SSHV1 Calculator
Hi all,
After several loops of small corrections, back and forth advises and recommendations from Salas (himself!), I am happy to present the latest version of the calculator for Salas SSHV1.
Most explanations needed are inside the spreadsheet. Ask if you need help.
https://docs.google.com/open?id=0B4Rnva0idfhAZDFiZmEyYTAtOTZlMS00NDFkLTgzMjUtOTNkMjExMzY3NTE5
Salas: you may post the link in the first page of the thread...
Fred
😀
Hi all,
After several loops of small corrections, back and forth advises and recommendations from Salas (himself!), I am happy to present the latest version of the calculator for Salas SSHV1.
Most explanations needed are inside the spreadsheet. Ask if you need help.
https://docs.google.com/open?id=0B4Rnva0idfhAZDFiZmEyYTAtOTZlMS00NDFkLTgzMjUtOTNkMjExMzY3NTE5
Salas: you may post the link in the first page of the thread...
Fred
😀
Nice. I will upload it in the original SSHV1 post as linked from page#1
You forgot to put your name on the calc by the way.
You forgot to put your name on the calc by the way.
SSHV2 Calculator
...and there's more !
Here is the calculator for SSHV2. I call this "Beta", until the circuit and more specifically calculator have both been extensively tested and gathered feedback.
The SSHV2 circuit is convenient enough that no complicated calculations are required to make a build... but the objective of this spreadsheet was to provide approximate values of resistors for those (like me) that wish to replace trimmers with fixed value resistors. For extreme accuracy, a bit of fine tuning should be necessary anyway....
https://docs.google.com/open?id=0B4Rnva0idfhANzM5MjdjNDItM2E0Ny00YjQxLWJjNmEtNzk1YmYyODI3NDYx
Cheers!
Fred
...and there's more !
Here is the calculator for SSHV2. I call this "Beta", until the circuit and more specifically calculator have both been extensively tested and gathered feedback.
The SSHV2 circuit is convenient enough that no complicated calculations are required to make a build... but the objective of this spreadsheet was to provide approximate values of resistors for those (like me) that wish to replace trimmers with fixed value resistors. For extreme accuracy, a bit of fine tuning should be necessary anyway....
https://docs.google.com/open?id=0B4Rnva0idfhANzM5MjdjNDItM2E0Ny00YjQxLWJjNmEtNzk1YmYyODI3NDYx
Cheers!
Fred
Ho yes...! I guess I'm too modest 😀
This is a modest contribution anyway, and anyone is free to use and modify
Will include in next update....
I mentioned it, its linked up already. Check it out: http://www.diyaudio.com/forums/powe...stic-mosfet-hv-shunt-regs-97.html#post2084348
Although that one has trimmers for both ICCS and Vout its good to know the dissipation for choosing sinks in each application. A welcome addition. Thanks.
There's one more thing I use it for: trimmers dissipation calculation!
If you're going to use SSHV2 at higher currents (say 60mA or more), you will set the trimmer at a fairly low value (around 15 Ohm for VR4 to get a Vgs of -1.4V and 60mA CCS if my calculation is correct.. *
). That is "only" 0.05W (or 10% of the trimmer rating), but with a 500R trimmer you're only using 3% of the trimmer resistive element, so theoretically exceeding the trimmer's "practical" rating.
I'm sure most trimmers will survive this treatment, but I've had a bad surprise in the past with a trimmer becoming hot (that was another shunt reg), and worst of all it had a negative tempco (meaning heat => lower resistance => more current => more heat => lower resistance, etc..)
In that case it would be preferable to use a 100R or 200R trimmer depending on the adjustement range desired, and/or to change R3 to a smaller value.
In the end I would suggest changing R3 for a 220 Ohm, and VR4 for a 100 Ohm in the schematic.
That way, the adjustment range would be 25mA to 100mA, and the dissipation would remain within acceptable levels
Fred
* Note: my calculations accuracy is still to be proven, I haven't built SSHV2 yet to verify my formulas work in real life..
We have one running at 60mA among the proto testers (with no problems), and I will ask at what value the trimmer and resistor combination measures. Its an area I am expecting some practical feedback due to possible differences to datasheet and IDSS spread of the Supertex. In the end we will designate the most ''safe'' values. But I would like to see a fixed resistor replacing the CCS trimmer in permanent installations after initial fixing. Its good for PPM & long term ease of mind.
* Note: my calculations accuracy is still to be proven, I haven't built SSHV2 yet to verify my formulas work in real life..
In that 60mA one the trimmer is at 21.5 Ohm, got a check. So Mosfet parts will inevitably deviate Vgs, but we are in ballpark.
Could he measure Q2 Vgs and Vds please ?
Edit: bugger me ! I can calculate Vgs by myself 😛 1.21V . But I'm still interested to know Vds of Q2.
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A little bit difficult because Q2 Vds enters into play, so it starts to be tough in Excel. 😛 I'll give it a try...
My Calc just neglects Q1 altogether. I suspect the difference between my value and the real life may come from this calculation approximation ( although my gut feeling would have been that R4 would be lower than what I calculate.. not higher....
)Need help on SSRHV1
Dear Salas
I've reduced R1 to 14ohm and mount the Q1 & Q3 on larger heatsink add heatsink to Q2. I connected a 5.6K 20W as dummy load and test the regulator. With input 300V, I adjust the VR to have 250V output but it drift up slowly to the same value of the input. Please advise the possible problem.
Dear Salas
I've reduced R1 to 14ohm and mount the Q1 & Q3 on larger heatsink add heatsink to Q2. I connected a 5.6K 20W as dummy load and test the regulator. With input 300V, I adjust the VR to have 250V output but it drift up slowly to the same value of the input. Please advise the possible problem.
Attachments
Possibilities: 2SK147? Very drifty especially if heated up enough. Try BF245A. Cable connections to the Mosfets? Possible oscillation. Bad trimmer? Can drift. Did you check there is VGS voltage on Mosfets and Vbe voltage on the transistor? All semiconductor parts should be checking OK first.
Checked the voltage at R1 drift from 1.54 down to 1.4x. Vgd a Q1 is 4.066, Q3 is 2.958. I believe is the 2sk147 problem. Can I use J201 to replace it?
J201 will have low IDSS, maybe less than 1mA sometimes so you will need double the R4 value plus maybe. Its also noisier. Use it if having nothing else. For drift is stable enough.
