Simplistic MosFET HV Shunt Regs

[Salas]

Make sure about the load current is covered like allowing more from the CCS initially. Because it kinda responds now better than before that was burning out right away. Check no small BJT is damaged first.

 

[merlin el mago]

No damaged 1381, how many mA to set the Jung mod CCS?

 

[Salas]

45?

 

[Salas]

The voltage trimmer is good?

 

[merlin el mago]

45?

OK

The voltage trimmer is good?

I will check it.

 

[merlin el mago]

Changed the trimmer.

Add 10R as T.P. to adjust CCS Jung mod

CCS set 45mA

Vout 20.6V

1st heatsink very hot.

 

[merlin el mago]

I connected directly the PSU to the load max Vout 75V but something is wrong or incorrectly wired because I used and old SSHV2 with the pads broken, please could you check the attached pic if all connections are OK?

 

[Salas]

Can't make out, its overworked. Anything could go wrong on that board. Why not building the whole circuit clean on a matrix board like you did the modded CCS, so to have control.

 

[merlin el mago]

You're right, I'll make a new board.

 

[merlin el mago]

Salas SSHV2 without the CCS can regulate Vout to 280v when Vin is 340v?

 

[Salas]

Salas SSHV2 without the CCS can regulate Vout to 280v when Vin is 340v?

Needs a ballast series power resistor if using only the parallel part. 1K-1.2K-1.5K 10W should do in your case (60mA or 50mA or 40mA flow).

 

[merlin el mago]

Thanks Salas I ask to test it.

 

[Salas]

Yes, alright. Needs a limiter (ballast) resistor even to test it of course.

 

[merlin el mago]

Without the resistor can be damaged?

 

[Salas]

Yes.

 

[merlin el mago]

The reg with the 1K ballast resistor doesn't works: fixed Vout 316V

 

[Salas]

Does the mosfet get hot?

 

[merlin el mago]

Wait a moment I will power on again.

 

[merlin el mago]

Not hot. I checked and isn't gone.

 

[Salas]

I think of no reason than some practical error not to work when having a limiting resistor.

Also:

"Another test tip is, as the circuit is off power, Q5 between E,B pins on Ohm meter with red probe on E should be reading in the hundreds of Ohm and changing reading when turning the R11 trimmer. When a blown Q5 could read a couple of Ohm near short. Q4 should be reading in the hundreds of kilo Ohm on same test probing (the trimmer is not involved in Q4)."