Power Factor Correction (PFC) and PWM Controller Combo# Technical Documentation: FAN4803CP1 Power Factor Correction (PFC) Controller
Manufacturer : Fairchild Semiconductor (FSC)
Component Type : Integrated Circuit (IC) - PFC/PWM Combo Controller
Package : 16-Pin PDIP (Plastic Dual In-Line Package)
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## 1. Application Scenarios
### Typical Use Cases
The FAN4803CP1 is a monolithic, high-performance controller designed for offline switch-mode power supplies (SMPS) requiring active Power Factor Correction (PFC). Its primary function is to shape the input current drawn from the AC mains to closely follow the sinusoidal waveform of the input voltage, thereby achieving a near-unity power factor (typically >0.99). This is accomplished by operating a boost converter in Continuous Conduction Mode (CCM) at the front end. The IC also integrates a pulse-width modulation (PWM) controller to regulate the output of a downstream DC-DC converter stage (e.g., a forward or flyback converter).
* Front-End PFC Pre-regulator: The core application is as the controller for a boost-type PFC stage . It takes a wide-range AC input (e.g., 85-265VAC) and generates a stable, high-voltage DC bus (typically 385-400VDC) with a power factor exceeding 0.95, complying with international standards like IEC 61000-3-2.
* Two-Stage Power Supply Systems: It is specifically architected for two-stage power conversion topologies . The first stage is the PFC boost converter, and the second stage is a DC-DC converter whose PWM controller is also provided within the same IC. This simplifies design and synchronization between the two stages.
* Critical Load Protection: The controller features comprehensive protection functions, making it suitable for systems requiring high reliability, such as over-voltage protection (OVP), over-current protection (OCP) for both stages, and inrush current management.
### Industry Applications
* Computer/Server Power Supplies: High-efficiency desktop PC, workstation, and server power supplies (e.g., 250W to 1000W+).
* Industrial Power Systems: Power modules for industrial automation, motor drives, and telecommunications infrastructure where clean input current and high efficiency are mandated.
* Consumer Electronics: High-end LCD/LED TV power supplies, gaming consoles, and large audio amplifiers.
* Uninterruptible Power Supplies (UPS): The online/double-conversion UPS systems benefit from the high-PF input stage to reduce harmonic pollution on the grid.
### Practical Advantages and Limitations
Advantages:
* High Integration: Combines a CCM average-current PFC controller and a PWM controller in one package, reducing component count and board space.
* Excellent Performance: Achieves high power factor (>0.99) and low total harmonic distortion (THD < 10%) across a wide load range.
* Synchronized Operation: The internal oscillator synchronizes the PFC and PWM stages, eliminating beat-frequency noise and simplifying EMI filter design.
* Robust Protection Suite: Includes peak current limiting, VCC under-voltage lockout (UVLO), output OVP, and soft-start for both stages, enhancing system reliability.
* Current-Mode PWM: The downstream PWM stage uses current-mode control, providing inherent cycle-by-cycle current limiting and simplified feedback loop compensation.
Limitations:
* Fixed Topology: The integrated PWM is optimized for single-ended topologies (e.g., forward, flyback). It is not suitable for half/full-bridge or resonant LLC topologies without external circuitry.
* Power Level: While versatile, it is most commonly applied in mid-to-high power applications (several hundred watts to over a kilowatt). For very
