# Basic Linear Power Supply

Joined Mar 7, 2020
10
Hello everyone!
I'm trying to make a power supply that goes between 10 to 15V and is able to supply a maximum current of 1 amp.
Here is a photo with my circuit so far:

One thing to note: R11 is supposed to be the load resistance.
First thing first, I'd like to ask if there is any way to lower the current going through the diodes of the bridge rectifier without damaging the final output.
I tried limiting it with an inductor between the rectifier output and the filter capacitor and it works, but sadly it damages my output signal.
Is there any way to do it, or I'll just have to use diodes with a maximum forward current of 10 amps?

Also if you could point any flaws in my design or things I could improve, I'd like to hear some advice.

Thanks in advance to anyone willing to help me!

#### AlbertHall

Joined Jun 4, 2014
11,129
You could replace most of that circuit with an LM317.

Joined Mar 7, 2020
10
I know, but It's for a project and I have to design it myself.

#### SamR

Joined Mar 19, 2019
3,192
So this is a school project to design a power supply regulator without using an existing voltage regulator IC?

#### atferrari

Joined Jan 6, 2004
4,244
Have you verified the maximum collector current for the 2N2222? Surely not apt for your specs.

#### AlbertHall

Joined Jun 4, 2014
11,129
Check the maximum current rating for Q1.
Q2 will draw lots of current from the TL02 output. I don't know whether it will like that.

#### dl324

Joined Mar 30, 2015
12,681
First thing first, I'd like to ask if there is any way to lower the current going through the diodes of the bridge rectifier without damaging the final output.
I tried limiting it with an inductor between the rectifier output and the filter capacitor and it works, but sadly it damages my output signal.
Is there any way to do it, or I'll just have to use diodes with a maximum forward current of 10 amps?
Why do you want to limit current? That's primarily determined by the load. Just use a rectifier rated for 3A.
Also if you could point any flaws in my design or things I could improve, I'd like to hear some advice.
Q1 won't handle 1A. The opamp will likely only source around 25mA. When you replace Q1 with a power transistor, it may need to be a darlington.

#### ci139

Joined Jul 11, 2016
1,696
? Q2 EC orientaion/direction -- the reverse ß is about 8 , ... , 4 or less (it will provide poor current limitting) . . . also to enshure less noise/ascillation at turn on put the ≤50kΩ from Q1.B to GND

for 1 amp output use at least 3 2N2222 in parallel - each with sufficient PCB cooling space or use more powerful "Switch" as MJE13005
( ... yes , as the prev post #7 notes the low ß for power transistors may need a darlington setup for the TL082 to able to drive it )

Joined Mar 7, 2020
10
So this is a school project to design a power supply regulator without using an existing voltage regulator IC?
Exactly. That's what I need.
Why do you want to limit current? That's primarily determined by the load. Just use a rectifier rated for 3A.
Q1 won't handle 1A. The opamp will likely only source around 25mA. When you replace Q1 with a power transistor, it may need to be a darlington.
I want to limit the current because the diodes in the rectifier are rated for 1A max. And when the load is pretty low, say 15 Ohms, the current through the diodes can get as high as 6A. I could replace the diodes, but I was curious if there is another way around it.

Joined Mar 7, 2020
10
I will try to replace the transistors as well, with something that can handle the load.

#### ci139

Joined Jul 11, 2016
1,696
value of the R6 and the pin assignment of the Q2 should limit your output current if the q2 is too insensitive use 2N3904 or double 1N4148 or give a mild cc bias to the emitter of the Q1 or use another TL082 to sense and limit the current (might be tricky to get such stable)

Joined Mar 7, 2020
10
value of the R6 and the pin assignment of the Q2 should limit your output current if the q2 is too insensitive use 2N3904 or double 1N4148 or give a mild cc bias to the emitter of the Q1 or use another TL082 to sense and limit the current (might be tricky to get such stable)
That's true. The R6 and Q2 are limiting my output current to 1A max. But I was wondering if I can limit the current through the diodes so I don't burn them up.

#### ci139

Joined Jul 11, 2016
1,696

Joined Mar 7, 2020
10
I've read about that but not the Inrush current is the problem but the overall current itself.

#### ci139

Joined Jul 11, 2016
1,696
and is able to supply a maximum current of 1 amp
the problem but the overall current itself.
? is there something you haven't mentioned yet your RMS input is 1A+regulator losses - use double or more 1N4002-s in parallel
... however "Non−Repetitive Peak Surge Current 30A (for 1 cycle)" . . . the Russian 1.5A low voltage rectifiers have some 3kΩ resistors in parallel with the diodes to protect from junction discharge currents damaging the diodes --e.g.-- a leaky bridge

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#### MrAl

Joined Jun 17, 2014
8,066
What is Q2 doing for you?