Hi Murugavel,
Thanks for your reply.
The schematic is below. The VM voltage is set to 20V, the frequency of PWM is 100KHz and the TEC is about 2ohms. The inductance in the LC filter is 47uH, the capacitance is 22uF.
Best,
Liu
Hi Liu,
Thanks for the additional info. The LC filter has a low pass transition at 5 kHz which is good and filters the 100 kHz PWM effectively. Was J9 pins1-2 shorted during the waveform capture? If not try capturing the waveforms with 1-2 shorted, no current regulation. The duty cycle of the PWM will set the TEC current.
See below scope capture done with an DRV8262EVM connected to a TEC load. with similar LC filter in the schematic you shared. The yellow trace is on OUTx side of the DRV8262, the green trace is the voltage waveform after the inductor and on one of the capacitors, the blue trace is the TEC current, 100 kHz PWM 50 % duty cycle. Current regulation was disabled. There was no abnormalities observed with the waveforms.
Based on the schematic you shared, the device is configured as Single H-Bridge in PWM control mode. In this mode below control sequence must be followed. While the TEC is not driven both IN1 and IN2 must be logic high. For driving with PWM input depending on the polarity one of the inputs must be high and the other input must be PWM input. The TEC load would be active during PWM off time. This is the control logic. Please verify and make sure you are following this control logic. Please also capture VM voltage and check if there are any abnormalities with it.
one in IN1 and IN2 has a continuous input high and the other input PWM.
I assume this was what you meant by this. We do not see any abnormal output while replicating your setup with a DRV8262EVM. Thank you.
Regards, Murugavel
Hi Murugavel,
Thanks for your reply. The output returns to normal when J9 is shorted.
Best,
Liu
