noise problem in voltage booster circuit
noise problem in voltage booster circuit
(OP)
hi all
my voltage booster circuit {http://john111smith.googlepages.com/vbstr.png}
shows the following noise levels:
A: <+-50mv
B:~ +-200mv at 67v output
D:~ 0
OpAmp: OP07 or LM741
How can I reduce noise level at point B to about +-50mv?
my voltage booster circuit {http://john111smith.googlepages.com/vbstr.png}
shows the following noise levels:
A: <+-50mv
B:~ +-200mv at 67v output
D:~ 0
OpAmp: OP07 or LM741
How can I reduce noise level at point B to about +-50mv?





RE: noise problem in voltage booster circuit
I also have a problem with your supply being +100 V and your maximum output the same voltage. That will not be possible with a 150 kohms source resistance that is loaded with around 1 Mohm.
I would change topology and resistor values. Use an opamp with PI or PID feed-back. Use a PNP transistor with level-shifting.
The reason for your ripple is probably either internal noise in opamp and transistor or marginal stability (most likely) or hum pick-up in long conductors going to inverting and/or non-inverting inputs of opamp. Possibly a little of each.
Scrap the whole thing, get a good reference design and go from there.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: noise problem in voltage booster circuit
+100V supply is a nominal label and it is about 126V
Could you please send me a good reference design.
RE: noise problem in voltage booster circuit
RE: noise problem in voltage booster circuit
RE: noise problem in voltage booster circuit
RE: noise problem in voltage booster circuit
RE: noise problem in voltage booster circuit
The forward path gain is very much larger than the opamp alone. The output stage simulates as having a gain of 40dB at LF. Your feedback factor is variable, but can be quite high (closed loop gain of 6.5 to the effective inverting input on R49). The circuit simulates as being unstable. If you reduce the loop gain the "noise" (instability) will reduce. This is most easily done by putting a series RC network across the base-emitter of Q2. 1K in series with 1µF should do the trick.
I think if you do what OperaHouse has suggested the noise/oscillation will increase.
RE: noise problem in voltage booster circuit
Also before there was a RC(1K,2n2) between collector and base that force circuit to oscilate, other values for C (20p to 100n) didnt produce good results.
because of low output impedance of +100V supply source, I have to use this resistances values, but if you think change of resistors, produce considerable change in noise, I will replace +100V supply.
I will try suggested configurations.
J.Smith
RE: noise problem in voltage booster circuit
Hanging a 330K on the base of a high voltage transistor is just asking for trouble. You haven't told us what your noise is, but if you disconnect the end of that resistor at the op amp and tie it to ground, that noise might still be there. Do this to define the noise source. Replace this with a base to ground resistor of 4.7K and base to op amp of 33K. If I was designing this, I would be grounding the base and driving the emitter. Well actually, using a single supply op amp like a LM324, base tied to V/3 supply with cap to ground and drive the emitter with the op amp.
I'm all for E-Star, but if you are driving a reactive load you should waste a little power. Change the 150K collector resistor to a lower value like 68K or lower. Does this circuit actually control the voltage now? My calculation indicates you can't get much over 70V as designed.
RE: noise problem in voltage booster circuit
today I changed configuration as below but the result was not good.
remove diode, connect emiter with R10K to -15VEE, chnage 330K to 10K, connect base to -15VEE with R10K,
change R150K to 47K
only a 1nF cap between opamp output and its negative input reduced noise to 50mv (equal supply noise)
Now, I try to reduce noise of +100V supply(by the way, it is a nominal label and actualy is about 126V).
parallel 220uF, 100nF, 10nF are after bridge diode and LRC [680uH,20K,parallel 100nF,10nF,1nF] are before load.
FFT view of noise shows 100Hz peak noise harmonies.
RE: noise problem in voltage booster circuit
But, you seem to be on your way to something that works, so - why not?
The fact that you have a 100 Hz ripple (Europe? Not US?) hints that you have some ripple from your rectifier left. Your "controller" has been slowed down so it can't reduce the ripple - or the ripple is entering some of the high-impedance nodes.
How much 100 Hz do you have? And, excuse me for asking that, where have you put your ground clip? How much ripple does your 126 V (the "100 V") have?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: noise problem in voltage booster circuit
RE: noise problem in voltage booster circuit
RE: noise problem in voltage booster circuit
But some of the things that you could do to the circuit in order to make it quiet also cause it to suppress higher frequencies in the signal you are trying to transduce here.
The members who are trying so hard to help you could do a much better job if you revealed the range of frequencies that will be presented at input D.
Mike Halloran
Pembroke Pines, FL, USA