mosfet gate drivers and negative voltages

[jackXallXmasterX0]

im trying to utlize a gate driver to switch two paired mosfets (half bridge) to generate a waveform at 50Khz from -100 to +100 V. The circuit works well to switch positive voltages (0 to 100V). When i add even small negatiuve voltage, ie -5 to +30V, the circuit becomes unstable.

Im not sure but is this a limitation of the gate driver itself (ie voltage sense pin or the bootstrap diode) or am i doing something wrong?

Ill attach a figure from the data sheet of the gate driver.

 

[benta]

I'm not certain I understand your question.
The IR21xx drivers are designed only to drive MOSFETs in the range of 0...600 V. The lower driver is ground referenced and does not like negative voltages.
If you want to generate a 0...200 V output signal and then AC-couple it to make it +/-100 V, then it'll work, otherwise not.

Benta.

 

[DHambley]

To which node in that circuit are you applying the -100V? Another item I noticed; Vs from the IC should be connected to both the top FET source and the bottom FET drain.

 

[jackXallXmasterX0]

benta, thank you, somehow this obvious fact in the spec sheet slipped past me.

hdldr. Sorry for not drawing out the full circuit, the mosfet connected on the low side can be connected to a negative voltage rather than ground.