Invertor output voltage not going beyond 9volts??

[musmanh]

Hi everyone.We have designed an inverter using TLP250 optocoupler(used for providing gate voltage to MOSFET).The optocoupler is working fine and giving desire voltage,but inverter's output is not going beyond 9 volts even if . Circuit of optocoupler and inverter's circuit are on different PCBs. Driving signal on gates of MOSFETs IRF840 are provided by connecting wires from output of optocoupler.I have no idea of what is going on.Please help me.

 

[FvM]

inverter's output is not going beyond 9 volts

A meaningless number without knowing the supply voltage respectively expected voltage.

As a wild guess for lack of substantial informations, you are possibly missing a suitable (floating) supply voltage for the high side driver?

 

[musmanh]

Sorry for missing input supply information.When I change input supply from 0 to 24 volts,the output goes to 9 volts but after 9 volts even I am increasing input supply the output does not change.Another point,ground of driving signal and input signal are separated.

 

[FvM]

You also didn't mention the invertor topology, I presume you are talking about the output voltage of a H-bridge or half-bridge.

We should see a schematic, my previous guess about high-side driver supplied with a DC- referenced supply (common with the low-side driver) holds.

 

[musmanh]

It is H-bridge topology.Driver circuit is working fine.

 

[FvM]

How do you supply the high-side TLP250?

 

[musmanh]

We supply 12 volts dc to input of TLP250,generate pwm using arduino and when a pulse is detected on TLP250 the 12volts input is transferred to gate of mosfet. then we supply a seperate dc supply to inverter to generate square wave.The problem is that output of inverter is not going beyond 9volts(18peak-to-peak) even if supply to inverter exceeds beyond 9volts.I will upload schematic shortly.

 

[musmanh]

We have found the problem,but not solution yet. Input supply to optocoupler and inverter are getting shot somehow...Thanks for you cooperation..