Battery Charging Circuit Using INN3947CQ for 48V, 2.9AH Li-ion, at 0.5A

Hello Pemendra Pardhi,

Good day and thank you for continuously choosing Power Integrations.

Regarding the battery charger circuit turning off when a lower load resistance is connected, this is an expected behavior of the IC because the output voltage during constant current condition is below the 90% AR threshold (based on the waveform you've shared), resulting in the InnoSwitch3-AQ triggering auto-restart. 

As you may notice on the feature code table that can be found on page 37 of the InnoSwitch3-AQ datasheet, the H907 Hcode device will trigger the auto-restart function when the output voltage (Vout) is less than 90% of regulation during constant current operation. Based as well on the waveform you have shared, the output voltage during this condition is ~34.2 V, which meets the mentioned condition.

If you want a much lower Vout auto-restart threshold, then choosing the INN3949CQ-H100 is recommended, as it will trigger AR function when the output voltage is below ~3.45 V as per the feature code table.

Then regarding the objective, my understanding is that the power supply circuit should be able to deliver a constant output current of 500 mA if a load is connected or when the battery is charging; then when the battery is fully charged, the power supply circuit should automatically be disconnected from the battery. I would really appreciate it if you could confirm if my understanding is correct.

If my understanding above is correct, then an external battery management circuit is required. Unfortunately, we don't have any solution/IC for an external battery management circuit.

I hope that the above information helps. Let me know if you need any further assistance or have any more questions or clarifications. We are glad to help you further and answer all your queries.

Thank you and I wish you a great day ahead!

Best regards,

Tommy

Hi Tommy,

Thanks for the reply,

 Yes,  as per your statement, "My understanding is that the power supply circuit should be able to deliver a constant output current of 500 mA if a load is connected or when the battery is charging; then when the battery is fully charged, the power supply circuit should automatically be disconnected from the battery. I would really appreciate it if you could confirm if my understanding is correct." Our objective is the same as per your statement.

As per the your suggestion, the feature of disconnection to the battery from the power supply circuit whenever, the battery gets fully charged is not available in the given IC.

So to disconnection to supply circuit from the battery, once the battery gets fully charged. Can we connect one optocoupler as given in the attached figure?

 The optocoupler-controlled will be controlled by a microcontroller based on battery voltage sensing.  

Without a change in the power supply circuit only IC INN3947CQ-TL will be replaced by  INN3949CQ-H100-TL

Can we proceed further as per my statement? 

Kindly confirm if we are correct, or suggest if any other kind of modifications are required.

Thanks and Regards

Pemendra Pardhi

Hello Pemendra Pardhi,

Good day and happy new year.

Yes, the concept of using an optocoupler to disconnect the battery when it is fully charged is okay. However, optocouplers tend to have a low collector current rating and might not be suitable for your 500-mA output current. That said, a better alternative that I suggest is using a load switch as it can operate at higher output currents.

Thank you and I wish you a great day ahead!

Best regards,

Tommy

Hi Tommy,

I want to point out that, as per the suggestion, we have considered the IC INN3949CQ-H100-TL,  but we are facing a problem with the samples.

For the last one and hlaf month, we have been trying to get the samples of the suggested IC from the direct power integration team (Bangalore, India). But we haven't gotten.

And we are not getting a proper response, so kindly confirm that the IC is under the launching stage or it is already in production.

Thanks  

Dr. Pemendra Kumar Pardhi

Hi Dr. Pemendra Kumar Pardhi,

I'm sorry to hear about the concern on the INN3949CQ-H100-TL IC samples. I will be reaching out to our local sales team regarding your concern. I will update you once I receive feedback from them.

Alternatively, you may also reach out to one of our distributors (listed on this link) nearest to you to inquire if you can also get some samples of the INN3949CQ-H100-TL IC from them.

Thank you for your understanding and I wish you a great day ahead!

Best regards,

Tommy

Hi Tommy,

Thanks for the reply.

Thanks And Regards 

Pemendra Kumar Pardhi

Hello Dr. Pemendra Kumar Pardhi,

Good afternoon.

Our local sales team confirmed that your sample request has already been sent to the relevant team and will be shipped soon.  For shipment updates, you may continue your communication with our local sales team based in Bangalore.

Thank you for your understanding and patience. I wish you a great day ahead!

Best regards,

Tommy

Hi Tommy,

Thanks for support 

Now the circuit is working fine.

Thanks and regards

Pemendra Pardhi 

Hello Dr. Pemendra Pardhi,

That's really great to hear and you're very welcome. We are glad to help.

If you need any help with your project or have any more questions or clarifications, feel free to raise again a new forum post or submit an inquiry on our support page, PowerPros Online Support.

Thank you and I wish you a great day ahead!

Best regards,

Tommy