power inverter output signal (help)

[etiquoe]

hi,
i'm working on my power inverter for bldc motor driver.
the circuit is like in this thread:

i'm using N channel MOSFET for high side, so the output should be like this:

but my power inverter signal is like this:

channel 1 is low side drive signal (0-5 v)
channel 2 is highside drive signel (0-5 v)
channel 3 is power inverter output (0-24v)

VDD = 24 V

when high side ON, output voltage is about 24v
when low side ON, output voltage is 0v
but when both high side and low side OFF, output voltage is also 0v :?:

could anyone axplain please?

 

[FvM]

Activating Hin and Lin simulataneously simply creates a bridge short, possibly damaging the output transistors. Setting
both off does nothing. But you have a load in parallel to the load side switch.
Think first!

Operation of a full- or three-phase bridge is different, of course.

 

[etiquoe]

the mosfets are fine, coz there's additional dead time provided.
But when Hin and Lin are inactive (low), V on high side mosfet gate is about 3.5 v. The output of the inverter is about 3.5v too, and 0v in fast switching. it should be 12v (half of VDD). shouldn't it?

 

[kabiru]

Hi,kindly check your driver's may be one of them is bad,but your swiching pattern should be alternate with the other side.

 

[etiquoe]

the driver is fine, i've checked it
and the switching pattern is alternated each other