2 September, 2020
Recently, Amazon issued an urgent warning over its Echo Buds earphones saying there is a risk they could overheat - so what is going on?
Thermal management is a key consideration for any wearable technology. Echo Buds may be worn against the skin for prolonged periods of time, and therefore have been designed to be completely cool while playing music and interacting with Amazon Alexa.
Figure 1: Thermal simulation of typical wireless in-ear bud using 6SigmaET CFD software
The device itself is powered by an integrated ‘system on chip’, providing the Bluetooth connection, music playback and microphone functionality. These chips are incredibly low powered to enable long battery life but also crucially low heat dissipation. Integrated chips used in the industry are as low as 2mW. Advancements with Bluetooth 5 have enabled much lower power usage during music playback. The outer casing of the wireless headphones often contains a heat spread made of materials such as a membrane of graphene, which helps to move heat away from the hot spots. Although the amount of heat being dissipated is quite small during normal operation.
Figure 2: A thermal model of a wireless ear bud from above using 6SigmaET
Amazon Echo buds and other wireless ear buds need fast charging as well as long battery life. However, quick charging speeds mean that there is a greater amount of power being supplied to the charging case, increasing the heat dissipation. The ear buds only need to dissipate a small amount of heat during normal operation, but the device must be able to handle the high-power during charging.
Amazon’s investigation into the thermal issues were prompted by a customer report about the Echo Buds overheating while in their case. There have only been a limited number of cases so far, but luckily no injuries related to the overheating issue have been reported.
Since becoming aware of the issue, Amazon has released a software update that addresses this potential safety risk, which is also said to improve the long-term performance of the Echo Buds' batteries.
Thermal simulation gives a unique visual representation of the temperature and airflow inside electronic equipment. This insight provides engineers with accurate information on the device to enable them to design the device that will work effectively, without altering the user experience.
Using thermal analysis of wireless ear buds such as the Echo Buds is crucial to ensure that the buds can carry out all their functions while maintaining a temperature that prevents the device from becoming too hot to touch.
Using a thermal simulation package like 6SigmaET, engineers can efficiently test and demonstrate how any electronic device will perform and determine if the device stays within an acceptable temperature range. By using transient thermal analysis, engineers can also calculate how the temperature of a device fluctuates over time and in different scenarios. In the case of the Echo Buds, this would allow engineers to see how the temperature changes both in ear and while charging in their case.
To improve reliability and ensure that an electronic device isn’t prone to overheating, thermal simulation should be used as early as possible during the planning stage of an electronics design.
To find out more about how engineers are using simulation to keep their products cool, download our Heat is On report.
Blog written by: Morna Baillie, Thermal Simulation Engineer Intern
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