L6520, L6521 Description
Doc ID 16998 Rev 3 3/19
1 Description
The L6520/1 is the first highly integrated ballast controller in the market able to drive both
BJTs and MOSFETs, providing all the necessary protections to ensure the maximum
reliability of the application in compliance with major safety and power consumption
regulations.
By adopting BJTs switches in the application, the IC allows to replace more expensive
MOSFETs, strongly reducing the system cost without compromises.
The IC represents also the best and cost effective solution to replace self oscillating
solutions when the key requirement is the reliability of the ballast. The benefits are an
increased MTBF and a reduction of the costs due to the return from the field.
The higher level of flexibility and integration provided allows the possibility to quickly design
ballast with any kind of lamp topology/size/power, without limitations. Depending on the
power of the lamp, the IC can work without PFC, with passive PFC or with active PFC. In the
latter case the L6562A from STMicroelectronics is the suggested IC for the most cost
effective solution.
The IC is fully programmable using only resistors and offers over current protections, choke
saturation control and hard switching protection thanks to a sophisticated current control
circuit (CCC). In ignition, the CCC limits both the maximum lamp voltage in case of old or
broken lamp, and also the lamp current in case of inductor saturation.
When the IC is driving bipolar transistors, a variable dead time ensures the correct base
discharge time avoiding cross conduction phenomena. Moreover, the IC prevents the failure
due to the lamp's end of life (EOL).
