Good evening Jan ,
Yes , this is the regulator discussed in this thread .
Wanted setting is 30 Volt out , 3 Volt dropout across the darlington .
I simply can't reach the output voltage of 30 Volt while remaining 3 volt dropout.
Simply said
Yes , this is the regulator discussed in this thread .
Wanted setting is 30 Volt out , 3 Volt dropout across the darlington .
I simply can't reach the output voltage of 30 Volt while remaining 3 volt dropout.
Simply said
Simply missed is the input voltage you are starting with to get your desired regulated 30V output?
That circuit will range from 24+0.65 to 24+0.65 * 47/49.5, ie 24.65V to 24.61717... V. So ya, not mutch adjustment. I should have noticed this before. The typical circuit that you want is like this
although I would add current limiting etc. I was tempted to post a pointer to Sinclair project 60 power supplies, but I couldn't find the version I had back in ~1970 . It had a feature that shut it down when overloaded. I know that I tripped it many times.
although I would add current limiting etc. I was tempted to post a pointer to Sinclair project 60 power supplies, but I couldn't find the version I had back in ~1970 . It had a feature that shut it down when overloaded. I know that I tripped it many times.
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What voltages and currents are people looking for in these regulated PSs for Class A amps?
If it's only small, like the JLH 10W or some of the Pass designs, Laptop power supplies work very well. You can spend your time working on EMI stuff with some of the poorer supplies and amps with poor PSR 😊
Regulated supplies really improve the sound of a small Class A amp.
If it's only small, like the JLH 10W or some of the Pass designs, Laptop power supplies work very well. You can spend your time working on EMI stuff with some of the poorer supplies and amps with poor PSR 😊
Regulated supplies really improve the sound of a small Class A amp.
If the aim is 3 volt dropout , the desired input voltage under 1A load should be 33 Volt
You keep mixing stuff up. If you want to test Vout to 30V, make sure that you have enough Vin, like 40V.
Then see if you can get to 30V out and fix that first, post #85 will help.
Then, with Vout at 30V, lower Vin until it runs out of regulation, that gives you the min dropout.
Divide and conquer.
Jan
Then see if you can get to 30V out and fix that first, post #85 will help.
Then, with Vout at 30V, lower Vin until it runs out of regulation, that gives you the min dropout.
Divide and conquer.
Jan
Is the actual measured voltage at the regulator input the ‘should be’ voltage?
What is the ‘can’t reach’ measured output voltage. I think real measurements would help better for troubleshooting.
What is the ‘can’t reach’ measured output voltage. I think real measurements would help better for troubleshooting.
In my elektor AXL amp, which demands +/- 30VDC, my transformer secondary delivered 35VAC. Using a 28-volt zener, I could easily adjust the output voltage from 28 to 32 volts DC.
I will repeat once again that this circuit works perfectly in my 4 class A amps. The only critical component is R2, which lowers the input voltage. A 1K resistor would be perfect.
I will repeat once again that this circuit works perfectly in my 4 class A amps. The only critical component is R2, which lowers the input voltage. A 1K resistor would be perfect.
R2 is the collector impedance for the error amplifier. R1 etc can also function as that.
Do you really need R2?
The regulator would be vastly better without it but there may be a start-up issue.
Worth a try.
Jan
Hi Jan,
I managed to find the article; here's the webpage with all the details:
https://www.elektormagazine.com/magazine/elektor-198299/45113
I am not sure why this wasn't shared with the DIY community straight away, in post #1, by the thread starter...
As I suspected, the start-up circuit is missing; it is simply not part of the schematics because the regulator is designed for thermal printheads. The start-up relies on leakage currents to build up the required voltages, so that the transistors become conductive enough to work as desired and regulate the current at the appropriate voltage.
However, if the current draw is too high (as with Class A amps), the start-up will never occur, and the circuit will not function correctly (regulate at high currents - see post #44). The original design was intended for thermal printheads that consume almost no current when stationary, which allows transistors to start conducting.
I advise the DIY community to steer clear of it (this design), especially if planning to use it with demanding loads that will draw a significant amount of current. Note that the article actually states that the current regulation is poor...
I see. Yet, a regulator is a regulator and the basic circuit I think is sound - like any regulator, it has a current amplifier, a reference and a feedback loop.
Now I know what that 0.1ohm is for, it was part of the current limit which the OP deleted but he forgot to delete the current sense resistor.
I'm sure it can be morphed into a fine regulator - if you know what you are doing.
Jan
Now I know what that 0.1ohm is for, it was part of the current limit which the OP deleted but he forgot to delete the current sense resistor.
I'm sure it can be morphed into a fine regulator - if you know what you are doing.
Jan
Hello ,
Yes , decreasing the 1K5 / 5Watt to 850R brought the voltage drop 2 Volt closer to the desired 3 Volt dropout that Metanastis mentioned.
I mentioned the desired 3 Volt dropout across the darlington transistors many times here !
I know that a pass device needs voltage headroom to function properly , on the other hand , we want to keep heat dissipation w.i. limits.
Will continue in trying to get the reg functioning properly and Will post results . Accompanied with value changes.
Thank you all so far
Yes , decreasing the 1K5 / 5Watt to 850R brought the voltage drop 2 Volt closer to the desired 3 Volt dropout that Metanastis mentioned.
I mentioned the desired 3 Volt dropout across the darlington transistors many times here !
I know that a pass device needs voltage headroom to function properly , on the other hand , we want to keep heat dissipation w.i. limits.
Will continue in trying to get the reg functioning properly and Will post results . Accompanied with value changes.
Thank you all so far
The dropout depends on the regulator and the ripple on the input voltage at max current.
Maybe you can get to 3V, maybe you can get lower (unlikely), maybe you need 4V. It all depends.
It is not wise to get hooked on 3V and go around in circles with the regulator because it is not possible in this particular implementation.
As I said before, the smart thing to do is get the reg operating properly with a high input voltage, like 40V, so you are absolutely sure that Vin is not the limiting factor. Then if you get that right, lower Vin until the reg goes out of regulation and then you know the lowest possible Vi9n.
And then, mindful of the variation in mains voltage over the day, add 1 or 2 V to be sure that ypour reg doesn't drop out of regulation on saterday evening. Your transformer and rectifiers are maybe not identical with the original design. 😎
It is one thing to use an existing design as the starting point, but it is not smart to follow someones detailed design withpout thinking about it what it does for you.
You have all the building blocks to make this a succes. It's up to you, with help from your friends here.
But you need to think it through and be receptive to the posts here. Wish you success.
Edit - it's an adventure, enjoy it!
Jan
Maybe you can get to 3V, maybe you can get lower (unlikely), maybe you need 4V. It all depends.
It is not wise to get hooked on 3V and go around in circles with the regulator because it is not possible in this particular implementation.
As I said before, the smart thing to do is get the reg operating properly with a high input voltage, like 40V, so you are absolutely sure that Vin is not the limiting factor. Then if you get that right, lower Vin until the reg goes out of regulation and then you know the lowest possible Vi9n.
And then, mindful of the variation in mains voltage over the day, add 1 or 2 V to be sure that ypour reg doesn't drop out of regulation on saterday evening. Your transformer and rectifiers are maybe not identical with the original design. 😎
It is one thing to use an existing design as the starting point, but it is not smart to follow someones detailed design withpout thinking about it what it does for you.
You have all the building blocks to make this a succes. It's up to you, with help from your friends here.
But you need to think it through and be receptive to the posts here. Wish you success.
Edit - it's an adventure, enjoy it!
Jan
I not refuse that , Will provide all details as soon as I can find the time for it .