Interleaving two UCC28950 with UCC39002 and Si8503

CWilson

Expert 1920 points

Other Parts Discussed in Thread: UCC28950, UCC39002, UCC29002

Hi everybody!

We're currently designing a Full Bridge ZVS 3400W converter with two UCC28950 (coupled as master/slave interleaving).

For current sensing we're using the Si8503 (recommended by a TI employee in another post). The output of the Si8503 is amplified in order to match the input of the CS on the UCC28950. The Si8503 should be a much better choice than a common current sense transformer due to it's leading edge blanking.

We're concidering load sharing using two UCC39002 since the output of the two UCC28950 is only tied together by the two output inductors (the UCC28950 is run from the secondary side of the full bridge transformer).

The output of the Full Bridge converters is 40V and up to 3400W output total.

How should we get this done?
Should the voltage feedback from the output be tied together on the two UCC28950 and only measured from one of the outputs?

over 13 years ago

0 Mike O' over 13 years ago

TI__Guru* 85616 points

If you are using the UCC28950 devices in peak current mode control you do not need the UCC39002. You will use one voltage amplifier for feedback to control both UCC28950 devices. We will call this the master controller. The second UCC28950 controller is the slave you just need to set is voltage amplifier in a voltage follower configuration. The output of the voltage amplifiers master needs to be fed into the none inverting pin of the amplifier.

You will also want to review the UCC28950 data sheet for instructions on how to synchronize the UCC28950 controllers.

0 CWilson over 13 years ago in reply to Mike O'

Expert 1920 points

We're regulating cycle-by-cycle.. Is that the same as peak current mode control here?

In many datasheets it's recommended to use the UCC29002 with the UCC29850..?

Can you show me how to connect the two UCC28950 together regarding the voltage amplifiers and resistors?

Regarding the sync, I've done it as shown/described in the datasheet.

0 Mike O' over 13 years ago in reply to CWilson

TI__Guru* 85616 points

Peak current mode control is where you use the current sense signal as the PWM comparator ramp.

0 Joachim Thor over 13 years ago in reply to Mike O'

Prodigy 50 points

I have attached a small schematic. Could you look at it and verify that this is the way the two controllers should be wired according to your suggestion?

0 Mike O' over 13 years ago in reply to Joachim Thor

TI__Guru* 85616 points

This looks like the correct configuration. Please refer to the data sheet and application note for other component placement and selection. There is also a MathCAD design file that you can download.

http://www.ti.com/lit/gpn/ucc28950

http://www.ti.com/litv/pdf/slua560c

http://www.ti.com/litv/zip/sluc222b

0 PHILIP HSU over 12 years ago in reply to Mike O'

Expert 1900 points

Hi Sir,.

the MATHCAD file was lost .. could share us by excel or link else please ? thanks

thanks

0 Mike O' over 12 years ago in reply to PHILIP HSU

TI__Guru* 85616 points

The following link will get you to the excel file.

http://www.ti.com/litv/zip/sluc222c

Also note the Excel file and MathCAD file can be found at the TI web site in the UCC28950 product folder. You just have to scroll down

http://www.ti.com/product/ucc28950

Regards,

Mike

0 Victor John1 over 11 years ago in reply to Mike O'

How to connect SYNC pin for Master UCC28950 and Slave UCC28950.

As you said "You will use one voltage amplifier for feedback to control both UCC28950 devices. We will call this the master controller. The second UCC28950 controller is the slave you just need to set is voltage amplifier in a voltage follower configuration. The output of the voltage amplifiers master needs to be fed into the none inverting pin of the amplifier", I wonder whether the master converter and slave converter will be current share.

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Interleaving two UCC28950 with UCC39002 and Si8503