power_transfer_architecture_of_the_qi_standard
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| power_transfer_architecture_of_the_qi_standard [2025/05/01 07:40] – tm | power_transfer_architecture_of_the_qi_standard [2025/05/01 14:11] (current) – [4.Negotiation phase] tm | ||
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| =====Power Transfer Architecture of the Qi Standard===== | =====Power Transfer Architecture of the Qi Standard===== | ||
| - | ====Establishing power transfer==== | ||
| - | The transmitter (Tx) and receiver (Rx) go through an advanced process for power to be transferred. This process comprises **four phases** in the **Baseline Power Profile | + | The transmitter (Tx) and receiver (Rx) go through an advanced process for power to be transferred. This process comprises **four phases** in the **baseline power profile |
| - | ====test==== | + | ====1. Selection phase==== |
| - | **1. Selection phase** | + | In the selection phase, the transmitter (Tx) monitors the characteristics of its resonant circuit to detect the presence of a potential receiver (Rx). This can also be an unwanted foreign object. When a Qi-compatible device is brought near, its coil interacts with the Tx coil through mutual inductance. This coupling alters the Tx's resonance frequency and impedance. By observing these changes, the Tx infers the presence of an object. No data communication occurs at this stage, and the Rx remains inactive (The Qi Wireless Power Transfer System Class 0 Specification |
| - | The Tx sends out an analog signal to detect placed objects on the base station. This method is based on the shift of the Tx’s resonance frequency. If a Qi-compatible Rx is present, it interacts with the transmitter’s coil which leads to inductive coupling via mutual inductance. This inductive coupling alters the resonance frequency of the transmitter and changes the overall impedance of the system. The transmitter detects this frequency shift, indicating the presence of a potential Qi device. This detection | + | ====2. Ping phase==== |
| - | **2. Ping phase** | + | During the ping phase, the Tx emits a low-power signal to detect whether a Qi-compatible Rx is present and responsive. This signal typically lasts 40 milliseconds. When a digital ping is executed the Tx awaits a response. If a Rx is present, the returned power signal is modulated by using **[[bidirectional in-band communication in the Qi standard|amplitude shift keying (ASK)]]**. The response itself takes the form of a Signal Strength Packet (SSP) or an End Power Transfer Packet (EPTP). A valid SSP means that Rx is ready for further communication. Therefore, the Tx extends the ping and transitions into the identification and configuration phase. Conversely, if the Rx sends an EPTP or if no response is received, the system reverts to the selection phase (Holtek, 2022, p. 3; The Qi Wireless Power Transfer System Class 0 Specification 1 and 2: Interface Definitions, |
| - | During this phase, the TX emits a low-power signal, typically lasting 40 ms. When a digital ping is executed the Tx listens for a response. When an Rx responds, it sends out a Signal Strength Packet (SSP) or a End Power Transfer Packet (EPTP). If the Rx responds with a SSP, the ping is extended and the system moves into the identification | + | ====3. Identification |
| - | **3. Identification | + | After a transition to the identification |
| - | This protocol extends the Digital Ping in order to enable the power receiver to communicate the relevant information. This information is provided as a packet and consists of four parts, namely a preamble, a header, a message and a checksum. | + | By default, all transmitters |
| - | All transmitters | + | |
| - | **4. Negotiation phase** | + | However, if the Rx indicates support for EPP or MPP than the system proceeds to additional protocol stages such as the negotiation, |
| + | |||
| + | ====4. Negotiation phase==== | ||
| This phase can only be accessed through EPP or MPP capable devices with **[[Foreign object detection in the Qi standard|foreign object detection (FOD)]]**. In this phase the Tx and Rx review their power transfer contract. The purpose of the negotiation phase is to fine-tune this contract. The Rx sends a negotiation request to the Tx to which it replies with a message of granting, denying or not recognising the request. Both the sender and the receiver keep a copy of the current contract. This temporary copy is used to store updated parameters until the negotiation phase is successfully completed. | This phase can only be accessed through EPP or MPP capable devices with **[[Foreign object detection in the Qi standard|foreign object detection (FOD)]]**. In this phase the Tx and Rx review their power transfer contract. The purpose of the negotiation phase is to fine-tune this contract. The Rx sends a negotiation request to the Tx to which it replies with a message of granting, denying or not recognising the request. Both the sender and the receiver keep a copy of the current contract. This temporary copy is used to store updated parameters until the negotiation phase is successfully completed. | ||
| + | |||
| As part of this phase, the Rx also sends the reference **[[Foreign object detection in the Qi standard|quality factor (Q-factor)]]** value to the Tx. This value reflects the Q-factor measured under ideal conditions without any foreign objects. The Tx uses this value to determine a threshold for FOD by comparing it with the Q-factor measured on its own primary coil. If the measured Q-factor falls below this threshold, the Tx may terminate the power transfer. These Q-factor evaluations and threshold settings are performed during the negotiation phase to ensure safe and efficient operation. | As part of this phase, the Rx also sends the reference **[[Foreign object detection in the Qi standard|quality factor (Q-factor)]]** value to the Tx. This value reflects the Q-factor measured under ideal conditions without any foreign objects. The Tx uses this value to determine a threshold for FOD by comparing it with the Q-factor measured on its own primary coil. If the measured Q-factor falls below this threshold, the Tx may terminate the power transfer. These Q-factor evaluations and threshold settings are performed during the negotiation phase to ensure safe and efficient operation. | ||
| + | |||
| With the MPP this process is simplified. The magnetic attachment within the new MPP mode tightly secures transmitter and receiver coils in optimal positions. Therefore, the coupling factor always hovers around a value of 1. This makes the negotiation and FOD procedures faster and more predictable than in EPP (The Qi Wireless Power Transfer System Class 0 Specification 1 and 2: Interface Definitions, | With the MPP this process is simplified. The magnetic attachment within the new MPP mode tightly secures transmitter and receiver coils in optimal positions. Therefore, the coupling factor always hovers around a value of 1. This makes the negotiation and FOD procedures faster and more predictable than in EPP (The Qi Wireless Power Transfer System Class 0 Specification 1 and 2: Interface Definitions, | ||
| - | **5. Calibration phase** | + | ====5. Calibration phase==== |
| In the calibration phase the TX and Rx can update their power transfer contract with the measurement data from the previous phase. Ideally, the calibration phase should involve the transmitter and receiver testing different power levels to find the appropriate power transfer. While multiple calibration points could provide a more detailed power loss profile, the Qi specification opts for a two-point method to balance accuracy with complexity and duration: | In the calibration phase the TX and Rx can update their power transfer contract with the measurement data from the previous phase. Ideally, the calibration phase should involve the transmitter and receiver testing different power levels to find the appropriate power transfer. While multiple calibration points could provide a more detailed power loss profile, the Qi specification opts for a two-point method to balance accuracy with complexity and duration: | ||
| Line 34: | Line 36: | ||
| Additionally, | Additionally, | ||
| - | **6. Authentication phase** | + | ====6. Authentication phase==== |
| - | After successful calibration the transmitter enters the initial power transfer mode where it limits the output to 5 watts (BPP mode). During this phase the receiver has the opportunity to request and initiate an authentication challenge. If the authentication process succeeds, the transmitter is permitted to continue with negotiated power delivery up to the maximum supported level. If the authentication challenge fails or is not initiated the transmitter remains limited to 5 watts for the duration of the charging session (Technologies, | + | After successful calibration the transmitter enters the initial power transfer mode where it limits the output to 5 watts (BPP mode). During this phase the receiver has the opportunity to request and initiate an authentication challenge. If the authentication process succeeds, the transmitter is permitted to continue with negotiated power delivery up to the maximum supported level. If the authentication challenge fails or is not initiated, the transmitter remains limited to 5 watts for the duration of the charging session (Technologies, |
| - | **7. Power transfer phase** | + | ====7. Power transfer phase==== |
| In this phase power is delivered from Tx to Rx but more importantly, | In this phase power is delivered from Tx to Rx but more importantly, | ||
| Line 45: | Line 47: | ||
| * **Safety stop**: The exit can also be triggered by various, previously discussed, safety features: overheating protection, FOD or aborted communication between Tx and Rx. | * **Safety stop**: The exit can also be triggered by various, previously discussed, safety features: overheating protection, FOD or aborted communication between Tx and Rx. | ||
| - | The BPP control architecture of the Qi standard is shown in Figure 1. Figure 2 presents the EPP control architecture. This architecture also applies to MPP, as the structure remains the same (An0578en, 2022, p. 4; Evolution of Qi Wireless Charging Standard & What’s New With Qi2, n.d.; The Qi Wireless Power Transfer System Class 0 Specification 1 and 2: Interface Definitions, | + | The BPP control architecture of the Qi standard is shown in Figure 1. Figure 2 presents the EPP control architecture. This architecture also applies to MPP, as the structure remains the same (GRL, n.d.; Holtek, 2022, p. 4; Technologies, 2023, p. 24; The Qi Wireless Power Transfer System Class 0 Specification 1 and 2: Interface Definitions, |
| - | {{: | + | | {{: |
| - | Figure 1 BPP architecture of communication | + | | Figure 1 BPP architecture of communication |
| - | {{: | + | | {{: |
| - | Figure 2 EPP architecture of communication | + | | Figure 2 EPP architecture of communication |
| Line 55: | Line 58: | ||
| <color # | <color # | ||
| - | * <color #808080>An0578en, N. : (2022). BP66FW1242 Qi Wireless Charger Receiver Application.</ | + | * <color #808080>Holtek. (2022). BP66FW1242 Qi Wireless Charger Receiver Application. |
| - | * <color # | + | * <color #808080>GRL. (n.d.). |
| - | * <color # | + | * <color #808080>MPS. (2018). |
| * <color # | * <color # | ||
| * <color # | * <color # | ||
power_transfer_architecture_of_the_qi_standard.1746085248.txt.gz · Last modified: by tm