Power Factor Correction (PFC) and PWM Controller Combo# Technical Documentation: FAN4803CP2 PFC/PWM Combo Controller
Manufacturer : FAIRCHILD (now part of ON Semiconductor)
Component : FAN4803CP2
Description : Integrated Dual-Mode PFC and PWM Controller IC
Package : 8-Pin PDIP (Plastic Dual In-line Package)
---
## 1. Application Scenarios
### Typical Use Cases
The FAN4803CP2 is a monolithic, dual-mode controller designed for high-performance, off-line switch-mode power supplies (SMPS). Its primary function is to integrate Power Factor Correction (PFC) and Pulse-Width Modulation (PWM) control into a single chip, simplifying the design of power supplies that require both high power factor and regulated DC output.
* Single-Stage PFC & PWM Control: It is most commonly employed in single-stage, boost-follow configurations. In this topology, the PFC stage operates in critical conduction mode (CrM) or transition mode (TM) to shape the input current, while the downstream PWM stage (typically a forward or flyback converter) provides tightly regulated, isolated DC output. This eliminates the need for two separate controller ICs and their associated circuitry.
* Low to Medium Power AC-DC Supplies: The controller is optimized for power supplies in the range of 100W to 300W . It is ideal for applications where space, component count, and cost are critical constraints but power quality (meeting IEC 61000-3-2 harmonic current limits) is still required.
* Synchronized Operation: A key feature is the internal synchronization of the PFC and PWM stages. The PWM stage is triggered at the valley of the PFC inductor current, which minimizes switching losses and reduces electromagnetic interference (EMI). This interleaved operation is a significant practical advantage.
### Industry Applications
1. Computer & Office Equipment: Desktop PC power supplies (particularly for entry-level and mainstream systems), monitors, printers, and copiers.
2. Consumer Electronics: LCD/LED TVs, audio/video receivers, gaming consoles, and set-top boxes.
3. Industrial Systems: Auxiliary power supplies for motor drives, control systems, and test equipment requiring compliant AC input stages.
4. Lighting: High-power LED drivers and ballasts for commercial lighting systems.
### Practical Advantages and Limitations
Advantages:
* High Integration: Reduces component count, board space, and overall system cost by combining two controller functions.
* Improved Efficiency: Valley-switching (ZVS) operation of the PWM stage reduces switching losses.
* Inherent Synchronization: Eliminates beat frequencies between PFC and PWM stages, simplifying EMI filter design.
* Comprehensive Protection: Includes features like over-voltage protection (OVP) for PFC, peak current limiting for both stages, and undervoltage lockout (UVLO).
* Power Factor Correction: Enables designs to easily achieve PF > 0.95, ensuring compliance with international harmonic standards.
Limitations:
* Power Range: Less suitable for very low-power (<75W) or very high-power (>500W) applications. At low power, the complexity may not be justified; at high power, thermal and current handling may require a two-stage discrete solution.
* Fixed Frequency Dependency: The PFC operates in transition mode, where switching frequency varies with line voltage and load. This can make optimizing the EMI filter more challenging compared to fixed-frequency controllers.
* Design Complexity: While it integrates two controllers, the surrounding power stage design (magnetics, MOSFETs, feedback loops) remains complex and requires careful tuning.
* Heat Dissipation: In a compact design, the 8-pin DIP package's thermal performance must be considered, especially if placed near heat-gener
