Fairchild FL7930和FAN7621S 150W LED街灯照明设计方案

发布时间：2011-7-25 14:07 发布者：Liming

关键词： Fairchild , FAN7621S , FL7930 , LED街灯照明

Fairchild公司的150W LED街灯照明设计方案是采用FL7930B和FAN7621S.而FL7930是用于低到高功率的有源功率因素修正(PFC)控制器,工作在临界导通模式(CRM),提供过压,开路反馈,过流,输入电压瞬态检测和欠压锁定等保护. FAN7621S是用于高效谐振转换器的脉冲频率调制控制器,包括高边栅极驱动电路,精密的电流控制振荡器,限频电路,软起动和内置保护功能.本文介绍了FL7930主要特性, FL7930B和FL7930C方框图, 应用电路图以及采用FL7930B和FAN7621S的150W LED街灯照明设计方案电路图和材料清单.

The FL7930 is an active Power Factor Correction (PFC) controller for low-to high-power lumens applications that operate in Critical Conduction Mode (CRM). It uses a voltage-mode PWM that compares an internal ramp signal with the error amplifier output to generate a MOSFET turn-off signal. Because the voltage-mode CRM PFC controller does not need rectified AC line voltage information, it saves the power loss of an input voltage sensing network necessary for a current-mode CRM PFC controller.

FL7930 provides over-voltage, open-feedback, overcurrent, input-voltage-absent detection, and undervoltage lockout protections. The FL7930 can be disabled if the INV pin voltage is lower than 0.45V and the operating current decreases to a very low level.Using a new variable on-time control method, THD is lower than the conventional CRM boost PFC ICs. The FL3930B provides an additional OVP pin that can be used to shut down the boost power stage when output voltage exceeds OVP level due to damaged resistors connected at the INV pin. The FL7930C provides a PFC-ready pin can be used to trigger other power stages when PFC output voltage reaches the proper level (with hysteresis).

FL7930主要特性:

 Additional PFC-Ready Function (FL7930C Only)

 Input-Voltage-Absent-Detection Circuit

 Maximum Switching Frequency Limitation

 Internal Soft-Start with Overshoot Prevention

 Internal Total Harmonic Distortion (THD) Optimizer

 Precise Adjustable Output Over-Voltage Protection

 Additional OVP Detection Pin (FL7930B Only)

 Open-Feedback Protection and Disable Function

 Zero-Current Detector

 150μs Internal Startup Timer

 MOSFET Over-Current Protection (OCP)

 Under-Voltage Lockout with 3.5V Hysteresis

 Low Startup and Operating Current

 Totem-Pole Output with High State Clamp

 +500/-800mA Peak Gate Drive Current

 8-Pin Small Outline Package (SOP)

FL7930应用:

 Ballast

 General LED Lighting

 Industrial, Commercial, and Residential Fixtures

 Outdoor Lighting: Street, Roadway, Parking, Construction and Ornamental LED Lighting Fixtures

图1. FL7930B方框图

图2. FL7930C方框图

图3. FL7930B PFC应用电路图

图4. FL7930B 单级反激转换器应用电路图

图5. FL7930C PFC应用电路图

采用FL7930B和FAN7621S的150W LED街灯照明设计方案

This application note describes a 150W rating design guideline for LED street lighting. The application design consists of CRM PFC and LLC SRC with high power factor and high power conversion efficiency using FL7930B and FAN7621S. To verify the validity of the application board and scheme, a demonstration board 150W (103V/1.46A) AC-DC converter was implemented and its results are presented in this application note. In CRM active PFC, the most popular topology is a boost converter. This is because boost converters can have continuous input current that can be manipulated with peak current mode control techniques to force peak current to track changes in line voltage. The FAN7930B is an active Power Factor Correction (PFC) controller for boost PFC applications that operate in critical conduction mode (CRM). Since it was first introduced in early 1990s, LLC-SRC (series resonant converter) has became a most popular topology because of its outstanding performance in areas such as the output regulation of switching frequency, ZVS capability for entire load range, low turn-off current, small resonant components using the integrated transformer, zero current switching (ZCS), and no reverse recovery loss on secondary rectifier. Figure 1 shows the typical application circuit, with the CRM PFC converter in the front end and the LLC SRC DC-DC converter in the back end. FL7930B and FAN7621S achieve high efficiency with medium power for 150W rating applications where CRM and LLC SRC operation with a two-stage shows best performance. CRM boost PFC converters can achieve better efficiency with light and medium power rating than Continuous Conduction Mode (CCM) boost PFC converters. These benefits result from the elimination of the reverse-recovery losses of the boost diode and Zero-Current Switching (ZCS). The LLC SRC DC-DC converter achieves higher efficiency than the conventional hard switching converter. The FL7930B provides a controlled on-time to regulate the output DC voltage and achieves natural power factor correction. The FAN7621S includes a high-side gate driver circuit, accurate current-controlled oscillator, frequency -limit circuit, soft-start, and built-in protections.

The high-side gate drive circuit has a common-mode noise cancellation capability, which guarantees stable operation with excellent noise immunity. Using Zero Voltage Switching (ZVS) dramatically reduces switching losses and significantly improves efficiency. ZVS also reduces switching noise noticeably, which allows a small-sized Electromagnetic Interference (EMI) filter.