一般描述

　　這100瓦特轉換器演示了廣泛的在NCP1650型特征。該芯片是能夠PFC變換器控制到千瓦范圍。除了優秀的功率因數，該芯片提供固定連續和斷續模式中的頻率操作操作。它具有多種保護功能，包括瞬時電流限制，平均電流限制，真正的功率限制。這個單位將提供400伏的穩壓電源輸入源的頻率范圍從50赫茲到60赫茲，和85 VRMS的電壓范圍為265 Vrms。它是完全自我包含并包括一個高電壓啟動電路，和偏置電源，操作的升壓電感關閉。

　　Features

　　? Fixed Frequency Operation

　　? Shutdown Circuit

　　? Operation Over the Universal Input Range

　　? Multiple Protection Schemes

　　? True Power Limiting

　　? Start-Up and Bias Circuits Included

　　Circuit Description

　　Start-Up Circuit

　　The start-up circuit allows the unit to use power from the

　　input line to begin operation， and then shuts down to allow

　　operation off of the bias winding， which reduces losses in the

　　circuit.

　　The start-up circuit has three modes of operation. One is

　　used for starting the NCP1650 when the chip is functional，

　　one is for bias power during shutdown operation， and the

　　third is the off state.

　　When power is initially applied to the unit， the gate of the

　　pass transistor will be high， and the FET will be fully

　　enhanced. The current into the VCC capacitance at pin 1 will

　　be limited by the three 10 k： resistors in series with the FET.