Design principle of coil inductive wireless charging system

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Overview:
Wireless charging means that a device with a battery obtains power by wireless sensing and is charged. The convenience of the device allows the consumer to pay for the wireless charging related product at an additional cost; because there is a business opportunity, the manufacturer is willing to invest in related product development. At present, it can be known that many well-known brand manufacturers have included wireless charging as one of the specifications of a new generation of products. Because this technology is quite novel and each manufacturer has its own description of technology, wireless charging, inductive power, non-contact charging, and contactless charging all refer to the same technology. The distance is from 1mm to several meters. The interaction between the power supply terminal and the power receiving terminal is called induction, so wireless charging is a general term without a certain specification.

The principle is simple and difficult to implement. The method of wireless charging has developed many methods in the experimental stage, but the only opportunity to mass-produce the product into a coil induction type. The principle of coil inductive is very simple. It was discovered physically a hundred years ago, but in the past, such coil induction has only been used in wound-type transformers. In the early days, it was discovered that the winding of the "E" type core of the winding type transformer can be inductively transmitted after being aligned and then connected to the listed electric power. However, the sensing effect disappears after the distance is slightly separated. At 60 Hz, electromagnetic wave transmission will rapidly decay with increasing distance.
In today's applications, since the device itself needs to be packaged in the outer casing, the thickness of the transmitting end plus the receiving end is at least 3 mm. When the early electric toothbrush product was developed, it was found that the operating frequency of the coil needs to be increased after the distance is opened. Power can be transmitted farther; there is a characteristic in electromagnetic waves that electromagnetic waves with higher frequencies can transmit longer distances and have lower energy attenuation.

Later, RFID applications began to develop, mainly in the three bands of LF low frequency (125~135KHz), HF high frequency (13.56MHz), UHF ultra high frequency (860~960MHz), and these bands also made the current wireless power. The reference point used by the system at the beginning of the design frequency. As early as 10 years ago, wireless charging of electric toothbrushes was already on the market. At that time, the transmission power was small and the charging time was long. In the current power consumption situation of smart handheld devices, the charging energy at that time was not enough, so it was not practical for 10 years. Turn. However, in the past few years, new technologies have been developed that can use higher "resonance" receiving efficiency. Because this technology is relatively new, there are many sayings from all walks of life, but there is a very important feature that there is a configuration capacitor on the receiving coil. To form a receiving antenna with frequency characteristics, a large power shift can be obtained at a specific frequency. This part is different from the early electromagnetic induction. When the distance is pulled apart, good power transmission can still be obtained. The principle of resonance is very simple. Just like a piano tuner, you can put a glass with different water volume. Under precise tuning, you can shake a glass through resonance. But other articles don't mention it. Ordinary people who have not been trained by a professional piano tuner may never be able to adjust the frequency at which the glass can be shattered! This is a simple principle and difficult to implement.
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