LCD Backlight Inverter Drive IC# Technical Documentation: FAN7316 Ballast Control IC
Manufacturer : FAIRCHILD (now part of ON Semiconductor)
Component : FAN7316
Description : Advanced Half-Bridge Resonant Controller for Electronic Ballasts and SMPS
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## 1. Application Scenarios (Approx. 45% of Content)
### Typical Use Cases
The FAN7316 is specifically designed as a high-performance resonant controller for electronic ballasts driving Cold Cathode Fluorescent Lamps (CCFLs) and Hot Cathode Fluorescent Lamps (HCFLs). Its primary function is to regulate and control the half-bridge inverter stage that powers fluorescent lighting systems.
* CCFL Backlight Inverters : In LCD televisions, monitors, and automotive displays, the FAN7316 provides the precise frequency and voltage control needed to drive the series-resonant circuit that illuminates CCFL tubes. It ensures stable lamp current, essential for uniform screen brightness and long lamp life.
* HCFL Electronic Ballasts : For general lighting applications (e.g., office, industrial, retail lighting), it controls the resonant inverter that drives standard fluorescent tubes (T5, T8, T12). It manages the preheat, ignition, and run phases critical for reliable lamp starting and efficient operation.
* Low-Power SMPS : While optimized for ballasts, its architecture allows use in isolated or non-isolated switch-mode power supplies (SMPS) requiring resonant or fixed-frequency half-bridge topologies, typically in the sub-250W range.
### Industry Applications
* Consumer Electronics : A cornerstone component in the power supply/inverter boards of LCD TVs, desktop monitors, and all-in-one PCs.
* General Lighting : Embedded in the electronic ballasts of commercial and industrial fluorescent light fixtures.
* Automotive Displays : Used in the inverter modules for center console displays and instrument clusters (for designs requiring CCFL backlighting).
* Industrial Controls : Provides power for signage and specialized lighting equipment.
### Practical Advantages and Limitations
Advantages:
* Integrated Control Logic : Combines preheat, ignition (frequency sweep), and run-mode control in a single IC, simplifying design.
* Soft-Switching Operation : Resonant zero-voltage switching (ZVS) minimizes switching losses in the MOSFETs, improving efficiency and reducing EMI.
* Robust Protection Suite : Includes features like open-lamp protection, over-current protection (OCP), and programmable preheat/run control, enhancing system reliability.
* Adjustable Parameters : Key timings (preheat, dead-time) and frequencies are set via external resistors/capacitors, offering design flexibility.
* Low Start-up Current : Reduces stress on the auxiliary power supply.
Limitations:
* Technology Specificity : Primarily optimized for fluorescent lamp ballasts. For driving LEDs, a dedicated LED driver IC would be more efficient and feature-rich.
* Frequency Jitter : Lacks built-in frequency jitter for EMI spread spectrum, which may require additional filtering in noise-sensitive applications.
* Discontinued Status : As FAIRCHILD was acquired and CCFL technology is largely superseded by LED, the FAN7316 is considered a legacy part. New designs should evaluate modern alternatives, though it remains relevant for maintenance and existing product lines.
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## 2. Design Considerations (Approx. 35% of Content)
### Common Design Pitfalls and Solutions
1. Pitfall: Unreliable Lamp Ignition
* Cause : Incorrect setting of the preheat time (`t_PH`) or the frequency sweep range (from `f_PH` to `f_IGN`). Too short a preheat or too high an ignition frequency prevents sufficient voltage build-up
