Class-G amplifier with PWM supply ! - diyAudio
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Old 7th February 2005, 06:25 PM   #1
B.I.G is offline B.I.G  Romania
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Default Class-G amplifier with PWM supply !

i was looking at the TDA7293 datasheet where you can fiind a class-g amplifier using the tda7293 !
how about building a car amplifier using a PWM circuit increasing the supply voltage when larger output swings are needed ! SG3525 would be a good start ...
i think this should be very efficient ... more eficient than a normal class-G .. or class-H.

any ideas ? could you use an optoisolator to PWM the output ?
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Old 18th March 2005, 07:28 AM   #2
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If you find any info please let me know.
by several years i try to build an pwm for 12v...
RO? me too....
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Old 19th March 2005, 07:32 AM   #3
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generally high power DIY SMPS are a little hit or miss...

the most promising designs i've seen for amplifiers in cars uses a transformer that has a center-tapped primary and center-tapped secondary. +12V is applied to the center tap on primary. A set of NMOS devices are on each of the primary leads and connected to ground. basically turning one one will run current through a winding, and turning the other on will run current through the winding backwards. this keeps core saturation down.

switching needs to be fast.

however i'm not sure, where to get the core, how to wind it, and what feedback method would be best.

not sure if the opto would be able to "PWM" the outputs. not sure what you mean. the optoisolation is use for transformer coupled SMPS where feedback is needed along with isolation.

i don't see why the SMPS in a car would be any more efficient then any other class G/H amplifier. also, you have to concider the PSU design complexity. if you want stereo, you either need dual supplies, or post regualtion which would need to be SMPS to be efficient. this is because if the left and right channel are out of phase, one will need a higher rail then the other. if they share rails then the efficiency would go down a bit.
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