L6572

Description

Doc ID 023882 Rev 1

3/22

1

Description

The L6572 is a high voltage half-bridge driver for current regulation, quasi-self-oscillating

ballast.

It contains all functions that are needed to preheat the filaments, to ignite and to operate a

fluorescent lamp.

During normal operation of the lamp, the ballast operates either with the nominal or with a

reduced resonant current which results in a nominal or a reduced light output of the lamp.

A change between those two possible light outputs of the lamp is triggered by disconnecting

the mains voltage for a short time (two-step dimming). The filaments are preheated before

the lamp is re-ignited after every disconnection of the mains voltage.

A powerboost function is included to accelerate the startup behavior of the fluorescent lamp

when the junction temperature is below a defined temperature.

An undervoltage lockout is active while loading the blocking capacitor via the startup resistor

as long as the supply voltage VS is below a defined value. The bootstrap capacitor is loaded

before the high-side transistor is switched on the first time to start the oscillation of the

ballast.

The output drivers are designed to drive external N-channel power MOSFET and IGBT

(max. input capacity Cinput ≤1 nF) without any additional gate resistor.

A constant deadtime for both switches can be programmed with one external resistor.

The rated resonant current for the nominal lamp operation with nominal light output, the

dimmed operation with reduced light output and the preheating phase is defined by three

external resistors considering the shunt resistance.

The ratio XPB between the nominal rated resonant current during normal operation and the

powerboost phase is fixed internally. The time lapse is given by an internally fixed number of

load/unload-cycles of an internal capacitor.

An absolute time base, used to regulate periods and intervals, is given by the duration of a

load/unload-cycle of the internal capacitor with a load current that is defined with an external

resistor.