I am using sepic topology.
I am trying to switch the output voltage from 30V to 15V, using mosfet. But i as add the feedback resistor. The Vfb starts to increase. Once it reaches above 1.4V the Pgood goes zero and SS is grounded. OVP/PGOOD forces a Soft Start after about a 4ms delay, the switching is stopped.
- When we switch from 30V to 15V, need to change the feedback from 1.76K to 3.46K
- During this transition as output voltage is at 30V, Vfb reaches to 1.9V
- As Vfb crosses the VUVTH (1.45V) and (Vref of 0.99-1.01V), Pgood become zero
- SS goes to zero and switching is stopped
- Output and feedback voltage starts to fall
- Once Vfb fall below 0.9V, SS start to rise again
- Switching starts after 8ms
- Output reaches to 15V after 14ms
I need the transition to be faster and delay less than 1-2 ms.
I have the verified the same using the TI pspice simulation, just added a MOSFET to change the feedback resistor. (LM5158x-Q1 PSpice Transient Model (Encrypted))
Any possible solution or way around to reduce delay.