Due to the advantages of power consumption and size, digital power amplifiers are first used in energy-limited car audio and demanding subwoofer active speakers. With the rapid development of consumer products such as DVD home theaters, mini audio systems, set-top boxes, personal computers, LCD TVs, flat-panel displays, and mobile phones, especially the emergence of new high-sampling-frequency sound source specifications such as SACD and DVDAudio, and audio The evolution of the system from stereo to multi-channel surround systems has accelerated the development of digital power amplifiers. In recent years, the price of digital power amplifiers has been declining, and patents in this area are also emerging in endlessly.

 

1. The ratio of class D output power and power consumption to class AB power amplifier consumption

 

An amplifier that uses low-frequency audio signals to modulate a fixed high-frequency pulse width is called a class D amplifier or a digital audio amplifier. Its major feature is its high efficiency (in theory, it can reach 100%. Above 85%), very small electronic devices can be used to make high-power audio amplifiers.

 

For low power, that is, 1W-3W power amplifiers, under the same playback content, the power efficiency of the class AB power amplifier and the class D power amplifier are about AB=15% and D=75%. Under the condition of playing 1W music, the class AB power amplifier needs to consume 6.7W of power, but the class D power amplifier only consumes 1.33W under the same playing conditions. Therefore, the use of Class D power amplifier can extend the battery life up to 5 times (6.7W/1.33W). In addition to mobile phones, DVD, MP3 and PMP, there are also some popular products such as iPods, mobile phones, and digital photo frames. In the case of medium power, that is, for a 10W-30W power amplifier, when the same playback content is mainly voice, the power efficiency of the class AB power amplifier and the class D power amplifier are AB=25% and D=80, respectively %.

 

Under the condition of playing 10W voice, the class AB power amplifier needs to lose 40W of power, but the class D power amplifier only loses 12.5Watts when playing under the same conditions. Therefore, the use of a class D power amplifier can reduce the cost of the power supply by nearly 3 times (40W/12.5W), and the 2.5W heat generated by the class D power amplifier can be handled by the general power package and PCB design without an additional heat sink. In the case of high power output, that is, 100W-200W Class D digital power amplifiers will also have a place in car audio. Under this high power, Class D power amplifiers still inevitably use heat sinks, but the heat dissipation area and heat dissipation are more than AB Class D power amplifiers need to be small. Due to high efficiency, Class D power amplifiers can have a long use time without starting the car engine without consuming too much battery power. Class D power amplifiers have become the current car The main application products of audio.

 

Second, the difference between digital power amplifier and digital power amplifier, digital power amplifier

 

The so-called digital power amplifier only uses digital signal processing on the pre-stage. After the analog audio signal or digital audio signal is input, the existing digital audio processing integrated circuit is used to realize some such as sound field processing, digital delay, and reverberation. And so on, and finally through the analog power amplifier module for audio amplification.

 

Although various integrated circuit manufacturers have introduced digital sound field processing, digital karaoke and digital Dolby decoding integrated circuits.

 

However, since the current amplifiers can only receive analog audio signals, the interfaces of each integrated circuit are mostly analog, which requires repeated analog/digital and digital/analog conversions, which will introduce quantization noise and deteriorate the sound quality.

 

In addition to the speaker interface (this is because the current speakers can only accept analog audio signals), the all-digital power amplifier is processed by digital signals (including power amplification) inside the power amplifier; for analog audio signals, It can be processed after being converted into a digital signal.

 

The introduction of digital power amplifiers in the era when digital audio is already available will likely have a significant impact on the development of audio technology.