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Class D Switching Power Amplifiers and Power D/A conversion

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Old 27th April 2011, 08:24 PM   #1021
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Almost done, still haven't figured out that AC connection, probably goes straight to the secondary of mains transformer...

The new pcb will have the dzony's protection part..
Dimentions are 96mm * 45mm
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Old 27th April 2011, 09:44 PM   #1022
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Quote:
Originally Posted by ghabrius View Post
Almost done, still haven't figured out that AC connection, probably goes straight to the secondary of mains transformer...

The new pcb will have the dzony's protection part..
Dimentions are 96mm * 45mm
The layout is not the best. One of the supply lines makes a loop around the comparator part. The other still goes straight next to them. Imagine the current path from power supply to speaker. Then imageine your right hand there, and check the induced magnetic field. It points right through the comparator part.
So this way there will be high noise, in the most sensitive part.
Lay the power lines so, that these high currents should flow next to less sensitive parts. The loop should newer contain noise sensitive parts.
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Old 27th April 2011, 09:48 PM   #1023
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Yes, AC conector goes to secondary of main transformer!

Relay will not turn on if you don have AC. On AC conector use 1N4007 and dont use 470nF, its bad, use 1uF 100V elko but be careful on polarity because on AC conector goes AC voltage from transformer and after 1N4007 its NEGATIV volatage, so negative pin of 1uF elko goes to R6 and positive pin goes to GND.

R6 has 0,5mA curent
so for example +-50V (50V / 0.5mA = 100Kohm)

Relay will not turn on if you dont have KTY81-122 sensor, but its D class amp, temp sens is not need if you have good heatsink and output coil.

If you conect short 1 and 2 conectors without sensor relay will turn on, if you don, relay will not turn on and protection led is turn on. That I want to use for overload protection with sunt resistor and mini relay (everuthing is ok, mini relay is turn on and have short conect to 1 and 2 pins, Amp is overload -shunt resistors turn of mini relay, 1 and 2 dont have conection and main relay is turn off, but temp led now have name overload )

If you have problem with cliping indicator (on example its show clip on 30VAC and true clip is on 38VAC), add before 1K resistor from amp before diodes 1N4004 10K trimer and calibrate him to show true clip (use osciloscope and constant signal, when sine is in clip, calibrate the trimer to turn on cliping led) but use R2 value from table that I post

Good luck
Regards

Last edited by Dzony988; 27th April 2011 at 09:52 PM.
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Old 27th April 2011, 10:12 PM   #1024
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I forgot, on relay coil pins you can use led - named Active (show when relay is turn on), but from R5 to raley track use 2.2Kohm resistor and after him conect + of led, - of led conect to colector of BC639.

I atached new schematic in protection.zip with all changes that i told you!
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Old 27th April 2011, 10:39 PM   #1025
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dzony, can I use 1N4148 instead of 1N4004? what is the current flowing there? I'll still use the temperature protection because who knows what can happen, even if the MOSFET losses are minimal..

Last edited by ghabrius; 27th April 2011 at 10:43 PM.
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Old 27th April 2011, 10:46 PM   #1026
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Here is a modification on supply paths.. I also switched to bigger relay from mfg Omron
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File Type: bmp old_pcb_path.bmp (59.2 KB, 211 views)
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Old 27th April 2011, 10:47 PM   #1027
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I think you can but I didnt try. 1N4007 is substitute for 1N4004 and 1N4002 (that i use and work perfectly)

I forgot 1N4007 paralel with relay, anode goes to colector of BC639 and katode goes to R5. Thats be all

Last edited by Dzony988; 27th April 2011 at 10:51 PM.
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Old 27th April 2011, 10:48 PM   #1028
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OK I remembered that too
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Old 27th April 2011, 10:58 PM   #1029
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I used 24V 2x16A relay (coil is 1Kohm).That is important to calculate R5

Relay:

24V 1Kohm coil (24V / 1Kohm = 24mA)

(Supplay Voltage - 24V) / 24mA = R5 in Kohms

on example:

(60V-24v)/ 24V= 1.5K
36Vdrop * 24mA = 864mW resistor, but I use 5W always

I dont know can you use smd resistors because R1..R8 must be 2W, for +-90v must be 5W, exept R3, btw you have all power dispiations of resistor in table

If you use relay with other resistion coil, measure resistion first and calculate values for R5

Last edited by Dzony988; 27th April 2011 at 11:03 PM.
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Old 27th April 2011, 11:08 PM   #1030
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I will use a 48V relay. Coil is 4kOhm so the current is 11.5mA.

So I will need a 820R resistor which will dissipate around 0.1W so 1206 SMD resistor should be enough. By the way I won't put an active LED because the voltage will be around 50V and current limiting resistor will dissipate too much power..
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