Application:DC/DC Converter
Design Parameter:
Input Voltage:200~430V
Output Voltage:9~16V
Maximal Output Current :160A
Transformer Ratio, Primary:Secondary: 11: 1:1
Switching Frequency:100kHz
Topology:
Issue Description:
The ripple Voltage of output is too high(Vpp=1V),to exclude the close-loop affection,customer to make UCC28950 run in open loop by clamp the voltage in COMP to 2V。but, the Vpp voltage is still too high,below is the comp voltage and primary side voltage:
Yellow:Vout Green:COMP Blue:Primary side voltage
The waveform shows that there is a jitter under 500kHz frequency, there is no jitter in COMP voltage,
above waveform shows that the duty cycle is not stable
Above waveform test condition:
Vin=300V
Vout=10.9V
Iout=120A
below is the UCC28950 schematic