AN3118

Test results and significant waveforms

Doc ID 16847 Rev 2

17/31

It is also possible to see, comparing Figure 24 and 25, that the input current of the latter has

a better shape and the 3rd harmonic current distortion is not noticeable; this demonstrates

the benefits of the new voltage feed-forward circuit integrated in the L6563H, allowing a fast

constant also provides very low THD and high PF at the same time, as confirmed by the

measurements in Figure 24 and 25:

Another function integrated in the L6563H is brown-out protection, which is basically a not-

latched shutdown function that must be activated when a mains under voltage condition is

detected. This abnormal condition may cause overheating of the primary power section due

to an excess of RMS current. Brown-out can also cause the PFC pre-regulator to work

open-loop and this could be dangerous to the PFC stage itself and the downstream

converter, should the input voltage return abruptly to its rated value. Another problem is the

spurious restarts that may occur during converter power down and that cause the output

voltage of the converter not to decay to zero monotonically. For these reasons it is usually

preferable to shutdown the device in case of brown-out.

Brown-out function is done by sensing the input mains through an internal comparator

voltage signal proportional to the input mains. The enable and disable thresholds at which

the L6563H starts or stops the operation can be adjusted by modifying that divider ratio. For

additional information please see [2].

Figure 24.

L6563 input current at 100 Vac - 50

Figure 25.

EVL6563H-250 W TM PFC input

RFF=1 M

Ω

THD= 4.36 %, 3rd harmonic=94.6 mA

CH2: MULT (pin #3)

CH4: I_AC

THD= 2.94 %, 3rd harmonic=30.5 mA

CH2: MULT (pin #3)

CH4: I_AC