Half bridge driver L6384E problems

[NZBen]

I am working on a project with a 6384 and it is giving me issues, i'm initially driving with no load and am wondering if that is my problem, however I dont really want to put a load on it until I have the circuit functioning properly. I'm sending a 60Hz PWM sine wave to the 6384 at 20kHz, the problem is, it appears that sometimes the high and low side turn on simultaneously, for other periods of the 60Hz cycle the high side isnt turning on at all, and most of the time it pulls the high side gate down to the -V rail. I'm using two IRF740 as my half bridge FETs and it's going to be running on +/-150V, currently I have it running on +/-15V to limit smoke and eye damage from exploding FETs.

I have a 100K resistor on the SD pin which gives pretty much 1us dead time, and a schottky return diode on the gate with a 20R resistor in parallel, also using a 0.1uF ceramic cap for the bootstrap.

The device it's intended to run is a linear motor with a static resistance of around 11R and static inductance of 160mH (I know that doesnt really mean much in itself) It's intended to have a peak RMS voltage of 115ac with peak power of around 140W so say around 1.5A

All of the problem seems to be on the high side, mostly either the high gate being pulled to -V or not going up high enough, sometimes it seems like it's fixed on and discharging slowly while the low side is still functioning properly (the high side fet gets very hot) - I will do a scope trace of the problem tomorrow to help visualize the problem.

I've combed the application notes etc and cant get it working properly so am stumped.

Thanks in advance for any guidance assistance
Ben

 

[Fidelis Anyanti]

Hi,
If you show your circuit, it maybe easy for you to get help.

Regards.