High Voltage Regulator

Status
Not open for further replies.
Jump to Latest
#26
Giaime said:
Take a look here, if it can help you...

http://giaime.altervista.org/maida.html
Click to expand...

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
 
#29
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
 
#30
mod_evil said:


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 ).
Click to expand...

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.
 
#33
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.
 
#35
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!
 
Status
Not open for further replies.
Top Bottom