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Post by Bogdan on May 7, 2015 23:38:44 GMT -8
Hello.
I the past I made a HV power supply that consist of a pulsed autotransformer , voltage multiplier, feedback to stop-start the PWM.
The first one I made was using LM339 as an multivibrator at 50kHz and the output from the
multivibrator has been connected to the output of a LF356 used with the feedback for the HV voltage divider and an potentiometer
to set 1V -> 1000v, 1.5v -> 1500v, 2v -> 2000v, 2.5v -> 2500v.
When the LF356 was active it pulled down the PWM line that pulsed the transistor where I had connected the
autotransformer. The output was not stable when I changed the resistive load.
Also I made one using 555 configured as astable PWM generator that pulsed the autotransformer transistor.
The feedback from the 1000:1 voltage divider was compared with a potentiometer used to set the HV output using the LF356.
The output from the LF356 was used to activate an 4N25 optocupler that actionate the 555 RESET line and stop the PWM.
This tipe of crude regulation did't work as espected.
I will come back with schematics.
All sugestions are welcome to make a stable supply!
(P.S: excuse the writing errors)
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Post by Gary Lecomte on May 8, 2015 5:26:16 GMT -8
Before anyone can help you, You need to tell us More Info:
What is the LOWEST Resistive Load you Expect to use When operating at these Voltages?
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Post by Bogdan on May 9, 2015 10:33:14 GMT -8
Hello.
The load will be between 100Mega ohm and 20Giga ohm.
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Post by Gary Lecomte on May 9, 2015 15:36:54 GMT -8
So your maximum Current (Besides current in your Sample Resistor String) is .000,025 Amps. 2500 volts / 100, 000 ohms = 25 Ua. trying to read Current Flows between.
Shouldn't be too difficult.
What is the Purpose, Just to test these Resistor Values?
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Post by Bogdan on May 9, 2015 18:26:17 GMT -8
Hello. The HV supply will be used to test the insolation of capacitors. The transimpedance amplifier will measure the absortion currents when capacitor charge, and the resorbtion currents when the capacitor discharge. The test will be at 500V, 1000V, 1500V, 2000V, 2500V. I need these steps to have a better caracterization of the dielectric. I am now reading the TL494 aplication note. Do you think that using : POTENTIOMETER -> TL494 -> MOSFET -> AUTOTRANSFORMER -> 2 STAGE GREINACHER MULTIPLIER -> VOLTAGE-DIVIDER(FEEDBACK) -> TL494 it will work? Do you think I better use the UC3843? I also seen the 12V to HV power supply made by you. The maximum current at 2500 needs to be 1mA.
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Post by Gary Lecomte on May 10, 2015 6:59:58 GMT -8
USUALLY when you Use a Multiplier Stage, It Will NOT give a Stable Output. Because Each capacitor in the Multiplier has capacitive reactance.
Definitely Not the best way to do this.
Do you think I better use the UC3843? NO.
I am Making a Custom Bobbin for a Transformer and Circuit for you. But I am Busy With MANY THINGS, so this will take some time to get Finished.
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Post by Bogdan on May 10, 2015 12:48:54 GMT -8
O my God! How can I thank you?! When you have time, please explain me the calculations involved in designing the HV transformer.
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Post by Gary Lecomte on May 11, 2015 7:47:25 GMT -8
First you need to Create a Suitable Drive Circuit.
The Circuit I am Considering making is Continuously Adjustable from Zero to Maximum Volts. (0- 2500 volts, or maybe even Higher.) Rather than Fixed Voltages.
But First I Need to Create This Special Bobbin to wind the Coils on. When I get it Made, I will post a Picture of this Bobbin.
But I have MANY Things on the go Right Now. My Main Priority This Week is to get my Vegetable GARDEN Planted.
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Post by Bogdan on May 11, 2015 14:45:45 GMT -8
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Post by Gary Lecomte on May 11, 2015 16:02:21 GMT -8
I have No Idea What that part from Digikey is?
I Did a Search for it on Digikey. (289-1026-ND) No Stock Available. Price and Delivery on Request, So Probably quite Expensive to Buy Just ONE!
home.comcast.net/~dprutchi/ccfl_based_hv_supply.jpg charliethompson.50megs.com/LowRippleHVsupply.html
Or What the HV Output is?
But what resistors are being used for those 2M2 in a String? 1/4 watt resistors are only rated at 250 volts. 1/2 watts are 450 volts.
And Sorry but No Time too look at all this stuff.
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Post by Bogdan on May 17, 2015 16:06:06 GMT -8
What type of transformer do you plan to make? What is the winding number of the primary and the secondary? Also the wire gauge? Thank you!
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Post by lamazoid on May 18, 2015 10:10:47 GMT -8
And My Vegetable Garden is MOST Important right now. Gary, can you tell more about this ? right now i am also more interested in village living rather that electronics (sorry for off-topic)
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Post by Gary Lecomte on May 18, 2015 14:09:09 GMT -8
Lamazoid........What do you want to know? I Created a New Topic, "Vegetable Garden". PLEASE ANSWER In that Topic
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Post by Bogdan on May 18, 2015 20:26:09 GMT -8
Tell me E30, E33? If I will know the number of the spacers you will use for the HV secondary winding, the windings and wire gauge an I will make one myself.
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Post by Gary Lecomte on May 19, 2015 4:19:14 GMT -8
Click on it to see Full Size Picture. This transformer with my driver circuit has an Adjustable Output from Zero to 8000 Volts with just a Single rectifier diode.. The Secondary winding is 700 turns total, spread over the 5 groves, using 40 AWG wire. Maximum Primary Current is 800mA at 12 Volts.
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