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Old 18th January 2007, 03:41 AM   #1
fumac is offline fumac  China
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Smile a very simple speaker protect just for class-d

a very simple speaker protect just for class-d
when the PWM is off, it turn off the speaker
r3 is wrong del it
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Old 18th January 2007, 03:58 AM   #2
fumac is offline fumac  China
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D3 pls use 4001,is better than 4148
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Old 18th January 2007, 06:16 AM   #3
Pierre is offline Pierre  France
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I assume that will be connected to the mosfets switching output, right?
It is very smart, but have you tested that it triggers when there is PWM but it has a fixed duty cycle, different from 50%, that produces DC at the output that is dangerous enough for the speakers?
In that situation, the circuit should also trigger. This is unlikely and not related to output mosfet failure, but...
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Old 18th January 2007, 04:37 PM   #4
fredos is offline fredos  Canada
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What I see Pierre is that he just try to mute output with a relay when there is no PWM signal...No protection at all here, just a mute..

Fredos

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Old 19th January 2007, 03:00 AM   #5
RX5 is offline RX5  Philippines
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mute function for PS
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Old 19th January 2007, 11:29 AM   #6
Eva is offline Eva  Spain
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It seems more like a mute function in case of a blown output stage.
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Old 19th January 2007, 12:02 PM   #7
fumac is offline fumac  China
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wellcome all
this sch just like a mute function
but it's allmost can protect ur speaker connet to ucd or ucd_like amp
it base on the great design of ucd,

i'll post some pics
to say it clearly

it depend on :when the pwm is off, it will take the speaker off the power amp


1.when ur fet are break,the pwm will be off
2. when ur input connet to the VDD(+50V), the output about 10v dc,and the pwm will be off
3. when daul the power is not the same No. dont worry that.
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Old 19th January 2007, 12:12 PM   #8
fumac is offline fumac  China
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this pic is that the input short to vdd,and the power output 10vDC,
if ur have no protec ur speaker will have a 1~2A DC

the sch will take an action, bcs,the pwm is off
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File Type: jpg shot to the vdd.jpg (96.0 KB, 891 views)
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Old 19th January 2007, 01:01 PM   #9
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this pic is when the power is +50v -25v
ucd is a great design, it can work on +50v -25v!
and the dc offset just +2v , it can't burn ur speakers
and u can hear the dis is very large,
this is a very Extreme State¡£

when the power is +50v -15v, the offset is 3v.
when the power is +50v -10v, the offset is 3.5v.
when the power is +50v -8v, the offset is 3.6v.
when the power is +50v -5v, the pwm is off

this is like that one of the FET is being Death (i dont know how to say it in english )
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File Type: jpg +50-25v.jpg (99.8 KB, 780 views)
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Old 19th January 2007, 01:23 PM   #10
fumac is offline fumac  China
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but sometimes it cant protect.
if u connet a 30k from input to vdd.
the pwm is on,but the output offset is 10v, is ham to ur speaker.
so, u must to insert a cap on the input pin.
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