The wireless charging power transmission power is gradually increasing. As the wafer control algorithm matures, wireless charging technology is making great strides toward medium-power applications. In the future, the charging rate of terminal products supporting medium-power wireless charging technology is expected to rise rapidly, and the user's operating environment will be more convenient.
Wireless charging products have been in the market for some time, and most of them are charging applications for handheld products below 5 watts, and such products do not maximize the benefits of magnetic induction (MI) wireless charging. The advantage of wireless charging is not that the power connector is removed before and after the charging of the handheld device. In many applications, the power plug (ie, the conductor contact) has other problems, such as high humidity causing contact corrosion, and easy gas environment to energize the contacts. Sparks pose a hazard, where vibration or moving objects cannot be accurately connected, etc., are applications where wireless charging applications can benefit.
Improve transmission power, wireless charging market is more spacious
At present, the application range of 5 watts of charging energy is limited, and many applications consume higher power, so the charging energy is insufficient, which makes the device unable to accumulate power and requires a longer charging time. In view of this, increasing the wireless charging power is an important direction for the next development of this technology, and it is more practical than the wireless charging to a longer transmission distance.
The main characteristic of wireless charging is that there is no conductor contact that transmits power, and the electromagnetic energy is transmitted through the non-conductor to transmit the power to the other end. At present, many studies have tried to increase the transmission distance through magnetic resonance technology, and can charge one or more devices, but there are still technical bottlenecks to overcome. For example, if electromagnetic energy is sent out from the source, if it is not limited to a limited space, it will cause a large electromagnetic interference problem. So far, there has not been any technical disclosure that can solve the problems related to magnetic resonance. In the industry, it is also seen that the manufacturers who originally studied magnetic resonance technology began to form alliances with the electromagnetic induction technology. It is obvious that the magnetic resonance technology is not yet mature.
There is no doubt that electromagnetic induction is still the mainstream technology at this stage, and the bottleneck with limited transmission distance under this technology can not be broken, but the electromagnetic induction does not lose the original intention of wireless charging, that is, the conductor contact is removed, which can be solved in practical applications. Trouble with inconvenient charging in various environments. In addition, the proximity of the inductive power transmission also brings the additional benefit that the electromagnetic energy will be limited to a small interval, so there is no electromagnetic interference problem in the energy increase, so the electromagnetic induction wireless charging system increases the power to make the application The broader level is its inevitable direction.
Left and right wireless charging system efficiency control algorithm role eaten
The technical problem of wireless charging to improve transmission power is efficiency and safety, and the solution is the control method dominated by software calculus. Most of the development engineers who are initially involved in wireless charging will always stick to the hardware circuit discussion. The hardware circuit is the basic structure of the system, and the high efficiency components need to be matched with each other, but the real difficulty is to control the software of the whole system. Algorithm. The soft shoulder power output control optimizes efficiency and also monitors system status to ensure safe operation of the wireless charging system.
In fact, software is also the part of the wireless charging master IC manufacturers to invest the most resources. First, the developer must understand how the software control affects the efficiency of the wireless charging system; the wireless charging Power Supply itself is a platform that can change the output power. After receiving the energy, the power receiving device can convert the charging or direct power supply, due to the transmitter ( Tx) has no physical connection with the receiver (Rx), and the relative position is not fixed. Therefore, the power output from the Tx output power to the Rx is unpredictable, so it is necessary to stabilize the power received by the Rx through the control system. value.
As for the implementation, Rx directly transmits the load modulation feedback on the energy carrier sent by Tx, and returns the power information on Rx to Tx, so that Tx receives the information, and then performs power adjustment to make Rx receive energy. Is a stable value. Since this method is to transmit data on the Tx energy carrier, the current practical frequency of the wireless charging system is about 125 kHz. At such carrier frequency, the data transmission rate is difficult to increase, so that the power output adjustment on the Tx cannot keep up with the load change on the Rx. To make the Rx output unstable, the common solution to this problem is that Tx maintains a high output power. After Rx receives energy, its rectified voltage is relatively high due to high power. In order to stabilize the output, a buck regulator is configured at the back of the Rx rectifier to make the final output voltage stable.
Through the above sections, the engineer can understand that the voltage control before the rectifier and the buck is very important on the Rx. At this point, the voltage is too high, which will cause a large voltage difference on the buck, resulting in poor efficiency and component heating. On the contrary, if the voltage is too low at this point, the voltage will drop sharply and the output will be insufficient when the load is increased. This part is the key to controlling the efficiency of the software.
To put it simply, the software is to adjust the power of the Tx terminal so that the power received by the Rx terminal is stable. In the Rx terminal, the voltage at the front end of the buck can be controlled to the optimum efficiency. This operation is very complicated.
Firstly, the Tx end must correctly interpret the data signal from the Rx end. It is difficult in the wireless charging system that the power supply noise of the energy carrier is quite large. When the Rx output is a variable load or an increased power, the noise is also increased. This part of the noise is difficult to filter out with hardware. When the signal is mixed with noise, it is necessary to take out the data signal due to the software calculation. This is the first step of control and many wireless charging. The system needs to develop the problem of improving power. It has not progressed from 5 watts to 10 watts for several years, mainly because it cannot solve the problem of data transmission after increasing power.
In addition, how to adjust the power level after receiving the data is the next problem. The output power control of the wireless charging power supply has a very complicated variation factor. Among them, the output power variation is based on the Tx coil and the capacitor resonance. When the driving voltage and the Rx terminal are close to each other, the magnetic material on the power receiving coil affects the inductance of the Tx coil, causing the resonance curve to shift, and the relative positions of Tx and Rx affect the variation amount after the power adjustment, etc., Under the situation, Tx can only be adjusted by Rx low-rate data. Under the condition that the most important discriminant source data update speed is limited, the software on Tx needs to have the learning analysis function of the coil output characteristics, and receive After the Rx data, the stable target value can be achieved with a minimum number of adjustments. The complexity is that there are many factors affecting the Tx control power. To design a feedback loop and an adjustment algorithm, more resources must be invested.
Metal foreign object detection and construction wireless charging application is safe and flawless
In addition to efficiency in wireless charging systems, another important design consideration is safety. In terms of products, safety should be the top priority, and security issues must be solved by techniques that control efficiency. Therefore, the method of data transmission from data Rx to Tx is discussed first. The biggest safety problem of wireless charging is metal foreign matter; since the Tx end itself is an electromagnetic energy emitting device, it is the same in electromagnetic induction or magnetic resonance. The biggest problem of electromagnetic energy is that it is heated on the metal object and heated. The efficiency is very good, only 10 watts of energy is needed to heat the coin to the boiling point in one minute.
The basis of the wireless charging system design is target recognition. The standby Tx terminal is the off state that does not output energy. After the corresponding Rx senses and proposes the power demand, the Tx will start to transmit power until the Rx leaves or proposes to stop the charging demand and is turned off. Here, the metal foreign matter is divided into three types of forms to discuss; the first type is to put metal in the power supply part under the condition of standby at the Tx end, because the metal object does not feed back the data code to the Tx start power, to the present The technology can easily accomplish this function; the second type is a metal object around the induction coil of Rx, or the metal is first placed on the Tx and then the Rx is pressed and sensed. The actual situation may be that the Rx housing contains metal. Substance, the condition of Tx operation is that when the data code is received, the power can be started, but the energy is absorbed and absorbed by the metal; the third type is that after the Tx and Rx induction are connected, metal foreign matter is inserted between them, and the metal foreign matter is not destroyed. The communication between Tx and Rx absorbs electromagnetic energy to generate heat, which is an abnormal use condition.
Regardless of whether the metal object is placed intentionally or unintentionally in the wireless charging sensor, the system should have a safety mechanism corresponding to the protection mode. The protection mode is roughly divided into two directions; one before the induction power is activated, the active safety mechanism detects the presence of metal and does not start the power. Output, this way can protect the first and second types of conditions; another passive security mechanism is to detect Tx to Rx power consumption and temperature protection after starting power, passive mode is already possible after starting power The existing metal is heated for a period of time and has safety concerns, but this is also the last line of defense for the third type of metal foreign matter. The passive safety mechanism is more complicated. The reason is that there are many interference discriminating factors. The wireless charging system has poor matching efficiency or coil corresponding Deviations are easily misjudged as having metal foreign objects, so there is currently no reliable way to accomplish this.
Intensified charging efficiency induction coil technology still needs to be refined
Wireless charging to improve efficiency In addition to control methods, hardware circuits are also very important. At present, the performance of commercially available power components such as metal oxide semiconductor field effect transistors (MOSFETs) is quite excellent, and the bottleneck of power increase today falls on the coils and their anti-magnetic sheets. The so-called wireless charging Tx is like driving electromagnetic energy to the Rx terminal, and then rectifying and filtering to the back-end output. Looking at the current path from the power input terminal, the first obstacle encountered is the MOSFET component, just mentioned the current advanced The impedance of the component can be less than 10 milliohms (mΩ). The current flows through the resonant capacitor to the coil to complete the current circulation of the driver. The capacitor is selected as the material, and the impedance is extremely low under AC and almost invisible. To loss.
However, the problem of the coil is more troublesome. In addition to the impedance of the wireless charging coil, the alternating current forms an eddy current on the wire and interacts with the anti-magnetic piece. The equivalent impedance is much larger than other components, so the thermal analyzer is used. When you look at it, you will see that the coil wire is the highest temperature of the whole system (Fig. 1). Therefore, if the efficiency is to be improved, it is necessary to further improve the coil technology. The industry is continuing to work hard.
Figure 1 From the thermal image during the operation of the wireless power system, it can be seen that the temperature of the coil is the highest, the Rx terminal rectification and voltage regulator components will also heat up, and the Tx circuit has almost no heat.
In summary, at present, the electromagnetic induction type wireless power system has a safety control mechanism, and the chip manufacturer can implement the output power of the 100 watt receiving end in Tx and Rx (Fig. 2), and the efficiency can reach more than 85%. It can be seen that the system circuit technology is quite mature. The 100 wattable level of application has been quite extensive, so the subsequent power should not be urgency to develop further. Another application is wireless charging of vehicles. For example, the power demand of electric vehicles and the sensing distance of several kilowatts and tens of centimeters is not the range that can be touched by the system in this paper. In practical terms, many products can be electromagnetically induced. Charging to solve some charging problems, the future direction of wireless charging system development should be toward the parallel development of better efficiency performance and security mechanisms.
Figure 2 The electromagnetic induction wireless power system has been implemented up to 100 watts to meet most application markets.
Product Name: Car Charger
Place of Origin: Guangdong, China (Mainland)
Brand Name: OEM
Output Type: DC
Connection: Other
Rated Voltage: 12V-24V
Working Temp: 0-55℃
Weight: 36g
Materials: PC+ABS
Color: White Black
Warranty: 1 year
Suitable for:Most digital devices
SMART PROTECTION & ATTRACTIVE DESIGN ------ Intelligent circuit design protects against short circuiting,over-heating,over-current,and over-charging. Charging stops when battery is full. Car charger with blue LED indicator,which makes it convenient to find exactly where the connection should go; And the light is soft enough not to distract at night.
Car Charger
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Shenzhen Waweis Technology Co., Ltd. , https://www.waweis.com