Light load losses evaluation

Here follows a number of relationships useful to evaluate the major losses in a lightly loaded flyback.

Table C1 - Start-up circuits of fig. 7a and 7b

Maximum Wake-up time

Circuit a)

1.41

2

3

Circuit b)

0.45

1

2

⋅

2

⋅

2

µA

Table C2 - MOSFET losses (refer to fig. 10)

Turn-on losses

Turn-off losses

Equivalent Drain Capacitance

≈

1

2

2

≈

2

6

≈

2

4

Table C3. Clamp network losses (refer to fig. 12)

RCD

Zener or Transil

LCD

≈

2

R

≈ 0

≈ 0

AN1049 APPLICATION NOTE

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