TPS61289: Automatic bidirectional operation battery <-> VCC

Hi Fritz,

This could be done by an external amp detecting the voltage or current to give out the MODE.

Could you share the customer and the application to me?

I will check the detail for you.

Best Regards,

Fergus

Hi Fergus

thanks for the feedback.

For ourselves it would be a 24V DC UPS with a 12V lead gel battery.

I know that the TPS61289 is not made for a 24V DC UPS - but it offers certain functions.
The automation for this is missing. The problem is how quickly does the switch from buck to boost mode and the adjustment of the charging current to the load current work.

The UPS could also be implemented with two TPS61289, so switching would no longer be necessary.

Best regards

Fritz

Hi Fritz,

For TPS61289, When working in Boost Mode, the inverting current will be limited (about -3.3A valley).

Let us discuss three scenarios：

1. the 24V have heavy loads and the device can support the load.

in this case, the device works in voltage mode and can regulate normally.

2. the 24V is a little higher(sightly reverse load).

the device has a -3.3A current and is capable of the reverse load, the current is controlled within -1.5A to 0A(valley current is not the average current, related to the inductor).

3. the 24V is much higher(heavy reverse load).

the device is not able to this reverse current at Boost mode, the mode should be change to Buck mode to regulate.

So, Could the Boost mode fulfil your demand or it needs to be changed to Buck mode?

For Buck mode, it needs external circuit to change the mode.

Please connect me if you have more questions.

Best Regards,

Fergus

Hi Fritz,

here is a solution for you, please check if this meets your demand.

One amplify or comparator is needed to build a hysteresis comparator.

the output voltage is sampled, and amplify output is connected to MODE.

The amplify can be supplied by input 12V and the Ilim pin is 0.6V which can be used to be reference.

when the output is higher than 24.1V, the MODE is high, and the device goes into Buck Mode.

when the output is lower than 23.9V the MODE is low and the device goes into Boost Mode.

when the voltage is between the two voltages, the device keeps the Mode unchanged, which will have limited reverse current.(as said in last chapter)

Please tell me if you have any questions.

I can build a circuit like that and do some test if needed.

Best Regards,

Fergus

Hi Fritz,

Could you provide your current scheme？

I see you are concerned about the current changing,

could you provide some spec and demanded waveform?

Best Regards,

Fergus