The NCP1654 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 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 NCP1654 a driver for robust and compact PFC stages like an effective input power runaway clamping circuitry.
The NCP1654 is a PFC driver designed to operate in fixed frequency, continuous conduction mode. The fixed frequency operation eases the compliance with EMI standard and the limitation of the possible radiated noise that may pollute surrounding systems. In addition, continuous conduction operation reduces the application di/dt and their resulting interference. More generally, the NCP1654 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: housed in a SO8 package, the NCP1654 requires a minimum of external components. In particular, the circuit scheme simplifies the PFC stage design and eliminates the need for any input voltage sensing. In addition, the circuit offers some functions like the Brown−Out or the true power limiting that enable the optimizations of the PFC design.
Low Consumption and Shutdown Capability: the NCP1654 is optimized to exhibit consumption as small as possible in all operation modes. The consumed current is particularly reduced during the start−up phase and in shutdown mode so that the PFC stage power losses are extremely minimized when the circuit is disabled. This feature helps meet the more stringent stand−by low power specifications. Just ground the Feed−back pin to force the NCP1654 in shutdown mode.
Safety Protections: the NCP1654 permanently monitors the output voltage, the coil current and the die temperature to protect the system from possible over−stresses. Integrated protections (Overvoltage protection, coil current limitation, thermal shutdown...) make the PFC stage extremely robust and reliable: − Maximum Current Limit: the circuit permanently senses the coil current and immediatel