A lot of portable speakers are entering the market to supplement the audio performance of modern cellular electronics and memory devices that either store or play media content. The current challenge is that the physical size of portable devices is a selling factor, but batteries do not have the power density or longevity to create good-quality audio playback. Physical dimensions also contribute to a lack of deep resonant bass, making music sound distorted and unattractive.
Many manufacturers are building portable (often Bluetooth®-enabled) speakers that contain larger batteries and also have the physical size to handle low-frequency bass. There are many challenges to overcome in such designs, often relating to system integration, thermal reliability, cost-effectiveness and using single lithium-ion cell drivers for the speakers.
TI has built a reference design, showcasing how a high-performance, compact and flexible boost converter can help overcome these challenges (Figure 1).
Figure 1: Portable speaker reference design
The LM3481 boost controller supports compact designs and high efficiency. Figure 2 illustrates a demonstration of the efficiency you can expect over the load range, the comparative solution size and thermal performance.
The LM3481 offers a compact, efficient and low bill of materials solution that helps customers overcome thermal-density issues associated with the attractive small designs and shapes their design engineers use to make the portable speakers. It also supports a low-cost implementation across the full range of power output to the speakers. You can see these point within Figure 2.
Figure 2: Efficiency, thermal and solution performance
The device also supports very low Vin capability; this is particularly important for single-cell lithium-ion designs. As the power capacity of a lithium cell starts to decay, the voltage provided to the circuity will start to decay. Typically, there is a “knee point” where the battery will start to droop faster. This often translates to a condition where the speakers start to distort and the dynamic music notes will not sound as clear, as shown in Figure 3.
Figure 3: Audio clipping associated with a dying single-cell battery
The LM3481 can support the boosting of the voltage and also the dynamic load so that the portable speaker continues to perform with high clarity until the battery is finally exhausted.
As with any switching regulator, there is noise associated with the use of high-frequency transistors used in the conversion of the voltage. It is important to understand the effects of this in the final design, as well as the methods of suppression and how to avoid this noise in the audio output. Designing the integrated circuit (IC) well in the first place can minimize this (see Figure 4), also sensible and good techniques used in your printed circuit board (PCB) layout is critical in maintaining high performance. Also with lower noise from the power supply there is less interference to the Audio output, the reference design can show this as seen in Figure 5.
It is possible to offer performance that is compact, with low implementation costs and ease of design, thus giving modern portable speaker designers the ability to satisfy demanding customers.
Figure 4: Output ripple of LM3481 demonstrating low noise
Figure 5: Solution audio performance (total harmonic distortion) versus frequency
All content and materials on this site are provided "as is". TI and its respective suppliers and providers of content make no representations about the suitability of these materials for any purpose and disclaim all warranties and conditions with regard to these materials, including but not limited to all implied warranties and conditions of merchantability, fitness for a particular purpose, title and non-infringement of any third party intellectual property right. No license, either express or implied, by estoppel or otherwise, is granted by TI. Use of the information on this site may require a license from a third party, or a license from TI.
TI is a global semiconductor design and manufacturing company. Innovate with 100,000+ analog ICs andembedded processors, along with software, tools and the industry’s largest sales/support staff.