By Zhang Jialiang, Chief Scientist for VOOC Flash Charge at OPPO [sponsored content]
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5G provides advanced connectivity that will enable the Convergence of Everything across many different scenarios and devices. But as our devices are used in more different ways, they will require more power, and the pressure on battery life and charging will continue to increase. Battery charging is a foundational technology for smart devices. It is responsible for enabling high-performance devices to safely support extended hours of use. So, what breakthroughs have been made in battery charging? What advances will come in the future? OPPO is a technology company that is committed to developing smart devices, and is a leader in battery charging technology. Here, OPPO offers some of its insights into the future of battery charging.
The 5G Convergence of Everything Needs More Power
The arrival of 5G is accelerating the Convergence of Everything. It has prompted the speedy emergence of a new generation of consumer electronics, including smartphones, tablets, Bluetooth speakers, and drones. Entire new categories of electronic products are appearing. And disruptive, power-hungry new functions like HD videophone calls are demanding more than ever from device batteries. The 5G era is predicated on a series of driving technologies, particularly power technologies. What this means is that a vital research problem for the industry is improving battery life and charging technologies until they can support the fast computation, large number of connections, and long periods on standby required by 5G devices. Batteries will need to adapt to more new usage patterns, and must be longer-lasting, lower-cost, and safer. Every additional feature that consumers demand from their smart devices means more stringent demands on their device batteries and charging technology. As a key focus of the Convergence of Everything , charging technologies are about to begin a new round of challenges and innovation.
OPPO’s Advances and Innovations in Charging
When smartphone batteries were made of nickel-cadmium, there were few safety issues. However, lithium ion batteries made safety as important an issue as charging speed. Over the last few years, OPPO has made a series of innovations in key charging technologies, and has been able to create simpler, faster charging systems, while also achieving ever higher levels of battery safety.
Precise control of voltage and current Conventional lithium ion batteries are charged in three phases: trickle charging, constant current, and constant voltage. The battery’s internal resistance and reactance can cause long charging times. To overcome this, the charging system required more precise control over the voltage and current, so that the system can accurately compensate for the drop in current due to the battery’s internal resistance and reactance. This enables it to boost voltage, current, and charging speed without degrading the cell.
Pulse charging Pulse charging allows for a simpler charging system, minimizes the impact of the charger on the electrical supply system, and smooths out the battery’s capacitive reactance. OPPO has two separate charging systems: a high-power system, and a low-power system. The low-power system uses trapezoidal or square wave pulses; the high-power system has sine wave pulses. These simple programs enable much smaller charging systems, and make them longer-lived and more robust.
Fused surge protection The biggest safety concern with lithium ion batteries is excessively high voltage during charging. Conventional surge protection devices use MOSFETs to cut current when it reaches dangerous levels. However, these devices are not sufficiently reliable. OPPO’s VOOC Flash Charge technology incorporates fuses alongside a triggering circuit in an innovative design that is compact and has low internal resistance. This offers much more reliable circuit protection. Today, fuses have been incorporated into the overcurrent protection devices on many smartphones, and are an important part of safe charging technology.
Redundant two-way communications between charger and battery management system (BMS) In a conventional battery charging system, the charger, the control circuit, and the battery all operate independently; there is no communication of their respective states. The charger delivers power as soon as it is plugged in; the control circuit mechanically follows the constant voltage, constant current charging program, without any access to the status or quality of the battery; the battery accepts the power output, without any way of perceiving how much power the charging circuit is delivering. Because of the potential hazards in a “dumb” charging circuit, OPPO developed a system in which the charger engages in redundant communication with the BMS. The various parts of the circuit can exchange information on the charging process within a few hundredths of a second. The adapter can find out what level of power the battery system requires, and can get feedback on how well the power that it outputs is being taken up, so it knows whether the power is being absorbed by the battery electrolyte. When it observes that impedance is rising, and the power that it outputs is being converted into damaging heat, the adapter can guarantee circuit safety by independently cutting power. The battery system can also report to the charger exactly what levels of power, current, and voltage it requires. It then compares the output from the adapter with the level of power being absorbed by the battery. Impedance levels for every section of the circuitry, wiring, connectors, and semiconductor components between the charger and the battery are under constant observation. If impedance rises, but remains within acceptable parameters, the power output of the charger will rise to match it. This means that the rate of charging will remain constant. If the impedance of a component rises higher than the acceptable limits, each component of the charging circuit will switch to protection mode. This ensures that no faults or safety hazards develop, such as overheating at the charging socket.
Monitoring for physical damage The battery’s internal resistance is constantly monitored, and its output voltage checked for microvariations, to determine whether the cell has suffered any physical damage. This monitoring is carried out by the BMS, and continues even if the battery is removed from the device. If the battery is subject to external pressure or pierced, or if its internal physical structure changes, then the damage is recorded. A signal is sent to the device’s systems that the battery can no longer be used or charged. Any excess charge in the battery is discharged to guarantee that the damaged cell remains safe.
OPPO’s Insights into the Future of Fast Charging
VOOC Flash Charge is OPPO’s own patent fast charging technology. Its launch in 2014 catapulted OPPO to the head of the pack, and changed the phone charging experience for consumers around the world. Today, OPPO has over 1,800 patents or patents pending in territories everywhere. The three fully mature charging technologies, VOOC, SuperVOOC, and wireless VOOC, are used by over 145 million people globally.
In 2019, OPPO launched SuperVOOC 2.0, a new generation of VOOC technology with peak charging rates of 65W. It can fully charge a phone with a 4,000mAh battery in just 30 minutes. The new OPPO Ace2, which hit the shelves not long ago, has OPPO’s 40W AirVOOC wireless charging. It supports full charge for a 4,000mAh battery within one hour—plug-in charger speeds on a wireless charger.
OPPO also licenses its VOOC patents, and is building a VOOC ecosystem to support the technology going forward. VOOC Flash Charge technology has been licensed to a total of 23 other manufacturers, which make other smart components such as charging chips, power banks, car chargers, and charging stands. The ecosystem continues to grow, so that more users can enjoy the convenience of high-speed VOOC Flash Charge.
The technology continues to evolve. OPPO monitors user needs and keeps VOOC at the forefront of the industry so that it can offer users an even more extraordinary charging experience. OPPO believes that the next advances in charging technology will have to go beyond the basic dimensions of bigger battery size, faster charging speeds, and higher power output. The arrival of 5G and the new Convergence of Everything ecosystem will demand more. But all advances in charging technology will demand a perfect balance between speed and safety. In the long term, new materials and manufacturing techniques will be opportunities for new breakthroughs in the charging experience.
Future Trends and Challenges for Battery and Charging Technologies
Looking at the power needs of 5G devices in the Convergence of Everything , both batteries and charging will require a thorough overhaul.
Higher power, more compact chargers Today, a 100W charger is the size of a bar of soap. With improvements in GaN materials, new circuit designs, and OPPO’s efforts to increase power density, OPPO predicts that these chargers will become smaller and more portable. They will offer new levels of ease for consumers charging their devices.
Advances in battery materials The current state of the art in battery materials is the lithium ion cell in an aluminum laminated film pouch. But for several years now, there have been very few advances in either safety or power density for these materials. OPPO engineers are exploring new techniques and materials with the potential for much higher power densities. They test new elements, and use a range of physical, chemical, optical, thermal, and electric techniques to address safety and manufacturing problems. Ultimately, they may be able to develop new battery materials that adapt to more use cases and a wider range of environments. These new materials could revolutionize product battery life and the user experience.
Improvements in wireless charging Wireless charging will continue to become more attractive. As charging cables and plugs are abandoned, charging will become safer, and new modes of connection will allow for increasingly futuristic phone form factors.
Power-hungry apps like video and games are increasingly popular among smart device users, which means in turn that they demand a better device charging experience. The arrival of 5G will only accelerate this trend. OPPO, one of the leaders in the field of battery charging, hopes to partner with companies around the world to invest more in R&D and innovation for charging over the long term. As the Convergence of Everything approaches, OPPO will be revolutionizing the charging experience.
About the author
ZHANG Jialiang, Chief Scientist for VOOC Flash Charge at OPPO, often called the father of flash charging. Zhang joined OPPO in 2004, and has been researching battery charging technologies for more than a decade. His team spent two years creating a number of breakthrough inventions to finally produce OPPO’s VOOC Flash Charge, a low-voltage, high-current fast charging technology. VOOC sparked a wave of fast charge solutions across the smartphone industry. The ongoing improvements in charging have given users a massive boost in charging speed. VOOC was one of the technologies referenced in the first fast charge standard published by China Telecommunication Technology Labs, an agency of the Ministry of Industry and Information Technology, and flash charging technologies are now one of the key planks in OPPO’s patent portfolio. Based on the VOOC blueprint, the company has gone on to develop SuperVOOC, the next generation of flash charge. OPPO phones now come equipped with 65W SuperVOOC 2.0 plug-in charging, and 40W wireless charging. ZHANG Jialiang and his team remain at the forefront of fast charge research across the industry.