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Class D vs Class AB amplifier
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<blockquote data-quote="d0dja" data-source="post: 773499" data-attributes="member: 2244"><p>Another little complication worth mentioning ... you probably need a really stiff power supply, because most of the maths that goes into the PWM model is assuming your rails are constant. If you're driving a heavy load hard and your rails sag, that will need compensation (feedback). </p><p></p><p>Another issue to bear in mind is shoot-through -- your MOSFETs are not perfect, and their switching time (in a full bridge implementation) can mean that both positive and negative sides of the bridge are on for a fraction of a second, creating a dead short across your rails, stressing the hell out of your devices.</p><p></p><p>But if you're up for it, having a go is well worth trying ... I built a D-class amp that could handle well over a kW twenty years ago to drive some medical lab apparatus down to 0Hz. It was fun ... used a sawtooth and comparator built from discrete components because we didn't know it was trivial to buy them as ICs.</p><p></p><p>We weren't smart enough or have enough time, and there were no published designs, to sort out feedback to compensate for back EMF, so at anything over a few tens of Hz it started to show severe distortion.</p></blockquote><p></p>
[QUOTE="d0dja, post: 773499, member: 2244"] Another little complication worth mentioning ... you probably need a really stiff power supply, because most of the maths that goes into the PWM model is assuming your rails are constant. If you're driving a heavy load hard and your rails sag, that will need compensation (feedback). Another issue to bear in mind is shoot-through -- your MOSFETs are not perfect, and their switching time (in a full bridge implementation) can mean that both positive and negative sides of the bridge are on for a fraction of a second, creating a dead short across your rails, stressing the hell out of your devices. But if you're up for it, having a go is well worth trying ... I built a D-class amp that could handle well over a kW twenty years ago to drive some medical lab apparatus down to 0Hz. It was fun ... used a sawtooth and comparator built from discrete components because we didn't know it was trivial to buy them as ICs. We weren't smart enough or have enough time, and there were no published designs, to sort out feedback to compensate for back EMF, so at anything over a few tens of Hz it started to show severe distortion. [/QUOTE]
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Class D vs Class AB amplifier
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