AN993

Description of the demonstration application

Doc ID 5656 Rev 10

19/27

4.5

Start-up and supply

The start-up procedure is very important in an application that contains two different

sections.

The ballast section starts before the PFC, avoiding any extra voltage at the output of the

PFC section, and so the L6561 dynamic OVP activation (see AN966). This behavior is

guaranteed under all conditions because the VS turn-on threshold of the L6574 is lower

than that of the L6561/2.

as to ensure the "before start-up current" of both the L6561 and L6574.

When the ballast section is running, the charge pump (C11, R14, R17, D3 and DZ1)

enables supply to both devices. R17 and C10 enable reduction of noise at VCC.

Figure 15.

Current feedback loop

Figure 16.

Cpre waveform (Ch1) and amplifier output (Ch2)

AM01323v1

Q3

STP4NB50

RS_2

0.68

C9 8.2nF

R16 100K

R18 100K

D4

1N4148

R19 10k

65

4

7+

RIGN

-

AM01324v1