Hello,
The Webench tool will give you a working schematic and instructions no how to build the transformer. However, these primary side regulated flyback converters are susceptible to aux winding noise.
I would study VDD, CS, VSENSE and Vout to…
Hello,
If the UCC28704 is shutting down you noise immunity test maybe accidently triggering and over voltage protection (OVP) fault, and input under voltage (UVLO) fault or an over current fault.
I have attached a draft of an application note that…
Hello,
Slide 10 you might want to look more into the first time VDD reaches VDDon. There are most likely three gate driver and CS pulses you are not seeing doing to scope resolution. The device may not be starting up because input under voltage lockout…
Part Number: UCC28740 Tool/software:
Dear Experts,
At present, we are designing a flyback power supply using UCC28740. The design requirement is to input 300VDC can start, but during actual testing, we found that it cannot start at this voltage. The…
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Hello,
Not sure why connecting the HV9961 to the output or your flyback would cause regulation issues. You might want to study VDD, Aux and CS to see if you are turning off do to a fault.
The attached application note explains how the fault sensing…
Hello,
Your waveform looks like your design is operating deep into DCM and may be running at lighter loads. If you are operating at 55 kHz at this load to get the design to work at higher frequency you may just need to increase the load.
The waveform…
