| mod_evil |
Dear Friends,
For a long time, I'm thinking to regulate the B+ voltage of mine vaccum tube amplifier.
I found many solutions but this is able to 400v ~ 350v in the input. I need a regulator to put on input 500v and in the output 400v.
I passed some time searching for some transistors which can put 800v or more on Vce. But It is very difficult to found.
Anybody have a solution to this?
Best Regards,
Felipe :) |
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| eatitdean |
| what are you building? |
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| eatitdean |
| most power amps that ive seen dont have a regulated supply, usually thats more of an issue in preamps, |
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| mod_evil |
eatitdean,
I will build a 6l6 Push-Pull Amp. I have 500v at the B+. But, I need 400v in the amplifer, and I would like to regulate this.
But In another time, I need to regulate this 500v to use in a 300v pre-amp.
Best Regards,
Felipe |
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| eatitdean |
| look inside an old tv, a tube one maybee, ill look through my stock and see what i got. i take apart every peice of electronic equipment i find and save components. |
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| eatitdean |
| the highest value i could find in my stock was 160 volt, try looking in a microwave oven, i know they use high voltages, but i dont know right off if they are regulated. remember to be carefull, discharge those big caps first. |
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| star882 |
| quote: | Originally posted by eatitdean
the highest value i could find in my stock was 160 volt, try looking in a microwave oven, i know they use high voltages, but i dont know right off if they are regulated. remember to be carefull, discharge those big caps first. |
Microwave ovens are not regulated, except the really fancy ones with continuous power control, but those regulate with high frequency PWM on the primary side just like modern power supplies.
High voltage MOSFETs are not very hard to find. Maybe use two along with an opamp circuit for control? |
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| mod_evil |
Star, eatitdean,
And the Horizontal Deflexion Transistors? Are they allow to High Voltage?
Do you have any idea to make the circuit with the mosfet? I don't know so much about some mosfets, but I can study this.
Best Regards,
Felipe |
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| star882 |
| quote: | Originally posted by mod_evil
Star, eatitdean,
And the Horizontal Deflexion Transistors? Are they allow to High Voltage?
Do you have any idea to make the circuit with the mosfet? I don't know so much about some mosfets, but I can study this.
Best Regards,
Felipe |
A horizontal drive transistor is rated for high voltages, but they're optimized for switching.
Have a resistor from drain to gate to bias the MOSFET on, a zener diode from gate to source to limit bias voltage, then the drain of another MOSFET connects to the gate of the first through a resistor. The second MOSFET is connected to an opamp that compares the voltage from a voltage divider on the output to a reference.
Interestingly enough, a similar circuit was designed by some HVAC engineers in the drive circuit for a piezoelectric expansion valve, which requires a varying bias voltage of up to hundreds of volts, although practically no current. From what I could remember, there was a small high voltage MOSFET, a small high voltage bipolar transistor, along with lots of resistors and a diode or two in the high voltage circuit. There was also a low voltage opamp for closing the loop and it accepts a signal from a DAC to allow digital control of the output voltage. |
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| mod_evil |
Star,
It can be simple... We needn't DAC. We can make a simple regulator. But the problem with the simple is the High Voltage.
How the Op-Amp can compare high voltages and correct it? Your idea is so good, but I think the Operational Amplifier isn't able to this high voltages.
I'm searching... And I see this schematic.
See this:
http://www.duncanamps.com/technical/mosfet.html
How can I change the ouput voltage in this regulator? Can this regulator able to have in the output 350v or 300v?
Best Regards,
Felipe Navarro |
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| star882 |
| quote: | Originally posted by mod_evil
Star,
It can be simple... We needn't DAC. We can make a simple regulator. But the problem with the simple is the High Voltage.
How the Op-Amp can compare high voltages and correct it? Your idea is so good, but I think the Operational Amplifier isn't able to this high voltages.
I'm searching... And I see this schematic.
See this:
http://www.duncanamps.com/technical/mosfet.html
How can I change the ouput voltage in this regulator? Can this regulator able to have in the output 350v or 300v?
Best Regards,
Felipe Navarro |
A voltage divider decreases the voltages to those well within the working range of a common opamp. |
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| mod_evil |
And Star how can the Op-Amp correct more voltages than the voltage of the op-amp?
Can you draw a schematic?
Best Regards,
Felipe Navarro |
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| star882 |
| quote: | Originally posted by mod_evil
And Star how can the Op-Amp correct more voltages than the voltage of the op-amp?
Can you draw a schematic?
Best Regards,
Felipe Navarro |
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| peranders |
I'll guess the picture only is an example becasuse 7805 is very unsuitable to use like this. For instance it doesn't like zero load!
IGBT has high Vce, Checked anyone?
What about this tube super regulator? |
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| star882 |
| quote: | Originally posted by peranders
I'll guess the picture only is an example becasuse 7805 is very unsuitable to use like this. For instance it doesn't like zero load!
IGBT has high Vce, Checked anyone?
What about this tube super regulator? |
It's just a concept. Note that there aren't even any component values. |
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| mod_evil |
Dear Peranders and Star
I'm not thinking to use a Tube Regulator Circuit like the "Tube Super Regulator", because this is will be more 3 heathers to power up. And We can make a simple circuit to regulate this.
About the Star882 regulator circuit, I think in place of 7805 we can put a REF01 or another good reference of voltage.
About the IBGT, I never used one before. Do you have any idea to use a IBGT here?
Best Regards,
Felipe Navarro |
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| star882 |
| quote: | Originally posted by mod_evil
Dear Peranders and Star
I'm not thinking to use a Tube Regulator Circuit like the "Tube Super Regulator", because this is will be more 3 heathers to power up. And We can make a simple circuit to regulate this.
About the Star882 regulator circuit, I think in place of 7805 we can put a REF01 or another good reference of voltage.
About the IBGT, I never used one before. Do you have any idea to use a IBGT here?
Best Regards,
Felipe Navarro |
You can substitute any low voltage reference for the 78L05. Before making a final design, test it on a breadboard with a current limited power supply and as small capacitors as possible. |
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| Gary P |
Hi Mod_evil,
Check out the "Swenson" regulator on my web page. To make a long story short several years ago I started down a path that led to a high performance high voltage CCS. John Swenson developed a HV regulator by adding an error amplifier to the CCS core turning it into a nice linear regulator. A couple of weeks ago I built up the regulator circuit and ran some performance tests. Based on the tests some circuit values were changed to maximize performance. I also added some protection circuitry and a current limit stage.
Gary
Gary P's DIY page |
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| mod_evil |
Dear Friends,
Today I'm seeing on my deposit and I have many 2sc3678. This is a High Voltage NPN transistor.
Do they have any idea to use this?
Dear Gary,
I looked on your website the Swenson Regulator, I think its very good. I looked on farnell for FQAF11N90 and LND150. No matchs.
Can I use another High Voltage Mosfet? Do you know a more commom?
Best Regards,
Felipe Navarro |
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| Gary P |
Hi Felipe,
For the pass element (Q2) just about any MOSFET that meets the voltage, current, and power requirements should work. The value of R15 may need to be changed for the best compromise of performance and circuit stability.
The SuperTex LND150 is a unique part and has no cross reference that I'm aware of.
Gary |
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| peranders |
| The LND150 is quite nice if you want to build a high voltage current source :nod: |
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| mod_evil |
Gary, Peranders,
I will test some designs and post here.
Where can I buy the LND150? No matchs in Farnell...
Best Regards,
Felipe |
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| peranders |
| LND150 is hard to get in smaller quantities but you could possibly ask for samples. |
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| jkeny |
| Can a DN2540 depletion mode mosfet (also a Supertex part) be substituted for the LND150? Both of these parts are available from Mouser.com The DN2540 is a higher current part also! |
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| mod_evil |
Dear Giaime,
I used for many years the LM317 and LM337 for low-voltages and I know this circuit for high voltage, but, can it regulate from 400v to 300v? ( It will be a regulator to down the voltage of B+ to drive a Tube Pre-amp ).
Dear peranders,
Where can I take some samples of LND150?
Best Regards,
Felipe Navarro |
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| peranders |
| Try to get in contact with Supertex. |
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| mod_evil |
peranders,
I sent a mail today to them.
Best regards,
Felipe Navarro |
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| KSTR |
Besides the excellently looking Pimm/Swenson reg, this design could be worth a try, as it looks easily scalable to the 500V ranges. You need a proper MOSFET, but there are many 900V++ designs out there, ie from Fairchild or ST, which might be easier to get than the Supertex parts.
- Klaus |
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| Giaime |
| quote: | Originally posted by mod_evil
Dear Giaime,
I used for many years the LM317 and LM337 for low-voltages and I know this circuit for high voltage, but, can it regulate from 400v to 300v? ( It will be a regulator to down the voltage of B+ to drive a Tube Pre-amp ).
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Hello Felipe,
of course it can, you only need to calculate an appropriate R6 for the output voltage you choose (in your case, 230kOhm should suffice) and use a suitable high voltage (>400V) power mosfet, TO220 ones are good (I used a 500V part, the IRF840).
Remember to heatsink it. The LM317 does not need heatsinking but be careful, its metal tab is at HV voltage.
For safety, also, I would uprate the cap's voltage, using 630V caps. |
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| mod_evil |
Giaime,
Thanks for all help. I'm searched in mine stock and I found two 2sk2611.
It able to use in your Maida Regulator, but I need your idea about it.
Best regards,
Felipe Navarro |
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| Giaime |
| That mosfet will work, although it's a bit oversized. Please note that it has a different package than IRF840, so you can't mount it on the PCB I made for the Maida Regulator: you have to build it on breadboard. |
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| TechGuy |
I would look at using a switching Regulators with a commerical PWM controller. Using a regular regulator that adjusts the conduction across a transistor to regulate voltage will disipate a lot of heat if the Vin is much greater than the Vout, or if your output current is high. Search all the usual Suspects for a DC-DC Buck controller (ie IRF, TI, ST, LinearTech, OnSemi, etc).
Because your voltage requirements are high, I would look for controllers designed for Florescent Ballast controllers or CFL. Most of the common PWM controllers with integrated gate drivers are designed to work at much lower input voltages ( < 60 volts).
You could use PWM controllers that do not use built in gate drivers like the TL494 PWM controller (http://www.onsemi.com/pub_link/Collateral/TL494-D.PDF See Page 11 for an example), but you'll need to add external gate driver, and use a voltage divider to reduce the output voltage feedback to a voltage the controller can handle. I wouldn't recommend using a Bipolar transistor used in the TL494 example.
A CFL controller would probably be the way to go since they usually have integrated gate drivers and are designed for high efficiency and high voltages. Some Ballast controllers include soft-start, filiment pre-heating delay and other control features that may be suitable for your tube design. After all, a CFL bulb is a tube. |
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| mod_evil |
Techguy,
It can be a great idea. But, i'm thinking to use a simple design. It would able to use in a future design.
I will study this PWM controller to use in mine lab power supply.
For now, i'm thinking to use the Maida in the tube.
Best regards,
Felipe Navarro |
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| star882 |
Yeah, PWM is the way to go. A flyback converter can be used to directly create the high voltage from a DC source (rectified mains or low voltage).
I found out that one of prototype expansion valves the "HVAC couple" is working on requires drive voltages of up to 800v (for wide open) with a capacitance of 4uF! They're currently using a small flyback transformer running from rectified 24v to generate that voltage, with a digital controller of some sort to allow digital control of voltage from 0v to 800v with 4096 steps in between, along with low speed PWM (using a special algorithm) between steps to allow for essentially an infinite number of steps! The flyback converter charges up the valve, the bleeder resistors/feedback network slowly discharge the valve, and a transistorized shunt quickly discharges the valve.
It seems like quite an engineering problem! |
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