good day.
Im trying to make a super regulator to have the output of 24V dc.
the input into the regulator is 49V dc, from the universal power supply, is it too high?
when i connected the DC input one of the capacitors (c6) exploded after 10-20secs🙂
the polarity is correct.
the capacitor is 120/25V, did it explode because the cap is rated to 25V and im feeding 49V or is it for some other reason?
If it is due to low voltage rating , what other parts should be changed so that it would work properly?
r6=r13=2.49K
r7=r14=1k
Im trying to make a super regulator to have the output of 24V dc.
the input into the regulator is 49V dc, from the universal power supply, is it too high?
when i connected the DC input one of the capacitors (c6) exploded after 10-20secs🙂
the polarity is correct.
the capacitor is 120/25V, did it explode because the cap is rated to 25V and im feeding 49V or is it for some other reason?
If it is due to low voltage rating , what other parts should be changed so that it would work properly?
r6=r13=2.49K
r7=r14=1k
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If it is rated 25V and you feed it nearly twice that this very likely explains the explosion. Get a higher rated cap. If you're making a reg for 24V, 25V rated caps is too close for comfort in my opinion.
ok, i will try different capacitors , any other components should be changed for 49in/24out voltage?
For C2 you will need a cap at least rated for 50V, or better 63V.
R2 with a power rating of 0.5W would be advisable. R2 will dissipate ca. 0.22W and I think that the usual 0,25W resistor will get a bit too hot.
And D2 can be a 12V zener to put the OP-Amp output near the middle of 24V regulator output voltage.
R2 with a power rating of 0.5W would be advisable. R2 will dissipate ca. 0.22W and I think that the usual 0,25W resistor will get a bit too hot.
And D2 can be a 12V zener to put the OP-Amp output near the middle of 24V regulator output voltage.
thanks for the reply.
all resistors are either 0.5 watt or 1watt so i geuss they are ok.
so should I change only the c2 and c6 or better to change all the capacitors to 63V?
all resistors are either 0.5 watt or 1watt so i geuss they are ok.
so should I change only the c2 and c6 or better to change all the capacitors to 63V?
No need to do that. After Q1/Q3 the highest voltage to expect is your output voltage. Otherwise the OPA would be toasted🙂
Christer’s measurements are for the noise of the voltage reference only, not the whole regulator.
Yes keep R 4 as 499 and R6/R7 as 1 k each ( use 1/2 watt ) and raised off the board 1/4 inch for higher voltages. Do not change the resistors, change the voltage reference and the output zener- both to 1/2 the output voltage you want. Consider using a low noise zener ( or for low voltages use series connected red or green leds for both the Vref and series zeners). Yes the original way to change output voltage is to change the R6/ R7 resistor values, but you can’t stay as close to keeping the input impedances equal as you can changing the Vref and series zener as long as they are low noise.
Yes not thermally as stable as the precision references and Walt’s tip of putting them in silicon helps reduce the drift.
Yes keep R 4 as 499 and R6/R7 as 1 k each ( use 1/2 watt ) and raised off the board 1/4 inch for higher voltages. Do not change the resistors, change the voltage reference and the output zener- both to 1/2 the output voltage you want. Consider using a low noise zener ( or for low voltages use series connected red or green leds for both the Vref and series zeners). Yes the original way to change output voltage is to change the R6/ R7 resistor values, but you can’t stay as close to keeping the input impedances equal as you can changing the Vref and series zener as long as they are low noise.
Yes not thermally as stable as the precision references and Walt’s tip of putting them in silicon helps reduce the drift.
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In my case I will implement 30v regulators, so I changed the zener and reference diodes for 15v types.
Which are the low noise zeners I should look for?
Which are the low noise zeners I should look for?
For a reference zener you could use any type with a desired stability and precision. Noise is filtered away with help from a low pass filter.
So for D5 and D10 I should pick a 2% zener, like BZX85B15-TR, or pick a 1% type, more expensive?
Mentioned type is a plain zener but if the stability is enough for your application then you can use it. You can always trim the feedback R6/R7 but you should strive to have the same DC resistance seen from pin 2 and 3 down to signal ground.
Mentioned type is listed as 2% zener by Mouser. How do I know if stability is enough?
Trim R6/R7 down to how much? Should I pick 0.1% types for them?
What would this affect?
The BOM does not specify resistors or caps types. Walt mentioned Panasonic HFQ or FC for the capacitors in his AE 4/00 article.
Trim R6/R7 down to how much? Should I pick 0.1% types for them?
What would this affect?
The BOM does not specify resistors or caps types. Walt mentioned Panasonic HFQ or FC for the capacitors in his AE 4/00 article.
Experience with this specific design counts, and it's what I would like to know about. The reason for the my questions.
Carl, really. How can we tell you what accuracy you need?
The ratio of R6/R7 times Vref sets Vout.
So YOU must decide how accurate it must be, and then chose your parts accordingly.
Jan
If by accuracy you mean the exact voltage output, that is not something I worry too much about. I will pair R6/R7 to get as close to my voltage output, but will not go into trimmers or anything.
But Peranders mentioned stability with the zener I was intending to use, which I think is a concern.
But Peranders mentioned stability with the zener I was intending to use, which I think is a concern.
Fully agree. Lots of people fret too much to get the 15V right on the dot. The preamp or DAC or whatever will not be upset if it is 14.5 or 15.5 or anything in between.
What stability did Peranders mean? It can't be stability as in avoiding oscillation; a zener can't cause that. Oscillations are caused by a signal going around in a circuit from output back to input with so much phase shift that it sustains itself. Not the case here.
Maybe he means that the zener voltage may vary or drift with time? P-A can you clarify what your concern is here?
Jan