Fairchild FSFR2100 200W LED电源参考设计

Fairchild 公司的FEB271 200W电源参考设计是采用FSFR2100 功率开关,通用输入电压从90VAC到265VAC,总输出功率200W,有六个DC输出,每个电压为48V,电流为0.7A,也可改变成0.35A/96V.本文介绍了FEB271 200W电源参考设计的主要电路和所用材料清单,主要器件包括FAN6961PFC控制器, FSFR2100功率开关, FOD2741光绝缘误差放大器和SG6858 / SG6859 PWM控制器的主要特性和方框图.此外还介绍了用于驱动LED的其它电路.

High Power Factor LED Ballast using FSFR2100 Fairchild Power Switch (FPSTM) for Resonant Half-Bridge Converter and FAN7529 PFC Controller This document describes the proposed solution for a 200 W Power Supply using the FSFR2100 Fairchild Power Switch (FPS). The input voltage range is 90 – 265 VRMS and there are six outputs with 0.7A / 48V max. each. The board consists of a high power factor pre-regulator based on the FAN6961 voltage mode PFC controller and an isolated DC/DC converter based on a resonant LLC topology.

This document contains the power supply specification, schematic, bill of materials and transformer documentation.

200W电源主要指标:

Universal AC Input Voltage ( 90 – 265 VRMS)

Total Output Power 200 W

Six DC Outputs with Constant Current: 0.7A / 48V max. each ( can be changed to 0.35A / 96V max.)



图1. 200W电源外形图

图2. 200W电源电路图(1)

图3. 200W电源电路(2)

主要器件介绍:

1. FAN6961 Boundary Mode PFC Controller

The FAN6961 is an 8-pin, boundary-mode, PFC controller IC intended for controlling PFC preregulators. The FAN6961 provides a controlled on-time to regulate the output DC voltage and achieve natural power factor correction. The maximum on-time of the external switch is programmable to ensure safe operation during AC brownouts. An innovative multivector error amplifier is built in to provide rapid transient response and precise output voltage clamping. A builtin circuit disables the controller if the output feedback loop is opened. The startup current is lower than 20μA and the operating current has been reduced to under 6mA. The supply voltage can be up to 25V, maximizing application flexibility.

FAN6961主要特性:

Boundary Mode PFC Controller

Low Input Current THD

Controlled On-Time PWM

Zero-Current Detection

Cycle-by-Cycle Current Limiting

Leading-Edge Blanking instead of RC Filtering

Low Startup Current: 10μA Typical

Low Operating Current: 4.5mA Typical

Feedback Open-Loop Protection

Programmable Maximum On-Time (MOT)

Output Over-Voltage Clamping Protection

Clamped Gate Output Voltage 16.5V

FAN6961应用:

Electric Lamp Ballasts

AC-DC Switching Mode Power Converter

Open Frame Power Supplies and Power Adapters

Flyback Power Converters with ZCS / ZVS

图4.FAN6961方框图

http://www.fairchildsemi.com/ds/FA/FAN6961.pdf

2. FSFR2100 Fairchild Power Switch (FPS™) for Resonant Half-Bridge Converter

The FSFR-series are a highly integrated power switches designed for high-efficiency half-bridge resonant converters. Offering everything necessary to build a reliable and robust resonant converter, the FSFR-series simplifies designs and improves productivity, while improving performance. The FSFR-series combines power MOSFETs with fast-recovery type body diodes, a high-side gate-drive circuit, an accurate current controlled oscillator, frequency limit circuit, soft-start, and built-in protection functions. The high-side gate-drive circuit has a common-mode noise cancellation capability, which guarantees stable operation with excellent noise immunity. The fast-recovery body diode
of the MOSFETs improves reliability against abnormal operation conditions, while minimizing the effect of the reverse recovery. Using the zero-voltage-switching (ZVS)technique dramatically reduces the switching losses and efficiency is significantly improved. The ZVS also reduces the switching noise noticeably, which allows a small-sized Electromagnetic Interference (EMI) filter. The FSFR-series can be applied to various resonant converter topologies such as series resonant, parallel resonant, and LLC resonant converters.

FSFR2100主要特性:

Variable Frequency Control with 50% Duty Cycle for Half-Bridge Resonant Converter Topology

High Efficiency through Zero Voltage Switching (ZVS)

Internal SuperFET™s with Fast-Recovery Type Body Diode (trr=120ns) for FSFR2100 and UniFETs with Fast-Recovery Type Body Diode (trr<160ns) for

FSFR2100U/2000/1900/1800/1700.

Fixed Dead Time (350ns) Optimized for MOSFETs

Up to 300kHz Operating Frequency

Pulse Skipping for Frequency Limit (Programmable) at Light-Load Condition

Remote On/Off Control Using Control Pin

Protection Functions: Over-Voltage Protection (OVP), Over-Load Protection (OLP), Over-Current Protection (OCP), Abnormal Over-Current Protection (AOCP), Internal Thermal Shutdown (TSD)

FSFR2100应用:

PDP and LCD TVs

Desktop PCs and Servers

Adapters

Telecom Power Supplies

Audio Power Supplies

图5.FSFR2100方框图

图6.FSFR2100典型应用电路

http://www.fairchildsemi.com/ds/FS/FSFR2100.pdf

3. FOD2741 Optically Isolated Error Amplifier

The FOD2741 Optically Isolated Amplifier consists of the popular KA431 precision programmable shunt reference and an optocoupler. The optocoupler is a gallium arsenide (GaAs) light emitting diode optically coupled to a silicon phototransistor. It comes in 3 grades of reference voltage tolerance = 2%, 1%, and 0.5%.

The Current Transfer Ratio (CTR) ranges from 100% to 200%. It also has an outstanding temperature coefficient of 50 ppm/°C. It is primarily intended for use as the error amplifier/reference voltage/ optocoupler function in isolated ac to dc power supplies and dc/dc converters.

When using the FOD2741, power supply designers can reduce the component count and save space in tightly packaged designs. The tight tolerance reference eliminates the need for adjustments in many applications. The device comes in a 8-pin dip white package.

4. SG6858 / SG6859 PWM Controller

This highly integrated PWM controller provides several special enhancements designed to meet the low standby-power needs of low-power SMPS. To minimize standby power consumption, the proprietary green-mode function provides off-time modulation to linearly decrease the switching frequency under light-load conditions. This green-mode function enables the power supply to easily meet even the strictest power conservation requirements.

The BiCMOS fabrication process enables reducing the start-up current to 9uA, and the operating current to 3mA. To further improve power conservation, a large start-up resistance can be used. Built-in synchronized slope compensation ensures the stability of peak current mode control. Proprietary internal compensation provides a constant output power limit over a universal AC input range (90VAC to 264VAC). Pulse-by-pulse current limiting ensures safe operation even during short-circuits.

To protect the external power MOSFET from being damaged by supply over voltage, the SG6859’s output driver is clamped at 17V. SG6859 controllers can be used to improve the performance and reduce the production cost of power supplies. The SG6859 is the best choice for replacing linear and RCC-mode power adapters. It is available in 8-pin DIP and 6-pin SOT-26 packages.

200W电源材料清单(BOM):





图7.200W电源方框图

图8.带整流和EMI滤波器的PFC电路

图9.电源控制电路

图10.LED电流源电路