Datasheet

Functional check AN3329
16/47 Doc ID 18376 Rev 1
and switching starts again. This protection and restart sequence lasts as long as the OVP
condition is removed. It is important to highlight that the Viper27LN OVP protection, thanks
to the internal logic, ensures a stable OVP intervention point, independent of the output
load, even if the voltage sensing is done on auxiliary winding at primary side. It can be
noted, by comparing Figure 21 to Figure 23 which report some OVP intervention with
different loads and input voltage conditions, that the maximum output voltage peak has a
negligible variation.
Figure 24 shows, in detail, the OVP intervention at 115 Vac. In Figure 25 a short-circuit
event on the standby supply output has been captured. In this situation the Viper27LN
enters a safe hiccup mode, providing protection against overheating of the auxiliary
converter power components.
Figure 23. Standby supply OVP at 115 Vac -
60 Hz - PFC on - 1 A
Figure 24. Standby supply OVP at 115 Vac -
60 Hz - PFC on - 1 A
CH1: DRAIN (pin #8)
CH2: +5 V standby
CH3: CONT (pin #3)
CH4: FB (pin #4)
CH1: DRAIN (pin #8)
CH2: 5 V standby
CH3: CONT (pin #3)
CH4: FB (pin #4)
Figure 25. Standby supply output short-circuit
at 230 Vac - 50 Hz, full load
Figure 26. Standby supply output short-circuit
at 230 Vac - 50 Hz, full load - detail
CH1: DRAIN (pin #8)
CH2: +5 V standby
CH3: V
DD
(pin #2)
CH4: FB (pin #4)
CH1: DRAIN (pin #8)
CH2: 5 V standby
CH3: V
DD
(pin #2)
CH4: FB (pin #4)