Four Key Steps To Design A Continuous Conduction Mode Pfc Stage Using The Ncp1653

This paper proposes the key steps to rapidly design a Continuous Conduction Mode (CCM) PFC stage driven by the NCP1653. The process is illustrated by the following practical application: − Maximum output power: 300 W − Input voltage range: from 90 Vrms to 265 Vrms − Regulation output voltage: 390 V − Switching frequency: 100 kHz INTRODUCTION The NCP1653 is a controller for Continuous Conduction Mode (CCM) Power Factor Correction step−up pre−converters. It controls the power Switch conduction time (PWM) in a fixed frequency mode and in dependence on the instantaneous coil current. Housed in a DIP8 or SO8 package, the circuit minimizes the number of external components and drastically simplifies the PFC implementation. It also integrates high safety protection features that make the NCP1653 a driver for robust and compact PFC stages like an effective input power runaway clamping circuitry. Generally, the NCP1653 is an ideal candidate in systems where cost−effectiveness, reliability and high power factor are the key parameters. It incorporates all the necessary features to build a compact and rugged PFC stage: • Compactness and Flexibility: Easy to implement, the NCP1653 yields near−unity power factor in a simple and robust manner. Despite the low external components count it requires, the circuit sacrifices neither performance nor flexibility. Instead, by simply adjusting an external resistor, you CAN even choose to have the circuit operated in traditional or follower boost mode (1) . • Low Consumption and Shutdown Capability: The NCP1653 particularly, minimizes its consumptions during the startup phase and in shutdown mode. Hence, the PFC stage losses are extremely low when the circuit is off. This feature helps meet the more stringent standby low power specifications. Grounding the Feedback pin (pin1) forces the NCP1653 in shutdown mode. • Safety Protections: The NCP1653 permanently monitors the input and output voltages, the coil current and the die temperature to protect the system from possible over−stresses. More specifically, the following protections make the PFC stage extremely robust and reliable: ♦ Maximum Current Limit: The circuit immediately turns off the MOSFET if the coil current exceeds the maximum permissible level. The NCP1653 also prevents any turn on of the power Switch as long as the coil current is not below this limit. This feature protects the PFC stage during the startup phase when large in−rush currents charge the output capacitor. ♦ Undervoltage Protection/Shutdown: The circuit keeps in shutdown mode as long as the feedback current indicates that the output voltage is lower than 8% its regulation level. In this case, the NCP1653 consumption is very low (<50 A). This feature protects the PFC stage from starting operation in case of too low AC line conditions or of a failure in the feedback network (e.g., bad connection). ♦ Overvoltage Protection: Given the low bandwidth of the regulation block, PFC stages may exhibit dangerous output voltage overshoots because of abrupt load or input voltage variations (e.g. at startup). Overvoltage Protection (OVP) turns off the Power Switch as soon as Vout exceeds the OVP threshold (107% of the regulation level).
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Four Key Steps To Design A Continuous Conduction Mode Pfc Stage Using The Ncp1653 application circuits
Four Key Steps To Design A Continuous Conduction Mode Pfc Stage Using The Ncp1653 application circuits

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