Simplistic MosFET HV Shunt Regs

[vgeorge]

No, I do not use parafeed. It is wired 4.5:1 as output transformer. Inductance is more than 200H on the primary.

 

[merlin el mago]

Thank you Nick

SSHV2 B.O.M.

Q1-2 DN2450 3.8W/C
Q3 IRF840 1W/C-1.5W/C
Q4-5 KSA1381 16W/C-80W/C
Q6 2SK117GR 3-5mA Idss, 4mA center value

D1-2-3 Z12V 0.5W
D4 LED red led, typically 1.9Vf

R1-2 100R 1/4W
R3 330R 1/4W
VR4 500R
R5 10R 1/4W
R6 1R86 1/4W
R7 100R 1/4W
R8 1K 1/4W
R9-10 68K 2W
VR11 500R
R12 1K 1/4W


C1 0.33uF 400V
C2 10uF400V

 

[Salas]

Board is 136X49mm I forgot to write. I have seen for capacitors it can also take axial like SCR or some REL-CAP too.

 

[wlodek3055]

@Salas - could you please suggest any less exotic substitute for KSA1381? I can't find this transistor neither in Elfa nor in Farnell. Wher do you buy it (EU countries preffered).

 

[Salas]

I had already in my text. MJE350 has been tested with success. Not as perfect result but rather near.

 

[wlodek3055]

Thanks for quick reply
Two more question - if I compare this project with yours previous one very visible is that only Q1 is currently on bigger (not even quite big) heatsink ( I am talking about your project of PCB). In previous version much bigger heatsinks used to be applied. What is the reason? Does it mean that Q1 dispatch the most power and only for Q1 the serious heatsink is required?
Do I understand rightly that S+/S0 is sensing circuit and F+/F0 is current output? If so, does it means that I can connect them parallel if i am not going to use sensing circuit?
Best Regards,
WW

 

[Salas]

Yes, Q1 takes the most in CCS. In post #2061 those things are discussed, including answer to your skip sensing question.

 

[dadedady]

Hi Salas. I am going to make new vercion of shunt reg. to power a stereo tube preamp. (2x 6N1P). The in V is about 330V the B+ of pream. is 260V. In order to drop down 330V, I am thinking to add two 2K2 resistors after 330V and 2 or 3 100μF/400V electr. cap and 2 or 3 1μF/400V polyester cap (for filter) and after that the shunt reg. in the same pcb. Also I'l join F+ and S+ - F0, S0. Any advice about that?
Thanks Dade

 

[Salas]

To use up voltage for pre filtering instead of burning it out across the CCS is better. It would be optimum if you could retain the 4 wires up to the load connection point, by adding a secondary sense line. If impossible in an existing build, OK.

 

[dadedady]

Thank yoy Salas. So I use the prefilter to drop down the 330V is OK. I'l feed the Anode of the tube whith 260V from F+ of CCS. At the same point I'l conect the S+ in order to corect the tence if drop down or go up if I use long wires. Is that OK?
Can I replace 10μF MKP cap. whith elecrolytic and add // 2,2 μF ?

 

[wlodek3055]

@ Salas
1/. Can you confirm/do you know something about that KSA1381 is the same part than 2SA1381? I found this information in Fairchild datasheet but I want to be more certain. See datasheet attached
2/. Have you tested difference between IRF840 and IRF840LC? See datasheet attached. Do you think they can be used alternatively?
Best Regards,

 

[Salas]

2SA1381=KSA1381 no doubt. Re-branded or process licensed from Sanyo to Fairchild. KSA1381 has been used in SSHV2 and MJE350 as second easy to source, but a bit worse choice. Cascode helps the lesser part in frequency, but not in basic linearity.
840LC has low Crss but lower min gfs. I have used simple 840 in SSHV till now. I don't know more.

 

[Salas]

Thank yoy Salas. So I use the prefilter to drop down the 330V is OK. I'l feed the Anode of the tube whith 260V from F+ of CCS. At the same point I'l conect the S+ in order to corect the tence if drop down or go up if I use long wires. Is that OK?
Can I replace 10μF MKP cap. whith elecrolytic and add // 2,2 μF ?

Yes, imagine the B+ point and ground point that you used to connect your older PSU at load to now receive +F,+S at B+ and F0,S0 at ground.
Yes you can replace with bypassed electrolytic but don't make it bigger than 15uF total. That capacitor is audible, remember.

 

[dadedady]

Thanks again. You were very helpful

 

[wlodek3055]

diodes for rectifier i this application

Friends,
Any input regarding type of diodes best to be used in Graet'z (rectifier) for this power supply? I was thinking of "traditional", popular in audio applications fst recovery MUR860 diodes. Anybody will suggest something better (I mean better sonically (tested) nor in therms of paper, datasheet parameters)
Best Regards,
WW

 

[dadedady]

Hi Salas. Some questions again
1. For C2 can I use 10u/200V? If no I'l replace it with 10u/400V electrolytic and a//2u2/400V
2. May I use 2SK170BL instead of 2SK117GR?
3. After S+, F+ is there need for filter capacitors or no?
4. In my old PSU, in order to protect cathode I used to conect B+ via a net of resistors to Heater+. Can I use the same net by conecting F+ to Heater+
Thanks Dade

 

[Salas]

1. Only if you will use your reg for below 200V output.
2. Avoid it will drift more, still it will work.
3. Avoid any capacitors there.
4. Normally yes. If any stability problems, float heater to raw DC in +.

 

[dadedady]

Thank you Salas.
But I can't find 2SK117GR. Any other proposal?
One CCS is enough for both chanels of my pream. or one per chanel?
Best Regards Dade

 

[Salas]

What do you mean one or two CCS? Either one or two whole regs. One is very good for two channels. Use K170 until you find K117.

 

[vgeorge]

Thank you Salas.
But I can't find 2SK117GR. Any other proposal?
One CCS is enough for both chanels of my pream. or one per chanel?
Best Regards Dade

Got mine from ebay.