DocID028766 Rev 1

19/24

STCH02

Application information

24

voltage. While it is disabled, however, no energy is coming from the self-supply circuit; and

a low frequency intermittent operation (hiccup mode operation).

Figure 11. OVP function: timing diagram

3.11

Soft-start and starter block

The soft start feature is automatically implemented by the constant current block, as the

primary peak current will be limited from the voltage on the internal CC block capacitor.

During the start-up, as the output voltage is zero, the IC will start in the CC mode with no

high peak current operations. In this way the voltage on the output capacitor will increase

slowly and the soft-start feature will be ensured.

3.12

Hiccup mode OCP

The device is also protected against the short-circuit of the secondary rectifier, short-circuit

on the secondary winding or a hard-saturated flyback transformer. A comparator monitors

To distinguish an actual malfunction from a disturbance (e.g.: induced during ESD tests), the

first time the comparator is tripped the protection circuit enters a “warning state”. If in the

subsequent switching cycle the comparator is not tripped, a temporary disturbance is

assumed and the protection logic will be reset in its idle state; if the comparator will be

tripped again a real malfunction is assumed and the device will be stopped.

voltage. While it is disabled, however, no energy is coming from the self-supply circuit;