AN3339 datasheet(17/44 Pages) STMICROELECTRONICS

17 / 44 page

AN3339

Functional check

Doc ID 18449 Rev 2

17/44

In Figure 23 and 24 the transitions from full load to no load and vice versa at maximum input

voltage have been checked. The most critical situation is when the PFC stage is operating,

as during no load operation the burst pulses have the lowest repetition rate, due to higher

input voltage, and the VDD might drop below VDDoff (8 V typ.), causing the controller to shut

down. As seen in the figures, both transitions are clean and there isn't any output voltage or

VDD dip.

Figure 21.

Standby supply o/p short-circuit at

230 Vac - 50 Hz, full load

Figure 22.

Standby supply o/p short-circuit at

230 Vac, full load - detail

CH2: 5 V stby

CH1: DRAIN (pin #8)

CH3: VDD (pin #2)

CH4: FB (pin #4)

CH2: 5 V stby

CH1: DRAIN (pin #8)

CH3: VDD (pin #2)

CH4: FB (pin #4)

Figure 23.

Standby supply dynamic load at

115 Vac - 60 Hz - PFC off

Figure 24.

Standby supply dynamic load at

115 Vac - 60 Hz - PFC on

CH2: VDD (pin #2)

CH1: FB (pin #4)

CH3: 5 V stby

CH4: 5 V stby current

CH2: VDD (pin #2)

CH1: FB (pin #4)

CH3: 5 V stby

CH4: 5 V stby current

AN3339 Datasheet(PDF) 17 Page - STMicroelectronics