Fairchild Power Switch(FPS)# Technical Documentation: KA1H0165RYDTU Off-Line Switcher
Manufacturer : FAIRCHILD (now part of ON Semiconductor)
Component Type : Integrated Off-Line Switcher with Built-in Power MOSFET
Primary Function : Primary-side regulated (PSR) flyback converter controller for low-power AC/DC power supplies.
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## 1. Application Scenarios
### Typical Use Cases
The KA1H0165RYDTU is specifically engineered for compact, cost-effective, and energy-efficient off-line switch-mode power supplies (SMPS). Its primary use case is as the core control and power conversion element in low-to-moderate power AC/DC adapters and power modules.
* Low-Power Adapters & Chargers : Ideal for powering or charging consumer electronics such as routers, modems, set-top boxes, small audio systems, and LED drivers, typically in the 5W to 15W range.
* Auxiliary Power Supplies (AUX PS) : Used to generate bias voltages (+12V, +5V, etc.) for control circuits within larger appliances like printers, white goods, and industrial equipment.
* Standby Power Supplies : Its low no-load power consumption makes it suitable for providing the always-on standby power in televisions, monitors, and other appliances that comply with energy efficiency standards (e.g., ENERGY STAR, EU CoC).
### Industry Applications
* Consumer Electronics : The dominant application area, providing the internal power conversion for a vast array of household and personal devices.
* Industrial Controls : Powers sensors, relays, and microcontroller boards in automation systems, where reliability and compact size are critical.
* Telecommunications : Used in power modules for network interface devices and fiber optic network terminals (ONTs).
* Lighting : Serves as the driver for non-dimmable and some basic dimmable LED lighting solutions.
### Practical Advantages and Limitations
Advantages:
* High Integration : Combines a current-mode PWM controller, a 650V avalanche-rugged power MOSFET, and a startup cell into a single 5-pin package (TO-220F-5L). This significantly reduces external component count, board size, and assembly cost.
* Primary-Side Regulation (PSR) : Eliminates the need for an optocoupler and secondary-side feedback circuitry to regulate the output voltage. This enhances reliability (no optocoupler aging) and further reduces cost and complexity.
* Low Standby Power : Features such as burst-mode operation under light loads minimize switching losses, enabling designs to achieve <100mW no-load power consumption.
* Built-in Protections : Includes comprehensive protection features like Overload Protection (OLP), Over-Voltage Protection (OVP), and Over-Temperature Protection (OTP), improving system robustness.
Limitations:
* Limited Power Output : Designed for lower power applications (typically <15W). For higher power needs, a discrete controller + MOSFET or a higher-rated integrated switcher is required.
* Regulation Accuracy : PSR control is inherently less precise than secondary-side feedback using an optocoupler. Output voltage tolerance is typically in the range of ±5%, which is acceptable for many applications but not for precision analog circuits.
* Dynamic Response : The response to rapid load changes can be slower compared to some secondary-feedback topologies, which may be a consideration for loads with high transient demands.
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## 2. Design Considerations
### Common Design Pitfalls and Solutions
1. Transformer Design for PSR : Incorrect transformer parameters (magnetizing inductance, turns ratio) are the most common cause of failure to regulate.
* Pitfall : Poor coupling or wrong inductance leads to inaccurate voltage sensing from the auxiliary winding, causing
