The design trend of TWS charging cases --- the pursuit of long battery life and high charging efficiency
The convenience of true wireless stereo (TWS) has ushered in the increasingly fierce competition in the global TWS consumer market. Even according to an analysis report by a research institute in 2022, the total market share of the top five brands has exceeded 50%. However, due to the relatively short service life of TWS products and the rise of emerging markets such as India, there are still quite a few emerging brands investing in TWS new product development in recent years (2022 - 2024). Therefore, how to differentiate from other mainstream brands in terms of development specifications and successfully attract the favor of many consumers has become the primary task for TWS product design engineers.
Since the advent of TWS products, insufficient battery life and relatively short continuous playback time have often become issues criticized by consumers. Therefore, the long-lasting battery life of TWS products has also become the focus of specification optimization for various brands. However, due to the design direction of TWS products that are lightweight and easy to carry, lithium batteries cannot be expanded without limit to obtain higher electric storage capacity. Therefore, various manufacturers have designed in the focus of improving charging efficiency and power to shorten the TWS charging time and optimize the user's product experience.
Specification requirements for wireless speaker charging terminals
Among the music equipment product series, apart from TWS, the market competition of wireless speakers is the most competitive. Wireless speakers equipped with voice assistants serve as the communication core of smart homes. Various brands have launched a full range of products from affordable to high-end products, hence, the wireless speaker market is gradually emerging. In addition to sound quality requirements, owing to the versatility of smart speakers, various brands are gradually integrating functions such as medical care monitoring and security services into their products. In order to meet the requirements of the increasing number of functions, the power consumption of wireless speakers is also gradually increasing. In the early speaker charging terminal designs before 2020, 5W (5V, 1A) Micro USB or DC Jack were the mainstream. However, new products released in recent years (2022-2024) have all adopted 15W (12V, 1.25 A or 14V, 1.1A), 25W (20V, 1.25A) or even higher power for design and development.
USB Type-C --- the future unified charging and transmission interface
As the European Union stipulates that all electronic devices must use USB Type-C as a universal standard starting from 2024, making it more convenient for consumers. Therefore, in recent years, the charging terminals of TWS and wireless speakers have gradually adopted USB Type-C as the mainstream. While using a unified charging terminal to reduce electronic waste, the complete USB Type-C Power Delivery power supply specifications also make it very convenient for product design engineers to select power specifications. Figure 1 below shows the power currently supported by the USB Power Delivery charging protocol:
Figure 1. In the USB Power Delivery charging protocol, the voltage and current used in each power range
ESD/Surge protection requirements and testing standards for charging terminals
Whether it is a conventional DC Jack, Micro USB or USB Type-C charging terminal, users will encounter very frequent plugging and unplugging. Users often even hot-swap wires while the power is on, which will cause the charging terminal to be exposed to a higher risk of ESD/Surge damage. That prompts TWS and speaker designers to use IEC 61000-4-2 Level 4 ESD testing to ensure the ESD tolerance of product charging terminals during the design and development stage. Furthermore, they will ensure that the cable will not be damaged when encountering a Cable Discharge Event when plugging and unplugging. More and more manufacturers require Direct Pin Injection to test their products, and stringent test conditions have also become challenges faced by engineers during the product design phase.
In addition to the basic IEC 61000-4-2 ESD test, some brand manufacturers will additionally conduct IEC 61000-4-5 EOS test on the charging terminals of their TWS and speaker products to simulate greater energy surge damage so as to prevent products from causing higher defective repair rates in areas with harsher environments. Among the industry's current IEC 61000-4-5 EOS test specifications for charging terminals of music products, the low-voltage surge test (2ohm) 300V is relatively stringent.
ESD/Surge solution for charging terminal
To ensure that the charging terminal can pass such stringent ESD and surge tests, it is recommended to select ESD/Surge protection components that meet the following conditions:
1. Low Clamping Voltage:
Clamping Voltage is the most important parameter to evaluate the protection effect of ESD/Surge protection components. ESD/Surge protection components with lower clamping voltages can effectively suppress energy when encountering large energy surges, and thereby protect IC components in advanced processes. Since today's quick-charging ICs are mostly developed and manufactured using advanced processes, their ESD tolerance is also gradually declining. Therefore, ESD/Surge protection components with lower clamping voltages must be selected to prevent sensitive fast-charging ICs from being interfered due to an ESD or EOS event.
- 2. High Surge Ipp:
- ESD/Surge protection components with high Surge Ipp can not only help charging terminals pass the stringent IEC 61000-4-5 EOS test, but also can further help electronic products reduce defective repairs caused by EOS after sale.
- 3. Uni-direction:
- Since the Power Rail is a DC voltage, the simple ESD protection circuit inside the quick-charging IC is often designed with a unidirectional ESD cell. Therefore, when selecting ESD/Surge protection components, it is recommended to choose Uni-direction components to obtain optimized negative conduction speed and better negative clamping voltage so as provide the best protection effect for quick-charging ICs.
- In order to ensure a good ESD/Surge protection solution for the charging terminal, Amazing Microelectronic Corp. has developed a full series of protection solutions for each charging voltage specification. The specifications are introduced in Table 1 and Table 2 below:
Table 1: DFN1610P2E packaged ESD/Surge protection component series, suitable for basic Surge protection needs
Figure 2: Circuit diagram of ESD/Surge protection solution for USB Type-C charging terminal
Table 2: DFN2020 packaged ESD/Surge protection component series, suitable for high Surge protection requirements
As consumers pursue longer battery life and charging efficiency for TWS and put forward more functional requirements for wireless speakers, design manufacturers are driven to increase the charging power of charging terminals. How to increase the power of the charging terminal while ensuring that the product has sufficient system-level ESD/Surge tolerance to avoid defective repairs caused by ESD/EOS surge damage has often become an important topic for product design engineers in the research and development stage. Amazing Microelectronic Corp has developed a full range of ESD/Surge protection solutions for various charging powers, hoping to help design engineers enhance the ESD/Surge tolerance reliability of products and speed up the time to market.