基于FAN6862设计的40W笔记本电脑电源技术

The FAN6862 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 is proprietary sawtooth compensation for constant output power limit over universal AC input range. The gate output is clamped at 18V to protect the external MOSFET from over-voltage damage.

Other protection functions include VDD over-voltage protection and over-temperature protection. For overtemperature protection, 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.

FAN6862主要特性：

􀂃 Low Startup Current: 8μA

􀂃 Low Operating Current in Green Mode: 3mA

􀂃 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 for OVP, OTP

􀂃 Fixed PWM Frequency (65KHz) with Frequency Hopping

􀂃 Feedback Open-Loop Protection with 56ms Delay

􀂃 Soft Start Time: 4ms

􀂃 400mA Driving Capability

FAN6862应用：

General-purpose switch-mode power supplies and flyback power converters, including:

􀂃 Power Adapters

􀂃 Open-Frame SMPS

􀂃 SMPS with Surge-Current Output, such as for Printers, Scanners, and Motor Drivers

图1。FAN6862方框图

图2。FAN6862典型应用电路图

图3。FAN6862起动电路图

图4。FAN6862 36W（12V/3A）应用电路图

36W（12V/3A）应用电路材料清单（BOM）：

采用FAN6862的40W参考设计RD-337

40W参考设计主要特性：

􀂃 Low Startup Current: 8μA;

􀂃 Low Operation Current in Green Mode: 3mA

􀂃 Green Mode: Frequency Reduction with Burst Mode at Light Load

􀂃 Fixed PWM Frequency at 65kHz with Frequency Hopping to Reduce EMI

􀂃 Constant Output Power Limit

􀂃 Soft-Start Time: 4ms

􀂃 Driving Capability: 400mA

􀂃 Various Protection Functions: VDD Over-Voltage Protections (OVP), Open-Loop Protection (OLP), and Over-Temperature Protection (OTP)

图5。40W参考设计电路图

图6。40W参考设计变压器连接图

变压器电特性：