[SOLVED] BQ2057WTS battery reverse and short connection protection

[Knife]

I designed a battery charger for 2 cell Li-po with BQ2057WTS as you can see "bq2057wts" picture attached. I have to short circuit protection and reverse connection protection for battery connection. I added a schottky diode as you can see "bq2057wts revised" picture attached but it didn't solve reverse connection. When I connected battery reverse, the IC burned.
I thinked to use P or N channel mosfet but I didn't realise that. Could you suggest a solution for this project ?

 

[mrinalmani]

1. The diode is not positioned correctly.
2. Is Vcc isolated or non isolated?

 

[Knife]

1. You mean, I have to connect diode after BAT pin (IC pin 2) connection. If yes, it influences the battery voltage measurement.
2. Yes, Vcc is isolated from mains.

 

[mrinalmani]

But then thats the only way how you can prevent opposite polarity across the IC. As far as the voltage drop is concerned, you may want to use a synchronous MOSFET rectifier. It does not give a forward voltage drop, however it will have an on state resistance ranging from 10 mOhm to 50 mOhm (typical)

 

[yassin.kraouch]

where is connected the battery_state_output and battery_state_input ?

 

[Knife]

mrinalmani, I have an idea to use PNP mosfet and control it via microcontroller like your idea. But I'm trying to find any other solution.

yassin.kraouch, This two pins are control the stat output of IC for condition of battery. Battery connected to "Battery" labeled pin.

 

[yassin.kraouch]

are they connected to + or - o fthe battery ?

 

[Knife]

No, battery_state_output and battery_state_input go to microcontroller. That's not what you are thinking.

 

[Knife]

But then thats the only way how you can prevent opposite polarity across the IC. As far as the voltage drop is concerned, you may want to use a synchronous MOSFET rectifier. It does not give a forward voltage drop, however it will have an on state resistance ranging from 10 mOhm to 50 mOhm (typical)

Dear mrinalmani,

Thanks for your idea. I will try to solve like this.

 

[mrinalmani]

Good luck, go ahead!