LTspice simulation with full bridge and synchronous rectifiers doesnt work

F

Flyback

Well-Known Member

• Feb 15, 2014

• #1

Hello,
I am using the LTC3901 synchronous rectifier controller to command the secondary diode bridge of a full bridge converter. However,it wont work. The full bridge does work without the LTC3901 .
Do you know what I am doing wrong here?
Schem and LTspice sim attached.

LTC3901 datasheet (sync rectifier controller)
http://cds.linear.com/docs/en/datasheet/3901f.pdf

LTC3723-1 full bridge controller
http://cds.linear.com/docs/en/datasheet/372312f.pdf

 

Attachments

• LT3723_1 syncfet forum.pdf

  35.3 KB · Views: 538
• LT3723_1 syncfet forum.asc

  17.6 KB · Views: 535

ronsimpson

Well-Known Member

Most Helpful Member

• Feb 15, 2014

• #2

First. Please check Q1, Q2 collector goes to the wrong spot. Exchange 111 and 222.

 

F

Flyback

Well-Known Member

• Feb 15, 2014

• #3

Thanks for spotting that... I did that and its still not working, I wonder if its something to do with the reverse current sensing resistors?

 

Attachments

• LT3723_1 syncfet forum_1.asc

  18.2 KB · Views: 541

ronsimpson

Well-Known Member

Most Helpful Member

• Feb 15, 2014

• #4

I think the supply is in current limit. It gets a big spike on the second pulse.
You said it works with diodes???

 

F

Flyback

Well-Known Member

• Feb 15, 2014

• #5

Yes I think during start up, there is too much current flowing through the sync fets....it works with diodes alone...the following simulation works with diodes, but when I put the LTC3901 with it, it doesn't work.

 

Attachments

• LT3723_1.asc

  10.4 KB · Views: 553

ronsimpson

Well-Known Member

Most Helpful Member

• Feb 15, 2014

• #6

I took out the FET(diodes) and it works. so maybe the phase is backwards. Right/Left side.

 

F

Flyback

Well-Known Member

• Feb 15, 2014

• #7

thanks, but ive swapped it round and it doesn't work.