Other Parts Discussed in Thread: UCC28740,
Tool/software:
Dear TI Engineers,
I'm currently designing a flyback converter using the UCC28740 controller, referencing the PMP41031 design, with the following specifications:
Input: 300-1500V DC
Output: Dual-channel 24V/12A
During the debugging process, I have encountered the following questions about the PMP41031 schematic and implementation:
1. VS Pin Circuit (R21, R48, D18, D19)
a) What is the purpose of diodes D18 and D19? Are they intended to suppress ground noise interference at the VS pin?
b) Why are D18 and D19 connected to the midpoint of R21/R48? What design objective does this achieve?
2. Transformer T12 and Diodes D5/D7 (TI-D5-D7-VDD Circuit)
a) Is the purpose of D5 and D7 to allow energy from the transformer to recirculate to VDD when Q3 is turned off?
b) How should reverse voltage issues caused by this configuration be mitigated? Could connecting D5/D7 directly to GND (instead of VDD) resolve this?
3. Transformer Design & CS Protection Triggering
Current transformer parameters:
LP = 280μH, Np = 33, Ns = 4, Na = 3
Issue: At 350V input, a secondary load of 24V/0.5A triggers CS protection (Rcs = 0.06Ω) due to excessive primary peak current.
a) What are potential root causes for this premature protection?
b) What corrective measures would you recommend (e.g., transformer optimization, CS network adjustments)?
Your expert guidance would be greatly appreciated. Please reply to: 1024242013@tju.edu.cn
Thank you for your support!
Best regards
