Key facts
- Brand
- Fairchild
- Model
- SG6846
- Category
- Power Management
- Documents
- 4
- Languages
- EN
- Last added
- 2012-08-01
Start here
Fairchild SG6846 Flyback Power Supply Control Application Note
The SG6846 is a highly integrated PWM controller IC designed for low standby power consumption and high-efficiency power conversion. It features a proprietary green-mode function that reduces switching frequency under light-load conditions and enters burst-mode at no-load. The IC incorporates multiple protection functions, including over-temperature protection, AC input brownout protection, and Vpp over-voltage protection, with an internal latch circuit for critical faults.
The document details the application of the SG6846 in flyback converters with surge-current output, such as those used in printers and motor drivers. It covers design considerations, mathematical equations for setting the PWM frequency and feedback loop, and guidelines for printed circuit board layout. Key features include built-in synchronized slope compensation for stable continuous conduction mode (CCM) operation and a two-level over-current protection function.
Fairchild SG6846 specifications
| Operating Current | 3.7mA |
|---|---|
| Gate Output Clamp Voltage | 18V |
| PWM Frequency (Nominal) | 65kHz |
| PWM Frequency (Green Mode) | 22.5kHz |
| FB Threshold Voltage for Frequency Reduction | 2.1V |
| FB Voltage for Termination | 1.6V |
Source: Fairchild SG6846 Flyback Power Supply Control Application Note
All Fairchild SG6846 documents by type
How to use the product for one specific task, with worked examples.
Ratings, dimensions and ordering codes, for selection and design work.
Questions answered in these manuals
What applications is the SG6846 designed for?
It is designed for general-purpose switch-mode power supplies and flyback power converters, including power adapters and SMPS with surge-current output for printers and motor drivers.
From: Fairchild SG6846 Flyback Power Supply Control Application Note
How does the SG6846 handle over-temperature protection?
An external NTC thermistor can be applied to sense the ambient temperature. When activated, an internal latch circuit shuts off the controller until the temperature cools sufficiently or AC supply is disconnected.
From: Fairchild SG6846 Flyback Power Supply Control Application Note
What are the applications for the SG6846A?
It is designed for general-purpose switch-mode power supplies and flyback power converters, including power adapters and open-frame SMPS.
From: Fairchild Semiconductor SG6846A Highly Integrated Green-Mode PWM Controller Datasheet
What is the switching frequency with a 26kΩ resistor?
The typical switching frequency is 65kHz when using a 26kΩ resistor on the RI pin.
From: Fairchild Semiconductor SG6846A Highly Integrated Green-Mode PWM Controller Datasheet
What is the function of the SG6846B?
It is a highly integrated PWM controller designed for flyback converters to enhance performance and minimize standby power consumption.
From: Fairchild Semiconductor SG6846B Highly Integrated Green-Mode PWM Controller Datasheet
How does the device handle light loads?
Under light-load conditions, the switching frequency continuously decreases, and under zero-load conditions, the power supply enters burst mode.
From: Fairchild Semiconductor SG6846B Highly Integrated Green-Mode PWM Controller Datasheet