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
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