Dear All,
I am building a 800W pushpull converter operating at 40kHz switching frequency with primary current going till max 100A. Converter input voltage on primary side can vary from 30-42V.
I want to implement peak current mode control for this converter. So, I used a shunt resistor of 1mOhm in the high side to sense the primary switching current. In order to amplify the sense voltage I used INA240A1 (20V gain). But the IC output is not replicating the primary current waveform. Please refer to the following figures for the type of errors I am getting at the output of INA240A1 IC.
In all the following figures, green waveform represent IC output and yellow waveform represent actual current.
Shunt Gain = 0.002 and INA240A1 gain = 20. Total gain = 20*0.002 = 0.04
Figure 1. Error in IC output - With current measurements @ cursor value = 28.8A
Figure 2. Error in IC output - With IC output measurements @ cursor value = 1.12V
Figure 3. IC output is deviating from its corresponding current waveform with peaky middle parts
Figure 4. IC output is deviating from its corresponding current waveform with peaky middle parts and slow falling at the edges.
Figure 3 & 4 are of big concern as the IC output sometimes not following the current waveform making it non suitable for current control. I didn't understand why the IC output is no falling fastly as the original current waveform and following that it is giving peaky values in the middle. Any suggestions/help in this regard would be greatly appreciated.
Thanks in advance!
Kashyap Gundlapalli