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Wireless Charging ICs Move Toward Charging and Conversion Efficiency

Update Time: 2023-03-20 15:01:18

Wireless charging technology, which has been going to market and applied for some time, especially among mobile device manufacturers, has been developing very rapidly in this field, and many manufacturers have launched their wireless charging solutions, the most well-known of which is Apple's Magsafe.

Wireless charging technology comparison
This contactless charging utilizes near-field induction, and the main common wireless charging technologies are electromagnetic induction, electromagnetic resonance, electric field coupling, and radio wave. Almost all of the current cell phone wireless charging uses electromagnetic induction technology. The transmitting coil is installed on the charging base, and the receiving coil is installed on the back of the phone. The magnetic field of the transmitting coil makes the receiving coil generate an induction current when the phone is close to the charging base.

This technology is more mature, does not require much space, the cost is not high, and is very suitable for small mobile devices and wireless charging applications. However, based on the current limitations of this technology, electromagnetic induction technology is the closest power supply distance among these technologies, the number of devices that can be charged at the same time is small, and the power supply efficiency is in the range of a few W to tens of W.

The principle of magnetic resonance wireless charging technology is that when the transmitter meets the receiver with the same resonance frequency, the electrical energy is transmitted through the resonance effect. The same resonance frequency is necessary for this technology, which is a one-to-many charging technology with a longer power supply distance and higher power supply efficiency compared with electromagnetic induction technology.

In the actual cell phone charging application, the charging distance of this technology is about 10cm at the farthest, and the power supply efficiency is slightly higher than that of electromagnetic induction due to the loss limitation. Strictly speaking, although the technical level of resonance type can improve a lot of places, the practical application has not yet reflected the "quality" of the improvement.

The electric field coupling technology uses coupled asymmetric dipoles to transmit power by forming a high-frequency electric field between the charging base and the device. Although this technology is low cost and does not require stringent equipment alignment, few wireless charging solutions based on this technology have been seen.

There remains radio-wave technology, which is currently one of the most attractive wireless charging implementations, and which can truly achieve long-range charging (>10m). Although the technology is currently not very efficient in terms of power supply, the flexibility brought about by the long charging distance can be a glimpse of the convenience of the future wireless charging that will be brought about by taking power from space. This technology is achieved by LDS technology to increase the antenna on the phone's plastic shell, the use of FPC configuration antenna components, and so on. Many manufacturers who previously did electromagnetic induction and magnetic resonance wireless charging are beginning to lay out radio wave technology.

The three most common wireless charging technologies mentioned above correspond to two wireless charging standards: the Qi standard of the WPC and the AirFuel standard of the AirFuel Alliance. Electromagnetic induction technology corresponds to the Qi standard, and magnetic resonance and radio waves correspond to the AirFuel standard. From the current performance of each technology, there are different advantages and disadvantages, and many problems need to be solved with the further development of technology.

The wireless charging market is developing rapidly.
The flexibility and convenience of wireless charging are undoubtedly, regardless of the technical approach based on, with the continuous breakthrough of technical bottlenecks, the wireless charging market scale is also increasing year by year, opening up more markets in smartphones, wearable devices, automotive electronics, household appliances, and other fields. According to a report by international market research firm Markets and Markets, the global wireless charging market is forecast to grow from $4.5 billion in 2021 to $13.4 billion in 2026, at a compound annual growth rate of 24.6% during the period.

By market segment, the electric vehicle wireless charging market will be the fastest-growing segment. According to the Markets and Markets report, the global electric vehicle wireless charging market is expected to grow from $15 million in 2022 to $377 million by 2027, at a CAGR of 88.4%.

Wireless charging IC by mainstream manufacturers
Wireless charging includes two parts: transmitter side and receiver side, and the upstream and downstream industry chain covers chips, magnetic materials, transmission coils, module manufacturing, and system integration. Here we focus on wireless charging IC, i.e., transmitter IC and receiver IC, which significantly impact the high efficiency and low power consumption of wireless charging.

ST Wireless Charging ICs
ST's wireless battery charger ICs cover all major standards and technologies, including a complete transmitter and receiver chipsets portfolio. The part numbers currently in mass production are STWLC38 and STWLC98 for the receiver-side ICs and STWBC2-HP and STWBC86 for the transmitter-side.

The receiver-side STWLC38 is for 15W applications, the STWLC98 is for 70W high-power applications, the transmitter-side STWBC86 is for 5W low-power applications, and the STWBC2-HP has a maximum power of 15W. However, the STWBC2-HP has a proprietary ST Super Charge extension for high-power charging. The receiver-side 70W power level STWLC98 is a highly integrated wireless charging IC that supports Qi specifications 1.2.4 and 1.3 and achieves high efficiency and low power consumption by integrating a low-loss synchronous rectifier and a low dropout linear regulator.

ST's receiver-side ICs have high efficiency and enhanced security for a wider range of applications. The transmitter-side ICs ensure fast and stable single/multi-coil wireless charging for 2.5 - 70 W applications.

Renesas Wireless Charging ICs (IDT Wireless Charging ICs)
Before its acquisition by Renesas, IDT, a core member (super member) of WPC, had a remarkable track record in the wireless charging IC market. In Renesas' wireless charging IC device list, there are 12 material numbers, with the receiver and transmitter sides accounting for half.

The receiver side power level is up to 60W from the WPC 1.2 enabled P9418. The P9418, as the receiver side, integrates a highly efficient synchronous full-bridge rectifier and control circuit to modulate the load to send message packets to the transmitter Tx to optimize power delivery. In contrast, the P9418, as the transmitter side, can also use an on-chip full/half-bridge inverter, PWM generator, or modulator/demodulator for communication. The P9418 can also be used as a transmitter to generate AC power signals to drive an external LC resonant loop using an on-chip full/half-bridge inverter, PWM generator, modulator/demodulator for communication, and microcontroller.

The highest power level on the transmitter side is the P9247, which supports 15W of power in compliance with the WPC-1.2.4 specification and up to 30W in proprietary applications, compatible with all popular wireless charging protocols (BPP, EPP, iPhone charging, and Android proprietary fast charging). Standby power consumption.

TI wireless charging ICs
TI's bq5105x series is Qi-compliant, high-efficiency wireless power receivers with integrated Li-ion/Li-polymer battery charge controllers. bq5105x uses the Qi v1.2 communication protocol to establish a global feedback mechanism from the receiver to the transmitter to stabilize the power transfer process. The bq5105xB series integrates a single package with a low-impedance synchronous rectifier, low dropout regulator (LDO), digital control, charger controller, and precision voltage and current loops. Low-impedance N-MOSFETs are used throughout the power stage to ensure high efficiency and low power consumption.
The transmitter side of the bq501210 series integrates the logic required to transmit power wirelessly from a WPC-compliant receiver, capable of transmitting up to 15W of power. The transmitter side can optionally provide 5W WPC low or 15W medium power by negotiating with a high voltage dedicated charging port adapter or higher power for compatible receivers with fast charging support.

NXP Wireless Charging ICs
NXP's wireless charging ICs are available in a total of 24 feeds. The 15W wireless charging IC on the transmitter side provides all the required controller functionality with a power transfer efficiency of over 75% and is configured with optimized foreign object detection algorithms. The 65 W power level on the receiving side has an 80-90% efficiency. These cost-effective 5 W and 15 W transmitter and receiver controller ICs combine high performance and reliability.

From these mainstream manufacturers of mainstream ICs, improving the efficiency of wireless charging and conversion efficiency has become the direction of manufacturers to make efforts. In the case of power determination, charging efficiency and conversion efficiency is the key to limiting the speed of wireless charging.

Final words
As a charging technology that does not require the transmission of energy through the connector, without the charger, or power cord, the flexibility of wireless charging since it is not necessary to say, compared with wired charging, in addition to flexibility, wireless charging not only has a lot of advantages in terms of safety, versatility, etc. but also can reduce the frequent charging of the device charging interface loss.

The wireless charging market size increased year by year. Also, it attracted many manufacturers to enter the market in smartphones, wearable devices, automotive electronics, home appliances, and other fields to develop more markets. With the development of each wireless charging technology and the progress of wireless charging IC in terms of efficiency and loss, more flexible and high-efficiency wireless charging will be further popularized.