Simplistic mosFET HV Shunt Regs

[Salas]

Link the individual B+ and GND points of each unit with solid copper or thick multi strand. At the middle of those links attach the associated cables coming out the shared shunt reg.

 

[ferrco]

Hi Salas,

What changes /or possible/ to SSHV2 for 180V / 120mA out?

 

[Salas]

Hi Salas,

What changes /or possible/ to SSHV2 for 180V / 120mA out?

Use 56K instead of 68K for the two in series Vref resistors so it starts lower for Vo. As for 120mA consumption I am afraid its not possible with the DN2540s cascode. You will need 140mA CCS for that and the Vgs of the upper DN is not large enough to open the lower one that much. Maybe if you will find an alternative depletion mode MOSFET for the upper one (input connected Q1) with same pin out but higher Vgs spec.

 

[AndrewT]

Would a pair of paralleled CCS do the higher duty job?

 

[ferrco]

Thaks!
Then 120mA is the max value of the DN2540 ccs?

 

[Salas]

Would a pair of paralleled CCS do the higher duty job?

Maybe but not in the certain single CCS board. No space even for a botch. I would prefer browsing some IXYS parts maybe for locating higher Vgs in Q1 alternative.

 

[Salas]

Thaks!
Then 120mA is the max value of the DN2540 ccs?

Depending in combo samples Q1 & Q2 the usual max is 90-100mA. You could check them on a breadboard before stuffing them, with low voltage something like 25V across, swap them for one another in a same CCS cascode circuit with the kit's same peripheral parts also. Find the one for Q1 that will yield the more current from the pair.

 

[heybobo]

Hello,

How do I go about purchasing boards or kits? Does the SSHV2 Full Kit have all required parts and board?

I can get to the spread sheet, but I cannot find the paypal payment details...how do I order and pay?

Thanks and Regards,

RC in VT

 

[kokonut]

Helo Salas,

if i have ca. 180 Vin (max 200V) and 150V Vout by I load 15mA ( +20mA for the shunt) which changes do you recommend?
Are Epcos B32674 or Wima MKP10 10uF a good choice for C2 (C1)? or have you some recommendations?

 

[Salas]

Hello, I recommend you use 47k+47k instead of 68k+68k for that voltage range. The capacitor types you mention are good, set at 40mA.

 

[kokonut]

Helo,

thanks for the info. with the previous data is a sk104 heatsink enough for both q1 and q3 ?

 

[Salas]

2W dissipation on the cascode DNMOS, 3.75W on the output MOS. From there your sinking calcs regarding your ambient temp etc. Degrade sinks C/W spec by 30%.

 

[kokonut]

Heatsinks

then 1" q1 and 2" q3 SK129 are safer? Yes? How did you calculate this?

Thanks a lot

 

[poty]

There are many examples how to do that. For example, for DN2540:
Look at page 4 of datasheet "Power Dissipation vs. Temperature", taking 2W dissipation (as mentioned by Salas) on vertical axis, got around Tc= 130°C/W on horizontal axis. Look at page 2 "Thermal Characteristics" for TO-220: θjc = 8.3 °C/W. Lets take max ambient temperature as 40 °C. Max temperature rising is 130-40=90 °C. Total temperature coefficient max: 90 °C/2 W = 45 °C/W, from which 8.3 °C/W is internally spent and around 1°C/W should be reserved for some losses in case-to-sink connection, so the max heatsink's coefficient should be 45-8.3-1=35.7 °C/W. Following Salas' suggestion of 30% degradation the final number should be 25 grad.C/W. SK104 heatsink has Thermal Resistance=14°C/W (less than counted), so in this case should be OK.
For IRF840 I got Vishay datasheet. 3.75W dissipation (from Salas). RthJC (Page 2, THERMAL RESISTANE RATINGS) = 1 °C/W, Linear Derating Factor (Page 1, ABSOLUTE MAXIMUM RATINGS) = 1 W/°C, Tj (in the same table) =150 °C. Max temp rising = 150-40=110 °C. Total temp.coeff.= 110/3.75=29 °C/W, heatsink capability = 29-1-1=27 °C/W -30% = 19 °C/W. Should be checked against derating: Total counted coefficient 19+1+1=21 °C/W at the 3.75W the temperature rising should be 21*3.75=79 °C. The datasheet mentions 25 °C as the nominal case temperature, we started at 40 °C, so for counting we should use 79+(40-25)=94 °C of temperature rising. At given derating factor there is max power dissipation of 125 - 94*1 = 31W - well over our planned dissipation. So even for this case the SK104 is still suitable.

 

[kokonut]

Thanks

Helo,

thanks a lot for this explanation. make some things a little bit clearer.

regards

 

[Salas]

then 1" q1 and 2" q3 SK129 are safer? Yes? How did you calculate this?

Thanks a lot

The dissipation I calculated by (200V-150V)*40mA for the DMOS CCS and 150V*(40mA-15mA) for the output MOS. The think of your sink as 30% smaller rule of thumb is because it is not driven evenly all over its surface as manufacturers spec but from a hotspot (MOSFET). So think of a 11C/W sink as 14C/W and so on and so forth. For the rest Poty wrote well.

 

[poty]

Sorry for several mistakes in the above text:
"Tc= 130°C"
in the second paragraph and
"The datasheet mentions 25 °C as the nominal case temperature for max power dissipation of 125W..."
in the third paragraph.

 

[bekim]

Great performance in practice, tried to keep em practical with easy to source components. 2N6520 is a -350V PNP and KSP94 is an alternative -400V PNP for the higher voltage shunt, as 2SA1625 is. That is if you wanna go to that 360V mark or go to a higher range. The IRF840 works up to 500V.

Hi

I red most of the thread in last past days, and I have question regarding Shunt regulator, can this circuit be adopted for higher voltage than 360V?
I need quality power supply for my PSE amp with 300B, 400V I=160mA (~200mA)

In mean time I will build one circuit as you provide for my Aikido preamp, DC=250V, so as you're suggesting DC in should be ~300VDC to regulate, is this right?

Thanks

 

[Salas]

SSHV2 goes to 400V but not over 100mA. It can regulate over 20V DCin-out mains play safety difference. Good for your Aikido. For the amp you would be better off with a series MOSFET reg because of the heat a shunt reg would create even if you make a high voltage safe and high current 400mA CCS for it. Or if you even settle for a ballast resistor instead.

 

[bekim]

Great.

Thank you for fast response.

Have you try with same circuit (preamp, amp..) simplistic regulator vs SSHV2??
Which one sounds better to you..? What you will suggest for line preamp and phono preamp?