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Old 30th December 2012, 08:44 PM   #2081
RCruz is offline RCruz  Switzerland
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Hi Salas

Starting to build the SSLV1.1 but my boards have 4 leds for biasing the ccs mosfet. The build guide only has reference to three.

Why the fourth led ?
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Old 30th December 2012, 09:13 PM   #2082
vgeorge is offline vgeorge  Greece
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Quote:
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Hi Salas

Starting to build the SSLV1.1 but my boards have 4 leds for biasing the ccs mosfet. The build guide only has reference to three.

Why the fourth led ?
Ricardo,
if you want to use higher current, you cant use a higher value resistor with 4 leds. That' s why they use 4 leds in the last pcb. You can always short the forth led and use 3.
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Old 30th December 2012, 09:24 PM   #2083
RCruz is offline RCruz  Switzerland
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Hi vgeorge, I usually use a lower value resistor to set higher current.

Using four diodes with a higher value resistor is new to me... but I found it:
(3xVf LED)-VgsQ101=VdR101. ICCS=VdR101/R101. Example: 3x2.1V LED and a Q101(201,301) MOSFET
with 4.3V Vgs will create 2V drop across a 10 Ohm R101. ICCS=2V/10R=200mA.

So 4 leds will create a 4V drop over R101... if I use R101=15 I get ICCS = 267mA

Perfect
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Last edited by RCruz; 30th December 2012 at 09:31 PM.
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Old 31st December 2012, 05:34 AM   #2084
vgeorge is offline vgeorge  Greece
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4 leds come handy if you want more than 500 mA.
Your calculations seem correct and the end result will depend on actual Vgs and leds Vref values.
If you compare with your 1.2 builds, I will be very interested for your opinion.
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Old 31st December 2012, 06:01 AM   #2085
Salas is online now Salas  Greece
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Quote:
Originally Posted by RCruz View Post
Hi Salas

Starting to build the SSLV1.1 but my boards have 4 leds for biasing the ccs mosfet. The build guide only has reference to three.

Why the fourth led ?
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Old 31st December 2012, 06:17 AM   #2086
RCruz is offline RCruz  Switzerland
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In reality the BiB spreadsheet allready has all the calculations needed... must be more carefull in the future
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Old 31st December 2012, 06:31 AM   #2087
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You should do the VGS curves of 9530 by eye because the curve embedded in the calc is for 9610. They are Interchangeable on board, but 9610 is the fastest one for open treble while 9530 being no real dork but not as good is the tougher one for special purposes like delivering 1A and beyond to things like WiFi music centre appliances.
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Old 31st December 2012, 06:33 AM   #2088
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Read http://www.diyaudio.com/forums/power...ml#post3274708 for an IRF9530 example and its curves annotated for calculations. By using another ICCS red horizontal line level you can find your own points for 3 or 4 Leds populated.
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Old 31st December 2012, 06:52 AM   #2089
RCruz is offline RCruz  Switzerland
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Thank you Salas

From what I read, IRF9610 is faster and if I do not need high currents, maybe the best choice would be to use it in both positions... right ?
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Old 31st December 2012, 07:22 AM   #2090
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Not both positions. CCS. It lacks enough transconductance for shunt position. You wrote at a point about using 9530 for CCS I saw.
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