We would like to make a smaller transmitter coil are there any options with TI's ICs, even if efficiency is decreased?
Could we use the 760308201 as transmitter?
Yes, you can use this coil with the transmitter controllers from TI. You will need recalculate resonant capacitors and chose lower input voltage. This will not be Qi certifiable solution. Please make note of newly released BQ500211 TX controller.
If you have further questions, please contact me directly.
I have tried similar the setup as Andrew's with Wurth 760308201 as transmit coil on bq500210 EVM. I replaced capacitors to tune new coil (10uH) to 100KHz. I am using same coil on receiver (bq51013 EVM) and find that it works, but intermittantly and I see significant current occasionally on transmitter with no load on receiver and I have blown up two receiver boards. The Receiver modulation looks very poor and I wonder if this is part of problem. Do I need to change the value of the modultaion capacitors (22nF) on the receiver to match the higher capacitance on the transmitter. How do I calculate new voltage to use with new transmitter coil.
Did you lower the input voltage for BQ500210 EVM? The 760308201 coil has only 15 turns while the original TX coil has 20. The voltage on the receiver side can be too high tripping OVP if you tune TX resoancne to 100kHz. Alternatively to lowering input volatge you may try tuning TX to lower frequency 80...90kHz. You may try this two hints before altering anything on the RX side.
Let us know which way worked best for you.
No I'm running it at 19V, but monitoring the receiver regulator output and this has kept below 15V, but still two receivers have failed, how resilient is the OVP? I'll try your two suggestions. In the meantime do you think the modulation would be affected by the transmitter coil design, as it does behave as if the communications are not reliable. i.e it will establish a good power transfer, but then drop out after a minute or so. I'm thinking that I need to modulate the receiver load more now that I have less coupling between the coils.
Thanks for your help.
The OVP will safe the RX chip in case of accidents but not in the case of permanent over powering. If you palnning using smaller TX coil it makes sense also reduce size of the RX coil otherwise coupling is definitely reduced. You may tru using the Wurth coil on both sides. Once more be carreful not overpowering the RX. The BQTESLA kit is designed in the way that secondary side input voltage is never dangerously high.
Increasing COMM capacitors has it's limits too. This is a resoant system and too many changes lead getting out of resoance and the system not working.
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