BQ24095: Battery backup switching circuit using relay

Omkar Inamdar1

Part Number: BQ24095
Other Parts Discussed in Thread: TPS61088

Hello,

I have designed the external battery backup circuit using BQ24095 as charging IC and TPS61088 boost converter. In my circuit , I have used external AC detection signal to drive the relay for switching from normal supply to battery supply and vice versa. When normal supply is ON , relay is energized and battery is charging and boost converter is OFF, we have used PG signal to control EN pin of TPS61088. When normal supply is OFF, relay is de-energized and now battery supply is used to boost the voltage to 5V. This should be the normal operation of circuit. But problem is relay chatters for few seconds before settling to one of the position . I have observed that when battery is absent in the circuit, relay does not chatter, it happens only when the battery is present. Please help

Regards,

Omkar

over 5 years ago

0 Bill Johns over 5 years ago

TI__Guru 68296 points

Hello Omkar

Can you describe the External AC detection circuit used to control the relay?

Is the BQ24095 controlling the relay?

The BQ24095 does have a battery detect feature.

0 Omkar Inamdar1 over 5 years ago in reply to Bill Johns

Prodigy 100 points

Hello Bill,

I am using following circuit for AC detection -

Open collector output of T1 is used further control PNP transistor which drives relay. So when AC power present, PNP transistor is ON to drive the relay. BQ24095 is not controlling relay. We have used PG signal of bq24095 to control EN of TPS61088.

0 Bill Johns over 5 years ago in reply to Omkar Inamdar1

TI__Guru 68296 points

Hello Omkar

Thanks for the schematic.

AC part of circuit looks OK, should not cause Relay Chatter.

Have you checked the voltages that supply opto isolator and relay drive circuit, could they be fluctuating during this transition time?

0 Bill Johns over 5 years ago in reply to Bill Johns

TI__Guru 68296 points

Hello Omkar

Any update on this question are you still seeing the relay chatter?

0 Omkar Inamdar1 over 5 years ago in reply to Bill Johns

Prodigy 100 points

Hello Bill,

I apologize for not replying on this. Currently I am working on different urgent assignment so was unable to look into this. Can we still keep this thread open so that I can reply to you once I start again with this issue. Thank you for your patience.

Regards,

Omkar

0 Bill Johns over 5 years ago in reply to Omkar Inamdar1

TI__Guru 68296 points

Hi Omkar

OK to keep open and pick up when you can get back to this project, have about 30 days.

I will mark as resolved, this does not close it until you click close. But no further action needed till you get back to it.

Power management

Power management forum

BQ24095: Battery backup switching circuit using relay