Have you ever thought about doing a very meaningful event but worried it hard to do? Then, when you finally courage to do it, and then look back, you will be surprised to find it is actually very easy.
In my recent discussions with car radio car audio design engineer solutions without using the traditional Class AB amplifiers Class D amplifier and switch, they also have such concerns. Now let's talk about the two main questions I hear most often: the printed circuit board (PCB) size and potential impact of electromagnetic interference (EMI) problems.
Question 1: Class D amplifier takes up more PCB space
Conventional D audio amplifiers use a switching frequency of about 400 kHz, which requires an ideal audio effect using 8.2-μH or 10-μH inductors.
TI's TPA6304-Q1D the class A amplifier using the 2.1-MHz switching frequency. Ripple current reduction means can use a smaller and lighter 3.3-μH inductors, as shown in FIG.
Figure 1: the size of the inductor and switching frequency comparator
TI TPA6304-Q1 using the latest manufacturing techniques mixed signal, when used with a 3.3-μH inductor, the entire 4-channel amplifier solutions (including all the necessary passive components) to reduce the overall size will be 272 mm2, as shown in FIG 2 Fig.
FIG 2: TPA6304-Q1 4-channel Class D amplifier
In this regard, the entire solution TPA6304-Q1 shown in FIG. 3 is smaller than a conventional class AB amplifier.
FIG 3: TPA6304-Q1 Class D amplifier solution comparison scheme and the size of class AB amplifier
Question 2: Class D amplifiers will cause electromagnetic compatibility (EMC) issues
In essence, Class D audio amplifier output will open and close during each clock cycle, and the class AB amplifier is not opened and closed. But this does not mean that the class D amplifier can cause electromagnetic compatibility (EMC) can not solve the problem.
I would like to recall several ways TPA6304-Q1 amplifier is designed to alleviate EMC problems:
· TPA6304-Q1 amplifier design has been highly optimized to handle the overall EMC behavior. In addition, the previously described 3.3-μH inductor is part of an inductor-capacitor (LC) filter, which helps to electromagnetic compatibility speed switching transients on the Class D output stages to a minimum.
· 4, in the conventional class D amplifier 400-kHz range, which switch is located directly within the AM band harmonics. These harmonics reduce the interference signal generated AM receiver sensitivity, thereby preventing the AM radio reception. Thus, some type of EMI must be implemented on the 400-kHz Class D amplifier design avoidance techniques to reduce the effect of these harmonics AM band.
Figure 4: A typical Class D amplifier 400-kHz harmonic
· By working at higher 2.1-MHz switching frequency, TPA6304-Q1 is no longer necessary to avoid EMI embodiment AM band technology, because TPA6304-Q1 provides a significant margin over the AM band. This design does not interfere with any low frequency peak of the AM band, as shown in FIG.
FIG 5: TPA6304-Q1 high switching frequency higher than the AM band
In order to prevent the emergence of some PCB layout EMI problems, TPA6304-Q1 has implemented Kilby Labs research and development of proprietary spread spectrum technology. Figure 6 illustrates how this feature helps to narrow-band source of energy dispersed over a larger band, thereby reducing the peak energy.
Figure 6: Spread Spectrum Technology Background
in conclusion
TPA6304-Q1 2.1-MHz high-frequency switching class D audio amplifier car needs of the industry for the next generation of car radio and external amplifier. In addition to reducing the thermal load of the system, the design of this amplifier also addresses the concern in the transition from Class AB amplifier PCB size to a class D amplifier and EMC problems. Read more
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