RD-342

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www.fairchildsemi.com

2009 Fairchild Semiconductor Corporation 1 RD-342_SG6742 Rev. 0.0.2

Reference Design RD-342

PWM Controller SG6742 - 60W Design

Featured Device ApplicationInput Voltage

RangeOutput Voltage(Rated Current)

Rated OutputPower Topology

SG6742 Notebook Adapter 90~264V AC 12V (5A) 60WFlyback

Converter

Key Features

Internal High-Voltage Startup Low Operating Current: 4mA Linearly Decreasing PWM Frequency to 22kHz Frequency Jittering to Reduce EMI Emission Fixed PWM Frequency: 65KHz Peak-Current-Node Control Cycle-by-Cycle Current Limiting Leading-Edge Blanking (LEB) Synchronized Slope Compensation Internal Open-Loop Protection GATE Output Maximum Voltage Clamp: 18V VDD Under-Voltage Lockout (UVLO) VDD Over-Voltage Protection (OVP)

Programmable Over-Temperature Protection (RT) Internal Latch Circuit (OVP, RT) Constant Power Limit (Full AC Input Range) Internal OTP Sensor with Hysteresis

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1. Schematic

Figure 1. Schematic

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2. Transformer

Figure 2. Transformer Schematic Diagram

2.1. Winding Specification

Pin (S F) Wire Turns Winding Method

N1 4 5 0.37 1 22 Solenoid WindingInsulation: Polyester Tape t = 0.025mm, 1 Layer

E1 Shield: 0.025mm 8mm, 1.1 turns, one end should be connected to pin 4Insulation: Polyester Tape t = 0.025mm, 3 LayerN2 A B 0.80 1 8 Solenoid Winding

Insulation: Polyester Tape t = 0.025mm, 3 Layer

N3 3 2 0.20 1 10 Solenoid WindingInsulation: Polyester Tape t = 0.025mm, 1 LayerE2 Shield: 0.025mm 8mm, 1.1 turns, one end should be connected to pin 4Insulation: Polyester Tape t = 0.025mm, 3 Layer

N4 5 6 0.37 1 20 Solenoid Winding

Insulation: Polyester Tape t = 0.025mm, 3 Layer

Core: PQ2620Bobbin: PQ2620

2.2. Electrical Characteristics

Pin Specification Remark

Primary-Side Inductance 4 6 600 H 5% 100kHz, 1V

Primary-Side Leakage Inductance 4 6 20 H Maximum Short One of the Secondary Windings

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3. Typical Performance

(1) Standby Power Consumption

Operating Conditions Input Power

VIN = 90V AC with No Load 0.06WVIN = 115 V AC with No Load 0.065W

VIN = 230 V AC with No Load 0.083W

VIN = 264 V AC with No Load 0.107W

(2) Efficiency

Operating Conditions Efficiency

VIN = 90 V AC with Full Load 82.34%

VIN = 115 V AC with Full Load 85.02%VIN = 230 V AC with Full Load 88.20%

VIN = 264 V AC with Full Load 87.70%

4. Related ResourcesSG6742 Highly Integrated Green-Mode PWM Controller Datasheet

Reference Design Disclaimer

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RD-342