Issue with STWBC86-Based Project and STEVAL-WBC86TX Evaluation Board

[DZaot1]

Hello everyone,

I'm reaching out to the community because I'm encountering an issue with a Wireless Charger board we designed, based on STWBC86 and a similar architecture to the STEVAL-WBC86TX evaluation board.

The main problem is the Power Transmitter locking up when the receiver is moved away.

As previously suggested by ST Employee @willzhou in a previous post, I have tried various attempts both with the STEVAL-WBC86TX and with my PCB, setting the "TX PING INTERVAL" parameter differently as you suggested, and I also tried clicking "TX PING HALF BRDG", but the issue has not been resolved.

Let me provide more detailed explanation of the issues encountered:

1. Upon removing the receiver, sometimes my PCB (WBC86TX component) continues to transmit for a few seconds and then gets stuck in an UNKNOWN condition where it draws only a few tens of mA, disconnecting from communication with WPSTUDIO.
2. The above-described stuck condition also occurs in standalone operation without WPSTUDIO connection.
3. It is possible to reach the same stuck situation by moving the receiver to increase the transmitted power to it.

 

In addition, I have conducted further tests with default parameters on both boards (both the STEVAL Evaluation Board and my WBC86TX PCB), and I have recorded the following charts directly from WPSTUDIO's "Charts" feature, hoping they may be useful to your community in assisting me with resolving the issue:

FIG 1

FIG 1 depicts the operation of the STEVAL-WBC86TX: after a certain runtime (approximately 419 s), as indicated by the "Voltage" graph, the system transitions from 8V to 7V when the receiver is removed and returns to the PING phase.

Now, considering the following graph referring to my PCB (WBC86TX):

FIG 2

FIG 2: Initially, the board was functioning correctly as it transitioned from the transmission phase to the Ping phase. However, after a certain period (approximately 410s), the Voltage dropped significantly before returning to the Ping phase. After bringing the receiver close again, the system became stuck, as described earlier.

I hope this is sufficient to outline my issue.

 

[willzhou]

Hi

Thanks for detail information.
1.Does STEVAL-WBC86TX and your WBC86TX board have any hardware different?
2.From you picture 2, TX input voltage drop from 8V to very low, TX chip have reset, also chip temp is higher than STEVAL-WBC86TX.Seems your TX have some damage.

4.What is input power limited current?
5.What is the volume of application? How about contract local FAE to check and gain more information.

 

[DZaot1]

Hi willzhou,

• Regarding the first point, there are no hardware differences between the STEVAL-WBC86TX and the WBC86TX board.
• The lock of our PCB is not indicative of permanent damage; if a reset is performed, the system will restart.
• The power supply for the WBC86TX (and also for the EVB) was 8.05 V, and the limited current was 1A.
• Regarding the volume application of our board, it's around 100 pieces per year. We haven't had any contact with FAE, so please let me know if you can assist us with a hypothetical reference.

 

[willzhou]

What is RX power, rx ouput and current? If you remove RX does RX absorb some power?

From your picture2, when you remove RX, TX chip temp rise from 50C to 70C. Seem TX chip consume many power inside, It is different with picture1.

How about you increase input limited current, Or set  WBC86TX input voltage lower.

[DZaot1]

Hi willzhou,

I made a new acquisition with  WBC86TX board for a total of 100 seconds, in which there is the PING phase for up to 15 seconds, then the RX is placed for up to 60 seconds, back to the PING phase and finally the RX is placed again.
The data was processed and plotted on Excel, where a maximum of 250 values can be entered for each graph.

I have attached to this message the Excel document containing the data and graphs. The graphs relate to voltage [V], current [mA], temperature [°C], RX power [mW] and TX power [mW].

The power curves show that the RX and TX power of the receiver is higher than that of the STEVAL-WBC86TX; also, I have tried reducing the supply voltage but the problem persists.

I have also tried increasing the maximum current that TX can draw to 1.5A, but the result is the same: if my PCB draws about 900mA during the transmit phase, the system crashes as soon as the receiver is removed and does not return to the PING phase.