Other Parts Discussed in Thread: UCC21521
Hi,
customer use UCC28951 as phase shift full bridge controller and use UCC21521C as SiC driver, input voltage is 500VDC, output is 27.5V /3kW。
the circuit is refer to datasheet as below show.
The question is that the output will has large ripple when the output power is higher than 1.3kW both in voltage mode and current mode. below is the test waveform of QD.
The yellow is UCC28951 output signal, the green is UCC21521 output signal and the blue is current of inductor.
you can see UCC28951 lost a pulse during the working, which lead to the large ripple on output. if the output voltage higher than 32V, the load will get in to OVP mode, the output voltage will return back to 27.5V.
When the output power is lower than 1kW, this circuit can work properly.
is it may caused by the loop response? could you help give some ideas about it.
many thanks.
