0-30V Stabilized Power Supply

[charlie500]

hellow there i have been looking at 30v supply and audioguro has stated that
power supply has to drop about 89 watt at lower voltage and high amps
has anyone thought of putting a voltage pre-regulater circuit at the bridge side of circuit that wiil cut down the voltage on main capacitor.this works by cutting voltage at main cap at say 7 volt above output this tracks voltage automatically.the circuit only consists of about 5 tansistors and a scr.will try and put drawing up i am new to this forum and am trying to find my way around.if there is any interest i will post?

 

[akademiker]

Hi guys, i assembled the first version of this p.s.u. and found the improved version just today, sampled the TLE2141 today and then i will update my board. But my first version does not work: Potentiometer for voltage regulation only changes the voltage from 34V to 17V when he hits zero ohm, also the led is glowing the whole time and when i set the current pot to nearly full limitation and add a load it glows brighter. Also the voltage at D8 (the 5,6V Zener Diode) is only 4,6V and the output of U1 is 9,2V. Are my TL081 broken or don't they work on this voltage correctly, U3 and U2 have about 39V and U1 34V? (I tested them in a test circuit afterwards, seemed not to be damaged).

thank you in advance

 

[audioguru2]

Hi guys, i assembled the first version of this p.s.u. .... But my first version does not work: Potentiometer for voltage regulation only changes the voltage from 34V to 17V when he hits zero ohm

The voltage setting pot should feed 0V to 11.2V to U2. If it is 0V but the output of the supply is 17V then maybe Q2 or Q4 have their pins mixed up and are acting like a zener diode.

also the led is glowing the whole time and when i set the current pot to nearly full limitation and add a load it glows brighter.

U3 is the current regulator that is supposed to act like a switch. when it does not regulate current then the LED is supposed to be turned off. When it regulates the current then the LED is supposed to be completely turned on.

Also the voltage at D8 (the 5,6V Zener Diode) is only 4,6V and the output of U1 is 9,2V.

The zener diode should be able to work at a low current. You probably used a zener diode thast works at a high current. R4 has a value that is too high since it limits the current in the zener diode to only 1.2mA. Use a BZX79C5V6 zener diode that is rated at 5mA and change R4 to 1k ohm for a current of 5.6mA.

Are my TL081 broken or don't they work on this voltage correctly, U3 and U2 have about 39V and U1 34V? (I tested them in a test circuit afterwards, seemed not to be damaged).

The absolute max allowed supply voltage for a TL081 is only 36V so yours have a higher voltage that might destroy them.

 

[akademiker]

The voltage setting pot should feed 0V to 11.2V to U2. If it is 0V but the output of the supply is 17V then maybe Q2 or Q4 have their pins mixed up and are acting like a zener diode.

Q4 was broken and is now a diode

U3 is the current regulator that is supposed to act like a switch. when it does not regulate current then the LED is supposed to be turned off. When it regulates the current then the LED is supposed to be completely turned on.

so i need to increase the resistance for the diode?

The zener diode should be able to work at a low current. You probably used a zener diode thast works at a high current. R4 has a value that is too high since it limits the current in the zener diode to only 1.2mA. Use a BZX79C5V6 zener diode that is rated at 5mA and change R4 to 1k ohm for a current of 5.6mA.

you're right, i got a 1,3W diode, i'm gonna buy a 500mW tomorrow

The absolute max allowed supply voltage for a TL081 is only 36V so yours have a higher voltage that might destroy them.

TLE2141CP   3 of 3 part(s) Shipped   10 Feb 2010   i love Texas Instruments

 

[audioguru2]

so i need to increase the resistance for the diode?

Something is wrong in the U3/R7 circuit.

you're right, i got a 1,3W diode, i'm gonna buy a 500mW tomorrow

No.
A 1N4734A zener diode is rated at 500mW. But its voltage is rated when the current is 45mA which is much too high. It might not regulate when its current is only 1.5mA or 5.6mA.
1N752A and 1N5232B zener diodes are also rated at 500mW. But their voltage is rated when the current is 20mA which is also too high.
1N5994B and BZX79C5V6 zener diodes are also rated at 500mW but their voltage is rated when the current is 5mA which is good.

 

[akademiker]

Something is wrong in the U3/R7 circuit.

Ah, finally found it, I mixed up the collector and emitter of the PNP transistor, can't believe I was that stupid, I should really use PNP more often  :
I guess this explains most of the led problems in this topic.

No.
A 1N4734A zener diode is rated at 500mW. But its voltage is rated when the current is 45mA which is much too high. It might not regulate when its current is only 1.5mA or 5.6mA.
1N752A and 1N5232B zener diodes are also rated at 500mW. But their voltage is rated when the current is 20mA which is also too high.
1N5994B and BZX79C5V6 zener diodes are also rated at 500mW but their voltage is rated when the current is 5mA which is good.

Of course i choosed one with 5mA, now my psu should finally work and with the new op amps even better. Thank you very much for your patience!

 

[GabrielRR]

I built the original version about two years ago ( with the Voltmeter + Ammeter LCD panel ) and it works wery good, but now i need some more power and i decided to built the new version with the 5 A output ( it is possible to become 7A with more powertransistors ? I have a 30V~ / 10 A trafo ). I used EAGLE ( i don't make publicity for EAGLE !! ) to make a single PCB layer with only 3 wire on top of PCB. The C1 ( 2x10.000

 

[audioguru2]

I want to generate square pulses using your 5A power source, but with 2MHz frequency using a simple circuit with a mosfet, a optocoupler and a signal generator. I want to now if there is any problem.

One guy powered a switching power supply from this project. It caused C7 at the output of this project to get hot and explode.

 

[GabrielRR]

I built the original version about two years ago ( with the Voltmeter + Ammeter LCD panel ) and it works wery good, but now i need some more power and i decided to built the new version with the 5 A output ( it is possible to become 7A with more powertransistors ? I have a 30V~ / 10 A trafo ). I used EAGLE ( i don't make publicity for EAGLE !! ) to make a single PCB layer with only 3 wire on top of PCB. The C1 ( 2x10.000

 

[GabrielRR]

One guy powered a switching power supply from this project. It caused C7 at the output of this project to get hot and explode.

Thanks

 

[lysium]

hi audioguru,

i have opa445 on hand right now, so which schematic should i use?

thanks,

 

[akademiker]

upgraded the psu and put in the 3 TLE2141. Pin 3 of U2 has now an input voltage from 0-11,2V, just like it has to be, but the output voltage at pin 6 of U2 is 33V when voltage at Pin 3 of U2 is higher than 0V and is 0V when Pin 3 of U2 is 0V. When the output voltage of pin 6 is 0V, then the voltage at the output of the power transistors is 3,5V. The across pin 4 and 7 of U2 is 35V. Please help, i have no clue  ???

EDIT// Nevermind, forgot to connect the Cathode of D11 (the Minus -) to the +-Output

Works like a charm, although it is only decreaseable to 100mV but I dont care

 

[audioguru2]

i have opa445 on hand right now, so which schematic should i use?

The original circuit has many overloaded parts.
The OPA445 will not work in the latest schematic.

I don't have the modified schematic for the OPA445 opamps because that was years ago and the schematic is the same as the original except R10 must be connected to -5.6V. Here is the parts list:View attachment 40879

 

[lysium]

ok

Thanks audioguru.

 

[jeroenj_1989]

I built the original version about two years ago ( with the Voltmeter + Ammeter LCD panel ) and it works wery good, but now i need some more power and i decided to built the new version with the 5 A output ( it is possible to become 7A with more powertransistors ? I have a 30V~ / 10 A trafo ). I used EAGLE ( i don't make publicity for EAGLE !! ) to make a single PCB layer with only 3 wire on top of PCB. The C1 ( 2x10.000

 

[Holt]

If you look at Tesseract

 

[jeroenj_1989]

If you look at Tesseract

 

[Holt]

If you look in the parts list in the first post at page 1 you can see 3 types of transistors suggestet, and that the resistors should be in the area of 0,33 ohm, two transistors for 3A and three transistors for 5A

http://www.electronics-lab.com/forum/index.php?topic=19066.msg87803#msg87803

 

[jeroenj_1989]

If you look in the parts list in the first post at page 1 you can see 3 types of transistors suggestet, and that the resistors should be in the area of 0,33 ohm, two transistors for 3W and three transistors for 5W

http://www.electronics-lab.com/forum/index.php?topic=19066.msg87803#msg87803

This is probably a very stupid question (maybe not   )
but why do I need 3 Transistors for a 5 amp supply?
I checked the datasheet for the MJ11015, and it states it can handle 200W.
From my calculations, I get : 30V * 5 Amps = 150 W...
I should say one transistor is enough...

 

[jeroenj_1989]

This is probably a very stupid question (maybe not   )
but why do I need 3 Transistors for a 5 amp supply?
I checked the datasheet for the MJ11015, and it states it can handle 200W.
From my calculations, I get : 30V * 5 Amps = 150 W...
I should say one transistor is enough...

Quoting on my one entry, pfffff

Anyway, it's probably because of the heat development in the transistor.
It's possible to use only one transistor, however a big (active) cooler is necessary.
It think I will go with 3 transistors, I will get back to you with the results.