FSQ510, FSQ510H - Green Mode Fairchild Power Switch (FPS™) for Quasi-Resonant Converter

Oct 12, 2026

FSQ510(H) is an integrated PWM controller with SenseFET designed for quasi-resonant offline switch-mode power supplies, delivering lower EMI and higher conversion efficiency than fixed-frequency hard-switched converters. Key functions include variable-frequency control with inherent frequency modulation, minimum-voltage switching for efficiency, burst-mode operation for low standby power, and pulse-by-pulse current limiting. The device integrates protection features such as OLP, AOCP, TSD with hysteresis, and UVLO with hysteresis, plus internal start-up and a 5 ms soft start. Compared with discrete solutions, it reduces component count, size, and weight while improving reliability for quasi-resonant flyback converters.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages15

Reading Time38 min

AccessFree to download

Features

Applications

Description

Ordering Information

Application Circuit

Internal Block Diagram

Pin Assignments

Pin Definitions

Absolute Maximum Ratings

PRELIMINARY DATASHEET | |
August 2006 | | --- | --- | | FSQ510, FSQ510H—Green Mode Fairchild Power Switch (FPSTM) for Quasi-Resonant Converter
– Low EMI and High Efficiency | | | Features
􀂃 Uses a DMOS Integrated Power Switch
􀂃 Optimized for Quasi-Resonant Converter (QRC)
􀂃 Low EMI through Variable Frequency Control and Inherent Frequency Modulation
􀂃 High Efficiency through Minimum Voltage Switching
􀂃 Extended Quasi-Resonant Switching for Wide Load Ranges
􀂃 Small Frequency Variation for Wide Load Ranges
􀂃 Advanced Burst-Mode Operation for Low Standby Power Consumption
􀂃 Pulse-by-Pulse Current Limit
􀂃 Various Protection Functions: Overload Protection (OLP), Abnormal Over-Current Protection (AOCP), Internal Thermal Shutdown (TSD) with Hysteresis
􀂃 Under-Voltage Lockout (UVLO) with Hysteresis
􀂃 Internal Start-up Circuit
􀂃 Internal High-Voltage SenseFET (700V)
􀂃 Built-in Soft Start (5ms) | Applications
􀂃 Cell Phone Chargers
􀂃 Auxiliary Power Supplies for PC and White Goods
Description
A Quasi-Resonant Converter (QRC) generally shows lower EMI and higher power conversion efficiency than a conventional hard-switched converter with a fixed switching frequency. The FSQ510(H) is an integrated Pulse-Width Modulation (PWM) controller and SenseFET specifically designed for quasi-resonant offline Switch Mode Power Supplies (SMPS) with minimal external components. The PWM controller includes an integrated fixed-frequency oscillator, Under-Voltage Lockout (UVLO), Leading Edge Blanking (LEB), optimized gate driver, internal soft start, temperaturecompensated precise current sources for loop compensation, and self-protection circuitry. Compared with discrete MOSFET and PWM controller solution, the FSQ510(H) can reduce total cost, component count, size and weight; while simultaneously increasing efficiency, productivity, and system reliability. This device provides a basic platform that is well suited for cost-effective designs of quasi-resonant switching flyback converters. | | Ordering Information
Part
Number Package Pb
Free Operating
Temperature
Range Current
Limit RDS(ON)
(MAX) Maximum Output Power (1) Replaces
Devices 230VAC ± 15%(2) 85-265VAC Adapter(3) Open
Frame(4) Adapter(3) Open
Frame(4) FSQ510 7-DIP Yes -25℃ to +85℃ 320mA 32Ω 5W 7W 4W 5W FSD210B FSQ510H 8-DIPH Yes -25℃ to +85℃ 320mA 32Ω 5W 7W 4W 5W FSD210HD
Notes:
1. The junction temperature can limit the maximum output power.
2. 230VAC or 100/115VAC with doubler.
3. Typical continuous power in a non-ventilated enclosed adapter measured at 50°C ambient.
4. Maximum practical continuous power in an open-frame design at 50°C ambient temperature. | | FSQ510, FSQ510H Green Mode Fairchild Power Switch (FPSTM) for Quas i-Resonant Converter © 2006 Fairchild Semiconductor Corporation [www.fairchildsemi.com](www.fairchildsemi.com) [FSCQ510](FSCQ510) , FSCQ510H Rev. 0.0.3 PRELIMINARY DATASHEET | Application Circuit | | | --- | --- | | AC
IN

| Vo
| | Figure 1. Typical Application Circuit
Internal Block Diagram
Sync VSTR Vcc D

Figure 2. Internal Block Diagram | | FSQ510, FSQ510H Green Mode Fairchild Power Switch (FPSTM) for Quas i-Resonant Converter © 2006 Fairchild Semiconductor Corporation [www.fairchildsemi.com](www.fairchildsemi.com) [FSQ510](FSQ510) , FSQ510H Rev. 0.0.3 2 PRELIMINARY DATASHEET | Pin Assignments | | | | | | | --- | --- | --- | --- | --- | --- | | GND
GND
VFB
Sync |
FSQ510

| VSTR
D
VCC | VSTR
VFB
Sync
GND |
FSQ510H | D
VCC
GND
GND | | Figure 3. Package diagrams for FSQ510 and FSQ510H
Pin Definitions
Pin \# Name Description 1,2(5)
(4,5,6)(6) GND This pin is the control ground and the SenseFET source. 3 (2) VFB This pin is internally connected to the inverting input of the PWM comparator. The collector of an opto-coupler is typically tied t

FAQs

What design and integration aspects reduce external components compared with discrete solutions?

The FSQ510(H) combines a PWM controller, an internal fixed-frequency oscillator, an optimized gate driver, internal soft start, loop-compensation current sources, and self-protection circuitry with a SenseFET-based power switch. This integration reduces total cost, component count, size, and weight while improving efficiency, productivity, and reliability.

Oct 12, 2026

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