FairchildFAN6863反激电源PWM控制方案

FAN6863：Highly Integrated Green-Mode PWM Controller

A highly integrated PWM controller, FAN6863 provides several features to enhance the performance of flyback converters. To minimize standby power consumption, a proprietary Green Mode provides off-time modulation to continuously decrease the switching frequency under light-load conditions. Under zero-load conditions, the power supply enters Burst Mode, which completely shuts off PWM output. Output restarts just before the supply voltage drops below the UVLO lower limit. Green Mode enables power supplies to meet international power conservation requirements.

The FAN6863 is designed for SMPS and integrates a frequency-hopping function that helps reduce EMI emission of a power supply with minimum line filters.

The built-in synchronized slope compensation provides proprietary sawtooth compensation for constant output power limit over universal AC input range. The gate output is clamped at 13.5V to protect the external MOSFET from over-voltage damage.Other protection functions include SENSE pin Short- Circuit Protection (SSCP), VDD Over-Voltage Protection (OVP), and Over-Temperature Protection (OTP). For OTP, an external NTC thermistor can be applied to sense the ambient temperature. When VDD OVP or OTP is activated, an internal latch circuit latches off the controller.

FAN6863主要特性：

Low Standby Power: Under 0.1W

Low Startup Current: 8μA

Low Operating Current at Green Mode: 600μA

Peak-Current Mode Operation with Cycle-by-Cycle Current Limiting

PWM Frequency Continuously Decreasing with Burst Mode at Light Loads

VDD Over-Voltage Protection (OVP)

Constant Output Power Limit (Full AC Input Range)

Internal Latch Circuit (FAN6863L) for OVP, OTP

SENSE Pin Short-Circuit Protection (SSCP)

Fixed PWM Frequency (65KHz) with Frequency Hopping

Feedback Open-Loop Protection: 60ms Delay

GATE Output Maximum Voltage Clamp: 13.5V

Soft-Start Time: 5ms

Soft Driving for EMI Improvement

Full Range Frequency Hopping

Internal OTP Sensor with Hysteresis

GATE Driving Capability: 400mA

FAN6863应用：

General-purpose switched-mode power supplies and flyback power converters, including:

Power Adapters

Open-Frame SMPS

SMPS with Surge-Current Output, such as for Printers, Scanners, Motor Drivers

图1。FAN6863方框图

图2。FAN6863典型应用电路图

图3。FAN6863起动电路图

图4。FAN6863详细的应用电路图