Suggestions how to increase the V on this Reg PSU.
The attached schematic shows the V is statically set to +/- 25Vout. For example a torroid that is rated at +/-35 V this Reg PSU steps it down to +/-25V.
The goal is to increase the PSU V by +/- 4V on each side. This PSU powers an 100W amp @ 8 ohms.
This part of the PSU is for the input stage only, hence the amp will be minimal.
See attached
The attached schematic shows the V is statically set to +/- 25Vout. For example a torroid that is rated at +/-35 V this Reg PSU steps it down to +/-25V.
The goal is to increase the PSU V by +/- 4V on each side. This PSU powers an 100W amp @ 8 ohms.
This part of the PSU is for the input stage only, hence the amp will be minimal.
See attached
Attachments
Last edited:
Build like the schematic you allready get + and -30V out !
Condition is, the input voltage has to be some 2volts higher then the output.
Mona
Condition is, the input voltage has to be some 2volts higher then the output.
Mona
,,
I have built two of these.
When using a trafo with a higher V say 30V or 35V etc. The V out is always +/-25V
I have built two of these.
When using a trafo with a higher V say 30V or 35V etc. The V out is always +/-25V
> V is statically set to +/- 25Vout
So, how?
On inspection, it is a 15V Zener, a BJT diff-pair (essentially zero V), and another 15V Zener. Output is 30V.
> V out is always +/-25V
So 15V+15V = 25V?
Look what voltage is really happening at each Zener. Maybe you got 13V Zeners. Maybe you got 15V Zeners so big that at the low (and unspecified) current used here they only drop 12V-13V.
So, how?
On inspection, it is a 15V Zener, a BJT diff-pair (essentially zero V), and another 15V Zener. Output is 30V.
> V out is always +/-25V
So 15V+15V = 25V?
Look what voltage is really happening at each Zener. Maybe you got 13V Zeners. Maybe you got 15V Zeners so big that at the low (and unspecified) current used here they only drop 12V-13V.
Attachments
me> unspecified) current used here
Apologies. I did not recognize "J505" as a type. It is 1mA.
And the Zener is specified 13.8V-15.V at 5mA. And 30r slope at that point.
The 4mA difference and say 50r slope to 1mA gives about a 0.2V droop. Assuming low-end voltage spec 13.8V, you should have 13.6V, twice, 27.2V. The 2Vbe can't possibly be another 0.1V (likely nearer 0.01V). This does not agree with your "25V" observation.
It is interesting that the design relies ONLY on Zener tolerances. Most regulators have a resistor ratio you could tweak. You could re-design this one that way. I don't know what benefits you might lose.
Apologies. I did not recognize "J505" as a type. It is 1mA.
And the Zener is specified 13.8V-15.V at 5mA. And 30r slope at that point.
The 4mA difference and say 50r slope to 1mA gives about a 0.2V droop. Assuming low-end voltage spec 13.8V, you should have 13.6V, twice, 27.2V. The 2Vbe can't possibly be another 0.1V (likely nearer 0.01V). This does not agree with your "25V" observation.
It is interesting that the design relies ONLY on Zener tolerances. Most regulators have a resistor ratio you could tweak. You could re-design this one that way. I don't know what benefits you might lose.
Bruno's surname is Putzeys.
It would be relatively easy to add a resistor in series with each of those Zeners.
Each ohm added to both Zeners will raise the output voltage by 2mVdc.
1k0 in series with both, lifts output by 2Vdc
T5 & T6 are low current and low power. Don't expect big current outputs.
It would be relatively easy to add a resistor in series with each of those Zeners.
Each ohm added to both Zeners will raise the output voltage by 2mVdc.
1k0 in series with both, lifts output by 2Vdc
T5 & T6 are low current and low power. Don't expect big current outputs.
Last edited:
Resistors in series with Zeners will reduce any regulation by increasing the virtual impedance of the zener. Use the correct value zener or adjust the gain of the multiplier accordingly!
A PM tells me that an added feature requires "300VA 30V" PT.
Because I was looking at the voltage-set question, I overlooked that the intent is to power a POWER amp as well as an "input stage".
The rectifier and filter affair shown will not share well with another power supply. The string of 2R2 in both legs of the filter cleverly break-up leak-paths in the filtering. There is not enough power at C11 C14 to tap a respectable power amp, sag will be bad and uFd quite low. If the Power amp has its own rectifier, it will effectively short-out the 2R2 strings in the common leg.
Mix-and-match is fun to a point, but you have to work out what really happens.
I'm avoiding the direct question in PM because I think there are larger issues, perhaps best discussed in public forum.
Because I was looking at the voltage-set question, I overlooked that the intent is to power a POWER amp as well as an "input stage".
The rectifier and filter affair shown will not share well with another power supply. The string of 2R2 in both legs of the filter cleverly break-up leak-paths in the filtering. There is not enough power at C11 C14 to tap a respectable power amp, sag will be bad and uFd quite low. If the Power amp has its own rectifier, it will effectively short-out the 2R2 strings in the common leg.
Mix-and-match is fun to a point, but you have to work out what really happens.
I'm avoiding the direct question in PM because I think there are larger issues, perhaps best discussed in public forum.
- Status
- Not open for further replies.