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Fairchild公司的150W LED街燈照明設計方案是采用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,工作在臨界導通模式(CRM),提供過壓,開路反饋,過流,輸入電壓瞬態檢測和欠壓鎖定等保護. FAN7621S是用于高效諧振轉換器的脈沖頻率調制控制器,包括高邊柵極驅動電路,精密的電流控制振蕩器,限頻電路,軟起動和內置保護功能.本文介紹了FL7930主要特性, FL7930B和FL7930C方框圖, 應用電路圖以及采用FL7930B和FAN7621S的150W LED街燈照明設計方案電路圖和材料清單. 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應用: Ballast General LED Lighting Industrial, Commercial, and Residential Fixtures Outdoor Lighting: Street, Roadway, Parking, Construction and Ornamental LED Lighting Fixtures 
圖1. FL7930B方框圖
圖2. FL7930C方框圖
圖3. FL7930B PFC應用電路圖
圖4. FL7930B 單級反激轉換器應用電路圖
圖5. FL7930C PFC應用電路圖 采用FL7930B和FAN7621S的150W LED街燈照明設計方案 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.
圖6.150W LED街燈照明設計板外形圖
圖7.典型應用電路
圖8.150W LED街燈照明設計電路圖 150W LED街燈照明設計板材料清單:
詳情請見: http://www.fairchildsemi.com/ds/FL/FL7930B.pdf 和 http://www.fairchildsemi.com/an/AN/AN-9738.pdf |
