Power Factor Correction (PFC) Controller# Technical Documentation: KA7526D PWM Controller IC
Manufacturer : SAMSUNG
Document Version : 1.0
Last Updated : October 2023
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## 1. Application Scenarios
### 1.1 Typical Use Cases
The KA7526D is a pulse-width modulation (PWM) controller IC primarily designed for offline switching power supplies . Its architecture supports both current-mode and voltage-mode control, making it versatile for various power conversion topologies.
Primary applications include:
- AC/DC Switch-Mode Power Supplies (SMPS) : Used in flyback, forward, and half-bridge configurations for power levels up to 250W.
- DC/DC Converters : Employed in step-down (buck) and isolated converter designs requiring precise voltage regulation.
- Power Adapters and Chargers : Commonly found in consumer electronics adapters (e.g., for laptops, monitors, and printers) due to its integrated protections and adjustable frequency.
- Auxiliary Power Supplies : Provides regulated low-voltage rails in industrial equipment, telecom systems, and automotive electronics (non-critical subsystems).
### 1.2 Industry Applications
- Consumer Electronics : Power supplies for TVs, audio systems, and gaming consoles.
- Industrial Automation : Control panel power modules, motor drive auxiliary supplies.
- Telecommunications : DC-DC converters in base stations and networking hardware.
- Lighting : LED driver circuits and ballast controls.
- Computing : PSUs for peripherals and low-power servers.
### 1.3 Practical Advantages and Limitations
Advantages:
- Integrated Protections : Includes over-current protection (OCP), under-voltage lockout (UVLO), and soft-start functionality, reducing external component count.
- Wide Operating Range : Input voltage range typically 8V to 35V, suitable for universal mains-derived DC rails.
- Adjustable Frequency : Oscillator frequency can be set via external RC components (range: 1 kHz to 300 kHz), allowing optimization for efficiency and size.
- Low Standby Power : Burst-mode operation enhances light-load efficiency, meeting energy-saving standards (e.g., ENERGY STAR).
Limitations:
- Limited Maximum Frequency : Not suitable for very high-frequency designs (>300 kHz) where smaller magnetics are required.
- Heat Dissipation : Requires adequate PCB thermal management when operating at high duty cycles or elevated ambient temperatures.
- External MOSFET Required : Lacks an integrated power switch, necessitating careful selection of external transistors for target power levels.
- Legacy Component : As a older design, it may lack advanced features found in modern controllers (e.g., digital control interfaces, frequency jittering for EMI reduction).
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## 2. Design Considerations
### 2.1 Common Design Pitfalls and Solutions
| Pitfall | Cause | Solution |
|---------|-------|----------|
| Oscillator Instability | Poor RC component selection or layout noise coupling. | Use low-ESR capacitors and place oscillator components close to IC pins. Add a small ceramic capacitor (100 pF) across timing resistor. |
| Over-current Triggering | Excessive current sense resistor tolerance or noise on CS pin. | Use a 1% tolerance current sense resistor. Add an RC filter (100 Ω, 1 nF) at the current sense pin. |
| VCC Undervoltage Lockout Cycling | Insufficient VCC bypass capacitance or high supply impedance. | Place a low-ESR electrolytic capacitor (≥47 µF) near VCC pin. Ensure auxiliary winding provides adequate sustaining voltage. |
| EMI Issues | Fast switching edges and poor layout causing radiated emissions. | Implement snubber circuits across transformer leakage inductance. Use twisted-pair wires for high-current paths
