Test results and significant waveforms

AN3065

18/33

Doc ID 16279 Rev 2

Comparing

Figure 22 and 23 we can see that the input current of the latter has a better

benefits of the new voltage feed-forward circuit integrated in the L6563S. Allowing a fast

low THD and high PF at same time as confirmed by the measurements below.

Another function integrated in the L6563S is the brownout protection, which is basically a

non-latched shutdown function that must be activated when a mains undervoltage condition

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

due to an excess of RMS current. Brownout can also occur because the PFC pre-regulator

works in 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 brownout.

Brownout function is done through sensing of the input mains by an internal comparator

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

L6563S will start or stop the operation can be adjusted by modifying that divider ratio. For

additional information please see [

2 in Section 8: References].

Figure 22.

L6563: input current at 100 Vac, 50

Figure 23.

EVL6563S-100W TM PFC: input

CH2: MULT (pin #3)

CH4: I_AC

CH2: MULT (pin #3)

CH4: I_AC