1W MONO POWER AMP# Technical Documentation: FAN7023 High-Voltage Green-Mode PWM Controller
Manufacturer : FAIRCHILD (now part of ON Semiconductor)
Component Type : High-Voltage Green-Mode PWM Controller IC
Primary Function : Primary-side regulation (PSR) controller for offline flyback converters, designed for high efficiency and low standby power.
---
## 1. Application Scenarios (Approx. 45% of Content)
### Typical Use Cases
The FAN7023 is specifically engineered for low-to-medium power offline switch-mode power supplies (SMPS) requiring high efficiency and minimal no-load power consumption. Its primary use case is as the core control element in flyback converter topologies .
* AC/DC Adapters and Chargers : For consumer electronics such as laptops, monitors, routers, and small appliances. Its green-mode operation helps meet stringent energy efficiency standards (e.g., ENERGY STAR, CoC, DoE Level VI).
* Auxiliary (Standby) Power Supplies : In larger systems like TVs, desktop PCs, and industrial equipment, where a highly efficient, always-on low-power rail is needed.
* LED Driver Modules : For non-dimmable or simple dimmable LED lighting applications, leveraging its constant voltage (CV) and constant current (CC) control capability via primary-side regulation.
* Low-Cost, Compact Power Modules : Where component count and transformer size need minimization, as PSR eliminates the need for an optocoupler and secondary-side feedback circuitry.
### Industry Applications
* Consumer Electronics : Power adapters, battery chargers, set-top boxes.
* Industrial Electronics : Control board power, sensor module supplies.
* Lighting : LED drivers for commercial and residential lighting fixtures.
* IT & Communication : Power for modems, routers, and network switches.
### Practical Advantages and Limitations
Advantages:
* High Efficiency Across Loads : Integrated Green Mode operation drastically reduces switching frequency under light/no-load conditions, minimizing switching losses and achieving very low standby power (<75mW typical).
* Reduced BOM Cost and Complexity : Primary-Side Regulation (PSR) technology eliminates the optocoupler, secondary reference (e.g., TL431), and associated resistors/capacitors. This simplifies design, saves board space, and improves reliability.
* Built-in Protections : Includes comprehensive protection features such as Over-Load Protection (OLP), Over-Voltage Protection (OVP), Open-Loop Protection, and Internal Over-Temperature Protection (OTP), enhancing system robustness.
* Fast Startup & Low Startup Current : High-voltage startup circuit allows quick initiation, and a low operating current minimizes losses during startup.
* Constant Current (CC) / Constant Voltage (CV) Control : Inherently supports CC/CV output characteristics ideal for battery charging and LED driving without secondary feedback.
Limitations:
* Regulation Accuracy : PSR inherently has slightly inferior line/load regulation (±5-7% typical) compared to secondary-side feedback (which can achieve ±1-2%). It is not suitable for applications requiring very tight output voltage tolerance.
* Dynamic Response : The control loop, based on sampling the auxiliary winding feedback, is generally slower in responding to rapid load transients than opto-isolated feedback.
* Transformer Design Sensitivity : Performance is more sensitive to transformer parameters (leakage inductance, winding coupling) and manufacturing consistency. Requires careful transformer design and characterization.
* Limited to Flyback Topology : Designed specifically for discontinuous conduction mode (DCM) flyback converters, not suitable for forward, LLC, or other topologies.
---
## 2. Design Considerations (Approx. 35% of Content)
### Common Design Pitfalls and Solutions
1. Poor Output
