Wireless Charger Usage Standards

In order to enable products of different brands to share the same charger and improve the versatility of wireless chargers, the world's first standardization organization to promote wireless charging technology, the Wireless Power Consortium (hereinafter referred to as the "Alliance"), has launched a "wireless charging" standard. Under the Wireless Power Consortium (WPC) standard, the power consumption of wireless transmission is only 0~5W. Systems that meet this standard range use inductive coupling between two planar coils to transfer power from the power transmitter to the power receiver. The distance between the primary and secondary coils is generally 5mm, and the output voltage regulation is handled by a global digital control loop. At this time, the power receiver communicates with the power transmitter and generates power consumption. This communication is a one-way communication from the power receiver to the power transmitter through backscatter modulation. In backscatter modulation, the power receiver adjusts the load, thereby changing the current consumption of the power transmitter. These current changes are monitored and demodulated into the information required for the two devices to work together. The communication protocol includes analog, digital sound pulses (ping), identification, configuration, and power transmission.

The typical startup sequence that occurs when the power receiver is placed on the power transmitter is as follows:
(1) An analog ping from the power transmitter detects the presence of an object.
(2) A digital ping from the power transmitter is an extended version of the analog ping and allows time for the power receiver to reply with a signal strength packet. If the signal strength packet is valid, the power transmitter keeps the coil powered and proceeds to the next step.
(3) During the identification and configuration phase, the power receiver sends a number of data packets to identify itself and provide configuration and setup information to the power transmitter.
(4) During the power transfer phase, the power receiver sends control error packets to the power transmitter to increase or decrease power. During normal operation, control error packets are sent every approximately 250ms and every 32ms during large signal changes. In addition, during normal operation, the power transmitter sends power packets every 5s.
(5) To terminate power transfer, the power receiver sends a "termination of charging" message or does not communicate for 1.25s, causing the power transmitter to enter a low-power state. Under the Qi standard, mobile phones, cameras, computers and other products can be charged with Qi wireless chargers, making large-scale wireless charging possible.