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Wireless charging Qi V1.2.4 standard plan analysis Apr 09, 2018

Recently, the WPC Wireless Power Consortium released the latest Qi standard for V1.2.4 on its official website. It is reported that the agreement will be enforced on March 8. After that, the wireless charging product of the ID number registered with the WPC shall follow the V1.2.4 standard. Over certified, not previous V1.2.3. The obvious changes are as follows:

(A) Registered product categories change from BPP, BPP+FOD, EPP to BPP, EPP;

(B) EPP increases temperature rise requirements;

(C) Magnetic material detection within the 7cm diameter area of the new Tx coil;

(D) Increasing the protection guidelines for NFC/RFID cards from Tx products;

After Qi's new standard was released, which of the Qi standard certification and Apple's 7.5W fast charging solution has become the focus of discussion in the industry, let's take a look at these two hot topics that are currently being discussed/discussed by the industry:

Hot topic No.1

About Qi standard certification, the current market discussion is more, Apple 7.5W and Samsung 10W is over 5W (BPP) or 15W (EPP)?

According to analysis and analysis by senior industry technicians and certified persons in the industry, most of the current launcher programs that support Apple 7.5W and Samsung 10W fast charging are based on Qi 5W, and they are not fully implemented. In accordance with the Qi standard to do fast charging agreement, so in the over-certification should also only need to pass BPP certification V1.2.4. In addition, the current support for Apple's 7.5W shipments of the largest 10W mid-to-high-end fast charging program, if each manufacturer to do 100,000 + / EPP certification is not realistic, and this for Qi in the world Popularization is also very unfavorable.

Hot topic No.2

Which of the programs currently supporting Apple's 7.5W is strong?

It is understood that the operating frequency is set between 127KHZ ~ 128KHZ, by adjusting the power (regulation, adjust the duty cycle) can achieve Apple 7.5W fast charge, the two circuit topology is as follows:

Fixed-frequency voltage regulator (15W-based): Main control chip + 2 bridge drive + buck circuit + op amp (some manufacturers to + crystal)

Fixed frequency modulation duty cycle (10W based): master chip + 2 bridge drive + op amp (some manufacturers to + crystal)

First of all, first briefly explain what is the fixed-frequency regulator, fixed-frequency modulation duty cycle. Constant-frequency voltage regulation refers to adjusting/controlling the output power of the transmitting terminal by adjusting the voltage, and adjusting the duty ratio of the fixed frequency adjusts/controls the output power of the transmitting terminal by adjusting the duty ratio. Apple's original adapter fast charging mode is selected fixed-frequency pressure regulator, which naturally Apple's own considerations. It should be pointed out that the performance of the two programs is basically the same, that is, can achieve Apple's 7.5W fast charge, but in the dynamic input fixed-frequency voltage regulation program will have a slight advantage, and the fixed frequency modulation duty cycle is excellent in the circuit The design is more concise. If you want to say the biggest difference between the two is the cost of PCBA. In terms of PCBA cost, the fixed-frequency voltage regulation scheme is higher, and the fixed frequency modulation duty ratio is relatively moderate. In the QI certification, the fixed-frequency voltage regulator is EPP, the cost of about 160,000 yuan/ton; the fixed-frequency modulation duty cycle can be selected over BPP or EPP; the over-BPP only costs about 30,000/section, EPP It also requires 160,000 yuan.

Although fixed-frequency voltage regulation and fixed-frequency modulation duty cycle can achieve Apple's 7.5W fast charge, but each chip maker's fixed-frequency voltage regulation and fixed-frequency modulation duty cycle are not the same, an important difference is It is whether or not an external crystal is used. According to the new page microelectronics research and development director Ren Lianfeng pointed out that the accuracy requirement of the fixed frequency program of the apple is ±6Hz. At present, domestic wireless charging manufacturers mainly adopt two methods to achieve the accuracy requirement of the Apple ± 6Hz. The first one uses an external crystal oscillator. Some domestic manufacturers use an 8M or 12M crystal oscillator. The frequency accuracy of the crystal oscillator can basically meet the requirements of Apple's 7.5W fast charge. However, there are also vendors that use software algorithms inside the chip to improve the frequency accuracy (second), so that the accuracy can meet Apple's 7.5W fast charge requirements. The biggest difference between these two methods is that the former uses an external crystal oscillator, which is a discrete component that requires additional purchases by the manufacturer and costs more; while the latter requires no additional purchase of the crystal oscillator, and the cost is lower.