Hot!High Voltage Power Supply

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PStechPaul
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Re: High Voltage Power Supply 2018/04/14 13:09:50 (permalink)
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I don't know why you want to use the LT3080 instead of simple, cheap discrete components as I simulated above. But if your heart is set on the Linear Technology (Now Analog Devices) part, here is a simple way to control it from a 0-5 VDC source. It's not linear, but it provides pretty much full range control.
 


 
#41
Ioannis
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Re: High Voltage Power Supply 2018/04/15 01:52:15 (permalink)
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Thank you Paul.
 
Well, I am not biased to use the LT3080 but it contains pretty much everything regarding protection.And of course its regulation is better. Also easier to find it at least for the experimental prototype.
 
The discrete circuits need parts of high voltage that was not able to find in my time frame and also the resistors dissipate more power as heat than of the L3080 circuit. The only part that is heating is the power Mosfet transistor. Rest are in low voltage/power.
 
Of course your circuits are easier to control from a PWM PIC controller. And certainly will try them when the parts are in hand. Will report the results of the real thing here. It seems that simulation is not always very reliable.
 
Ioannis
 
P.S. your new simulation lacks one resistor (for current limit) in the S of Power Mosfet. I am very anxious to try your non so "political correct" approach of bipolar transistor use to control the voltage.
post edited by Ioannis - 2018/04/15 01:53:29
#42
PStechPaul
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Re: High Voltage Power Supply 2018/04/15 21:03:10 (permalink)
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Here is a regulator circuit using two NPN and two PNP, showing output load regulation:
 
(See next post - Access Denied nonsense again)
post edited by PStechPaul - 2018/04/15 21:07:03

 
#43
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Re: High Voltage Power Supply 2018/04/15 21:07:43 (permalink)
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#44
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Re: High Voltage Power Supply 2018/04/16 00:01:12 (permalink)
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Another design using PMOS and dual NPNs:
 


 
#45
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Re: High Voltage Power Supply 2018/04/16 01:16:15 (permalink)
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And, finally, for the "purists", a design with NMOS and PMOS devices:
 


 
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Re: High Voltage Power Supply 2018/04/19 14:04:51 (permalink)
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Hi Paul.
I am testing your suggestion to use an NPN transistor, in its narrow linear region, to control by a PWM signal the output voltage.
Unfortunately it is dependent  very much on the temperature.
Tried also to use a Mosfet in the place of the BJT with better control range but worse in regard to the temp stability.
I 'll pass it.
While I wait for some high voltage BJT to arrive and test your suggestions with the differential pair, I'd like to clarify a couple of things.
1. Why there is no collector or drain resistor on M3/Q3 transistors? Won't these parts be overloaded?
2. The purpose of D1/D2 is to have temp compensation?
Thanks
Ioannis
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Re: High Voltage Power Supply 2018/04/19 14:57:11 (permalink)
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Also, if you want, have a look at the VOM1271 that is a Mosfet driver. But works like a photo generator kind of.
When this arrives I try to make a Mosfet pass controled by this little chip.
#48
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Re: High Voltage Power Supply 2018/04/19 23:06:47 (permalink)
+1 (1)
The simulations are mostly to show some possibilities. I used the diodes to get a better range and linearity, but the circuits are hardly ideal. I would design it using an op-amp, which gives perfect linearity. I also would assume that the PIC would use an ADC to monitor actual output voltage. So here is another simulation. I had to add some capacitors in the feedback circuitry to avoid oscillation. If you build an actual circuit, you may need to adjust values.
 


 
#49
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Re: High Voltage Power Supply 2018/04/23 12:00:25 (permalink)
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Paul,
based on your simulations of #45 and #49 I built two circuits both working quite good, though some oscillations do exist for the opamp version. Especially in the region 50-70 volts.
 
With proper grounds and decoupling this is manageable, as the test is done with breadboard and some air wiring.
 
What is funny, in the Mosfet pass transistor, is that adding a PNP transistor for the current limit, the Mosfet is cutoff.
 
In the circuit attached, the PNP is not driven (is in off state). But the P-mosfet is off too! Disconecting the collector, all is good then. Cannot explain why. Various PNP same result...
 
R1, R2 around 10K and R3 at 47K and R4 at 22K if that matters.
 
post edited by Ioannis - 2018/04/23 12:04:47

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Re: High Voltage Power Supply 2018/04/23 12:30:36 (permalink)
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Also tried this version, same result. Is it haunted???
 
 

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#51
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Re: High Voltage Power Supply 2018/04/23 22:26:12 (permalink)
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I see what you are trying to do in your second circuit (#51) but not #50. Here is how I would add current limiting to my simulation:
 

 
What do you have for your full circuit? The capacitors seem to be needed to reduce oscillation, and the op-amp I chose (LT1498) is fairly high speed.
 
Here is another simulation using a PNP series transistor. The current limit is more consistent among devices.


 
#52
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