Problem with my h-bridge circuit

[SVS1988]

Hi everyone,

I designed a H bridge circuit and I have attached the circuit.
The circuit s motive is to convert 300 v D C into pulsed DC at various frequency levels (10-60KHz).

so, first i divided the circuit into two half bridges and i tested both the halves independently.
it worked perfectly . No error .(See the attached scope)

But now when i drive the whole h bridge circuit , I get noise and distortion after 35-40 Volts.
what could be my problem?

Thank you !

 

[KonstanU]

I am sure that problem is input, output capacitances of MOSFET.
Change your MOSFET! Take less powerful (you have just only 0,3A)

 

[SVS1988]

I am sure that problem is input, output capacitances of MOSFET.
Change your MOSFET! Take less powerful (you have just only 0,3A)

This is just a test circuit. In the future i will be having a inductive load and the current flowing will be approximately 3-4 Ampere.

if Input output capacitance of the MOSFET is the problem, then how did the half bridge circuit work?

Thank you!

 

[FvM]

what could be my problem?

E.g. bad circuit layout, insufficient DC-bus capacitors, output stage crosstalk to gate control signals

 

[SVS1988]

E.g. bad circuit layout, insufficient DC-bus capacitors, output stage crosstalk to gate control signals

can you please be specific??

 

[KonstanU]

Could you just change load (R with 100 Om) and to show your result.
And FvM is right, DC-bus capacitance must be.

 

[mrinalmani]

The output contains a high frequency voltage superimposed on the DC voltage. This suggests oscillating components in the signal or/and power path.
1. What is the distance between the MOSFET driver and the MOSFET? At high frequencies, a few centimeters long wire can cause a noticeable oscillation due to parasitic inductance of the wire.
2. The driver should be placed as close as possible to the MOSFET.
3. Use thinner signal wire to reduce parasitic inductance.

 

[FvM]

can you please be specific??

I mentioned several problems that are often observed in MOSFET bridges.

You didn't give substantial informations about your design except for showing a (simulation) circuit.
No, I can't be presenly more specific.