Lithium-ion Charger Controller# Technical Documentation: FAN7563D Power Factor Correction Controller
Manufacturer : FAIRCHILD (now part of ON Semiconductor)
Component Type : Critical Conduction Mode (CRM) Power Factor Correction (PFC) Controller IC
Document Revision : 1.0
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## 1. Application Scenarios
### 1.1 Typical Use Cases
The FAN7563D is specifically designed as a high-performance, low-cost controller for building Power Factor Correction (PFC) pre-regulator stages in switch-mode power supplies (SMPS). 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 and minimizing harmonic distortion.
Core Applications Include:
* AC-DC Front-End Converters: Serving as the active PFC stage in power supplies requiring compliance with international harmonic current standards such as IEC 61000-3-2 .
* Critical Conduction Mode (CRM) Boost Topology: It operates the PFC boost inductor at the boundary between continuous and discontinuous conduction modes. This eliminates the reverse recovery loss of the boost diode, making it highly efficient, especially in mid-power applications.
* Standalone PFC Modules: Used in systems where power factor correction is a distinct module separate from the downstream DC-DC conversion stage.
### 1.2 Industry Applications
The FAN7563D finds widespread use across industries requiring efficient, compliant AC-DC power conversion:
* Computer & Server Power Supplies: For desktop PCs, workstations, and server power supplies (typically in the 200W to 500W range).
* Consumer Electronics: LCD/LED TV power supplies, audio amplifiers, gaming consoles, and adapter/chargers for high-power devices.
* Industrial Equipment: Motor drives, automation control systems, and test/measurement equipment requiring clean input power.
* Lighting: High-intensity discharge (HID) lamp ballasts and high-power LED driver power supplies.
### 1.3 Practical Advantages and Limitations
Advantages:
* High Efficiency: CRM operation minimizes switching losses and eliminates boost diode reverse recovery losses, leading to excellent efficiency, particularly at medium load and high line voltages.
* Simplified Design: Internal start-up timer and zero-current detection (ZCD) circuitry simplify the control loop design.
* Inherent Overvoltage Protection (OVP): Integrated OVP function protects the system and downstream components from output overvoltage conditions.
* Low Component Count: Compared to fixed-frequency average current mode controllers, the CRM approach often requires fewer external components, reducing cost and board space.
* Good EMI Profile: The variable switching frequency (highest at line voltage zero-crossings, lowest at peak) can help spread EMI spectrum.
Limitations:
* Variable Frequency Operation: The switching frequency varies with input voltage and load. This complicates EMI filter design, as the filter must be effective across a wide frequency range. Frequency can become very high at light loads or high line voltages, potentially increasing gate drive and core losses.
* Higher RMS Currents: Compared to Continuous Conduction Mode (CCM) PFC, CRM operation results in higher RMS currents in the boost inductor and switch, which can necessitate larger components for the same power level.
* Power Range Constraint: Most suitable for medium power applications (typically up to 300-400W). For higher power levels (>500W), CCM controllers are generally preferred due to lower peak/current stresses.
* Audible Noise Risk: At very light loads, the switching frequency can drop into the audible range (<20kHz), potentially causing inductor or ceramic capacitor whine.
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## 2. Design Considerations
### 2.1 Common Design Pit
