Leakage inductance affects forward converter more than flyback?

[Flyback]

The LTspice simulation attached shows a 2-transistor-forward converter , both with, and without leakage.
Also shown is a flyback converter, again, both with, and without leakage.
The 2-transistor-forward converter is far more affected by leakage than the flyback. Even a slight amount of leakage in the forward converter means it must significantly increase its duty cycle to maintain its output.
Why is this? Why is the forward more affected by leakage?

 

[ronsimpson]

In the forward mode it is taking about 1uS for the leakage inductance to reset. This eats up 1uS of your on time. Look at primary to secondary delay.

In the forward mode you have the primary inductance 10X that of the flyback mode. There fore the flyback mode model will have 1/10 the leakage inductance delay.

There might be another reason for a 2:1 difference but it will take some time for me to think about it. 5:30 am and my head is not working yet.

edited-----
.ic V(VOUT3) = 50V
Now I see why the output starts out high.

There seems to be a soft start function. It must be the large cap on the Vref pin.

 

[Flyback]

yes I agree the primary inductance is much more in the forward converter than the flyback...but this is always the case....As you know, forward converters always have bigger primary inductances (than the same smps done with a flyback)_ because they tend not to use gapped cores, and also, the primary inductance must be large in order to keep the magnetising current down. In a flyback, magnetising current is the be all and end all....in a forward converter, magnetising current is not actually wanted at all.

I mean, you rightly say that the forward is more affected by leakage than the flyback, and that this is because the forward has a higher primary inductance.....but I don't see it in the design guidelines of forward converters, saying to make their primary inductances as small as possible in order to reduce the problem shown here of high leakage inductance?

So can we make the formal declaration here, that "forward converters are more detrimentally affected by leakage inductance than flyback converters?"

 

[crutschow]

Can you add an RC snubber circuit in place of the diodes to reduce the time it takes to dissipate the leakage inductance energy?

 

[Flyback]

yes, could do , but don't want the dissipation.