a 0 ... + 15V / 1 ... 10A power supply modeled on the power supply from post # 45, which differs only in the maximum voltage at the power supply output.
The board is correctly designed according to the scheme.
On the board, there is a place for the use of a 47k (P3) assembly potentiometer, which allows you to accurately set the maximum voltage (+ 15V) at the output of the power supply.

The second figure shows a board adapted to the mounting of the 0 ... + 25V / 1 ... 10A power supply (post # 45), but with a changed arrangement of the elements, taking into account the possibility of attaching small heat sinks to two BD911 transistors and to the LM317T stabilizer.
The T3 transistor and the LM317T stabilizer must necessarily be screwed to small heat sinks in the form of e.g. an aluminum plate with dimensions of at least 50mm x 50mm x 2 ... 3mm.
You can use three electrolytic capacitors C1 - 3 x 4700uF / 50V or 3 x 6800uF / 50V if the board does not fit three 10000uF / 50V capacitors.
Four BD249C transistors or other four TO-3 case transistors (eg MJ15003, KD502 ... 3) should be placed on a large ribbed heat sink with additional forced air cooling with fans.
The value of four resistors (0.33 Ohm / 5W) located in the emitter circuits of the BD249C power transistors should be selected during the power supply tests, preferably 4 x 0.39 Ohm / 5W or 4 x 0.47 Ohm / 5W, because the efficiency and range of current limiting at the output of the power supply depends on the value of these four resistors.
Both boards are shown from the component side.

Hello, the board design is not compatible with the diagram attached earlier (in post 45), it is about the T3 transistor (BD911) from the 2 board design that was connected by mistake, the collector and the emitter are swapped, and the same is with the first board. If I have noticed something wrong, please correct it.
greetings

scalaktrafo wrote:

Hello, the board design is not compatible with the diagram attached earlier (in post 45), it is about the T3 transistor (BD911) from the 2 board design that was connected by mistake, the collector and the emitter are swapped, and the same is with the first board. If I have noticed something wrong, please correct it.
greetings

Thank you for your good attention. If the terminals of the BD911 transistor are connected incorrectly, there could be problems with the important protection that is the short-circuit protection.
The tiles posted in post # 53 have been corrected.

greetings

Hello, I have a question for you regarding the power supply diagram from post 45, how could the current limitation measurement be carried out, and more specifically, I mean the possibility of setting the limiting current before connecting the tested system and displaying the result on the display.

I encountered such a solution in a laboratory power supply, before connecting the tested device to the power supply, it was necessary to shorten the output and set the assumed limiting current value.
greetings

scalaktrafo wrote:

a question about the power supply diagram from post 45, how could the measurement of the current limitation be carried out, and more specifically about the possibility of setting the limiting current before connecting the tested system and displaying the result on the display.

I encountered such a solution in a laboratory power supply, before connecting the tested device to the power supply, it was necessary to shorten the output and set the assumed limiting current value.

In the power supply from post # 45, such a measurement cannot be performed, because the short-circuit protection here is of the foldback type. Each time the output sockets are short-circuited, the short-circuit current value will always be lower than the set current value at the output of the PSU.

Hello, I will warm up the topic because I have a problem with the power supply (Mr. Krzysztof723) from the post No. 53, it is about PCB No. 2, I made such a PCB and assembled the system and it turned out that the current regulation with a 500ohm potentiometer does not work after the system is loaded with a receiver. Voltage regulation works fine. When increasing the voltage, the current increases, but I cannot lower it or increase it with a 500ohm potentiometer. The system is powered by a 24v 630VA transformer, 50A bridge, 18800uF 63V capacitors.
I am asking for a hint what I did wrong.
Greetings.

I have already figured out why I did not have current regulation - you need to choose emitter resistors.

Do you have a print pattern for this tile?