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limbo243

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  1. Hello PicMaster! Have a look at my post from August 27, 2009, 05:18:37. I posted my schematic with my bill of materials. I built this power supply and it works perfectly! I used a 2x30V/230VA transformer in order to build a dual version. Link to transformer: http://shop.conrad.at/ce/de/product/518458/RINGKERNT2X30V230VA My tip for using a 30V transformer: Build up the circuit with D15 (in my schematic). And then measure the positive supply voltage. If there are 44V you don't need D15. If the voltage is higher - use a Zener-diode which fits to your circuit. For example: Positive Supply: 45V Max OAMP Supply: 44V 45V-44V= 1V Zener-Diode. In my circuit, I did not need D15, although I used a 30V transformer! I don't know if the OPA445 will work. The MC34072 I used was 0,97
  2. Hello! Yesterday I got an oscilloscope to see if there is an output voltage ripple. And I have to say: I was not able to see a ripple. Not even by 0,05V/div. I measured it by 30V 0A; 30V 3A; 1V 3A;... with current limiting and without My power supply works very fine! ;D Thx for all your help! bye Markus
  3. Hi audioguru! Thank you :D The schematic is for simulation only. I added a small statement in the schematic: "For parts value see bill of materials". There you can see that I used a BD139 for Q2. In LTspice IV there is no BD139 in the database ::) I also don't know why the current limiting failed by min current. I was not able to find a mistake in my circuit. I decided to say it is because of the oamp offset :P I have no oscilloscope to see if there is a ripple by 30V at 3A. I only have the small multimeter which shows 30V and 3A. But if I get the chance for an oscilloscope I'll post a picture. Do anyone have a 10Ohm 90W resistor for testing the power supply at maximum? ;) by limbo
  4. Hy Guys! Okay - after 1 damaged Zener and 2 damaged power transistors my power supply is now finished. My experience: - I used the MC34072 oamps with max.44V instead of the MC34071. With the MC34072 I was not able to do the offset compensation. So the current limiting became a problem. ( When I turned the current limiting to minimum, it stopped limiting the current and damaged the power transistors with 24A output >:( ). So I used a 68Ohm resistor for R17 and all worked perfectly. - I used a 2x30V - 230VA Transformer with 32.47VAC without load. The problem is the voltage without load of about 45.91VDC - too much for the oamp. So I decided to use D15 in my shematics. In practice, the max voltage is about 44.1V so it will also work without D15. Here are pictures of my working Power Supply, my shematics with the (hopefully...) correctly bill of materials for my shematics. I decided to give you my bill of materials because there are a view mistakes and missing parts in the existing list. Sorry for my bad english - hope everyone can understand me :-[ means Markus PS: More pictures in my next reply Update: After a view tests at maximum output (30V 3A) I saw that D15 (10V Zener) in my schematic only allows an max output of about 24V at 3A. Or about 2.7A at 30V... So I decided to throw D15 away and replaced it with a peace of wire. Now I am able to get 30V with 3A. If someone has the same problem as I (The rectifier voltage is to high for the oamps with 44V) you can use D15 which should have only as much voltage as you need to get under the 44V. The voltage in my circuit is about 39.6V - 44V and nothing is damaged. billofmaterials_V1_2.txt
  5. Hi! Thank you for your fast answer! I can put your mind at rest - the rectifiere-diodes are for simulation only 8) I have found a diagram for the Fuse - it will not be blown by the current :) I haven't found a MC34071 so I decided to use 3xMC34072. But thanks for the advice! The transformers data are correct - it has two secondary windings with 30V means 2x30V with 3.83A=230VA. The second winding will be for a second power supply if the first works. ;) But now I still have the Problem with the transformer: Without load it has 32.47V*sqrt(2)=45.9V minus 1.2V from the 10A Bridge Rectifiere = 44.7V! The Simulation shows that the voltage is increasing slowly to about 45V (don't know why :-[ I don't care...) It's close... I have no experience with oamps and too much supply voltage but could it be possible to work with them or are there any other oamps I can use? Maybe a "OPA 551PA"? Datasheet: https://www.distrelec.com/distrelec/datasheets.nsf/WebAttachments/F11F0007492D7988C12570E90019A751/$File/641297.pdf Thanks! Markus
  6. Hey Guys! It seems to be a view gurus here and I hope someone is able to help me! I bought the whole parts which are needed for the second project shown in the schematic. I have simulated the schematic and now I am not sure if some parts will be damaged. I used a 30V 230VA Transformer with max. 3.83A. My first Problem - the voltage of the transformer without load will be 32.47V. 32.47V*sqrt(2)=45.9V :o Is this to much for the MC34072? Maybe I can use a smaller value for R1 to hold the transformer-voltage small? And the second question is shown in the simulation file of I_C1. The current through the capacitor by 3A output will have peaks up to 6.5A. The fuse will be "4A slow" and the transformers max. current is 3.83A. The same problem in the first view milliseconds. Will the transformer or the oamps be damaged? And if it will be - what should I do because the transformer and C1 are very expensive!!! Thanks for your help!!! Markus
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