Fairchild Design Guidelines for New-Generation FPS FSB-Series Data Handbook
Summary
Optimized design guidelines for implementing Fairchild's FSB-Series Power Switch in next-generation standby auxiliary power supplies. This manual details how the integrated AX-CAP™ discharge function and mWSaver™ technology enable circuit designers to achieve outstanding energy efficiency, significantly reducing constant power draw while complying with global standards (e.g., ENERGY STAR, ErP). Ideal for engineers creating compact, highly reliable SMPS solutions that require advanced low-power switching capabilities.
Page 1 Text Content
www.fairchildsemi.com
AN-9752 Design Guidelines for New-Generation FPS™ FSB-Series
This application note focuses on design consideration of
1. Introduction two unique functions of FSB-series: AX-CAP™ discharge
and adjustable peak current limit. It introduces AX-CAP
The FSB-series is a next-generation Green-Mode Fairchild
operation principle and provides the equations of discharge
Power Switch (FPS™) incorporating Fairchild’s innovative
time for worst-case scenarios. Then it shows how to achieve
m WSaver™ technology, which dramatically reduces
the constant power limit and how to design the IPK pin
standby and no-load power consumption, enabling
level for appropriate Over-Power Protection (OPP) level.
conformance to worldwide standby efficiency guidelines. It integrates advanced current-mode pulse-width modulator The design consideration for applying FSB-series to a (PWM) and an avalanche-rugged 700V Sense FET in a standby auxiliary power supply with single output is well single package; allowing auxiliary power designs with described in Fairchild application note AN-8024. It covers higher standby energy efficiency, reduced size, improved designing the transformer, selecting the components, reliability, and lower system cost than previous solutions. feedback loop design, and design tips to maximize The typical application circuit is shown in Figure 1. efficiency. For multi-output applications, refer to Fairchild
application note AN-4137.
Figure 1. Typical Application Circuit
© 2011 Fairchild Semiconductor Corporation www.fairchildsemi.com Rev. 1.0.0 • 12/28/11
Page Summary Contents For Fairchild Design Guidelines for New-Generation FPS FSB-Series Data Handbook
Manual Details
| Brand | Fairchild |
|---|---|
| Pages | 6 |
| File Size | 423.57 KB |
| Published | June 18, 2026 |
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Frequently Asked Questions
How does AX-CAP™ technology improve power efficiency?
It replaces traditional X-cap discharge resistors by intelligently discharging the filter capacitor upon power loss, while maintaining low standby consumption during normal operation.
What safety standards are met with this FSB-series solution?
The design ensures compliance with major regulations such as UL 1950 and IEC61010-1 concerning required capacitor discharge times.
Can these components be used in life support systems?
No, the products are not authorized for use as critical components in life support devices without explicit written approval from Fairchild Corporation.
What are the specified current limits for the FSB127H?
The typical flat level of current limit (I) is 0.666 A, and the valley level of current limit (LMT-FL) is 0.503 A.