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0-30V Stabilized Power Supply


redwire
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OK, so I ecthed my first double sided boards, not too bad if I say myself!  :)

Just need to trim and drill. hopefully will have a the components early next week.

Stupid question, but how do you get the board that nice green colour? is it the protective stray or a differnent type of board?

post-53956-14279144204276_thumb.jpg

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The green coating is a solder resist layer which ensures the solder only sticks to the parts of the board that need to be soldered.

I don't know if there's a way to do it yourself but you can get a green conformal coating which protects the copper track from corrosion and makes it look nice. I don't bother myself, if I use a conformal coating, I use a clear lacquer which is less expensive.

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If I had to run the output from this PSU to a PWM controller, would this have any ill effects on the PSU, even when current limiting?

PWM will run at a 1khz.

One guy used this project to power a high frequency (hundreds of kHz) switching power supply. The electrolytic capacitor C7 on the output blew up due to the high ripple current in it. A film capacitor will not blow up and your low PWM frequency will be gentle to a film output capacitor.
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Hello! What do you guys think about this schematic I made?

I would like 7 amps output. That means I should use around a .22Ω shunt resistor, right? I also plan to have 9 TIP3055's in parallel on a large heatsink. Couldn't modify it for the TO-3 one. I left that part out because this is just what's going to be on the PCB!

Thanks in advance!

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I would like 7 amps output. That means I should use around a .22Ω shunt resistor, right? I also plan to have 9 TIP3055's in parallel on a large heatsink. Couldn't modify it for the TO-3 one. I left that part out because this is just what's going to be on the PCB!

Each output transistor will have a max current of 778mA. At this current their minimum current gain is 60 so the driver transistor must supply 117mA and will need a heatsink. A TIP3055 is too slow for the driver and its minimum current gain is too low. Use a BD139 transistor instead. 
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  • 2 weeks later...

this power supply is incredibly amazing. can you please give me the eagle file for the latest modified schematic and final pcb design?..


thanks in advace...

I am working on this. I completed .sch file in eagle and now I am working on PCB project. When I am finished, I will publish it here.
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  • 2 weeks later...

Hi All

I'm having a bit of a problem with the adjustments...

1 - With the current pot set to min the current limit LED lights up, and it has a MIN voltage of about 100mv, can't get it any lower by adjusting RV1.

2 - I find RV2 makes no changes to anything when adjusting?

3 - The Voltage pot is LINEAR, but behaves like a LOGs, when adjusting the voltage, anything over say about 10V becomes extremely difficult to dial into, when you get to about 14V the current limiting kicks in, and the POT is SO SO sensitive. Same applies with the current limiting LIMIT adjust (RV3) behaving the same way, changes the limit from about 1A to 2.5A with about 3/4 turn on a 20 turn VR.

4 -  I also only seem to get a max of 2.5A output.

Thanks in advance

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Hi Lighty,
Which opamps did you use?

Did you use Redwire's schematic? It is very hard to read with most opamps shown upside-down, many diagonal lines and missing output transistors and adjustment pots.

U2, Q2 and the output transistors are simply an amplifier of the 0V-11.2V from the voltage adjust pot with a gain of 1.93 to 6.6. The gain is adjusted with RV2 and with the voltage pot at max RV2 is adjusted for an output of 30.0V. But your transformer voltage is too low for 30.0VDC at 3A.

The current in the load is also in R7 which is 0.47 ohms for a max of 3A output. The voltage across R7 is caused by the load current and is compared by U3 with the voltage set by the current-setting pot. RV3 adjusts the sensitivity of the current-setting pot.
With no load current then R7 has no voltage drop and the current-setting pot feeds a small positive voltage to the (+) input of U3 so its output goes high and it does not limit the current.

RV1 nulls the input offset voltage of U2 and is adusted for an output of 0.0V when the voltage setting pot is set to minimum. But C7 is an electrolytic capacitor that stores a charge (electolyte absorption) which causes a positive output voltage for a long time. If C7 is a film capacitor then adjusting for 0.0V is easier.

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Hi all
I have redrawn the schematic again and I've managed to find some time and finial got round to lay out a single side PCB 75mm X 100mm, Now I have checked the schematic over and for checking and checking it over I'm 99% sure it is correct and can't see anything for looking, I'm ready for the next stage to etch the PCB and get it built up, But before I do that I would like a second opinion to make sure the schematic is 100% correct this will help me to save waisting time and money on the PCB'S. Some of the values may be incorrect, So far I've mainly focused on the connections, The Values and be corrected later and I can draw up the parts lsit.

Once I know the schematic is 100% correct I know the PCB will be 100% has I've ran the DRC rule check without any errors. I will then share the PCB layout for everyone. This will also cause less confusion over which layout is correct if I uploaed cerytime corrections where made if any

Thanks

Power_supply_V1.pdf

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Hi Audioguru

I've used the TLE2141 opamps.

I used Redwire's Eagle BRD along with your parts list.

OK OK,  :-[ Stupid me, I had the wipers from the POTs connected incorrectly, not meant to be in the middle screw... >:(

But I still have one problem, I can't seem to set the max current limit by means of VR3. I have shorted the output though my meter, and no matter the adjustment of VR3 the current rises over the 4amp mark when I quickly increase and decrease the current POT setting.

What else could I have messed up with?

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I can't seem to set the max current limit by means of VR3. I have shorted the output though my meter, and no matter the adjustment of VR3 the current rises over the 4amp mark when I quickly increase and decrease the current POT setting.

What else could I have messed up with?

Since your current regulator does not work then U3 or D9 are not working. Maybe D9 is open or is disconnected.
Maybe you messed up the connections to the current-setting pot or VR3.
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Since your current regulator does not work then U3 or D9 are not working. Maybe D9 is open or is disconnected.
Maybe you messed up the connections to the current-setting pot or VR3.


Sorry Audioguru, I think I wasn't clear, the current limiting function is working when adjusting on the POT, but the VR3 "MAX" limit doesn't seem to be working. Since my transformer is only 125va, I need to limit the maximum at 3A prevent any damage.
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Sorry Audioguru, I think I wasn't clear, the current limiting function is working when adjusting on the POT, but the VR3 "MAX" limit doesn't seem to be working. Since my transformer is only 125va, I need to limit the maximum at 3A prevent any damage.

VR3 is in series with R18 and the current-setting pot so it sets the max current before the current-regulation reduces the output voltage. The max resistance of RV3 is 100k and it is in series with R18 which is 20k so their total is 120k ohms. The original project used a total of only 56k so its max current was about 4.1A. With RV3 at 100k plus 20k in series for R18 your max current should be 2.06A.
If your RV3 is set at halfway to 50k then in series with R18 the total is 70k then the max current should be 3.35A. The current-setting pot should be 10k ohms. R17 should be 33 ohms. R7 should be 0.47 ohms.
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You missed the second output transistor, the emittrer resistors for both output transistors and the emitter resistor for the driver transistor.


Thanks for that, I did for get to add the resistor to the BD139, The reason is I had the idea of having the BD139 and the ouput transistors and the emitteres resistors on a seperate board so they can bolt direct to the main heathisnk rather than have 2 heatsinks for them. I wll sort that out either add them to the main board or go back to the first idea,
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Thanks for that, I did forget to add the resistor to the BD139, The reason is I had the idea of having the BD139 and the ouput transistors and the emitteres resistors on a seperate board so they can bolt direct to the main heathisnk rather than have 2 heatsinks for them. I wll sort that out either add them to the main board or go back to the first idea,

Then your schematic is confusing like Redwire's since parts not on the pcb are not shown.
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