T
treez
Guest
Hello,
we are designing a flyback (35W) for vin = 85-265VAC.
Vout = 25V
F(sw) = 70KHz.
We wish to be in DCM across the mains range, and also be dcm across the range.
This means that at the peak of high mains (374VDC) the on time of the fet is just 1us.
is this too short a time for a fet to be on?
If not, what woudl be the limit of fet on time?......would 300ns be ok?
I thought that if the switching transition times become a significant portion of the on time then control problems start to occur and oscillations are seen in the output voltage?
we are designing a flyback (35W) for vin = 85-265VAC.
Vout = 25V
F(sw) = 70KHz.
We wish to be in DCM across the mains range, and also be dcm across the range.
This means that at the peak of high mains (374VDC) the on time of the fet is just 1us.
is this too short a time for a fet to be on?
If not, what woudl be the limit of fet on time?......would 300ns be ok?
I thought that if the switching transition times become a significant portion of the on time then control problems start to occur and oscillations are seen in the output voltage?