Bq51050

Adrian,

Thank you for the scope shots.  I do not see anything wrong in the schematic.  The scope shot of RECT shows that the device is trying to turn on, but the communication fails so the TX stops power transfer.  Can you verify the resistance from the ILIM to ground?  Do you have a load on the BAT pin when you start this?  Recall from an earlier exchange that the bq51050B provides a 4.2V output and is not compatible with a 3.3V battery.

Figure 3 in the bq51050BEVM shows a method to emulate a battery with some resistors and a power supply.  The goal is to debug the battery charging cycle more proactively than following a battery cycle.  BAT+ / BAT- are connected to the bq51050B (BAT and GND).  P/S+ and GND are connected to a power supply.  D1 protects the power supply from current supplied by the bq51050B.  R1 and R2 are used to dump the current produced by the bq51050B.  

Using the power supply as the battery voltage, you can increase the level of the battery to move the charger from pre-charge to charge to taper charge.

Ls is simply the coil inductance in free air.  Ls' is the coil inductance with the 50 mm x 50 mm x 1 mm Ferrite material PC44 as discussed below Figure 29 in the datasheet.  The inductance will increase with the Ferrite and shield in place.  This emulates how the inductance will change when placed in a system with the transmitter in place.  This is the specified step to calculate the tuning capacitors (68nF, 68nF and 47nF in your schematic).  Measure the Ls and Ls' with an inductance meter.  The test conditions for the meter should be set to 1V RMS at 100kHz.

Regards,

Dick

Dear Dick,

Thank you for your answer. I check the resistance to ILIM. i have one resistor of 2.78K ohms and the other resistor is 199 ohms so a total of 3K ohms. 

No i don't have any load. what can i use as a load?

i just order the components to build the battery emulator. About the PR1010 just to make sure can I neglect the 5.6 ohm resistor?

Regards,

Adrian 

Adrian,

I would suggest a resistive load so the system can supply current to a load.  Since your planned charge is 100mA you should plan your resistor to draw slightly less than that.  

I have included a photo of the PR1010.  You can see the (massive) heat sinks used.  The resistors are attached to the heat sink to provide proper heat dissipation.  You do not need a 5.6 ohm resistor.

You can see from this photo that there are 2 resistors in parallel, one return sense resistor and two diodes in parallel on the power supply side.  This board has 3 options for connection - you'll only need what you decide.  The switch at the top is added by engineering to allow removal of one of the resistors for some applications - this is not something you'll need to do.

Regards,

Dick

Dear Dick,

The receiver is working now. thank you for your help.

I have a question, the device will be placed in a shoe sole and i need a flexible coil for the propose. Do you have any idea what kind of coil i could use?

Regards,

Adrian

Adrian,

Congratulations on getting your system up and running?  Can you tell me what got you over the last hurdles?

Do you need a coil that can be formed or a coil that will flex during each step?  Most of the coils I have used do have some flexibility during placement.  There are truly flexible coils available.   I am working with a supplier of flexible coils.  I should have more information tomorrow that I will pass on if possible.

Regards,

Dick

Dear Dick,

Thank you!

Well as i said i re-soldered the components. There was a grounding problem with the board.

I am looking forward to hear about those coils. 

Thank you for your help,

Regards

Adrian

Dear Dick,

Do you have any new information of the flexible coils?

I need a coil that can be flexed during each step. 

Regards,

Adrian 

Dear Ti,

Do you have any information of the flexible coils?

Regards,

Adrian

Adrian,

The company I am working with is not ready to release any information.  Their product is not in production.  I will continue to work with them to get information as it is possible.

Regards,

Dick

Dear Dick,

Do you have any other recommendation?

Adrian

Hi Adrian,

I have exactly the same circuit, with exactly the same 100mA charging current and finally your same problem, the Vrect is like a square signal as you showed in the attached pictures.

So, finally what was the communication problem between the Qi Rx and Tx? it was a missing ground or it was the matching capacitors for the COM? for sure your answer would give me a big clue about my problem.

thanks in advance,

PS: By the way if you speak spanish, you can answer me in spanish.

Hello guys again,

As I already mentioned, I have more or less the same conditions as Adrian. 100mA and 3.7 V_Avg. battery but I think I have problems in the reception and I'm trying to figure it out why the receiver is functioning in this weird way.

Here attached are the oscilloscope plots of the signals in the coil terminals(AC1 - AC2) and V_rect respectively. So as you can see is like it works well with a 50% duty cycle, hehehe, I'm joking, but is not so far from reality is like 500 milliseconds is working well and then the other 500 milliseconds is off, and again and again and again.

V_rect:

AC1-AC2:

What do you think it could be my problem?

I have Rterm= 480ohms for finishing at 2% of the charging current and Rilim is 2.8kohm + 180ohm from the FOD so around 3k as recommended in the datasheet.

Thanks all for your valuable help,

Edgar,

My apologies for the very long time to reply.  Can you tell me the current status of your wireless power solution?

Can you tell me the inductance of your RX coil, what the value of your series capacitors are on the AC1 pin and what transmitter you are using?

One other note I will make is that the 2% charge termination current gives 2mA.  The bq51050B is optimized for higher power solutions and the accuracy of termination at such low currents is not what you might hope for.

Another solution might be the bq51013B (same footprint as the bq51050B) and the linear charger bq25100.  This charger has quite good resolution for termination currents down to 1mA.  A reference design can be found here:  http://www.ti.com/tool/TIDA-00318.

Regards,

Dick

Hi Dick,

Thanks a lot for your suggestions, they will be useful for future designs.

Now, my problem with the Qi charging, I realize that it wasn't a big deal the poor precision of the termination current from the BQ51050, the problem was as already someone mentioned it, a GND problem, because I didn't pay much attention to connect the thermal pad to GND, so I just remake the footprint with the pad connected to GND and it worked perfectly. Could have been also an error on the first soldering process.

Thanks,

Dick,

Is this PR1010 available in kit form? I did not find it anywhere on ti.com.

Dear Adrian,
Can you please tell me the conditions in which you got your receiver working. I mean if you had applied any load on battery? Is that necessary? If I don't put any battery; will I get any output voltage on BAT (around 4.2V) ? I am also not able to get my Rx working. Your help will really be appreciated.

Thanks

Muhammad
The battery or a battery emulator is required for the battery charger to start.