[SOLVED] problem with simiultion of mosfet switches

[fareen]

hi
i m tring to make a h bridge using mosfet but my simulation in ltspices is not giving the required result infact the results are quite bizarre
i dont understand whatto do
can naybody help???

 

[alexan_e]

Without a schematic how can anyone help?

 

[FvM]

You should absolutely show the circuit. I love mixed-up circuits and bizarre results.

 

[fareen]

oh my bad
im so forget ful
switch circuit is a simple switch im trying to implement pmos switch but the result is constant voltage
while the other circuit give output in mv????

 

[FvM]

Without claiming completeness, I see these issues:
- wrong polarity of D6 and D7
- pulse voltage levels for V2 and V3 result in M1 and M2 always on
- no models selected for any semiconductor device. Default devices are small signal types
- gate resistor values unsuitable when used with power transistors
- no dead time provided for bridge control
- control method for low side switches is likely to trigger bridge self-destruction

I append a schematic copy for convenience

 

[fareen]

thanks for the reply
can you suggest power mosfet for driving 24V and 10A dc motor
and can you explain the dead time becuz i got no idea of it
and then i was tring just with two mosfet but output is just not right
give sum hint to correct it

 

[fareen]

here is the circit

 

[FvM]

Suitable power MOSFETs are availabe in the LTSpice standard library. It's easy to select one with sufficient ratings for a simulation.

Dead time is required to achieve "break before make" action of the H-bridge switches. A few 100 ns is a usual number for MOSFET. In a simulation, it's easy to provide separate gate voltage sources for each transistor and adjust the timing parameters accordingly.

Your latest circuit from post #7 has serious errors. I can only suggest to design the circuits less hastily and double check correct polarity of each transistor and voltage range of control sources.