How to design the Rx coil of wireless charging based on different chip

Hello user4289149,

1. The TX and RX are working together indepentently of the TX`s input voltage. The RX gives feedback to the TX on how much power is need while the TX provides more or less power to the RX.

2. Could you be more precise on this question? What exactly do you want to know?

The RX datasheet also provides an application example on how to design the RX coil.

Best Regards,

Markus Fleck

Hi Markus Fleck,

       Thank you for your reply.  But I have another questions,

1.The TX's input voltage are different. For example bq500210EVM-689's input voltage is 19V. If I want to design the RX coil for the Rx device which the output voltage is 5V. Then we can calculate the RX coil's inductance based on V2/V1=k*sqrt(L22/L11), here V2=19V,V1=5V. Than, the coil design is finished. My question is, Does the designed Rx coil suitable for any other Transmitter device(for example bq500412 that the input voltage is 12V, bq500212A that the input voltage is 5V) that the input voltage is not same as bq500120EVM-689 that the input voltage is 19V. If the designed RX coil work normally, I can't understand. So, I want to kown the reason why the designed Rx coil suitable different input voltage's Tx?

2.I want to konw the Tx and Rx chip's inner structure. And how to work  of the whole IC link.  Especially the Tx chip,could you tell me the which equipment the Tx's chip include and how they work together.

Best Regards,

                      wen zi

Hello Wen,

1. The equation you mentioned is a rough starting point for designing a RX coil since the RX RECT voltage and TX input voltage vary. Also the TX is driven by a current with a half bridge which makes the interoperability independent of the input voltage. There are many other paramters which influence the RX coil design like shape of the coil, z distance, shielding material, coil material, wire gauge, number of turns and so on. All these parameters influence the coupling coefficient k.

Figure 7 of the Power Management article Designing a Qi-compliant receiver coil for wireless power systems, Part 1 and the article in general describe the RX coil design process. www.ti.com/.../slyt479.pdf

2. The inner structure of the RX chip can be found for example on page 8 of the bq51013B datasheet:

www.ti.com/.../bq51013b.pdf

The inner structure of the TX can be found on page 5 of the bq500212A datasheet and the link between external components can be found in the EVM

www.ti.com/.../bq500212a.pdf

www.ti.com/.../slvu928a.pdf

Best Regards,

Markus Fleck

Hi Markus Fleck,

                 Thank you for your reply.

               1.I have another question, which kind of  waveform input the TX coil  from half-bridger or full-bridge inverter. Is it square waveform or sina waveform? Which kind?

                 2.How does the Tx realize the current regulation to regulate the output power , ie how to realize the output power increases with the frequency decrease. And which equipments is key to finish the regulate process.

Best regards,

                          wenzi

Hello wenzi,

1. The TX coil is driven by a square waveform.

2. Input current (external current sense) and voltage is sensed by the TX. The RX sends Error Packets to the TX to get more or less power. The RX includes low resistance synchronous rectifier, low-dropout regulator, digital control and accurate voltage and current loops.

Best Regards,

Markus Fleck

Hi Markus Fleck,

    I'm sorry to trouble you again. And I have some questions, as A1 coil

1.How much the peak current through the A1 coil?

2.How to evaluate the B and H of the A1- transmitter transmit.

3.Is the current through the A1, A6 or A11 coil same. 

    we have make some tests and find that when a battery is on the back of the ferrite the battery will be hot seriously( base on A1 transmitter 19V A1 coil), the systerm could not work normally.  Then we change the transmitter to A612V , the battery is not hot ,the system could work normally. why?

looking forward to your reply.

     Thank you.

                                                    wenzi