Is anything wrong with interleaved Boost converter?

[treez]

Hello,
We wish to interleave four LT3791-1 based boost converters, each with a switching frequency of 222KHz.
The switching of each will be 90 degrees phase shifted.
(so the overall switching ripple in the input and output caps will be at 888KHz)
The schematic and LTspice simulation is attached.
Is there any problem with this (somewhat unusual) SMPS configuration?

The overall spec is
vin=28v
vout=34v
iout = 25Amps (total of all four stages)


LT3791-1 datasheet
http://cds.linear.com/docs/en/datasheet/37911fa.pdf

 

[FvM]

Paralleling FB inputs doesn't guarantee equal current share. You need to bridge Vc, respectively copy the Vc signal from one controller to the others with a buffer.

 

[treez]

thanks, though the LT3791-1 datasheet says nothing about bridging Vc pins. The LTC3791-1 datasheet says that two can be paralleled and anti-phase sync'd with help from the CLKOUT input.
So I cannot understand why the datasheet didn't say what you discussed about bridging the Vc pins?....I am not even sure that the vc pins can be bridged.....since they appear to have output current sources?
I am really not sure that the vc voltage can be copied across in that way?

Though I do see your point....the vc pins need to be driven to the same voltage.....how may we do this, is it just a case of connecting a suitably driven opamp output to the vc pins?

However, as the attached simulation (LTspice) shows, (schematic attached also) tying the vc pins together gives funny results..the chip (LT3791-1) doesn't seem to work properly...the opamp draws several mA's out of each of the the Vc pins at first....I presume the FB pins must be grounded?