TPS54020: Parallel Operation

Hi Anthony,

Thanks for your help! 

I was asking about running the devices in parallel, because I am designing a 2+1 (or even 3+1) redundant buck converter system to provide 5V for a safety critical subpart of our system. The power source are two 6S LiPo batteries, meaning the input voltage can vary between 18 and 25.2 V. Because of this the TPS54020 does actually not work in our application (max Vin=17V). 

What I mean with the 2+1 redundant system: In normal mode all 3 buck converters would share the load and deliver roughly 3.3A each. If one of the buck converter fails, we require the 2 remaining buck converters to be able to carry on and therefore supply roughly 5A each. They should bridge the time to keep the system running, until maintenance can be conducted safely. I think it makes more sense to use a 2+1 solution because the differences between the normal and the failure mode is small. In a 1+1 redundant system the normal load would be 5A whereas during the failure mode the buck converter would need to deliver 10A.

For your reference I post my original question just below:

I am looking for a solution to create a parallel and redundant power delivery within our product. It is powered by a 6S LiPo-battery, meaning the input voltage can vary between 18 and 25 Volts. Our maximum current consumption is roughly 10A.

Here (www.ti.com/.../slva389.pdf) I have found a buck converter, which can be hooked up in parallel to share the load with a second of its kind, meaning you could get a maximum current of 12A (=2*6A). Unfortunately the maximum input Voltage is 17V, which is not compatible with our system. I am looking for something like this, but where 3 buck converters work in parallel in a 2+1 redundant system. This means that during normal operation all 3 converters share the load equally (~3.3A each), but if one of the converters fails, the remaining 2 are still capable of delivering the entire 10A by delivering 5A each.

I am looking forward to hearing from you.

Best regards,

Claudio Fritsche

Hi Anthony,

I am developing a power supply (5V) for the processing board of our mobile application. This power supply is safety critical, which is why it needs to be redundant. The product is powered by a 6S-LIPO Battery, meaning the input voltage varies between 18V and 25.2V. Therefore, the TPS54020 is not suited for us, since its maximum input voltage is 17V.

Regarding the redundancy, we are thinking of implementing a 2+1 redundant system. This means that during normal operation all 3 Buck converters share the load (roughly 10A) by providing roughly 3.3A each. If one of the buck converters fail, the other parts should not be protected from this failure and be able to take over the whole operation. This would result in the "failure mode", where only 2 converters provide the entire 10A (roughly 5A each). Does TI have such ICs? 

The thought process behind a 2+1 redundant system is that the load difference between the normal mode and the failure mode becomes smaller (3.3A to 5A, compared to 5A to 10A for a 1+1 system). 

As a reference I post the original question right below:

I am looking for a solution to create a parallel and redundant power delivery within our product. It is powered by a 6S LiPo-battery, meaning the input voltage can vary between 18 and 25 Volts. Our maximum current consumption is roughly 10A.

Here (www.ti.com/.../slva389.pdf) I have found a buck converter, which can be hooked up in parallel to share the load with a second of its kind, meaning you could get a maximum current of 12A (=2*6A). Unfortunately the maximum input Voltage is 17V, which is not compatible with our system. I am looking for something like this, but where 3 buck converters work in parallel in a 2+1 redundant system. This means that during normal operation all 3 converters share the load equally (~3.3A each), but if one of the converters fails, the remaining 2 are still capable of delivering the entire 10A by delivering 5A each.

Thank you and best regards,

Claudio Fritsche

Hi Claudio,

Something to be careful of is the failure mode for a buck converter can cause a short to ground on the input rail and output rail. You would want to add something which can break the connection to the input rail and output in case this failure mode occurs. You might be able to protect form this scenario by putting an eFuse device in line with the input and a load switch in line with the output of each regulator.

I'm not sure if we have any bucks in the 20V-30V range which allow paralleling as all the devices I currently support are <20V. I will need to get someone else who supports the higher voltage devices to comment.

Anthony