The simplistic Salas low voltage shunt regulator

[canvas]

Hi Salas,



From the HV 1.2R schema, how can I increase the input voltage from 45v to 60v?
And, what is the requirement for Q5? I only know if I want LV output, I need to pick a low threshold version. How about capacitance and rise/fall time? Thanks.

[massimo]

...and what about BC547B instead of BC546B (Vceo 45 vs. 65 and Vcbo 50 vs 80) for Q7 when Vout 35V?

[canvas]

Originally Posted by massimo

...and what about BC547B instead of BC546B (Vceo 45 vs. 65 and Vcbo 50 vs 80) for Q7 when Vout 35V?

How about BC550C/560C? Do you think they will work at 60Vin?

[marcus1]

Thanks dimkasta. Great calculator, now better.

Originally Posted by dimkasta

I did some changes to the calculator excel.
It now can calculate the dummy load resistance and its watt rating based on the expected consumption, and then the total mA consumption based on the voltage across the CCS resistor

[Salas]

Originally Posted by canvas

Hi Salas,
From the HV 1.2R schema, how can I increase the input voltage from 45v to 60v?
And, what is the requirement for Q5? I only know if I want LV output, I need to pick a low threshold version. How about capacitance and rise/fall time? Thanks.

R5 & R6 break the output voltage referenced across Q3 & Q4 in two. I don't see what is may hinder you for feeding 60Vin beyond the extra heat created across Q1 the larger the Vin to Vout DC difference becomes. The higher the DC across Q1, its parasitic capacitance tames lower. Just know to have Vout/(R5+R6)~3 to 5mA for the LED with resistors that handle the dissipation (Vo/2)*IR5,6 and adequate Q1 sinking with calculated Q1 temp to be still safe. Q5 should sustain the Vout and have capacitance specs similar to what used in the regular schematic. Dropping with RC,RC if the Vi-VoDC is very large is to be also considered.

[RCruz]

Originally Posted by marcus1

Thanks dimkasta. Great calculator, now better.

+1

[canvas]

Originally Posted by Salas

R5 & R6 break the output voltage referenced across Q3 & Q4 in two. I don't see what is may hinder you for feeding 60Vin beyond the extra heat created across Q1 the larger the Vin to Vout DC difference becomes. The higher the DC across Q1, its parasitic capacitance tames lower. Just know to have Vout/(R5+R6)~3 to 5mA for the LED with resistors that handle the dissipation (Vo/2)*IR5,6 and adequate Q1 sinking with calculated Q1 temp to be still safe. Q5 should sustain the Vout and have capacitance specs similar to what used in the regular schematic. Dropping with RC,RC if the Vi-VoDC is very large is to be also considered.

Sorry, I should have mentioned earlier. I am going to build a 1.2R regulator for my amplifier VAS stage. My Vin is about 60V, but Vout is around 50V@20ma max. There is only 8V~10V in difference. So, I guess the original schema is fine?

[Salas]

Q7 will have problems with its dissipation sooner or later at 50V Vo. Better use some TO-126 there with highest beta and lowest Cob you can get.

[Salas]

Also watch what I wrote for R5, R6.

[masterat]

Originally Posted by dimkasta

I did some changes to the calculator excel.
It now can calculate the dummy load resistance and its watt rating based on the expected consumption, and then the total mA consumption based on the voltage across the CCS resistor

Hi all,
Have some one guide me how to use?