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On Semi公司的NCP1250是高度集成的PWM控制器,電源電壓高達28V,峰值電流模式工作,開關電路的頻率為65kHz或100kHz,內部可調整超功率保護(OPP)電路,斜坡補償,固定4ms軟起動,220VAC時的待機功耗小于100mW, EPS 2.0兼容,主要用在TV,機頂盒和打印機的AC/DC轉換器,筆記本電腦和上網本的離線適配器.本文介紹了NCP1250主要特性,方框圖, 典型應用電路圖和40W評估板NCP1250B40WGEVB電路圖和材料清單. The NCP1250 is a highly integrated PWM controller capable of delivering a rugged and high performance offline power supply in a tiny TSOP−6 package. With a supply range up to 28 V, the controller hosts a jittered 65 kHz or 100 kHz switching circuitry operated in peak current mode control. When the power on the secondary side starts to decrease, the controller automatically folds back its switching frequency down to a minimum level of 26 kHz. As the power further goes down, the part enters skip cycle while limiting the peak current. Over Power Protection (OPP) is a difficult exercise especially when no−load standby requirements drive the converter specifications. The ON proprietary integrated OPP lets you harness the maximum delivered power without affecting your standby performance simply via two external resistors. An Over Voltage Protection input is also combined on the same pin and protects the whole circuitry in case of optocoupler failure or adverse open loop operation. Finally, a timer−based short−circuit protection offers the best protection scheme, letting you precisely select the protection trip point irrespective of a loose coupling between the auxiliary and the power windings. NCP1250主要特性: Fixed−Frequency 65 or 100 kHz Current−Mode Control Operation Internal and Adjustable Over Power Protection (OPP) Circuit Frequency Foldback Down to 26 kHz and Skip−Cycle in Light Load Conditions Internal Ramp Compensation Internal Fixed 4 ms Soft−Start 100 ms Timer−Based Auto−Recovery Short−Circuit Protection Frequency Jittering in Normal and Frequency Foldback Modes Option for Auto−Recovery or Latched Short−Circuit Protection OVP Input for Improved Robustness Up to 28 V VCC Operation +300 mA / −500 mA Source/Sink Drive Capability Less than 100 mW Standby Power at High Line EPS 2.0 Compliant These are Pb−Free Devices NCP1250典型應用: ac−dc Converters for TVs, Set−top Boxes and Printers Offline Adapters for Notebooks and Netbooks 
圖1.NCP1250方框圖
圖2.NCP1250典型應用電路圖 40W評估板NCP1250B40WGEVB The NCP1250 is a highly integrated PWM controller capable of delivering a rugged and high performance offline power supply in a tiny TSOP-6 package. With a supply range up to 28 V, the controller hosts a jittered 65 kHz or 100 kHz switching circuitry operated in peak current mode control. When the power on the secondary side starts to decrease, the controller automatically folds back its switching frequency down to a minimum level of 26 kHz. As the power further goes down, the part enters skip cycle while limiting the peak current. Over Power Protection (OPP) is a difficult exercise especially when no-load standby requirements drive the converter specifications. The ON proprietary integrated OPP lets you harness the maximum delivered power without affecting your standby performance simply via two external resistors. An Over Voltage Protection input is also combined on the same pin and protects the whole circuitry in case of optocoupler failure or adverse open loop operation. 評估板說明
圖3.40W評估板NCP1250B40WGEVB外形圖
圖4.40W評估板NCP1250B40WGEVB電路圖 圖評估板NCP1250B40WGEVB材料清單:
詳情請見: 
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