BQ51013B: Output disconnects after few hours.

Hi Kobayashi

The values look good:

TAKAO KOBAYASHI said:

The parameters I'm using are as follows.

COIL=Würth  760 308 101 214(Ls=26uF, Ls' = 31uF)

C1=78nF, C2=1000pF, Ccomm1,2=10nF

R1=75, Ros=20k, Rfod=200 (Ohm)

TS=Pull Down via 10kOhm

Do not see porbelms with above.

TAKAO KOBAYASHI said:

The board I made shuts off the output after several hours.

Some other things to look at:

1.) Thermal shutdown -- check thermal rise of the BQ51013B, does it seem high.  Does the Transmitter indicate a fault condition and not restart?

2.) AD pin -- is this pin pulled down or grounded.  A min of 1uF capacitor on the pin is needed.

3.) EN1 and EN3 -- Pull low to make sure they do not caused issues.

Can you send schematic?

Hi Bill

I didn't tell you that I added a 1uF capacitor on the AD terminal.

So, in order to avoid the shut-off phenomenon, I changed the capacitor value (22nF->10nF) and added a capacitor to the AD terminal.

I will send you the revised schematic.

4380.schematic.pdf

Hi Kobayash

Is the circuit working now, has the shut-off phenomenon been resolved?

Hi Bill

After implementing the above modification, the BQ51013B no longer suddenly stops after a few hours, but I am not sure if the modification have been taken completely.

(For example, it may suddenly stop after 20 hours.)

So I would like to ask you if there are any other reasons why the BQ51013B stops after a few hours.

Hi Bill

I will add the following conditions.

There is a 5mm spacer between the TX and Rx coils.

Hi Bill

I have confirmed that even with the modifications shown above, the BQ51013B shuts off within a hour.

It seems that the BQ51013B is shut off more often when the load current of the BQ51013B is small (e.g., 30mA).

Hi Kobayashi 

A scope capture of RECT pin could possibly indicate what is causing the problem,  Just before the unit shutdown.

Should see a series of pulses riding on the DC level about 250ms apart.  If the pulses are 30ms it indicates the error is large.

Pulse just before voltage drops indicates a shutdown command from RX.

Hi Bill

I was not able to check the RECT pin waveform when BQ51013B shutdown.

I have attached the waveform of the RECT pin which is working fine.

(It seems that pulses are being output from the RECT pin at 30mS intervals.)

I will fix the AD terminal to ground and check the operation of BQ51013B.

Hi Kobayashi 

Every 5 sec the RX will send an extra packet and this will reduce the spacing to 30ms and is not a problem.   We see packets before and after are at about 250ms which is correct. 

This points to the unit reaching the operating point it is needs to, system gain does not look like a problem.

Hi Bill

I got the waveform when BQ51013B shuts off. BQ51013B starts receiving power within a few minutes after shuts off.

I still don't understand why the BQ51013B shuts off.

Is there any reason why BQ51013B shuts off?

Even if I fixed the AD pin to ground, the phenomenon did not change.

Hi Kobayashi

The scope capture is very good.

Can you send the below 3 captures in higher resolution?

Hi Bill

I will upload high resolution waveform data.

RECT_0929.xlsx

Isn't the BQ51013B suddenly shuts off due to FoD?

Hi Kobayashi

Thanks for the additional scope capture.

The below and others look like communications problems.

Note that for the first three packets, SS, ID, Conf if the transmitter decode detects any errors power  transfer stops then restarts.

This is what we see below when transmitter tries to restart.  

Also see decode problems with the first three packets in below.:

After the first three packet unit enters power negotiation phase and rule to stop power transfer changes.  During this and later time the transmitter must decode a valid packet in 1.5 sec to keep power applied.  We probably see this type of shutdown at the start of this waveform.

Another thing to look at is the voltage at start up is running low, UVLO is 2.7V.  The receiver is starting but margin is low at 3.0V. 

This is more of a function of the Coil L and spacing between RX and TX.

TAKAO KOBAYASHI said:

sn't the BQ51013B suddenly shuts off due to FoD?

This does not look like FOD, looks like a communications issue.

Hi Bill

I understand that the VRECT voltage margin when starting up the BQ51013B is small.

So I decided to reduce the distance between the RX and TX coils.

By the way, are you saying that the reason why the BQ51013b suddenly shuts off is also due to a communication problem?

Hi Kobayashi

TAKAO KOBAYASHI said:

By the way, are you saying that the reason why the BQ51013b suddenly shuts off is also due to a communication problem?

Yes, it looks like a communication. issue.

Which transmitted are you using?

Hi Bill

>Yes, it looks like a communication. issue.

Does that mean that it is necessary to adjust the gap between Tx and Rx coils and the capacitance of Ccomm1 and 2?

>Which transmitted are you using?

I use a commonly available charger as a power transmitter.

ケーブル一体型　Qi規格対応ワイヤレス充電器(5W・卓上・1ｍ) - W-QA16BK (elecom.co.jp)

(Sorry, only Japanese)

I also need to design a power transmitter, but I can't find a good power transmitter IC.

I'm wondering why TI discontinued production of power transmitter ICs.

Hi Kobayashi

TAKAO KOBAYASHI said:

Does that mean that it is necessary to adjust the gap between Tx and Rx coils and the capacitance of Ccomm1 and 2?

Yes -- this would be the right area to try and adjust.

TAKAO KOBAYASHI said:

I use a commonly available charger as a power transmitter.

Can you test with a couple of other transmitters?

If possible test with TYLT Vu Solo.  This is a design based on a TI IC that I understand.

TAKAO KOBAYASHI said:

I also need to design a power transmitter, but I can't find a good power transmitter IC.

I'm wondering why TI discontinued production of power transmitter ICs.

I will contact you on this question.

Hi Bill

I think that the amplitude of VRECT should be adjusted by a combination of the gap value and the capacitance of Ccomm1,2.

Is this correct?

And I'm wondering if the VRECT amplitude is too small. What is the normal amplitude value for VRECT?

>Can you test with a couple of other transmitters?

I plan to evaluate another charger, but unfortunately not the TYLT Vu Solo.

Are you saying that it can be used as a standard machine?

Hi Kobayashi

"I think that the amplitude of VRECT should be adjusted by a combination of the gap value and the capacitance of Ccomm1,2."

"Is this correct?" -- Bill J - Yes

TAKAO KOBAYASHI said:

And I'm wondering if the VRECT amplitude is too small. What is the normal amplitude value for VRECT?

Bill J - This is a low power digital ping with the output disconnected.  Typical value is in the 4 to 5V range.  3V is close to UVLO is 2.7V .

TAKAO KOBAYASHI said:

Are you saying that it can be used as a standard machine?

Bill J - The TYLT Vu Solo is a good one to test with, it is based on TI device and we understand the behavior.

Bill 

Should I increase the capacitance value of Ccomm1,2 in order to increase the voltage of VRECT? Otherwise, should I change the parameters somewhere else?

Hi Kobayashi-san

Yes increase C value for Comm 1/2.

Also try changing the resonant capacitor C1 this may help.

Hi Bill

Ok, I will try adjusting the capacitance values of C1 and Ccomm1,2.

Hi Bill

I've been dealing with another product for a while, but I've come back to this problem.

By the way, I will be using the BQ51013B for power reception, but since there are only a few types of power transmission ICs, the configuration of the power transmission system has not yet been determined.

Is there a Qi power transmission IC that you recommend?

First of all, why are there so few types of Qi power transmission ICs?

Hi 

Will your device only use only the transmitter you build or off the shelf Qi transmitters?

Hi Bill

In my project I will be designing a dedicated transmitter.

I will contact you on this question..

Hi Bill

I am evaluating BQ51013B with the following settings.

Current limit 500mA

C1: 98nF, Ccomm1/2: 22nF

Coil: 760308101214

Coil Gap: 4.5mm

When the load current of the BQ51013B output (OUT pin) is small, the RECT output waveform becomes distorted.

Does this mean that the values of Ccomm1/2 need to be adjusted?

Hi 

This is not a problem, RECT is rectified AC1 & AC2 and will be unregulated.

Increasing filter capacitors on RECT will help, Vmax is on pin is 15V.   

Hi Bill

I have changed the capacitance value of the RECT terminal from 20uF to 35uF, but there was no change RECT waveform.

Looking at the waveform of the RECT terminal that I attached the other day, I think that there is no problem with the capacitance values of C1 and Ccomm1/2.

I think this problem is caused by the distance between the primary and secondary coils being 4.5mm.

I'm curious that other users don't have this problem.

Hi

Communications ripple or signal on the RECT pin is not a problem, this is an un-regulated signal.  Changing Ccomm1/2 can cause communication problems, if they change proceed with caution.

HI

I obtained multiple RECT waveforms by changing the values of C1, C2, and Comm1/2.

And we are currently evaluating BQ51013B at No.9.

However, even after looking at this waveform, I don't know which one is the best.

Could you please tell me the number you recommend?

0247.BQ51013B.pdf

Hi 

Configuration 9 looks OK.  But none of the waveforms show the unit starting successfully.