AN3339 datasheet(16/44 Pages) STMICROELECTRONICS

16 / 44 page

Functional check

AN3339

16/44

Doc ID 18449 Rev 2

In Figure 21 and 22 a short-circuit event has been captured. In this situation the VIPER27LN

works in hiccup mode, protecting the standby converter power components against

overheating. At short detection, the device internal circuitry stops the auxiliary converter

operation until the VDD has dropped down to VDD_RESTART.

Then the internal current source charging the VDD capacitor is activated until the VDDon has

been reached, when the VIPER27LN restarts switching. Hiccup cycles are repeated as long

as the short-circuit condition exists. The IC resumes normal operation only at short-circuit

removal.

Figure 17.

Standby supply OVP at 115 Vac - 60

Hz, full load

Figure 18.

Standby supply OVP at 230 Vac - 50

Hz, full load

CH2: 5 V stby

CH1: DRAIN (pin #8)

CH3: CONT (pin #3)

CH4: FB (pin #4)

CH2: VDD (pin #2)

CH1: DRAIN (pin #8)

CH3: 5 V stby

Figure 19.

Standby supply OVP at 115 Vac - 60

Hz, 0.5 A load

Figure 20.

Standby supply OVP at 115 Vac, 0.5

A load - detail

CH2: 5 V stby

CH1: DRAIN (pin #8)

CH3: CONT (pin #3)

CH4: FB (pin #4)

CH2: 5 V stby

CH1: DRAIN (pin #8)

CH3: CONT (pin #3)

CH4: FB (pin #4)

AN3339 Datasheet(PDF) 16 Page - STMicroelectronics