AN993 Datasheet, PDF (12/27 Pages) STMicroelectronics – Electronic ballast with PFC using L6574 and L6561

Device block description
AN993
3.2
Control section
The L6574 has two control functions, EN1 and EN2. Both functions are active high. To fully
understand how these functions work, refer to Figure 9 and Figure 10.
● EN1 (latched enable) is dedicated to stopping all device functions and is usually
activated when a strong fault is detected (for example, when the lamp is disconnected).
This status can be cancelled in two different ways: either by reducing the supply voltage
below its minimum threshold, or by activating the second control pin EN2 (EN2
overrides EN1). When the device restarts, the start-up sequence is reactivated.
● EN2 (repeating startup) is dedicated to restarting the preheating and ignition
procedure; it is normally activated when the application fails to ignite the lamp. When
EN2 is activated the starting procedure restarts. The L6574 operates to the maximum
frequency all the while that EN2 remains active.
Figure 9. Controls timing diagram
VSupply
LVG
HVG
EN1
EN2
Latched enable
Forced restart
Time
AM01318v1
12/27
Doc ID 5656 Rev 10