“Artificial intelligence and mobile devices continue to increase. Chargers, adapters, and charging piles have become commonplace, and wireless charging has also entered people’s sight. Which one is better than wired charging or wireless charging?
Abstract: Artificial intelligence and mobile devices continue to increase. Chargers, adapters, and charging piles have become commonplace, and wireless charging has also entered people’s sight. Which one is better than wired charging or wireless charging?
1. Types and principles of wired charging
You must be familiar with the way of wired charging. Wired charging is used in many occasions in daily life, such as mobile phone chargers, computer adapters, battery car charging stations, electric car charging piles, and so on.
There is no mystery in the principle of wired charging. Its basic principle is an AC-DC power supply circuit. As shown in the figure below, its circuit is often composed of rectifier bridge, filter circuit, switch tube and PWM controller, output rectifier filter, etc. composition. According to the needs of different power and different voltage output, adjust the device parameters in the circuit, PWM control, output transformation ratio, etc.
Larger charging devices such as car charging piles work similarly to ordinary adapters, but in addition to the basic AC-DC, there are billing control units, charging controllers, insulation detection modules, displays, and meters. , Lightning protection and other modules, between different modules, the charging pile and the BMS also communicate through the CAN bus to ensure the safety of the entire charging. The core module of the charging pile-the power module of the charger, its principle is similar to the AC-DC circuit in the figure above.
2. Types and principles of wireless charging
Wireless charging methods have also been increasingly used in various fields, such as the well-known wireless charging of mobile phones, wireless charging of watches, wireless charging of electric vehicles, wireless charging of drones and so on. In the future, more devices will be applied to wireless charging technology.
How does wireless charging work? As shown in the figure below, the core of wireless charging lies in two coils, a power supply coil and a receiving coil. The coils transmit power in a non-contact manner (to achieve wireless transmission). The power supply coil end is compensated by the primary power conversion circuit and harmonics. Circuit composition. The receiving coil is composed of a resonance compensation circuit and a secondary electric energy conversion circuit. After the electric energy is converted, the output signal is used to charge the energy storage device. The two coils exchange energy through a coupled magnetic field. This principle is generally used for static wireless charging, the two coils cannot be too far apart, generally within 50cm, and the frequency of the coupling magnetic field is in the range of tens of kilohertz to hundreds of kilohertz. In addition, there is a magnetic resonance method of wireless charging, which can be used for mobile wireless charging. The wireless distance can be 50cm~5m, and the working frequency is between several MHz to tens of MHz.
3. Comparison of the pros and cons of the two
The principle and application of wired charging and wireless charging are analyzed above, so is there any difference between the advantages and disadvantages of these two charging methods. Let’s first compare the advantages and disadvantages of the two charging methods.
Wired charging: Because the charging device and the device to be charged must be in contact with the wired charging method, there must be a plug and socket structure. Therefore, there will be problems such as inconvenience to use, easy to produce sparks, leakage, easy to wear, contacts may heat up, catch fire, and limited power. However, the power conversion efficiency of wired charging is high, the product production test is mature, and the application range is wide. Wired charging is still the current main charging method.
Wireless charging: In wireless charging, there is no need for direct contact between the charger and the device being charged. It is easy to use and has strong environmental adaptability. It avoids physical interfaces, so there will be no interface wear, sparks, leakage and other problems. In addition, wireless charging can also achieve high voltage and large Current, high-power charging. But the current wireless charging test scheme is not perfect, especially the electric energy conversion power and efficiency test of the wireless part.
In terms of future development trends, I personally think that wireless charging will have greater prospects, but wireless charging requires better and more complete test systems and solutions to ensure that wireless charging can be used by people better and safer.
Four, wireless charging test difficulties
More and more wireless charging is used in various occasions, and the test requirements for wireless charging are getting higher and higher.The test items for wireless charging include
l Input characteristics: input voltage and frequency test, input power test, input power factor test, input current harmonic limit test, etc.;
l Output characteristics: DC output voltage error test, DC output current current test, output voltage response test, etc.;
l Interoperability features: efficiency test under WPT system without offset, efficiency test under WPT system with offset, etc.;
l Protection features: input over-voltage, under-voltage protection, over-temperature protection, output over-voltage, under-voltage protection, output short circuit, etc.;
l High-frequency characteristics: voltage response, output waveform rise and fall time test, coil parameters, coil voltage, etc.;
l Safety features: contact current, insulation resistance, insulation strength, long-term stability test, etc.;
Among the many test items, the most difficult to test is the power transmission of the wireless part. Let’s first look at a table
We can find that under the same frequency, the lower the power factor, the higher the delay error requirement; under the same power factor, the higher the frequency, the higher the delay error requirement. For example, in the case of 85KHz, when the power factor is 0.2, the 1% accuracy delay error is 3.59ns, and when our commonly used current sensor tests 85KHz signals, the phase difference between the primary signal and the secondary signal may be greater than 3.59ns, so The test equipment must have a phase calibration function, otherwise it will not be able to accurately test the power and efficiency of the wireless terminal.
The PA8000 power analyzer developed and produced by ZHIYUAN Electronics has a basic accuracy of up to 0.01%, a bandwidth of up to 5MHz, and supports phase calibration of voltage and current. It is very suitable for high-frequency electrical power testing. It has been successfully applied in multiple wireless charging environments. among. In addition to the PA8000 power analyzer, ZHIYUAN also introduced a complete set of wireless charging test solutions.
Five, Zhiyuan wireless charging test plan
The wireless charging comprehensive test system developed by ZHIYUAN Electronics can help users efficiently and quickly test the functions, performance and safety indicators of wireless charging products. The entire wireless charging test system includes XYZ three-axis platform, mechanical motion control, power supply, load and test instruments,
It can realize automatic or manual testing of about 50 features of wireless charging products, and conduct a comprehensive and in-depth evaluation of wireless charging products. The wireless charging test system is shown in the figure below.