BQ51013B: bq51013

Adrian Whale

Prodigy 10 points

Part Number: BQ51013B

Tool/software:

I have a problem when using the wireless charger. This is my setup:

TX coil is a Baseus QI charger. It has an LED indicator which is very handy for resolving issues.
RX coil is a TDK WR222230-26M8-G 27uH and 22 mm diameter.
BQ51013B configured for wireless charger and USB charger. Both EN1 and EN2 are pulled down to make USB charger the default source. An LED is connected to /CHG to provide a visual representation when the device is charging.
A BQ25120AYFPR battery charger.

The schematic is as follows:

I see the following behavior:

When I only use the USB charger, Vout is 5V as expected, but the D1 LED doesn't turn on, so I assume /CHG is not pulling down but /AD-EN is.
When I only use the wireless charger, Vout is 0V, and the D1 LED doesn't turn on.
When I plug both power sources, the output depends on the EN2 value as expected: 0V when pulled up, 5V when pulled down. D1 LED doesn't turn on.

I am fairly confident that the BQ51013B is communicating correctly with the Baseus charger. I have performed the following tests:

At first, I placed the wrong resonant capacitor, and the Baseus charger didn't react to the RX coil. The Baseus LED indicator was constantly on.
When I placed the correct capacitor, the Baseus LED was blinking slowly, which means it is charging. With the oscilloscope, I can see that Vrec is approximately 7.4V, and the power consumption of the Baseus charger is approximately 1W. When I separate a few mm from the RX coil from the TX coil, I can see that Vrec voltage drops briefly but is adjusted again to 7.4V, and the charger consumption increases to 4W. I assume this means that the RX coil is correctly communicating with the TX coil to increase power output.
If I force a failure by removing the 10K NTC, the Baseus charger LED flashes rapidly to indicate failure, and I can only see a ping that lasts a few ms on my oscilloscope. This to me confirms that there is actually communication between the two coils.
If I connect the Baseus charger and the USB power at the same time, the Baseus LED stays ON (not charging), and I can only see a ping on my oscilloscope.

I don't know what's causing the BQ51013B to not output any voltage on Vout. I have tried replacing the BQ51013B, but that didn't solve the issue.

Thank you in advance.

6 months ago

0 Bill Johns 6 months ago

TI__Guru 71166 points

Hi Adrian

Couple of things to check / Try:

1.) The AD pin may be floating, this would turn off Wireless Power. Try grounding with a 10k.

2.) If you have voltage at RECT but no voltage at OUT. Try increasing the Current Limit by reducing R-ILIM value for test go with 100 ohms

3.) Check the RECT start up with an o scope -- do you see the unit start up cycle (figure 7-17 in Data Sheet)?

0 Adrian Whale 6 months ago in reply to Bill Johns

Prodigy 10 points

Hi Bill,

Thank you for the fast response.

Tried 1. and 2. with no luck.

Checking RECT startup sequence gives me the following result:

Does that look good to you?

0 Bill Johns 6 months ago in reply to Adrian Whale

TI__Guru 71166 points

Does not look right, I think you are at 500uS / Div which would be too fast.

Should look like attached.

5758.TX Start up and Comm Packets Guide.pdf

0 Adrian Whale 6 months ago in reply to Bill Johns

Prodigy 10 points

Thank you for your answer.

I can't reproduce the V-RECT signal. Is it possible that the capacitors I have chosen are not correct?

The RX coil I am using is this: https://product.tdk.com/system/files/dam/doc/product/wireless-charge/wireless-charge/rx-coil-module/catalog/wlc_rx_wr222230-26m8-g_en.pdf

Manufacturer indicates 27uH at 100KHz 1Vrms, which would coincide with the value L's of the datasheet.

Solving the equation for C1 gives me a value of 94nF, which I have approximated to 100nF.

I can't resolve equation 2 as TDK does not provide the value of Ls, but it should be lower than 27µH, so let's say around 20µH. Solving equation 2 for 20µH gives a C2 capacitance value of 1.28nF.

I have tried to slightly tweak both capacitor values by trying different capacitors in parallel, and I am using 50V capacitors.

Also, the quality factor using Ls = 20uH gives me a value of 114, which is greater than the required 77

Am I doing something wrong here?

0 Bill Johns 6 months ago in reply to Adrian Whale

TI__Guru 71166 points

Hi Adrian

The Ls value is free space and Ls' is when coil is on TX coil.

Data sheet value is free space, nothing around it.

The Ls' you will have to measure when on a TX and in the case. It will go up in this condition.

Values close.

0 Adrian Whale 6 months ago in reply to Bill Johns

Prodigy 10 points

Thank you for that correction.

I ended up swapping the IC and this time it worked flawlessly. My guess is either pin 4 was not propperly soldered the last time, or I somehow damaged the component the previous component when using the hot air gun.

Again, thank you so much for your help

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BQ51013B: bq51013