Here is my flyback converter design.
Iout: 1A (max)
Desired efficiency: 85%
S2: 5T (aux)
I determined 15uH for Lp
Ls1: 15uH and Ls2: 8uH
SMPS IC: NCP1252-A (max duty cycle: 48%) datasheet
Mosfet: STP75NF20 datasheet
When the transformer is not connected at the circuit, PWM signal at the mosfet gate is CLEAR and PROPER.
But, the transformer is connected at the circuit, gate signal form is being broken.
I thougth that the SMPS IC could not be able to generate the gate signal when directly connected with mosfet. So, I used a mosfet driver. But, the result is the same. Frustration! So, my efficiency remains low (25%)
Why is the gate signal being broken?
I measured leakage inductance as 5uH. Does the leakage inductance cause a problem about PWM?