BQ51050B: Assistance Needed for Wireless Charging Project Using BQ51050B IC [Final]

Hello Sean

The BQ51050B is optimized for 500mA to 1A charge currents and will lose current regulation accuracy at lower currents, 250mA charge current will work but need to terminate at 50mA, 20% not the typical 10%. R-TERM is 6800 ohms or about 28%, that would work.

ILIM and FOD connection, see figure 32 in data sheet.  The R-ILIM need to connect to ground thru R-FOD, also need pull up resistor R-OS from RECT to FOD.

A good value to start with for R-FOD is 200 ohms, that would put R-ILIM at about 1056 ohms.

For R-OS start with 42.2k ohms.

What Coil are you using?

Hi Bill,

Thank you for your help. Right now we are using a 12.5uh Wurth receiver antenna.

Here is the link to it:https://ie.farnell.com/wurth-elektronik/760308101220/power-charge-receiver-coil-12/dp/2543257

Thank you.

Here is the updated schematic so far.

Hi Sean

Schematic looks good.

Update on coil

The coil is 12.5uH and 17mm round.  This could be a problem due to size, may have trouble starting.  Low coil to coil distance will help.

Hi Bill, 

Thank you for your help.

What coil inductance and size is generally recommended? (Our pcb is currently 36mm squared)

Thank you.

Hi Bill,

I just wanted to thank you for all of your help. 

I really appreciate it.

Thank you,

Seán

Hi Bill, 

I want to modify and use this circuit to charge ab(8ma capacity) LIR1220, how should I adjust R_ILIM accordingly, and are there any other passives that I would need to additionally change.

Thank you,

Seán

Hey Sean

I will reply on the conversation feature of forum.