The simplistic Salas low voltage shunt regulator - Page 290 - diyAudio
 The simplistic Salas low voltage shunt regulator
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diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by AndrewT R1=22r is not 500mA. What is R1? the CCS dissipation is [Vin - Vr1 - Vout] * Iccs I'll guess at some inputs: Vin =61V Vr1 =2V Vout = 46V Iccs =0.5A Pq1 = 6.5W Ta=25degC It would take quite a few seconds even with a tiny heatsink to burn out the CCS FET. With an small but adequate sink say 10C/W the sink rise would be 65Cdegrees above ambient. Tc ~ 70Cdegrees above ambient. That puts Tc ~95degC The temperature de-rating for the FET is 0.44. [150 - 95] / [150-25] Your 150W FET is de-rated to 66W Pq1 ~ 10% of maximum rating. If the FET is cold it is not passing current. It has almost certainly not been damaged by over-voltage. It may have been damaged by soldering or handling or simply the circuit has a fault.
R1 is 3R8 to get 500mA

 11th August 2010, 09:08 PM #2892 diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe 150R 10W before the reg measure 54V
 11th August 2010, 10:22 PM #2893 diyAudio Member   Join Date: Jul 2004 Location: Scottish Borders the current is ~0.5A The dropping resistance is 150r How hot does it get? Have you done the arithmetic? P=I*I*R=37.5W Why use 10W resistor? Why use 150r? __________________ regards Andrew T. Sent from my desktop computer using a keyboard
 11th August 2010, 10:38 PM #2894 diyAudio Member     Join Date: Sep 2009 Location: Catalonia - Europe AndrewT you are right was a bad connection 2nd mosfet, now is all ok after adding the 150R 10W in series to lower till 54VDC after reg, this reg after 15 minutes the heatsink don't hot & the other heatsink it's hot....
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by AndrewT the current is ~0.5A The dropping resistance is 150r How hot does it get? Have you done the arithmetic? P=I*I*R=37.5W Why use 10W resistor? Why use 150r?
It's very very hot can left the finger few seconds.

To low the voltage to 55VDC after the reg.

 12th August 2010, 12:56 AM #2896 diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece Is it CRC or RC configuration? From bridge to filter cap (+) just a resistor is RC. Is there a capacitor before the R?
 12th August 2010, 11:08 AM #2897 diyAudio Member     Join Date: Sep 2006 Location: Wallis Blog Entries: 1 Hi Salas For the zobel on the output, can I use 0,5w 1r resistors ? What is the minimum power requirements ?
 12th August 2010, 11:56 AM #2898 diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece No power requirements. 1/4W OK.
diyAudio Member

Join Date: Sep 2009
Location: Catalonia - Europe
Quote:
 Originally Posted by Salas Is it CRC or RC configuration? From bridge to filter cap (+) just a resistor is RC. Is there a capacitor before the R?
It's CR so after PSU filter cap (+) the resistor & after connected the reg.

 12th August 2010, 12:53 PM #2900 diyAudio Chief Moderator     Join Date: Oct 2002 Location: Athens-Greece Do it the other way. Bridge to R to cap. 10R and see. Maybe you will need even less.

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