Protection features

AN3290

22/34

Doc ID 18038 Rev 1

5.2

Auxiliary winding disconnection (brownout)

At any switching cycle, the current sourced from the ZCD pin during turn-on is sensed and

compared with an internal reference, IZCDON (50 µA).

When the auxiliary winding is accidentally disconnected, no more current is sourced from

the pin and the IC enters brownout, therefore, immediately stopping switching. After restart,

present, the protection is maintained active.

This feature has been tested and the results are shown in Figure 24.

Figure 24.

Brownout protection activation