Fairchild 公司的FAN6754B是高度集成的綠色模式PWM控制器,能提高反激轉換器的性能,最小化待機功耗.高壓起動,低工作電流1.5mA,固定PWM頻率65kHz,頻率跳頻以降低EMI,峰值電流模式控制,主要用在LCD監視器,LCD TV和筆記本電腦.本文介紹了FAN6754B主要特性,功能方框圖,典型應用電路圖以及65W(19V / 3.42A)反激轉換器的主要指標,電路圖,材料廠清單和PCB布局圖.
FAN6754B: Highly Integrated Green- Mode PWM Controller
The highly integrated FAN6754B PWM controller provides several features to enhance the performance of flyback converters. To minimize standby power consumption, a proprietary green-mode function provides off-time modulation to continuously decrease the switching frequency under light-load conditions.
Under zero-load and very light-load conditions, FAN6754B saves PWM pulses by entering deep burst mode. This burst mode function enables the power supply to meet international power conservation requirements.
FAN6754B integrates a frequency-hopping function internally to reduce EMI emission of a power supply with minimum line filters. Built-in synchronized slope compensation is accomplished by proprietary HV monitor to adjust VLimit for constant output power limit over universal AC input range. The gate output is clamped at 13V to protect the external MOSFET from over-voltage damage.
Other protection functions include AC input brownout protection with hysteresis, and VDD over-voltage protection. For over-temperature protection, an external NTC thermistor can be applied to sense the external switcher’s temperature. When VDD OVP or OTP are activated, an internal latch circuit is used to latch-off the controller. The latch mode is reset when the VDD supply is removed.
FAN6754B is available in an 8-pin SOP package.
FAN6754B主要特性:
High-Voltage Startup
AC Input Brownout Protection with Hysteresis
Monitor HV to Adjust VLimit
Low Operating Current: 1.5mA
Linearly Decreasing PWM Frequency to 22KHz
Frequency Hopping to Reduce EMI Emission
Fixed PWM Frequency: 65KHz
Peak-Current-Mode Control
Cycle-by-Cycle Current Limiting
Leading-Edge Blanking (LEB)
Internal Open-Loop Protection
GATE Output Maximum Voltage Clamp: 13V
VDD Under-Voltage Lockout (UVLO)
VDD Over-Voltage Protection (OVP)
Programmable Over-Temperature Protection (OTP)
Internal Latch Circuit (OVP, OTP)
Open-Loop Protection (OLP); Restart for MR, Latch for ML
Built-in 8ms Soft-Start Function
FAN6754B應用:
LCD Monitor
LCD TV
Notebook PC
圖1.FAN6754B功能方框圖
圖2.FAN6754B典型應用電路圖
用于筆記本電腦適配器的低成本綠色模式PWM控制器反激轉換器65W(19V / 3.42A) This document describes a 65W power supply using FAN6754AMR and FAN6204MY synchronous rectification IC. This power supply is targeted towards power adapters and open-frame consumer products.
With the internal high-voltage startup circuitry, the power loss due to bleeding resistors is eliminated. To further reduce power consumption, FAN6754AMR is manufactured using the BiCMOS process. This allows an operating current of only 1.5mA and low startup current of 30μA. Built-in synchronized slope compensation ensures the stability of peakcurrent-mode control. In addition, FAN6204MY improves conduction losses in heavy load, and the SR controller stops all SR switching operation to reduce the operating current in light load.
反激轉換器主要指標:
圖3.65W反激轉換器外形圖
圖4.65W反激轉換器電報掛號路圖
65W反激轉換器材料清單(BOM):
圖5.65W反激轉換器PCB布局圖(頂層)
圖6.65W反激轉換器PCB布局圖(層) |
