原标题：ST L6520 14W或25W T5微型镇流器参考设计方案

　　ST公司的L6520是一款可以驱动BJT管和MOSFET管的高集成镇流控制器，按照重要安全性和最低功耗规则，在确保最大可靠性的同时提供必须的保护功能。由于可以采用BJT开关管，在性能不变的情况下极大地减少了系统的成本。该芯片可工作在没有PFC,被动PFC和主动PFC三种情况下，提供了更多的灵活性。本文首先介绍芯片的简介、特性、内部框图及应用领域，并给出相应设计方案的设计原理图、元器件列表及制板图。

　　The L6520 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).

　　L6520主要特性：

　　■ Half bridge circuit able to drive both BJT and MOSFET transistors

　　■ Very accurate oscillator precision in wide operating temperature range

　　■ BJTs’ storage time compensation

　　■ Preheated start and instant start

　　■ Hard switching protection

　　■ Overcurrent / voltage protection

　　■ Choke saturation control

　　■ End-of-life protection

　　■ Programmable without capacitors

　　L6520应用：

　　■ Electronic ballasts (TL, Industrial CFL)

　　■ Integrated CFLs

　　图1. L6520内部方框图

　　L6520方案介绍：

　　The L6520 low voltage ballast controller is intended to drive extremely compact applications based on either MOSFETs or bipolar transistors.

　　The EVAL6520-1421 is capable of driving either a T5-14W-HE or T5-21W-HE lamp, with the same miniatured (16 mm wide) ballast.

　　The selection of both the resonant components and the bipolar transistors, together with the design of the suitable pulse transformer, and IC power supply is also described.

　　L6520方案特性：

　　■ Drives either T5-14W-HE or T5-21W-HE lamps

　　■ Standard form factor (19 mm x 120 mm)

　　■ Compliance with IEC61347-2-3, IEC61000-2-3 and EN55022 Class-C

　　L6520方案原理图：

　　图2. L6520方案原理图

　　L6520方案材料清单：

　　制板图：