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STWBC86 Overheating

MikeP
Senior

 

Hello,

I've designed a PCB with a schematic nearly identical to the STEVAL-WBC86TX. The only modifications are a capacitor and coil size change, which I've also implemented on a development board for direct comparison.

On the development board, my receiver PCB performs almost flawlessly, with the only issue being a charging current of around 60mA (which may be unrelated). However, on my new transmitter board, it almost immediately overheats and shuts down.

I've attached an image from WPSTUDIO showing the temperature reaching 100°C before shutting down and repeating this cycle.

Can anyone suggest potential causes for this issue or point me in the right direction for troubleshooting?

Thank you, Mike

1 ACCEPTED SOLUTION

Accepted Solutions

1.For TX/STWBC86 12V input voltage, you must set ping in the half bridge, otherwise the energy will be very high for RX.

2.Also i suggest you modify TX/RX Ctank value. TX use 400nF and RX use about 152nf.

willzhou_0-1720781982998.png

 

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14 REPLIES 14
Andrew Neil
Evangelist III

Show the schematic

Screenshot 2024-07-10 155232.jpg

willzhou
ST Employee

Hi Mike
Have you test STWBC86 pins, any shortage? From your GUI logs, vin change from 12V to 5V, what is STWBC86 input voltage?

Our reference is 5V input, please limited input voltage and current.

What is your application power, 5W or above?

@Didier HERROUIN please help to add comments, thanks.

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Hello,

Your post was helpful, thank you. I've discovered some interesting results:

  1. I was initially powering the development board with a 5V USB supply.
  2. My transmitter PCB, however, is designed for 12V operation.
  3. When I reduced the voltage to 5V on my transmitter PCB, I observed results similar to those of the development board.

My application has low power requirements (less than 5W). The goal is simply to charge a 950mAh LiPo battery in under 8 hours.

Given these observations, I'm puzzled as to why I'm experiencing overheating issues at 12V, but not at 5V?

Thanks

Didier HERROUIN
ST Employee

Hi Mike,

I confirm that if you target 5V output at Rx side, you should supply the STWBC86 with 5V.
What is your targeted current at Rx side ? And please describe your receiver.

What is the inductance value and the size of your Tx coil ? 

Finally, please check your layout to confirm that you follow the layout guidelines provided in the Application Note UM3161, and that you have designed a ground plane below the chipset.

Regards,

Didier

 

Hello. 
Thanks again for your help. I will send a snippet of my receiver circuit when I am back at my desk (tomorrow) and I’ll also send across the coil information.

My receiver is powered from my lipo battery 3.7v nom. I guess this is an issue?

The layout does have a ground plane underneath the chip. 

Hi Mike
Our reference design is for 5W application and input is 5V or 5.5V,
also for RX side, power should be RX vout 5V output, then connect to battery charge, then to the battery.

In order to give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.

Hello, 

I have attached an image of the receiver.

The RX coil is PN: 760308101214, Ind: 26uH, Dia:17mm

The Tx Coil is PN: 760308101104, Ind: 6.8uH, Dia: 20.5mm

 

 

MikeP_0-1720684196391.png

 

Uwe Bonnes
Principal III

Overvoltage on pins ofter leads to overheating, partial with some MCU functionality still working.