AN3119 datasheet(16/32 Pages) STMICROELECTRONICS

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Test results and significant waveforms

AN3119

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Doc ID 16849 Rev 2

voltage has a significant deviation from the nominal value. The circuit has the same behavior

in the case of mains surge at any input voltage, and it is not affected even if the input mains

surge happens at any point of the input sinewave.

In Figure 23 the circuit behavior in the case of mains dip is shown; as previously described,

the internal circuitry has detected the decreasing of the mains voltage and it has activated

the CFF internal fast discharge. As seen, in this case the output voltage changes but in a few

mains cycles it comes back to the nominal value. The situation is different if we compare it

with the performance of a controller without the VFF function. In Figure 22 the behavior of a

PFC using the L6562A and delivering similar output power is shown; in the case of a mains

dip from 140 Vac to 90 Vac the output voltage variation is not very different but the output

voltage requires a longer time to restore the original value. In tests with a wider voltage

variation (e.g. 265 Vac to 90 Vac) the output voltage variation of a PFC without the voltage

feed-forward fast discharging is far more emphasized.

Figure 20.

L6562A input mains surge 90 Vac to

140 Vac - no VFF input

Figure 21.

EVL6563S-250W TM PFC: input

mains surge 90 Vac to 140 Vac

CH1: Vout, CH2: MULT (pin #3), CH4: I_AC

CH1: Vout, CH3: VFF (pin #5), CH2: MULT (pin #3)

CH4: I_AC

Figure 22.

L6562A: input mains dip 140 Vac to

90 Vac - no VFF input

Figure 23.

EVL6563S-250W TM PFC: input

mains dip 140 Vac to 90 Vac

CH1: Vout, CH2: MULT (pin #3), CH4: I_AC

CH1: Vout, CH2: MULT (pin #3), CH2: VFF (pin #5)

CH4: I_AC

AN3119 Datasheet(PDF) 16 Page - STMicroelectronics