In the recent years the semiconductor industry has made amazing progresses in delivering higher performance at lower power consumption. However, the gap between the energy need and availability not only persists, but is continuously widening.
For example, while a user was typically able to use his fully charged phone for an entire week a couple of years ago, it’s now often the case that after a single day of smartphone usage the battery is flat. Inadequate battery life is one of the biggest sources of frustration for today’s smartphone owners.
One way to address this dilemma is to design bigger or denser batteries for the phones, impacting cost or weight or both, but this is not enough to effectively close the energy gap. A smarter way is to multiply the sources of available energy and recharge the battery continuously. This means charging the phone as fast as possible when it is plugged into a wall or a USB charger, and supplementing this with charging the phone “on the go” or anytime while using the device. This is the approach ST-Ericsson has taken with the recently announced PowerHUB product family, which combines conventional charging technologies and new energy sources for unprecedented flexibility and scalability.
At Mobile World Congress 2011 in Barcelona, ST-Ericsson demonstrated an innovative three-way solution to power the cellular phone system and charge the Li-Ion battery: 3Amps fast charger, solar harvesting and Near Field Communication (NFC) harvesting.
To start with, ST-Ericsson focused on improving conventional charging methods. The newly introduced PM2300 is a 3Amps charger which reduces up to 50 percent the charging time of tablets and smartphones using large single cell or parallel Li-Ion batteries. With conventional charging, instead of 5-6 hours now only 2-3 hours are needed to charge for example a 6.5Ah battery.
New battery technologies allow to charge during a short period with high current and thus charging up to 80-90 percent in only 45 minutes for a 1500mAh battery. But another very important aspect is that some intensive use cases of mobile devices, such as tablets for example, could consume almost all the 1.5Amps provided by a normal charger, which means the battery is not even charging when you are connected to the wall outlet.
In other words, even while being plugged, the battery is being drained because the intense use of the modem, gaming and graphics capabilities will consume more energy than the charger can provide. With the PM2300 supporting up to 3A of charging, the battery will always charge while in use and your mobile device will be fully powered. Charging with high current represents two main challenges: power dissipation which heats the phone up, and the size of the external components required for charging.
Common charging plate
PM2300 introduces an innovative structure with a dual charging path enabling better power efficiency (around 500mW less power dissipation compared to a single path structure) with the use of conventional small external components. PM2300 has been selected by several manufacturers whose products will be on the market by the end of 2011. PM2300 samples are available in a wafer chip scale package featuring a total PCB footprint of 55mm².
Today, end users want to have a common charging plate that is compatible with all of their mobile devices either at home or in public places. To that end, the Wireless Power Consortium (WPC), of which ST-Ericsson is a member, has established the WPC international standard. This standard is based on the energy transfer from a transmitter, a so-called charging plate to a receiver, the portable device, with a maximum power of 4 to 4.5W being delivered to the battery.
WPC charging uses coils coupled in a resonant inductive way. The standard allows multiple devices to be charged at the same time. It uses a closed loop and a specific protocol to control the power provided to each device up to its end of charge. The charging plate is connected to the wall outlet and provides energy only when a receiver is detected, otherwise the plate does not consume any significant energy.
ST-Ericsson will sample WPC charger ICs for mobile applications this year. Additionally, ST-Ericsson is also looking at alternative energy sources, such as power harvesting to solve battery life issue of future devices. Solar energy is one alternative source that was demonstrated at Mobile World Congress 2011. Today’s solar cells, at a typical smartphone size, can harvest up to 600mW of solar energy, enabling longer music playback time, while charging the phone battery at the same time.
Future flexible or transparent photovoltaic (PV) cells technologies will offer an even better end user experience with solar energy harvesting. This year, ST-Ericsson will sample PowerHUB solutions combining solar charging as well as other energy charging solutions.
Other wireless communication protocols also offer an opportunity for energy harvesting. With a standard NFC coil for example, harvesting energy from any NFC access point can deliver another 150mW to the phone system. This energy may be a solution in the future for some NFC applications even when the mobile phone battery is flat. It is important to understand that energy harvesting is unpredictable, contrary to a USB or wireless charger.
The distribution part of the energy management system must be built in order to harvest energy where and when it is present, with the best possible efficiency. It also needs to mix with the conventional energy sources whenever it is possible. STEricsson is committed to make these energy sources available to the end user, with more solutions from the PowerHUB family being introduced in the coming years that include thermal, motion, fuel cell and other energy combinations.
The possible sources of energy and charging options for mobile devices are about to grow significantly and the PowerHUB family should drive the introduction of new energy sources while maintaining hardware and software compatibility over the entire product range. This opens the door to an intelligent, scalable and flexible energy management for future portable devices.
This article was previously published in EE Times Europe.