Good quality LM723 LAB Power Supply

[IconicPCB]

Thanks for the link, interesting read.

[blackdog]

Hi Wolfgang, 

Only the digital 30V 5-Ampere has no good dynamic behavior.
The 30V 1-Ampere model is the best of the pictures shown.
It has a low Ri and fast respons.

Measuring phase (bode plot)
I found a small transformer that had a good frequency respons and used this transformer in a measuring device.
Bolow you see the schematic of this measuring device.
the design is by Wenzel but I adjusted it to get a larger frequency range and to lower output impedance.
In the drain I included a coil and replaced the buffer circuit at the output with a Fet and a transistor with a LH0002 buffer.
This increased the bandwidth to 0.1dB at 1MHz.
The large input capacity of the 2SK170 low noise Fets is not important here, because of the low impedance at the input of the Fets.
Nice preamp! 

Schematic



Front
The box is a old Cisco PIX firewall.



Back side



Inside de box



The two outputs at the back I then connect to two inputs of my HMO3004 scope for phase measurements or if the frequency is not too high,
I can also use my Audio Precesion One measurement set for phase measurements.
But usually I use one of my Dynamic Loads for stability testing.
For the smaller power I use a design by Jim Williams with a very high bandwidth, so of the top of my head about 3 to 4 Mhz bandwidth.
And my 200-Watt dynamic load with a much smaler bandwidth say 100Khz.

I am aware of the measurement conditions when doing dynamic testing.
If you already look at my pictures of the tests I show here, you can see that there is no HF overshoot visible anywhere.
But later more on this if i test this LM723 power supply.

Kind regards,
Bram

[xavier60]

Bram,

What is this Harrison concept You refer to?
I know Harrison were bought ou by HP i guess in the sixties may be seventies, but i do not know what this concept is You refer to.

http://www.hpl.hp.com/hpjournal/pdfs/IssuePDFs/1962-07.pdf

The reason that it uses a PNP series pass transistor in the negative rail is likely because mainly PNP power germanium transistors were available back then.

[Wolfgang]

Hi Bram,

what I can see you are using the classic injection transformer technique to measure the transfer function. Why not, a lot of other phase/gain/loop stability systems do the same.

Some comments:
You measure with the control loop opened up and your injection transformer inserted there. For a homebrew PSU, no problem, for a commercial DUT it is sometimes unpractical to cut PCB traces and so on. Some modern PSUs contain IC regulators where the output divider is *inside* the IC. In this case, you have no chance to open the loop and to insert your transformer. Another example of this are chips like 78XX.

In case you cannot or want not to "invade" your DUT you can work with current injectors to determine phase and gain margins. This method is called NISM (non invasive stability measurement) and is aggressively promoted. As all hyped stuff, it does have restrictions (exactly only works for second order systems), but still better than nothing.  Personally I think measuring step response is more "honest" because it also works with large transients that could drive the PSUs internal regulator out of its linear range. Even nonlinear systems *can* oscillate

[blackdog]

Hi,

I didn't feel like working today, so I worked on the schematic of the LM723 power supply.

Four parts were tackled, the current source with Q3, the extra rectifier with D3 and C8, L1 and R37 and finally the extra MOSfet Q7.
I would like to hear from you what I try to achieve with these changes. 

Version = 0.9 of the schematic.
The component values of the new sections are a starting point, these have not yet been optimally determined by testing.


I wil be happy if i hear some explanations from you.

Kind regards,
Bram

Sorry, i placed the wrong schematic, it is now corrected.
No, it is not the alchohol! 

[Kleinstein]

One could get away without R9, if the lower end of the pot is connected to the negative output terminal level. For the regulation I would expect a slight improvement from this, though not much. Independently C12 could also be better of towards the neg. terminal level - this way the filter would be active for the negative supply contribution too. 

After the charge pump through C1, I see no need for the very high voltage. So it could be possible to reduce C1, up to the point that the voltage before the 7912 gets reduced. My guess would be that a low smaller cap (e.g. 220 µF) could be sufficient. It better to drop the excess voltage at the capacitor than with the resistor and 7912.

I think one half of D3 should go to the other side of the AC, to use full wave rectification.

If pin 10 of the 723 is used as an output, I would expect an extra resistor from base to emitter for Q4, so that there kind of a minimum current flowing from pin 10.

With the added Q7 and R31, I would expect that a larger value for C20 might be better suited.

[blackdog]

Hi,

Kleinstein good input!
About R9, i feel so stupid... changed and also removed Trim-1 and changed R7 to 221 Ohm to make the LM337 a 3.1V regulator, trim is no longer necessary!

As for C20, you are right, it must be bigger to keep a sufficiently low impedance at this point, it is now 1000uF.

A quick explanation about R21, the 4.7 OHm 25-Watt resistor.
This resistor limits the dissipation in the 2SA1943 transistor at lower output voltages of the power supply.
The switching point will probably be somewhere around the 8V output voltage.
The value of the resistors around Q8, the 2N3904 and the zener D11 will be determined later.

D3, L1 and R37 ensure a less voltage drop compared to the single resistor and the 1N4007.
L1 is a high impedance for disturbances from the 230V grid and R47 helps to prevent the Q of the coil from being too high.
With this setup I hope to have a little more voltage for the TL431b regulator.

As for the negative rectifier, I will do some more research on this.
but I don't like to drop large AC voltages over electrolytic capacitors.

About Pin-10 of the LM723, You are probably right about the extra load resistance that is needed.
The Darlington in the LM723 probably can't work well with the very high Hfe (low base current) of my power stage.
I will come back on this point.

I will also make a test setup where both the extra positive power supply line and the negative power supply line will be built a bit different.

Here is version 9b of the schematic.


Kleinstein thanks!

Kind regards,
Bram

[blackdog]

Hi,

Yesterday and today I did measurements on the transformer and rectifier.
These measurements indicate that at 220V mains voltage, 20V at 2-Ampere output current is not possible with the first 20V transformer I tested with.
That in itself is not a big problem because it is a "test" power supply and a learning project.

This is the first transfomator I did all the tests with, is is a 20V at 70VA model.
The top is normally closed with a lid, but removed here to see if it was posible to adjust the windings.
While removing the lid I remembered that I also have another transformer of 20V and this transformer I started comparing with the first transformer.



This is the second transformer it is a toroidal core of 20V and 100VA.



Both transformers side by side.



And now the big differences between these transformers.
The mains voltage is now a bit higher because I did these measurements with a separation transformer that gives a higher voltage at low load and for my savety. 
This is the first transformer of the E-I type, tested at 231.6V



Holy Moly 42.3VA no-load!



Because of the lower zero load of the toroidal transformer, the voltage here is 237.8V.



This transformer is much better and not only in terms of the no-load. very nice value at 237.8V.
Thise toroidal transformer is much nicer for Mother Nature, the power plant does not need to generate 40VA extra with this model transformer.



I also measured the DC resistance values of the windings of both transformers.
The first transformer, that's the rectangular model.
The primary winding is 23.85 Ohm.
The secondary winding is 0.23 Ohm.
Transformer wattage = 70-Watt

The second transformer, that's the toroidal model.
The primary winding is 13.35 Ohm.
The secondary winding is 0.17 Ohm.
Transformer wattage = 100-Watt

It is tempting to increase the current to e.g. 3-Ampere when using the toroidal transformer, but then I have another problem, cooling!
I have not yet discussed the cooling of the power section, but I almost always keep a maximum of 50-Watt per power transistor.
Below a picture of a PC heat sink that I used for another power supply test.
The parts that are now mounted on it will be replaced by parts that I ordered this week.


I have many more of these PC heatsinks, also larger models.
From experience I now know that 50-Watt dissipation is possible at a not too high sound volume of the van.
I want to try to build the power supply in a not too large housing and the toroidal transformer and this small forced cooled heat sink should help.

Tomorrow I will continue measuring the toroidal transformer, the first measurements already showed that with this transformer 20V at 2-Ampere must be possible at my minimum mains voltage of 220V.

Kind regards,
Bram

[Doctorandus_P]

I just wanted to know you' all that I enjoyed reading this thread.
Too many newbies who have no clue about what a dynamic measurement of a power supply is, nor even have an oscilloscope.

The HP article was also fun. Stating that it was becoming possible to build such power supplies with new advances in electronics.
Gosh, that was only in the 60's. Just a few years before I was born in this ever more faster morphing strange world.

[blackdog]

Hi,

Some short extra remarks about the transformers.
The "zero load" of the first transformer also causes extra heat.
This also happens when you supply a light load like an Arduino or other microcontroller with this power supply.
And of course I am aware that the 25mA current source at the output also dissipates about 1.5-Watt.
Then there is also the current from the bleeder resistors, that do not help the efficiency.
This will not be a high efficiency power supply, but one that has little noise and hum and is kind to the load.

Some info about the mains voltage deviation in the Netherlands.
If you are going to measure the voltage (which comes from the socket or wall socket) at home, the voltage is not always exactly 230 volts. 
There is a minimum and maximum margin.  In the Netherlands standards have been drawn up to which the voltage must comply.
On the connection in the meter box (the connection point), the voltage must comply with the European standard NEN-EN 50160. 
For the voltage it has been agreed that the voltage to the bottom may not deviate more than 6% (207 volts) and to the top no more than 10% (253 volts). 
This data is a shortened summary and is not complete in detail, but gives a global picture, in the NEN-EN 50160 is exact way of measuring.

I am in the middle of the city of Amsterdam and there is almost always the mains voltage on the low side.
I haven't measured any mains voltage here yet in my LAB that was above 232V.
This power supply is intended for use here in my LAB.
If anyone is going to use this schematic or any other schematic and/or transformer, think about it.

If you design a power supply that has to work at multiple locations and cannot break down at 253V mains, you have to take that into account when designing!

Just think about the following, the first transformer already consumed over 42VA at 232V without load.
This almost always means that the transformer is designed so that the core is against saturation.
There is a chance that this is a 220V transformer, I can't check this further because I don't have enough information.

What kind of power consumption would this transformer have if you offer it 253V, the core will be fully saturated!
Offering these 253V for a longer period of time, even at low or no load would result in a too high transformer temperature.
One of the positive points of this transformer is the built-in temperature fuse witch will blow at 253V afther a while.

And then the second positive point of this transformer, the windings are well separated.
The capacity between the secondary and primare winding is only 30pF, and if I use the iron package as a shield it is only 20pF.
The toroidal transformer has a windings capacity of 760pF, which is many times higher than the normal transformer.
This toroidal core is not equipped with a shield, which do exist, and are often found in medical equipment and/or measuring instruments.

One of the last pieces of this power supply design, is to deal with are the parts on the mains side.
Now back to the bench to do more tests on the toroidal transformer and its rectifiers.

Kind regards,
Bram

[blackdog]

Hi

The schematic has been slightly modified again.
I have tested the rectifiers but I still need to do some tests with the minimum power needed to make my setup work properly.

The charche pump made with D1 and D2 in the schematic together with C1 and C3 require a certain load on the power supply rails.
So the next test is to apply the bleeder resistors and two current sources that will form the load for the extra positive and negative power lines.
The transformer loaded by one of my dummy loads with 2-Ampere for more than half an hour and the 10,000uF capacitor, became just noticeably warm, good!
R5 is this last schematic keeps the dissipation of the 7912 down en helps to filter fast pulses from the mains, it wil be around de value in the schematic (15 Ohm)

The measured values in the schematic are those of the toroidal transformer.


Laters more 

Kind regards,
Bram

[coromonadalix]

Im gona do some comments, i dont want to critize your design  but i find it too complicated for nothing

Ref1 r15 r16 c10 r12 are not needed if the vcc supply max is under 40 vdc for the lm723  as per datasheet

I understand the q8 dissipation circuit,  but it add  thermal loss and voltage drop before the q8 emittor, i would  not do that,  why ?

The 723 as i see this circuit is not a floating regulator, you try to do this with d3 dual diodes, but its not.  You must have dual secondaries x-former.

You have some negative -3vdc  rail with your power on/off and enable on/off, i checked lots of 723 based circuit  and never saw one applied liked this ??

To negate the 723 output to zero, you bring a negative voltage on the output potentiometer voltage ... like the attached photo  (it's not a floating design)

What is the purpose of the  q3 r21 c16 r22 rref2  on the 723 CL pin ?   is it to have a very low current adjustment ??

To have a very low current adjustment you add a power diode in serial of your current sense resistor, that way (with current sense pot adjusted value) you will have a minimal voltage who will permit to set a very low curent ...   i have a similar 723 design at home, i can drive a led with no resistor on it can go down to 10 ma ... if i turn down the current adjustment the supply kicks into shutdown.

As i wrote  i understand your design considerations, but it is over complicated in a way ... i know you have some parts laying around and do what you can with them.

If you want  say 20vdc at the output, be sure to have at least 10vdc "overrange" dc supply at the q8 emittor,  you could have used an all npn circuit for the output section ?


https://electronicprojectsforfun.wordpress.com/power-supplies/a-collection-of-proper-design-practices-using-the-lm723-ic-regulator/

The term floating is :  the 723 ic ircuit has its own supply isolated from the main output transistors,  the 723 supply will always be higher (on top) than the output power supply, that way  any loads variations on the output will not affect the 723 regulation.

You have some mastech psu designs schematics who will show you that.


Check this link : https://bama.edebris.com/manuals/b&k/1602/

Its an b&k precision 1602  with an 723 in it, this lab grade circuit is very well designed ...

I will try to find my 10 year 723 design loll, my current limitter is "before" the output transistors section, that way all the voltages loss aren't affecting the 723 regulation, i dont use the 723 internal current limitter circuit, and the 723 is used in a foldback design if i recall.  Have to ask my friend to give it back to me for a week ...     

Kinda look a like this second attached photo

[blackdog]

Hi coromonadalix, 

Have you read all my starting points for this power supply?


Ref1 r15 r16 c10 r12 are not needed if the vcc supply max is under 40 vdc for the lm723  as per datasheet
The point is not the maximum voltage of the power supply of the LM723 but the suppression of hum and other signals from the grid!
It is also important that the DC value is stable with varying mains voltage and/or load of the power supply.
This schematic is to show what it takes to get a low Ri and a noise-free powersupply and to learn, and to learn that power supply's are not "easy" if you want to do it right.
Does everyone need such a nice low noise power supply, I don't think so, but that is not important for this topic.
This topic is there to learn from, what is important when developing a power supply.
And I have set some starting points like a single transformer winding, good dynamic behavior and no on/off abberations, what is wrong with that?
This power suppy I will never take into production, the one I build is to show anyone who wants to know how to do it with good results.

I understand the q8 dissipation circuit,  but it add  thermal loss and voltage drop before the q8 emittor, i would  not do that,  why ?
This is fitted to limit the dissipation of Q8, R10 taking over part of it to dissipate, at output voltages of the power supply below 10V.
This helps with the SOA of Q8 at larger output currents at low output voltages.
This is not so strange, was also used in HP and Harrison power supplies.

The 723 as i see this circuit is not a floating regulator, you try to do this with d3 dual diodes, but its not.  You must have dual secondaries x-former.
Yes and? Have I talked about a floating regulator? D3 is intended to make a power supply as clean as possible, so little ripple. and Ref1 makes the power supply clean like a battery.

You have some negative -3vdc  rail with your power on/off and enable on/off, i checked lots of 723 based circuit  and never saw one applied liked this ??
Yes and? am I not alowd to do it my way? If Frank Sinatra is allowd to do it his way, i have the same rights 
Have you ever tested the schematic you show yourself for on/off abberations, sensitivity to mains voltage variation hum and noise at the output, dynamic behavior etc.?
I did, because the schematic you show, was my starting point. 

What is the purpose of the  q3 r21 c16 r22 rref2  on the 723 CL pin ?   is it to have a very low current adjustment ??
This is intended to create an adjustable current limit from about 50mA to about 2.2-Ampere.
Q3 injects a current into the LM723 to make the current limit more sensitive, say my 50mA.
And yes that's a bit sensitive to temperature, but I'm not going to explain it again. 

To have a very low current adjustment you add a power diode in serial of your current sense resistor, that way (with current sense pot adjusted value)
you will have a minimal voltage who will permit to set a very low curent ...   i have a similar 723 design at home, i can drive a led with no resistor on it can go down to 10 ma ...
My starting point is that everyone can think up and build schematics the way they want.
The diode in series with the sense resistor is a solution but also creates more drop out voltage.
And I just had too little voltage available to apply this properly.
Furthermore I find 50mA as a minimum for this power supply sufficient.
If you want to test LEDs without qa serial resistor be my guest, if you would work in my company and do this kind of tricks, I would fire you. 

If you want  say 20vdc at the output, be sure to have at least 10vdc "overrange" dc supply at the q8 emittor,  you could have used an all npn circuit for the output section ?
The point is precisely to show how you can achieve good results with a little extra attention even if you have less voltage available, see also my remarks about noise and hum.

Its an b&k precision 1602  with an 723 in it, this lab grade circuit is very well designed ...
You don't find BK's LM723 power supply complex?
If I'm going to use a transformer with multiple windings, I'll build something according to the Harrison concept and throw the LM723 in the garbage can. 

Kind regard,
Bram

[coromonadalix]

I read all of the points,  that was my 2 cents comments   I simply dont like your charge pump idea and some deviations route you take, it adds complexity many other parts  etc...

You do know for the "grid hum" you have very good EMI RFI line filters who will help a lot, you know if you build an electronic supercapacitor, there's a limit too to
what the lowest noise floor will or can be (IE:  like adding tons of filtering capacitor, in the end it will have an adverse effect)

It's a classic circuit with no pfc correction.


I still dont like your q3 r21 c16 r22 ref2 circuit to go down to 50ma ...  thermal drift and other problems will or may rise.   

This is not following datasheets design and for other who may be tempted to follow or build your design,
You're right its your design, you can do what you want, but some warning should be issued, some people take things for granted you know.


If your project works and is reliable and stable  etc ...  with the specs you need,  test with inductive / resistive / capacitive loads ... shorts, reversed voltages etc...


My design was an assemblage of 2 separate designs put together, To have best of both worlds.

I will wait your final design and hope to see some reports, o-scope screenshots etc .. i'm curious too to see where it goes. and i applaud all your efforts and design considerations.

I tried tons of time to build an good 723 circuit, there was always something missing for one need or the other  loll  There should have been a new 723 chip design like the old mc1466 was ( higher voltage input / output )  there was an L146 ic who was supposed to have higher voltages ?? but same 723 functions.

Kind regards
Martin L

[blackdog]

Hi,

You do know for the "grid hum" you have very good EMI RFI line filters who will help a lot
I have already explained that I will show the 230V side later, and yes that will also contain some filtering.

It's a classic circuit with no pfc correction.
Have you also read that the first transformer is against the saturation that you do not just solve it with a pfc circuit.
That quickly becomes too complex, it is better to use a good transformer and yes that is not perfect because of the double phase rectification.
Saturation and rectification, I do not think that is a good plan.
And why do I only come up with this now, because the transformer always felt warm and I have done more tests as shown here and naturally comparing it to the toroidal transformer.

This is not following datasheets design
Do you get insecure because I don't use the example circuits in the datasheet?
I have already indicated several times that this is a learning project and that it is not meant to be "build this kit too!" "Its all  purposes! power supply!" No it is not!
If the reader of this topic does not want to become aware of this, that is his problem, not mine.

Martin, please show us your design and some power on/of behavior, noise performance on the output and pictures of the inside of you power supply.
I have become intrigued. 

Kind regards,
Bram

[iMo]

As a big fan of 723 (I own 16 pcs of it) I've always been looking for an improvement of the Current Limiting circuitry. I see there the current source feeding the CL and the 1k pot. Could you briefly explain the benfit/improvement, plz?

PS: I built my first 723 source in the simplest form many many many decades back and used it for maybe 20y. And it worked fine, with an exception of the current limiting - I always had it set to a fixed max level, what was not good, as I smoked a lot of silicon stuff with it..

I want to build another 723 one, but with the option of CL setting of 10mA, 100mA, and full xxAmp. I think those are the typical ranges which cover most scenarios with hw experiments..
10mA - the smoke test
100mA - running my latest duino design
xxAmp - charging my batteries or running my drill machine

[coromonadalix]

Managed to re-find the link example circuit.

Here's what i tought for the current limitation by adding a powerdiode, just need to recalculate the sense resistor with the adjustment potentiometer for your needs.

Only miss an powerdiode between emitor collector of the power outputs transistors.

http://www.tonyvanroon.com/oldwebsite/circ/ps3010/ps3010a.html

And the unobtanium L146 regulator :
http://www.electroniccircuitsdesign.com/power-supplies-circuits/0-40v-lab-power-supply-circuit-diagram-electronic-project-using-lm723-l146.h

See the current limiter is before the collector output, that way all the voltage loss does not affect the output regulation.


But i'm not high jacking your thread, i just want to show you another current limitation design ... simpler, same functionality and less parts ?

[blackdog]

Hi coromonadalix, 

I think it is clear that I'm going for good performance and not "less" parts, or easy for someone els.
With all those designs that you and others show, dit you see any pictures of the dynamic behaviour under pulse load and or off/enabled behaviour.
More than 90% of all schematics or designs don't talk about that, ask yourself why?

All the points I have addressed so far relate to the best possible power supply to do with a 20V transformer and 20V output voltage at max 2-Ampere.
This means that I have to deal with a lot of points and some things I can't do as nicely as with a modern power supply.
And now I'm talking about current limitation again, and I don't want to do that anymore, it's good enough for many conditions and fast!

I work more than 50 years in electronics, almost every schematic shown about the 723 on this forum i already know.
That doesn't mean I know everything, No Way! but use these schematics to develop my own version and my specification, almost all of us are standing on the shoulders of our predecessors. 

Back to the schematic, my SPlan CAD software crasht, my own fault...
I had to draw all my changes again. 

OK,
The transformer and rectifiers are tested with the bleeder resistors fitted and the supply lines loaded with about the currents I expect to run there.
After testing the coil with the resistor to dampen the Q, I decided to remove it again, it brought too little improvement.
Lets do it "Old School" R11 22 Ohm and a second capacitor brings the ripple at this point more than 20dB down, and lose about 400mV DC



My scope does not have a 500uV/Div sensitivity, but I use one of my broadband preamplifiers.
This preamp is designed by me for measuring circuits that have a low output impedance.
Therefore the input impedance is only about 25K.
This is the schematic of the preamp.



Project page on: https://www.circuitsonline.net/forum/view/135863#highlight=preamp+40db


Rippple suppression of the LM7912.
This is the input "Yellow Trace" and the output "Blue Trace" of the LM7912 regulator under full load of the rectifiers, so there is also 2-Ampere from the main power line used.


Noisefloor preamp
The noise of the preamp with the scope in its most sensitive position and the largest bandwidth, this is about 2.5MHz at -3dB.
To show that I am measuring the noise from the regulator.


Later I will explain how the current limitation works, now no more time, I still have to do some work for my customers.

Kind regards,
Bram

[dardosordi]

Really looking forward to see your progress. I’ll would like to build it! Keep up the good work.

[blackdog]

Hi, 

Yes, there is a new version of the schematic, but i want to talk about some other stuf...

This is a picture of the box where the LM723 power supply will be built in.
I decided not to use the smaller heatsink and to choose a larger model.
This heatsink comes from a DELL computer, this brand used very nice cooling material, which I have already used for several projects.
The CD box is to better estimate the dimensions, it is a CD from New Order and Joy Division are English bands and one of my favorites.



Front view.



This will probably be the setup of the transformer, 10.000uF C5 fan and the heat sink.
Also note the bridge rectifier on the side of the heat sink, now still glued at the moment of the photo, but it will be screwed on later.


This is one of the fans I have in stock which I have tested for this power supply.
It has been tested up to 18V power supply voltage and I will offer it up to 15V.
Most fans have a fairly large voltage range, just look at the big brands in the datasheets.
But apply what you like yourself, this is a fan of not so high power that cools much better at 15V, this with little noise.
Of course, the fan wears faster when running at 15V for a long time, but this will not happen too often, only at low output voltages and at the maximum current this power supply can deliver.
It is not a production power supply, it is a power supply for my LAB Bench, for testing various circuits.
But tlater I tell you more about the fan and its control.



Here you see the bottom of the heatsink that is normally printed on the Intel processor.
First I mounted four nylon bushes to isolate the heat sink.
The Collector of the 2SA1943 is mounted directly on the heat sink for the lowest thermal resistance.
This helps with the efficiency of the cooling block and also helps to keep the chip temperature of the 2SA1943 as low as possible and eventually results in a lower fan speed and noise.
All parts that are screwed onto the cooling element are provided with a thin layer of silver compount just like a processor cooling.
This picture shows what I want to mount on the cooling block, that are many parts.
The white part is "clickson" of 50 Celsius which interrupts the 230V mains voltage when you exceed this temperature.
I have here the 50 and 60 degrees Celsius in stock.
There will be two of these "clicksons" in this power supply, I will also mount one on the transformer.


These are the parts that are most important and for that I drilled holes and tapped M3 thread.
The setup was chosen with care and in the end it took me two hours to come to this setup.
I wanted the wiring to be as short as possible and the two big heat sources, that is the 2SA1943 and the 4.7 Ohm resistor not too close to each other and not too close to the edge of the heat sink.
With this setup that I show here, I think I succeeded well.
Right next to R34 the 0.22 Ohm resistor, we assemble the driver transistor for the 2SA1943.
There is still room left for the MOSFet that will control the fan and another power resistor that will only dissipate 1-Wat maximum.
When I have determined the position of all the parts on the cooling element, I'll flatten the heat sink and also the 2SA1943 transistor for the best heat transfer.


This is the fan controller, I have used this schematic several times with good results.
I designed it so that the fan always runs at a minimum speed at which the fan runs reliably.
The noise level at this speed is so low that it can only be heard close to the fan.
I also chose the fan on Power On which runs at full speed for a short time.
I use a MOSFet to control the fan, the sensor is a small glass of NTC that is mounted in the Heatsink just below the chip of the 2SA1943.
R5 in the schematic sets the minimum fan speed.
If the NTC measures above a certain temperature, the IRF540 slowly starts to conduct.
 P2 sets the temperature at which the fan starts running at a higher speed.
Usually I set it in such a way, that around 35C heatsink temperature the speed increases.
Always running the fan ensures, among other things, that the temperature inside the housing and provides more DC stability.

Depending on the fan used and how well the NTC is connected to the heat source, the IRF540 can be replaced by an IRF840 for a low power fan.
The IRF840 is less Transconductance about 5S and the IRF540 is 9S.



This is the starting point for the 230V grid voltage side.
Here too I have to do some tests to determine the optimal component values.


This is it for today. 

Kind regards,
Bram

[xavier60]

It's a bit difficult to see, the wiring of the IRF4095 doesn't look right. Current flow would need to be into the Source pin.

[blackdog]

Hi xavier60,

Current flow would need to be into the Source pin Why?  i like "MagicSmoke!" 

That will be the third time I have to change this...
My brain is trolling me 

Thanks,
Bram

[blackdog]

Hi xavier60, 

It is incredible how blind I can be from time to time for errors I draw in the schematic and then also apply in building this power supply.
Of course, those mistakes come to light when I'm testing.
But of course they take a lot of time.
So I'm happy with your comments about the schedule and its setup.
To show even better how things go wrong, I'll show you here below how I first draw the schematic while thinking of the dissipation limiter.
No errors...
But it went wrong when I started turning the IRF4905 to fit it easy on the schematic sheet and forgot to mention the S, D and G for the connections.
I find it valuable to show the mistakes I make, because this is part of designing circuits. 



The last schematic, I hope I have drawn the dissipation limiter correctly now.



Then some info about the fan control.
On the breadboard just behind the heatsink is an IRF540/IRF840 MOSFet and the power comes from the Rigol DP832.
The middle output is set to 15V and the right output of the Rigol varies between 0 and +5V.



I like it when I slowly vary signals to read them via an analog meter.
I use a beautiful PHILIPS PM2505 meter here.
There was some dust on the meter scale because I hadn't used this measuring instrument for a while and I removed it with my finger and continued measuring...
Que! what is this, this is not possible. The meter indicated values that were not possible on the chosen measuring ranges, is it broken?
Of course I checked the batteries, which turned out to be good.
Measuring instrument switched off and then it indicates 5V!!!
Then I got an inspiration, this I have had more with analog meters with a plastic housing, static electricity..
I could vary the needle by keeping my finger closer or further away from the meter scale.
I cleaned the entire measuring instrument with screen cleaner and then the problem was over.
One of the reasons this happened is that the humidity value here is currently around 30%, it freezes a little here and the central heating is on.
These are bad conditions for electronics.



When I finished determining the control range I fed the fan from 15V and started experimenting with the distance between the fan and the heat sink.
If the fan is against the heat sink, the fan makes the most noise, I think this is because there is too much turbulence.
About 3mm distance is enough to get the minimum noise level with the fan I use and this heatsink.

Later this afternoon/evening I will test the heatsink and transistor with 60-Watt dissipation power to see what the cooling power of this setup is.
For this I drill an extra hole in the heatsink to mount a 5K measure NTC which will be connected to one of my Keysight 34461A measuring instruments to log it properly.
The energy I then let come from the Rigol DP832 Power Supply, then I can directly read the power consumption on the display.
I will show some pictures of that, just like the corrected wiring around the 4.7 Ohm resistor and the IRF4905 MOSFet.

Kind regards,
Bram

[iMo]

FYI - you may try with this precision current limit with log pot scale when keen on good quality
All you need is: dual opamp, 6 resistors, 1 diode, 1-2 caps, 1 linear potentiometer.

[blackdog]

Hi imo, 

I'm looking forward to your real hardware tests and scoop pictures of how your circuit is working.

Kind regards,
Bram