原标题：On Semi NCP1351 40W打印机电源解决方案

　　On Semi公司的NCP1351是电流模式控制器,主要用在小功率离线反激开关电源(SMPS),由于采用固定峰值电流技术,在轻负载时控制器可降低开关频率,使得无负载功耗极低,从而优化了其它负载时的开关频率,使得峰值电流降低大概30%.主要用在辅助电源,打印机,游戏机和低成本适配器和离线电池充电器.本文介绍了NCP1351主要特性,四种类型框图,以及应用电路,40W打印机电源16V/32V评估板电路图,材料清单和PCB设计图.

　　The NCP1351 is a current-mode controller targeting low poweroff-line flyback Switched Mode Power Supplies (SMPS) where costis of utmost importance. Based on a fixed peak current technique(quasi-fixed TON), the controller decreases its switching frequency asthe load becomes lighter. As a result, a power supply using theNCP1351 naturally offers excellent no-load power consumption,while optimizing the efficiency in other loading conditions. When thefrequency decreases, the peak current is gradually reduced down to approximately 30% of the maximum peak current to preventtransformer mechanical resonance. The risk of acoustic noise is thusgreatly diminished while keeping good standby power performance.

　　An externally adjustable timer permanently monitors the feedbackactivity and protects the supply in presence of a short-circuit or anoverload. Once the timer elapses, NCP1351 stops switching and stayslatched for version A, and tries to restart for version B.Versions C and D include a dual overcurrent protection trip point,allowing the implementation of the controller in peak-powerrequirements applications such as printers and so on. When the fault isacknowledged, C version latches-off whereas D versionauto-recovers.

　　The internal structure features an optimized arrangement whichallows one of the lowest available startup current, a fundamentalparameter when designing low standby power supplies.

　　The negative current sensing technique minimizes the impact of theswitching noise on the controller operation and offers the user to selectthe maximum peak voltage across his current sense resistor. Its powerdissipation can thus be application optimized.Finally, the bulk input ripple ensures a natural frequency smearingwhich smooths the EMI signature.

　　NCP1351主要特性:

　　•_Quasi-fixed TON, Variable TOFF Current Mode Control

　　•_Extremely Low Current Consumption at Startup

　　•_Peak Current Compression Reduces Transformer Noise

　　•_Primary or Secondary Side Regulation

　　•_Dedicated Latch Input for OTP, OVP

　　•_Programmable Current Sense Resistor Peak Voltage

　　•_Natural Frequency Dithering for Improved EMI Signature

　　•_Easy External Over Power Protection (OPP)

　　•_Undervoltage Lockout

　　•_Very Low Standby Power via Off-time Expansion

　　•_SOIC-8 Package

　　• Standard Overcurrent Protection, Latched orAuto-Recovery, A & B Versions

　　• Dual Trip Point Overcurrent Protection, Latched orAuto-Recovery, C & D Versions

　　• These are Pb-Free Devices

　　NCP1351典型应用:

　　• Auxiliary Power Supply

　　• Printer, Game Stations, Low-Cost Adapters

　　• Off-line Battery Charger

　　图1. NCP1351 A型框图(锁短路保护)

　　图2. NCP1351 B型框图(自动恢复短路保护)

　　图3. NCP1351 C型框图(锁短路保护)

　　图4. NCP1351 D型框图(自动恢复短路保护)

　　图5. NCP1351应用电路

　　图6. NCP1351 19V适配器应用电路

　　40W打印机电源16V/32V评估板

　　This board is a printer power supply operated by the NCP1351, a fixed ton / variable off time controller. The board can deliver 10 W average on a 16 V output and 30 W average on a 32 V output with a transient peak power capability of 80 W. It however exhibits a low standby power: below 150 mW at no load whatever the input voltage.

　　40W打印机电源16V/32V评估板主要指标:

　　The design must fulfill the following specifications:

　　Input Voltage: 88 – 265 Vac

　　Output Voltage: 16 V @ 0.625 A and 32 V @ 1 ANominal (40 W); with Transient 80 W Peak PowerCapability during 40 ms, and 62 W Peak during 400 ms

　　Over Power Protection below 100 W for the WholeInput Voltage Range (LPS)

　　Latched Short-circuit Protection

　　Latched Over-voltage Protection

　　Latch Recovery Time below 3 s

　　Brown-out Protection

　　Start-up Time below 3 s

　　图7.NCP1351评估板外形图

　　图8.采用NCP1351简化40W打印机电源评估板电路图

　　图9.采用NCP135140W打印机电源评估板电路图

　　40W打印机电源评估板材料清单: