Battery Power - Summer 2016 - (Page 12)

Feature Enhancing Smartphone Battery Performance During GSM Pulses Through The Use of a Parallel Supercapacitor Ron Demcko * AVX Fellow Patrick German, Field Applications Engineer * AVX Corp. The continual addition of smartphone features and functionality, combined with users' growing dependence on them for both business and personal use, has made battery life and reliability increasingly vital. The digital transmission signals that these devices rely on to operate require quick pulses of current from the battery. However, these pulses can also cause the battery's instantaneous voltage to drop below the phone's minimum operating voltage, which can temporarily interrupt the flow of power from the battery. To solve this problem, engineers performed a series of tests on multiple battery chemistries to determine whether placing a supercapacitor in parallel with the battery could effectively improve the life of the battery and the quality of the power it provides. The Trouble with Batteries Battery life can be a significant source of frustration for people who rely on their smartphones to execute an ever-expanding number of personal and professional tasks, as even the latest and greatest of these devices have a relatively short battery life and require daily charging. The battery life of most smartphones under heavy use conditions (e.g., extended video recording or playback, streaming music and data, numerous active and background applications, etc.) ranges from five to 20 hours, or less than a day1. Rechargeable batteries, like those used in smartphones and other handheld devices, begin to have trouble maintaining a charge as the batteries age, and certain battery chemistries, such as nickel/cadmium (NiCd) or nickel/metal hydride (NiMH), can develop a memory that degrades the maximum charge that's able to be achieved over the lifetime of the battery. Additionally, most rechargeable batteries, regardless of their chemistry, are limited to a certain number of charge and discharge cycles before their maximum charge capacity begins to diminish. Replacing a smartphone battery that has a reduced maximum capacity can be quite expensive, costing anywhere from $30 to $130, depending on the type of phone and battery2. To reduce the overall cost of smartphone ownership and improve upon their convenience, engineers have experimented with several circuit designs intended to increase the reliability of smartphone batteries. Employing a supercapacitor in parallel with the battery has proven to be one of the most effective such design developments, as this arrangement successfully improves both talk-time and overall battery life by allowing the battery to have a more constant draw than is normally experienced during GSM Pulses. GSM Pulses: Digital Transmission Smartphones operate using a digital transmission signal called Global Systems Mobile (GSM). GSM signals operate in two frequencies: 900 MHz and 1,800 MHz. These signal bands are comprised of hundreds of frequency bands split into 200 kHz increments, and each of these frequency bands are further split into eight segments to allow multiple conversations on a single band3. When a smartphone processes a call, the digital transmission operates within its specified frequency with a short-burst duty cycle of 0.125, which strains the battery a lot more than analog signals normally do3. In digital systems, like GSM, the transmissions occur in short pulses. Consequently, the batteries in such systems only produce power for the purpose of trans- 12 Battery Power * Summer 2016 Figure 1. An Example of a GSM Pulse with a 0.125 Duty Cycle

Table of Contents for the Digital Edition of Battery Power - Summer 2016

Toolbox Energy Storage Systems: Modeling, Simulating and Testing Battery Systems of (H)EVs
Enhancing Smartphone Battery Performance During GSM Pulses Through The Use of a Parallel Supercapacitor
ICs & Semiconductors
Charging Systems
Testing & Monitoring
Editor’s Choice
Research & Development
Conference Preview
Industry News
Calendar of Events

Battery Power - Summer 2016