The L6572 is a high voltage half-bridge driver for current regulating, quasi-self-excited oscillating ballasts. It contains all the functions necessary for preheating the filament, igniting and operating the fluorescent lamp.
During normal operation of the lamp, the ballast operates with a nominal or reduced resonant current, resulting in a nominal or reduced light output of the lamp.
A change between these two possible light outputs of the lamp can be triggered by a short interruption of the supply voltage (two-step light). After each disconnection of the supply voltage, the filament is preheated before reigniting.
When the junction temperature is below the specified temperature, the power enhancement function is included to accelerate the starting behavior of the fluorescent lamp.
As long as the supply voltage VS is below the specified value, undervoltage locking is activated when the locking capacitor is loaded by starting the resistor. The bootstrap capacitor is loaded before first switching on the high voltage side transistor to start the ballast oscillation.
The output driver is designed to drive external N-channel power MOSFETs and IGBTs (maximum input capacity) ≤ 1 nF) without any additional gate resistors.
The constant dead-time of the two switches can be programmed through an external resistor.
The rated resonant current is defined by three external resistors that take shunt resistance into account for nominal lamp operation (with nominal light output), dimming operation (with reduced light output), and the warm-up phase.
The ratio XPB between the nominal rated resonant current and the power lift stage during normal operation is internally fixed. The time interval is given by a fixed number of load/unload cycles inside the internal capacitor.
The absolute time base for regulating periods and intervals is given by the duration of the load/unload cycle of the internal capacitor, and the load current is defined by the external resistor.
All functions
600V half-bridge driver
Integrated bootstrap diode
Fault protection logic
Programmable dead time
Programmable preheat start
Two - step light with programmable dimming current
Thermal power lifting
Closed loop control operation