关于改进低成本D类功放的一种设想
看到有人用开关电源+D类功放推低音炮，板子小，发热低，效果尚可（只是尚可）。突然想到，此二级本是同根生也，电路可以简化。如果直接对整流后的300Ｖ高压进行音频ＰＷＭ调制，输出信号可直接连至扬声器，电路简化很多，降低了成本。比较难解决的是５０Ｈz交流声，设想的解决方案有两种：1.大环路差分负反馈，将输出信号与音频相减后引入负输入端。
2.使用单片机软件采样电源，实现“50Hz锁相环”，预先在音频信号中减去市电交流部分。对于深度的控制需要算法就行实时修正。
音质虽不好，但推低音炮可能行。不知这个想法可行吗？ it can be done, but has not been done.
TI has an application note for one of its class d chip on how to vary supply voltage to change volume and in that application note, it talked about the possibility of directing rectifying ac mains as a power amp - essentially your idea.
the difficulties lay with physics. for good sound quality, you need the amp to switch in excess of 250Khz, and usually in the 380 - 400k+ range. to find power devices and associated drivers at that kind of frequency + power delivery, it is very difficult.
To test its feasibility, you can get a dc/dc converter chip like the lm2596 series and apply an audio signal (ac coupled) to its feedback node, and you will get audio signal on the output.
millwood0 发表于 2012-6-5 19:03 static/image/common/back.gif
it can be done, but has not been done.
TI has an application note for one of its class d chip on ho ...
感谢您的回答，受教，膜拜您啊元老！
我用3842+MOSFET装过一个高压开关电源，100KHz的，接上音频音质“相当凑合”，可以用作汽车喇叭.......
现在感到这个设想基本上就是成本、频率、音质三者的折中，发展前景不大。
另外很好奇，TI的应用文档您老挨个都看过么？ TI的应用文档您老挨个都看过么？
No. That's not possible. I just happened to run into that particular one.
millwood0 发表于 2012-6-6 20:03 static/image/common/back.gif
No. That's not possible. I just happened to run into that particular one.
能否提供一下这份TI的应用笔记？或者给个名字？ It is one of those application notes for their "Pure Path" Class D amplifiers, and it was written around mid-2000. Don't recall a particular name. Sorry. the chip (TASxxxx) was used in a Panasonic avr that was dub'd "Kreil Killer" (XR-30 or XR-55).
If you google, you should get a lot of hits. 感觉隔离可能还是问题。毕竟整流后的GND是浮地，如果接了一些，比如计算机这种GND直接接地的估计会烧……
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