BQ24195: What will happen when there is a loop from the output to the input?

Roberto,

In your loop design, what if battery voltage drops too low to support VSYS output?

Thanks,

Ning.

I want to set the Vsys minimum voltage to 3V. And if the battery voltage drops below the 3V then the system shouldn't work anymore. 

Dear Ning T,

My awnsers are still not awnsered so I hope you can still solve them.

Regards,

Roberto del Pozo Gallardo

Roberto,

As you know, when the battery voltage is too low, the system voltage could drop to 0V, then the boost converter may stop working also.

Thanks,

Ning.

Dear Ning T,

Your answer and question are totally unrelated.  

I want to know what will happen in normal conditions?

For example if the battery voltage is 4V.

What  I think what will happen is the following:

The battery activates the dc/dc converter and convert the voltage to 12v and then the battery charger sees the 12V input and switch from the battery to Vbus but when the capacitor of the converter is discharged the battery is activated again. And this will switch continuously.  

Is this right?

And is this recommended?

Or should I choose another dc/dc converter without power path control?

Regards

Roberto

Hi Reberto,

If you want the power is used from the battery instead of the Vbus input, you can set the charger in HIZ mode REG00[7] = 1. The charger converter will not switch during HIZ mode, so the power will be only from the battery.

Dear Eric,

But what will happend if I dont put it in hiz mode?

Regards,

Roberto del Pozo Gallardo

Hi Roberto,

It looks like the battery energy will circulate and I am not sure there is stability issue. It is not a desired operation mode and the design can avoid it. In your diagram, there are two 12V DC/DC modules. You want to disable the top one to maintain the 12V. V generated from the bottom one.