Doubler circuit not putting out 340v

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entreri

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The doubler circuit in the attached schematic for some reason is not giving me 340v. Without load at most I get 330v. Under load it starts at 325v and slowly degrades to about 320v. I have checked the two 100k resistors one reads 103.5k the other reads 104k at 5%. Checked 3 caps(2 200v 1000uf and 1 450v 150uf) in doubler circuit area all are within listed uf range. I am getting a severe strobing effect from the lamp and I am suspecting this low voltage is the cause. Any ideas as to what could be causing the low voltage. And where I could start as far as trouble shooting.
 

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  • pwb power.pdf
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The voltage doubler is extremely simple and has no voltage regulation. Its max output current is very small but I don't know how much current your lamp draws. I don't see the lamp on your very complicated circuit so I don't know what it is and I don't know how much current it draws.
 
The peak voltage of 120VAC is 170V. The circuit has a rectifier loss of up to 2V so the capacitors are charged to 168V which is doubled to 336V without a load.
Maybe your input is only 115V instead of 120V. Then the output will be "only" 321V without a load.
 
What is the input voltage from the mains?
If the mains is 120v then you will get 339v give or take the voltdrops in the diodes.
If the mains is less than 120v you will get less than 339v.

Is the 340v critical?
I suspect not, otherwise the circuit designers would have used a different approach to the 340v supply.

Measure the mains supply, measure the 340v output it should be approx 2.8 times the mains voltage.

JimB
 
I suggest you put another 150u across it and see what happens. You cannot test ANYTHING in this world.
 
i apologize. let me start over. This power supply is from a tv. the 340v feeds the lamp ballast. However when checking the output voltage its 330v without the ballast connected. it gets nowhere near the 340v the schematic specifies. as a result i have a strobing effect in my television. when it is connected to the ballast the voltage drops to 320v. a 20v difference. do you think thats enough of a drop to cause the strobing of the lamp?
 
The problem is the 150u is not filtering the 100Hz or 120Hz. I asked you to bridge the 150u with another 150u. That will bring up the voltage and remove the strobing.
 
Doubler circut not putting out 340V

I checked the doubler circuit which you attached at the forum but I still don't understand how the circuitry work,would you mind simplify the doubler circuit (only doubler part components) then do simple description how the circuitry work such that we can analyse the problem.
 
The doubler DOES WORK. It's just the fact that if the output is low and has ripple, it is due to the 150u. This type of circuit was used in old back-and-white TV's as the transformer needed less turns on the secondary and by using two 200u electrolytics with low peak voltage ratings, you could get a good power supply up and running at a lower cost. The only thing was the need for a final filter capacitor to remove the ripple. If this capacitor was dry, the output voltage sagged and ripple was introduced. This seems to be exactly the fault with this circuit.
 
Sure the circuit work because you measured 325V at output stage.I don't understand the doubler circuit operate at your post schematic.By my understand the doubler circuit should be below:
 

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gilmanli said:
Sure the circuit work because you measured 325V at output stage.I don't understand the doubler circuit operate at your post schematic.By my understand the doubler circuit should be below:
Click to expand...
You show a voltage tripler that is missing an output filter capacitor.
1) The peak voltage of 120VAC is 169.7V. The first capacitor in the other circuit charges to 169V and the second capacitor also charges to 169V. The charge in the two capacitors are in series and produce 338V across the third filter capacitor..
 
Thanks for your explain how to make the input voltage from 120V to 340V of the doubler circuit but I still don't understand operation.Below is my questions:

1.I know first charge up capacitor C9A02 then C9A03 or vice verse ( diode 12,diode13 charge up 169V to capaciotor C90A02 then go to the neutral connection between C9A02 and C9A03) how to charge up other capacitor C9A03 ? I don't understand,please explain.

2.What is the function of capacitors C9A00 and C9A01 ?
 

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Sorry, when I zoom into the complete schematic to read the details, the parts are so far apart that I can't see what connects to what.
The low value capacitors filter away high frequency transients.
 
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