UCC28600: Consultation on the Use of UCC28600

You can set your OVP point far away from normal operation by setting the Rovp1 and Rovp2 resistor. You cannot disable the protection completely.

I am curious why you want to disable the OVP feature. Can you share more background? Maybe there are better ways to address your concern.

Thank you for your reply.

We are using the TI UCC28600 switching power supply solution on a three-phase driver board. The power supply operates normally in standby mode, but there is a probability of resetting when the compressor enters the open-loop driving phase, particularly under high-voltage conditions.

After adding a 0.1μF filter capacitor to the OVP pin, the switching power supply no longer resets. Could there be any risks associated with adding a 0.1μF capacitor to the OVP pin? If this modification is implemented, are there other considerations or test points we should evaluate?

What is the implication when the compressor enters the open-loop phase? 

Adding 0.1uF cap on OVP pin may invalidate the OVP function as the cap acts like a filter. But since you don't need OVP feature, I assume it is ok.

Thank you for your response.
Compressor open-loop refers to a control method for the compressor. During compressor bridge startup, V/F (Voltage/Frequency) control is used to deliver a higher current for forced startup. After startup, the compressor switches to closed-loop control (with reduced current). The GND of the switching power supply shares the same ground as the IGBT in the compressor's inverter PIM through the large electrolytic capacitor. Using V/F control during the open-loop phase implies higher currents, which may cause interference from the compressor side to affect the voltage sampling at the UCC28600 OVP pin, triggering false overvoltage protection.

In actual testing, the voltage waveform at the OVP pin was observed to be proportional to the VDS waveform. After adding a 0.1µF capacitor, combined with the R_OVP1 and R_OVP2 resistors, an RC filter is formed to suppress ringing. This lowers the OVP voltage and eliminates ringing, effectively disabling the input overvoltage and load overvoltage protection functions. However, reviewing the datasheet, this pin also serves as the QR (Quasi-Resonant) control pin. Adding a 0.1µF capacitor to the OVP pin raises questions:
1. Does this affect QR functionality?
2. Could it impact the stability of the switching power supply?
3. Might the power supply lock into a fixed operating mode or fixed frequency?

0.1uF is definitely not a small cap you can ignore and may impact the QR detection like timing. I suggest to measure the waveform before and after the 0.1uF cap to compare. 

I don't think it will lock the operating freq to fixed value though.

Best,

Ning

Thank you for your reply.

Today I tested the voltage waveform of the VCC pin. The test points are as follows:

Does the ringing present on the VCC pin when the MOSFET is turned on indeed cause false triggering of the OVP (Over-Voltage Protection) pin?
Would adding an RC circuit to the auxiliary winding diode and inserting a resistor in series with the RCD snubber circuit effectively eliminate this ringing issue on the VCC pin?