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WPC 1.2 Receiver and Evaluation Board for that

Pawel Gielmuda
Prodigy 40 points
Other Parts Discussed in Thread: BQ501210, BQ51025, BQ500212A

Hi,

I would like to ask someone from TI if you are planning to release a WPC 1.2 Receiver 15W in the near future. We are planning to use this technology in our next year project and we wonder if it would be available till May/June of 2017. Especially the evaluation board will be useful. 

Regards

Pawel Gielmuda

  • 0
    TI__Genius 14890 points
    Pawel,

    TI has no current plans to release a WPC v1.2 15-W receiver.

    The bq51025 is a 10-W receiver when paired with the bq501210 15-W v1.2 transmitter, or a 5-W receive when paired with any other Qi transmitter. The bq51025EVM has been certified to the v1.1 standard and meets all requirements to be certified to the v1.2 5-W receiver standard.

    Regards,

    Dick
  • 0 in reply to Dick Stacey
    Prodigy 40 points

    Thanks for answare. 

    What will be the output voltage of receiver (based on bq51025) if we connect 19V DC supply to 15W transmitter  (based on bq501210 ). Is there some kind of white paper about that?

    Is there a way to achieve 19V on output of bq51025 receiver circuit?

    Regards 

  • 0 in reply to Pawel Gielmuda
    TI__Genius 14890 points
    Pawel,

    The bq51025 has a programmable output. It can be set from 4.5V to 10V. The RX output voltage is not related to the TX input voltage.
    The bq51025 cannot generate 19V output. You would be a boost converter at the output of the bq51025.

    Regards,

    Dick
  • 0 in reply to Dick Stacey
    Prodigy 40 points

    I thought so.
    Unfortunately additional DC-DC step is another lost of power so bq51025 is not appropriate for us. We will need to use MWPR1516 from NXP instead. Thats a pitty cause we trust TI much more then them.

    Your eval board for bq501210 say you have a 84% efficiency with typical 1.2 WPC receiver at 19V. Does that mean that on receiver side you can get only 84%*15W=12,6W on the output of such receiver.

    How much the efficiency depends on receiver? If we use NXP solution (which claim to have only 75% efficiency with theirs transmitter) do you think that the efficiency with your solution will be higher then 75%? I know you will just guess but it would be nice to hear your opinion about that.

    Regards.

  • 0 in reply to Pawel Gielmuda
    TI__Genius 14890 points
    Pawel,

    Our 84% efficiency number is input power to the TX to output power from the RX. That is when 15W is delivered by the RX. So, the input power would be 15W/0.84 = 17.86W. This was measured with an internally developed 15W RX that will not be available for sale.

    Efficiency losses come from several sources. The key factors tend to be: TX and RX coils, DC/AC conversion on TX, AC/DC conversion on RX and RX LDO. Additionally, the Cs capacitors (in series on the AC1 pin) can be a big loss area. Boosting the output voltage higher does reduce the I2R power losses (lower current as a result of higher voltage for the same power). This is shown pretty clearly on the plot on page 1 of the bq51025 datasheet. Finally, the alignment of the RX/TX and the spacing are external factors that will impact efficiency.

    I cannot comment on the competitor solution.

    Optimization of efficiency must be done on a design by design basis.

    Regards,

    Dick
  • 0 in reply to Dick Stacey
    Prodigy 40 points

    Thanks for comprehensive answare.

    One more thing. You said that with a bigger distance between RX/TX coils the efficiency decreases. Also when they are not align to each other the efficiency goes down. Do you mean that the max output power is lower and transmitter gets less power from supply? Or do you mean that we lost more power on the transmitter side? 

    From our experience it is somewhere in the middle. The TX gets a little hotter and the RX output much less power. However for 5W applications (or even less then 5W) few tens/hundreds of mW wasn't  a big deal. In 15W application extra 0.5-1W could be quite important so your knowledge would be most helpful, especially on the planning phase of project. 

    Regards

  • 0 in reply to Pawel Gielmuda
    TI__Genius 14890 points

    Pawel,

    The Qi-protocol requires the receiver to request more or less power from the transmitter.  The goal is that even with poor power transfer (whatever the reason) the RX will receive the power that it needs.  However, once the TX reaches its maximum power transfer capability, it will not be able to meet the needs of the receiver.  Generally, a TX will be able to provide the required output power until the system efficiency drops too low.  

    An example of a TX limiting power is when the TX is power limited.  Many of the TI transmitters have Dynamic Power Limiting (DPL).  This feature allows the system to keep operating even with an undersized power supply - at a limited power transfer.  For example, if the bq500212A is operating from a 5V USB supply that is limited to 500mA the maximum power it can use is 5V*0.5A = 2.5W.  The TX monitors the input power supply.  If it detects a drop in the voltage below a specified limit, it will scale back the power transfer to keep the system operational.  Limited power is better than no power.  If the RX requests more than that (accounting for efficiency, maybe 2W) then when the TX tries to deliver it, the VIN droops.  In response, the TX scales back the power transfer to keep the system operational.

    The bq501210 does the same, but there is not a good explanation in the datasheet (I will fix that).  The bq501210 uses the initial power level to determine when the power drops too low and compensates from there.

    Regards,

    Dick

  • 0 in reply to Dick Stacey
    Prodigy 70 points
    Just as a feedback, we'd use a TI medium power RX solution if it would be available in 2017