AN1484 - APPLICATION NOTE

5/11

The position of the auxiliary winding on top gives

the following benefits:

- better coupling of primary and secondary

windings thus lower leakage inductance and

energy stored in the ringing circuit

- no coupling between primary / secondary leakage

inductance and auxiliary windings

- less capacitive coupling between primary and

auxiliary windings

Figure 4a and Figure 4b show the drain voltage of

the VIPer12 (Trace 1) and Vdd voltage before R2

(Trace 2) at full load and in short circuit with the

auxiliary in sandwich (1) and on top (2) of the

windings.

Figure 4a1: At full Load at 100V (Sandwich)

Figure 4a2: At full Load at 100V (On Top)

Figure 4b1: In Short Circuit at 100V (Sandwich)

Figure 4b2: In Short Circuit at 100V (On Top)

The VIPer12A auxiliary supply shows the following

voltage on Vdd pin:

Table 4: VIPer12A Vdd with an optimized

transformer

Conditions

100V

380V

Standby

12V

11V

Load 6V/100mA

18V

18V

Load 6V/600mA

20V

19.5V

Short Circuit

Hiccup

Hiccup