How to integrate audio amplifier DSP to improve the efficiency of audio amplifier

Have you ever thought that the integrated digital signal processor (DSP) in an audio amplifier is only for digital filtering, equalization or audio mixing? The reality is that the DSP integrated in modern audio amplifiers can bring many more benefits, including improving the efficiency of the amplifier and audio system.

Have you ever thought that the integrated digital signal processor (DSP) in an audio amplifier is only for digital filtering, equalization or audio mixing? The reality is that the DSP integrated in modern audio amplifiers can bring many more benefits, including improving the efficiency of the amplifier and audio system.

Battery-powered speakers remain one of the super-convenient ways to play audio, indoors, outdoors, or anywhere else you’re playing music. In this article, I’ll discuss how audio amplifiers with integrated DSP can improve the efficiency and runtime of speakers.

“How long will the battery last?”

Clearly, consumers want portable speakers that last longer with their favorite playlists or podcasts and require less time to recharge. Speaker production companies have taken notice, sometimes even listing the speaker’s play time on retail packaging.

If battery life is so important to a portable speaker, you should go for a bigger battery, right? That’s true for some designs, but for compact speakers, there’s simply not enough room. Alternatively, the extra battery capacity could significantly increase the system cost.

Without the flexibility to increase battery capacity, the question for designers becomes, “How can I achieve longer playback time with the same capacity battery?” The answer is to improve efficiency. For audio applications, the more efficient amplifiers for medium to high power (assuming greater than 10W) ​​are still Class D amplifiers with a theoretical efficiency of 100% (actually greater than 90%).

Although greater than 90% efficiency is the benchmark, this is typically measured in the lab using a constant input signal and output power. In fact, for a typical audio clip or song, the measured efficiency of the amplifier varies continuously depending on the output power provided. This is because at lower output powers, the ratio of power lost to heat in the amplifier’s MOSFETs increases. In order to reduce these unnecessary losses, the simplest solution is to reduce the voltage of the power supply. For audio, designers may be reluctant to do this because lowering the supply voltage may reduce the system’s ability to deliver higher output power, especially peak power at higher dynamic range.

Battery Life Solutions for Mid to High Power Speakers

To improve efficiency without compromising output power, TI introduced the TAS5825P Class D audio amplifier with Hybrid-Pro algorithm in DSP, which continuously analyzes the incoming audio signal and provides pulse width to external DC/DC converter Modulate feedback to improve system efficiency and reduce unnecessary losses. Using feedback, the DC/DC converter can increase the supply voltage when audio peaks demand it, and decrease the supply voltage when the higher output power is not required. This feature reduces power consumption and increases efficiency when playing audio at low volume levels without limiting the amplifier’s ability to deliver maximum output power. Figure 1 shows the block diagram of the TAS5825P.

How to integrate audio amplifier DSP to improve the efficiency of audio amplifier
Figure 1: TAS5825P block diagram

The Hybrid-Pro concept is simple, it’s the same way we try to save energy at home or at work. For example, when the lights in the room are not in use, you can turn them off to reduce electricity bills. With an audio amplifier, though, you don’t want to just turn off the music! For a more precise comparison, think of the Hybrid-Pro as an automatic dimmer. The light sensor doesn’t turn off the light (audio amplifier), but automatically dims the light to just the brightness needed at the time (supply voltage to the amplifier). Figure 2 illustrates this concept, where the amplifier’s supply voltage (PVDD) increases with the desired output voltage.

How to integrate audio amplifier DSP to improve the efficiency of audio amplifier
Figure 2: TAS5825P Hybrid-Pro Envelope Tracking

Enabling the Hybrid-Pro run test enables longer run times for battery powered speakers. Compared to typical amplifiers with fixed voltage rails, the TAS5825P configured in Hybrid-Pro mode can extend battery life by more than 20%. Additionally, the adjustable audio look-ahead buffer in the TAS5825P provides advanced voltage rail control without the risk of audio clipping.

Although DSPs were only used for equalization and audio filtering in the past, the benefits of integrating DSPs in audio amplifiers are unprecedented. TI’s family of Class-D audio amplifiers with integrated DSP continues to push the envelope for higher system-level efficiency. Learn more about using DSP to process voice commands.

The Links:   CXA-0538-A 7MBI75N-060 PM800HSA120

Author: Yoyokuo