OnSemi公司的NCP1612是一款采用創新的CCFF（Curret Controlled Frequency Fold-back）方式的PFC增壓階段芯片，在這種模式下，當電感電流超過預設值時，典型工作電路工作在臨界導通模式。當電流低于該預設值時，NCP1612線性降低頻率下降到約20千赫時，電流值最終降至零。特別是待機的損失減少到最低限度?？刂破魈峁┝艘徽坠δ軓姶蟮谋Ｗo功能，能夠妥善處理好電源陣列的運行和故障情況。本文主要介紹了該芯片的主要特性及功能強大的保護特性，并給出芯片內部框圖、方案介紹、方案原理圖、方案PCB圖及元器件列表。
The NCP1612 is designed to drive PFC boost stages based on an innovative Current Controlled Frequency Fold−back (CCFF) method. In this mode, the circuit classically operates in Critical conduction Mode (CrM) when the inductor current exceeds a programmable value. When the current is below this preset level, the NCP1612 linearly decays the frequency down to about 20 kHz when the current is null. CCFF maximizes the efficiency at both nominal and light load. In particular, the stand−by losses are reduced to a minimum.
Like in FCCrM controllers, an internal circuitry allows near−unity power factor even when the switching frequency is reduced. Housed in a SO−10 package, the circuit also incorporates the features necessary for robust and compact PFC stages, with few external components.
NCP1612主要特性：
• Near−Unity Power Factor
• Critical Conduction Mode (CrM)
• Current Controlled Frequency Fold−back (CCFF): Low Frequency Operation is Forced at Low Current Levels
• On−time Modulation to Maintain a Proper Current Shaping in CCFF Mode
• Skip Mode Near the Line Zero Crossing
• Fast Line / Load Transient Compensation (Dynamic Response Enhancer)
• Valley Turn On
• High Drive Capability: −500 mA/+800 mA
• VCC Range: from 9.5 V to 35 V
• Low Start−up Consumption
• A Version: Low VCC Start−up Level (10.5 V), B Version: High VCC Start−up Level (17.0 V)
• Line Range Detection
• pfcOK Signal
• This is a Pb−Free Device
NCP1612保護特性：
• Separate Pin for Fast Over−Voltage Protection (FOVP) and Bulk Under−Voltage Detection (BUV)
• Soft Over−Voltage Protection
• Brown−Out Detection
• Soft−Start for Smooth Start−up Operation (A version)
• Over Current Limitation
• Disable Protection if the Feedback and FOVP/BUV pins are not connected
• Thermal Shutdown
• Latched Off Capability
• Low Duty−Cycle Operation if the Bypass Diode is shorted
• Open Ground Pin Fault Monitoring
NCP1612應用：
• PC Power Supplies
• All Off Line Appliances Requiring Power Factor Correction
圖1. NCP1612內部方框圖
NCP1612GEVB方案介紹：
Housed in a SO-10 package, The NCP1612 is designed to drive PFC boost stages in so-called Current Controlled Frequency Fold-back (CCFF). In this mode, the circuit classically operates in Critical conduction Mode (CrM) when the inductor current exceeds a programmable value. When the current is below this preset level, the NCP1612 linearly decays the frequency down to about 20 kHz when the current is nearly zero. CCFF maximizes the efficiency throughout the load range. Incorporating protection features for rugged operation, it is furthermore ideal in systems where cost-effectiveness, reliability, low stand-by power and high-efficiency are the key requirements.
Extremely slim, the NCP1612 evaluation board is designed to be less than 13-mm high. This low-profile PFC stage is intended to deliver 160 W under a 390 V output voltage from a wide mains input. This is a PFC boost converter as used in Flat TVs, High Power LED Street Light power supplies, and all-in-one computer supplies. The demo board embeds the NCP1612 B-version which is best appropriate for the self-biased configuration. The board is also configurable to have the NCP1612 powered from an external power source. In this case, apply a VCC voltage that exceeds the NCP1612B start-up level (18.2 V max) to ensure the circuit start of operation or solder the NCP1612A instead. The low VCC start-up level of the A-version(11.25 V max.) allows the circuit powering from a 12-V rail. Both versions feature a large VCC operating range (from 9.5 V up to 35 V).
NCP1612GEVB方案原理圖：
圖2. NCP1612GEVB方案原理圖
NCP1612GEVB方案材料清單：
PCB元件布局圖：
詳細資料如下
EVBUM2051-D.PDF
NCP1612-D.PDF
NCP1612GEVB_SCHEMATIC.PDF
