本文介绍了FAN6791 / FAN6793主要特性，功能方框图，典型应用电路图，参考电路图及其材料清单（BOM），以及参考设计RD-343主要特性，电路图和所用变压器特性与电路。Fairchild 公司的FAN6791 / FAN6793是高度集成双PWM组合控制器，具有高压起动，低工作电流。FAN6791/3集成的频率抖动功能降低了EMI，内置的斜率补偿可得到稳定的峰值电流模式控制。主要用在开关电源和反激电源转换器，包括PC-ATX电源。

FAN6791 / FAN6793应用：

General-purpose switch-mode power supplies and flyback power converters, including:
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PC-ATX Power Supplies

图1。FAN6791 / FAN6793功能方框图

图2。FAN6791 / FAN6793典型应用电路图

图3。FAN6791 / FAN6793参考电路图
材料清单（BOM）：

参考设计RD-343

参考设计RD-343主要特性：

FAN6791

High-Voltage Startup

Low OperaTIng Current

Interleaved Standby PWM / Forward PWM Switching

Green Mode Standby PWM / Forward PWM

Linearly Decreasing Standby PWM Frequency to 20kHz

Remote On / Off

AC Brownout ProtecTIon

Forward PWM with Soft-Start

Frequency Hopping to Reduce EMI Emissions

Cycle-by-Cycle Current LimiTIng for Standby PWM / Forward PWM

Leading-Edge Blanking for Standby PWM / Forward PWM

Synchronized Slope CompensaTIon for Standby PWM / Forward PWM

GATE Output Maximum Voltage Clamp

VDD Over-Voltage Protection (OVP)

VDD Under-Voltage Lockout (UVLO)

Internal Open-Loop Protection for Standby PWM / Forward PWM

Constant Power Limit for Standby PWM / Forward PWM

SG6521

Two 12V Sense-Input Pins: VS12 and VS12B

Over-Voltage Protection (OVP), Over-Current Protection (OCP), and Under-Voltage Protection (UVP) for 3.3V, 5V, and Two 12V

Open-Drain Output for PGO and FPO Pins

300ms Power-Good Delay

300ms Turn-On Delay for 3.3V, 5V, and Two 12V

2.8ms PSON Control to FPO Turn-Off Delay and 48ms PSON Control Delay

No Lockup During the Fast AC Power On / Off

Wide Supply Voltage Range: 4.2V to 15V

Additional Protection Input (Pext)


图4。参考设计RD-343电路图

变压器电路框图
变压器线绕指标：

反激转换器变压器(TX2)

变压器电路框图
变压器线绕指标：