problem in H bridge hardware implementation

[istian]

hi every body
i am implementing the following circuit on bread board.but unfortunately i am encountering few problems
my first problem is V(gs) is zero due to which no current is passing through the mosfet
what is the possible reason behind it?
i am applying 50hz pwm signal at input of gate driver ic having a dead time of 100 micro-seconds.still my mosfets are not turning on.
what measure do i need to take in order to make this circuit efficiently
p.s: this circuit is taken from tahmid's blog

 

[barry]

Your problem is that U1 (the part that has no identification that might help us understand your problem) is defective. You should replace it with a new one.

 

[istian]

Your problem is that U1 (the part that has no identification that might help us understand your problem) is defective. You should replace it with a new one.

you mean driver ic is not working properly?
i have used ir2110 and ir2112 but every time i am facing the same issue

 

[barry]

you mean driver ic is not working properly?
i have used ir2110 and ir2112 but every time i am facing the same issue

I'm sorry you missed my sarcasm.

You didn't give us any information about your circuit, like the fact that you were using an IR2110, or where you were measuring Vgs, or what the other circuit voltages were.

 

[istian]

I'm sorry you missed my sarcasm.

You didn't give us any information about your circuit, like the fact that you were using an IR2110, or where you were measuring Vgs, or what the other circuit voltages were.

oppss my fault
yes i am using ir2110 in my circuit but in the schematic i have given is ir2112 is being used.
actually you know this fact that for proper switching of mosfet gate voltage Vg should be 10-15V more than source voltage.right? but in my case both the voltage i.e Vg and Vs are appeared to be same.
for example if i give 12V at drain then approximatly 11v will appear at gate and source of mosfet
and i measured Vgs by placing probes of voltmeter at gate and source

 

[barry]

You are certainly not going to get any useful measurement using a DC voltmeter on a 50Hz PWM signal. Do you have an oscilloscope? Maybe your MOSFETS are in backwards. Maybe your bootstrap circuit is not working at such a low frequency.

 

[istian]

You are certainly not going to get any useful measurement using a DC voltmeter on a 50Hz PWM signal. Do you have an oscilloscope? Maybe your MOSFETS are in backwards. Maybe your bootstrap circuit is not working at such a low frequency.

yes barry i have oscilloscope. actually my requirement is to made a variable frequency drive varying frequency from 5hz to 50Hz in order to drive a ac induction motor at variable frequency and speed.

what does this mean? that my mosfets are in backward?
actually i am also thinking about my bootstrap capacitor that they are not providing the necessary voltage that is required to switch the mosfet
what would you suggest in such situation?
do i need to change them? currently i am using 22uf electrolytic capacitor along 100nf ceramic capacitor connected in parallal.

one more question? in this circuit should i use -Vbat instead of ground across capacitors and mosfets?

 

[fedaye]

do you consider these

 

[istian]

do you consider these
View attachment 116577

yes i have gone through this
but can you specifically highlight those parameters which i need to focus while troubleshooting my circuit?

 

[fedaye]

please scrutinize this. i have a half bridge and i do not have any Vgs problem

 

[barry]

I question whether the bootstrap circuit will work at 5 Hz.

I mean maybe you have installed the mosfets the wrong way.

Have you tried replacing the driver?