Giaime 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 ).
Dear peranders,
Where can I take some samples of LND150?
Best Regards,
Felipe Navarro
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
- Klaus
mod_evil said:
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.
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.
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.
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!
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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