UCC28950: ucc28950 could not find examples for parallel use

analog06

Prodigy 240 points

Part Number: UCC28950
Other Parts Discussed in Thread: TLC555, , PMP6712, UCC28951, TINA-TI, UCC39002, UCC29002

I'm looking for an example created using the tlc555 and 4015 integration, or a sample parallelization file

over 5 years ago

0 Colin Gillmor over 5 years ago

TI__Mastermind 25570 points

I don't have an example of parallel use using the components you suggest. The PMP6712 is a reference design where we have paralleled 2 PSFB power stages using the UCC28950. https://www.ti.com/tool/PMP6712?keyMatch=PMP6712&tisearch=Search-EN-everything&usecase=part-number

This system uses the basic idea in the diagram below.

The arrangement above can be extended to multiple slaves but all the slaves will run at 90 degrees from the master. This is correct for one slave but for more than one slave the phases of the slave devices need to be equally spaced for optimum interleaving. This is described in the app note below - which is where I think you got the TLC555 and 4015 device references from.

https://www.ti.com/lit/an/slua609/slua609.pdf?ts=1588236625767

Let me know if you need any more information but as I said I don't have an explicit, worked example.

Regards

Colin

0 analog06 over 5 years ago in reply to Colin Gillmor

Prodigy 240 points

first of all thank you for your reply,

I'm trying to build the structure described in the slua609 document, I'm trying to build the structure containing tlc555 and 4015, but I can't find any sample schema.

4015 integrated outputs do I need to connect directly to the sync pin?

if I did an example design can we talk on accuracy?

0 Colin Gillmor over 5 years ago in reply to analog06

TI__Mastermind 25570 points

The SYNC input to the UCC28950 requires a 0/5V or 0/3.3V signal. It depends on how you use the 4015 and you may need to use an attenuator if its output signal amplitude is larger than that but the 4015 output can go directly to the SYNC pin given that the amplitude is correct.

The UCC28950 must be configured as a SLAVE device, RT connected to GND.

I'd suggest you use the UCC28951 instead of the UCC28950. The UCC28951 device is an enhanced version of the UCC28950. It is a fully compatible drop-in replacement for the UCC28950. Refer to application note SLUA853 at http://www.ti.com/lit/an/slua853/slua853.pdf for more details. The UCC28951 is typically the better choice, especially for applications where the system may have to operate simultaneously at a duty cycle> 90% and current limit.

I can check your design for you if you wish - that's not a problem

Regards

Colin

0 analog06 over 5 years ago in reply to Colin Gillmor

Prodigy 240 points

Will this be the parallel connection so that the other parts are the same

What is the duty rate that should be for 555 also ?

0 analog06 over 5 years ago in reply to analog06

Prodigy 240 points

I think this is a more accurate design, please consider this

The frequency of 555 is 2 times the switching, i.e. 400 khz

I will put other values the same as working single design
duty is 500 ns

if there is an error please say

thanks

0 Colin Gillmor over 5 years ago in reply to analog06

TI__Mastermind 25570 points

Hello

Unfortunately, only half of the TLC555 circuit is visible - can you repost the image please or simply post the TINA-TI file.

Regards

Colin

0 analog06 over 5 years ago in reply to Colin Gillmor

Prodigy 240 points

In addition to the single unit, would it be enough just to add them?

0 analog06 over 5 years ago in reply to analog06

Prodigy 240 points

tina file is attached

paralell.TSC

0 Colin Gillmor over 5 years ago in reply to analog06

TI__Mastermind 25570 points

Hello

Your circuit should work fine - I hacked your file to remove the UCC28950 devices (makes the sim run much faster) and the output signals to the slaves are correct. I've also attached the modified tina file.

Let me know if there are any other issues

Regards

Colin

/cfs-file/__key/communityserver-discussions-components-files/196/paralell_2D00_2.TSC

0 analog06 over 5 years ago in reply to Colin Gillmor

Prodigy 240 points

hi ,

thank you so much

For ucc28950's slave operation, do I need to add anything next to the additions shown in the picture?

0 Colin Gillmor over 5 years ago in reply to analog06

TI__Mastermind 25570 points

The resistors above are correct, You will need a capacitor at the SS/EN pin if you want the soft start function to operate correctly.

That is all you need for synchronisation. You may also want to have the power stages share the load current and for that you will need a circuit like that below. The error amplifier of the controller on the left sets a current demand which is shared between the other two controllers. This method can be extended to more stages. This method was used in the PMP6712 reference design at http://www.ti.com/tool/PMP6712

0 analog06 over 5 years ago in reply to Colin Gillmor

Prodigy 240 points

For that problem, I designed a load share unit using ucc39002

which one do you think works healthier?

0 Colin Gillmor over 5 years ago in reply to analog06

TI__Mastermind 25570 points

They are different and both will work well. However, like many things it depends on what you want the system to do - here are the main comparisions / tradeoffs.

Transient response will always be slow with the UCC29002 because its control loop bandwidth must be about a decade slower than that of the modules it is controlling.

Load share accuracy can be better with the UCC29002 because it has been designed specifically with highly accurate load sharing in mind.

The UCC28951 load sharing has a master controller and the other modules are slaves.

The UCC29002 is a 'democratic' system because the master controller is chosen automatically (it will be the one attached to the power stage with the highest output voltage). This means that a true N+1 redundant system can be built. If the Master UCC28951 fails in the system shown above then the whole system will stop.

If you are happy with these tradeoffs then the UCC29002 is a good solution.

Regards

Colin

0 Colin Gillmor over 5 years ago in reply to analog06

TI__Mastermind 25570 points

It looks like we have two threads on the same topic - I'm going to close this one and we can continue the discussion on the other - https://e2e.ti.com/support/power-management/f/196/p/901679/3337312#3337312

Regards

Colin

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UCC28950: ucc28950 could not find examples for parallel use