Proper Design of Snubbers and Clamps

Note that cleverly designed commercial Rybacks use an RCD clamp instead of a zener clamp. This can reduce dissipation in the clamp by around 20% at low line (where it is 

Measure the in-circuit primary-side leakage inductance Llk in Henries. 

Measure the peak of the Drain current waveform Ium at rated power at 90VAC. 

Tentatively select one of the three clamp capacitor values 4.7nF, lOnF, or 22nF (prefer the 22nF usually). 

Draw a vertical line from the calculated Elk to intersect with the solid line curve corresponding to the selected C and K. 

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