Is Now Part of
To learn more about ON Semiconductor, please visit our website at
www.onsemi.com
Please note: As part of the Fairchild Semiconductor integration, some of the Fairchild orderable part numbers
will need to change in order to meet ON Semiconductor’s system requirements. Since the ON Semiconductor
product management systems do not have the ability to manage part nomenclature that utilizes an underscore
(_), the underscore (_) in the Fairchild part numbers will be changed to a dash (-). This document may contain
device numbers with an underscore (_). Please check the ON Semiconductor website to verify the updated
device numbers. The most current and up-to-date ordering information can be found at www.onsemi.com. Please
email any questions regarding the system integration to Fairchild_questions@onsemi.com.
ON Semiconductor and the ON Semiconductor logo are trademarks of Semiconductor Components Industries, LLC dba ON Semiconductor or its subsidiaries in the United States and/or other countries. ON Semiconductor owns the rights to a number
of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of ON Semiconductor’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent-Marking.pdf. ON Semiconductor reserves the right
to make changes without further notice to any products herein. ON Semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does ON Semiconductor assume any liability
arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. Buyer is responsible for its products and applications using ON
Semiconductor products, including compliance with all laws, regulations and safety requirements or standards, regardless of any support or applications information provided by ON Semiconductor. “Typical” parameters which may be provided in ON
Semiconductor data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer’s
technical experts. ON Semiconductor does not convey any license under its patent rights nor the rights of others. ON Semiconductor products are not designed, intended, or authorized for use as a critical component in life support systems or any FDA
Class 3 medical devices or medical devices with a same or similar classification in a foreign jurisdiction or any devices intended for implantation in the human body. Should Buyer purchase or use ON Semiconductor products for any such unintended
or unauthorized application, Buyer shall indemnify and hold ON Semiconductor and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out
of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that ON Semiconductor was negligent regarding the design or manufacture of the part. ON Semiconductor
is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
FSQ0465RS/RB
Green-Mode Fairchild Power Switch (FPS™) for
Quasi-Resonant Operation - Low EMI and High Efficiency
Features
Description
! Optimized for Quasi-Resonant Converters (QRC)
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 FSQ-series is an integrated
Pulse-Width Modulation (PWM) controller and
SenseFET specifically designed for quasi-resonant
operation and Alternating Valley Switching (AVS). The
PWM controller includes an integrated fixed-frequency
oscillator, Under-Voltage Lockout (UVLO), LeadingEdge Blanking (LEB), optimized gate driver, internal softstart, temperature-compensated precise current sources
for a loop compensation, and self-protection circuitry.
Compared with a discrete MOSFET and PWM controller
solution, the FSQ-series can reduce total cost,
component count, size, and weight; while simultaneously
increasing efficiency, productivity, and system reliability.
This device provides a basic platform for cost-effective
designs of quasi-resonant switching flyback converters.
! Low EMI through Variable Frequency Control and AVS
(Alternating Valley Switching)
! High-Efficiency through Minimum Voltage Switching
! Narrow Frequency Variation Range over Wide Load
and Input Voltage Variation
! Advanced Burst-Mode Operation for Low Standby
Power Consumption
! Simple Scheme for Sync Voltage Detection
! Pulse-by-Pulse Current Limit
! Various Protection Functions: Overload Protection
!
!
!
!
(OLP), Over-Voltage Protection (OVP), Abnormal
Over-Current Protection (AOCP), Internal Thermal
Shutdown (TSD) with Hysteresis, Output Short
Protection (OSP)
Under-Voltage Lockout (UVLO) with Hysteresis
Internal Startup Circuit
Internal High-Voltage Sense FET (650V)
Built-in Soft-Start (17.5ms)
Applications
! Power Supply for LCD TV and Monitor, VCR, SVR,
STB, and DVD & DVD Recorder
! Adapter
Related Resources
Visit: http://www.fairchildsemi.com/apnotes/ for:
! AN-4134: Design Guidelines for Offline Forward
!
!
!
!
!
!
!
Converters Using Fairchild Power Switch (FPS™)
AN-4137: Design Guidelines for Offline Flyback
Converters Using Fairchild Power Switch (FPS™)
AN-4140: Transformer Design Consideration for
Offline Flyback Converters Using Fairchild Power
Switch (FPS™)
AN-4141: Troubleshooting and Design Tips for
Fairchild Power Switch (FPS™) Flyback Applications
AN-4145: Electromagnetic Compatibility for Power
Converters
AN-4147: Design Guidelines for RCD Snubber of
Flyback Converters
AN-4148: Audible Noise Reduction Techniques for
Fairchild Power Switch (FPS™) Applications
AN-4150: Design Guidelines for Flyback Converters
Using FSQ-Series Fairchild Power Switch (FPS™)
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
December 2009
Maximum Output Power(1)
Product
Number
FSQ0465RSWDTU
FSQ0465RBWDTU
PKG.(5)
Operating Current RDS(ON)
Temp.
Limit
Max.
TO-220F
230VAC±15%(2)
Adapter(3)
85-265VAC
Open
Open
Adapter(3)
Frame(4)
Frame(4)
Replaces
Devices
1.8A
3.0A
FSQ0465RSLDTU
TO220F(L- -25 to +85°C
Forming)
1.8A
FSQ0465RBLDTU
TO220F(LForming)
3.0A
FSCM0465R
FSDM0465RE
2.6Ω
60W
70W
33W
48W
FSCM0465R
FSDM0465RE
For Fairchild’s definition of Eco Status, please visit: http://www.fairchildsemi.com/company/green/rohs_green.html.
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 temperature.
4. Maximum practical continuous power in an open-frame design at 50°C ambient.
5. Eco Status, RoHS.
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
2
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Ordering Information
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Application Diagram
VO
AC
IN
VSTR
Drain
PWM
Sync
GND
VFB
VCC
FSQ0465 Rev. 00
Figure 1. Typical Flyback Application
Internal Block Diagram
Sync
5
AVS
Vstr
VCC
Drain
6
3
1
OSC
VCC
VCC
Vref
Idelay
FB
4
Vref
0.35/0.55
VBurst
VCC good
8V/12V
IFB
PWM
3R
R
SoftStart
S Q
LEB
250ns
Gate
driver
R Q
tON < tOSP
after SS
VOSP
LPF
AOCP
VSD
VCC
S
TSD
Q
2
VOCP
(1.1V)
GND
R Q
LPF
VOVP
VCC good
FSQ0465 Rev.00
Figure 2. Internal Block Diagram
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
3
6. VSTR
5. Sync
4. FB
3. VCC
2. GND
1. Drain
FSQ0465 Rev.00
Figure 3. Pin Configuration (Top View)
Pin Definitions
Pin #
Name
1
Drain
SenseFET Drain. High-voltage power SenseFET drain connection.
2
GND
Ground. This pin is the control ground and the SenseFET source.
3
VCC
Power Supply. This pin is the positive supply input, providing internal operating current for
both startup and steady-state operation.
4
FB
Feedback. This pin is internally connected to the inverting input of the PWM comparator. The
collector of an opto-coupler is typically tied to this pin. For stable operation, a capacitor should
be placed between this pin and GND. If the voltage of this pin reaches 6V, the overload protection triggers, which shuts down the FPS.
5
Sync
Sync. This pin is internally connected to the sync-detect comparator for quasi-resonant switching. In normal quasi-resonant operation, the threshold of the sync comparator is 1.2V/1.0V.
Vstr
Startup. This pin is connected directly, or through a resistor, to the high-voltage DC link. At
startup, the internal high-voltage current source supplies internal bias and charges the external capacitor connected to the VCC pin. Once VCC reaches 12V, the internal current source is
disabled. It is not recommended to connect Vstr and Drain together.
6
Description
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
4
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Pin Configuration
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The
absolute maximum ratings are stress ratings only. TA = 25°C, unless otherwise specified.
Symbol
Parameter
Min.
Max.
Unit
Vstr
Vstr Pin Voltage
500
V
VDS
Drain Pin Voltage
650
V
VCC
Supply Voltage
VFB
Feedback Voltage Range
Sync Pin Voltage
VSync
20
V
-0.3
13.0
V
-0.3
13.0
V
9.6
A
4.0
A
120
mJ
Drain Current Pulsed
IDM
IDSW
Continuous Drain Switching
Current(6)
EAS
Single Pulsed Avalanche Energy(7)
PD
Total Power Dissipation (TC=25°C)
45
W
TJ
Operating Junction Temperature
Internally limited
°C
TA
Operating Ambient Temperature
-25
+85
°C
Storage Temperature
-55
+150
°C
TSTG
ESD
TC = 25°C
Human Body Model, JESD22-A114
2.0
kV
Charged Device Model, JESD22-C101
2.0
kV
Notes:
6. Repetitive peak switching current when inductor load is assumed: limited by maximum duty and maximum junction
temperature.
IDS
DMAX
fSW
7. 7. L=14mH, starting TJ=25°C.
Thermal Impedance
TA = 25°C unless otherwise specified.
Symbol
θJA
θJC
Parameter
Junction-to-Ambient Thermal
Junction-to-Case Thermal
Package
Resistance(8)
Resistance(9)
TO-220F-6L
Value
Unit
50
°C/W
2.8
°C/W
Notes:
8. Free-standing with no heat-sink under natural convection.
9. Infinite cooling condition - refer to the SEMI G30-88.
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
5
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Absolute Maximum Ratings
TA = 25°C unless otherwise specified.
Symbol
Parameter
Condition
Min. Typ. Max. Unit
SENSEFET SECTION
BVDSS
Drain Source Breakdown Voltage
VCC = 0V, ID = 100µA
IDSS
Zero-Gate-Voltage Drain Current
VDS = 560V
Drain-Source On-State Resistance
TJ = 25°C, ID = 0.5A
2.2
COSS
Output Capacitance
VGS = 0V, VDS = 25V, f = 1MHz
60
pF
td(on)
Turn-On Delay Time
VDD = 350V, ID = 25mA
12
ns
Rise Time
VDD = 350V, ID = 25mA
20
ns
Turn-Off Delay Time
VDD = 350V, ID = 25mA
30
ns
Fall Time
VDD = 350V, ID = 25mA
16
ns
RDS(ON)
tr
td(off)
tf
650
V
250
µA
2.6
Ω
CONTROL SECTION
Maximum On Time
TJ = 25°C
8.8
10.0
11.2
µs
tB
Blanking Time
TJ = 25°C, Vsync = 5V
13.5
15.0
16.5
µs
tW
Detection Time Window
TJ = 25°C, Vsync = 0V
fS
Initial Switching Frequency
tON.MAX
ΔfS
tAVS
Switching Frequency Variation(11)
On Time
6.0
59.6
66.7
75.8
kHz
-25°C < TJ < 85°C
±5
±10
%
at VIN = 240VDC, Lm = 360μH
(AVS triggered when VAVS >
spec. and tAVS < spec.)
4.0
µs
1.2
V
VAVS
AVS Triggering
Threshold(11)
tSW
Switching Time Variance by AVS(11)
Sync = 500kHz sine input
VFB = 1.2V, tON = 4.0µs
13.5
IFB
Feedback Source Current
VFB = 0V
700
Minimum Duty Cycle
VFB = 0V
DMIN
VSTART
VSTOP
UVLO Threshold Voltage
tS/S
Internal Soft-Start Time
VOVP
Over-Voltage Protection
Feedback
Voltage
µs
After turn-on
20.5
µs
900
1100
µA
0
%
11
12
13
V
7
8
9
V
With free-running frequency
17.5
ms
18
19
20
V
0.45
0.55
0.65
V
0.25
0.35
0.45
V
BURST-MODE SECTION
VBURH
VBURL
Burst-Mode Voltages
(10)
TJ = 25°C, tPD = 200ns
Hysteresis
200
mV
Continued on the following page...
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
6
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Electrical Characteristics
TA = 25°C unless otherwise specified.
Symbol
Parameter
Condition
Min. Typ. Max. Unit
PROTECTION SECTION
ILIMIT
Peak Current Limit of FSQ0465RS
TJ = 25°C, di/dt = 480mA/µs
1.6
1.8
2.0
A
ILIMIT
Peak Current Limit of FSQ0465RB
TJ = 25°C, di/dt = 370mA/µs
2.64
3.00
3.36
A
VSD
Shutdown Feedback Voltage
VCC = 15V
5.5
6.0
6.5
V
Shutdown Delay Current
VFB = 5V
4
5
6
µA
1.4
µs
IDELAY
tLEB
Leading-Edge Blanking
TJ = 25°C
OSP triggered when tON < tOSP,
VFB > VOSP and lasts longer than
Feedback Blanking Time tOSP_FB
Output Short Threshold Feedback
Protection(11) Voltage
tOSP_FB
TSD
Hys
250
Threshold Time
tOSP
VOSP
Time(11)
Shutdown Temperature
1.2
1.8
2.0
2.0
2.5
ns
V
3.0
+125 +140 +155
Thermal
Shutdown(11) Hysteresis
+60
µs
°C
SYNC SECTION
VSH1
VSL1
tsync
VSH2
VSL2
VCLAMP
Sync Threshold Voltage 1
VCC = 15V, VFB = 2V
1.0
1.2
1.4
0.8
1.0
1.2
Sync Delay Time(11)(12)
230
Sync Threshold Voltage 2
VCC = 15V, VFB = 2V
Low Clamp Voltage
ISYNC_MAX = 800µA,
ISYNC_MIN = 50µA
V
ns
4.3
4.7
5.1
4.0
4.4
4.8
0.0
0.4
0.8
V
V
TOTAL DEVICE SECTION
IOP
ISTART
ICH
VSTR
Operating Supply Current
VCC = 13V
1
3
5
mA
Start Current
VCC = 10V
(before VCC reaches VSTART)
350
450
550
µA
Startup Charging Current
VCC = 0V, VSTR = minimum 50V
0.65
0.85
1.00
mA
Minimum VSTR Supply Voltage
26
V
Notes:
10. Propagation delay in the control IC.
11. Guaranteed by design; not tested in production.
12. Includes gate turn-on time.
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
7
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Electrical Characteristics (Continued)
Function
Operation Method
EMI Reduction
FSDM0x65RE
FSQ-Series
Constant
Frequency PWM
Quasi-Resonant
Operation
Frequency
Modulation
Reduced
EMI Noise
! Reduced EMI noise
! Reduced components to detect valley point
! Valley Switching
! Inherent Frequency Modulation
! Alternate Valley Switching
CCM or AVS
Based on Load ! Improves efficiency by introducing hybrid control
and Input Condition
Hybrid Control
Burst-Mode
Operation
Burst-Mode
Operation
Advanced
Burst-Mode
Operation
Strong Protections
OLP, OVP
OLP, OVP,
AOCP, OSP
TSD
145°C without
Hysteresis
140°C with 60°C
Hysteresis
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
FSQ-Series Advantages
! Improved efficiency by valley switching
! Improved standby power by advanced burst-mode
! Improved reliability through precise AOCP
! Improved reliability through precise OSP
! Stable and reliable TSD operation
! Converter temperature range
www.fairchildsemi.com
8
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Comparison Between FSDM0x65RNB and FSQ-Series
1.2
Normalized
Normalized
These characteristic graphs are normalized at TA= 25°C.
1.0
0.8
1.2
1.0
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
-25
0
25
50
75
100
0.0
-25
125
0
Temperature [°C]
1.2
1.0
0.8
0.4
0.2
0.2
75
100
0.0
-25
125
0
Normalized
Normalized
1.2
1.0
0.8
125
0.8
0.4
0.4
0.2
0.2
75
100
0.0
-25
125
0
25
50
75
100
125
Temperature [°C]
Temperature [°C]
Figure 8. Initial Switching Frequency (fS) vs. TA
Figure 9. Maximum On Time (tON.MAX) vs. TA
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
100
1.0
0.6
50
75
1.2
0.6
25
50
Figure 7. Startup Charging Current (ICH) vs. TA
Figure 6. UVLO Stop Threshold Voltage
(VSTOP) vs. TA
0
25
Temperature [°C]
Temperature [°C]
0.0
-25
125
0.8
0.4
50
100
1.0
0.6
25
75
1.2
0.6
0
50
Figure 5. UVLO Start Threshold Voltage
(VSTART) vs. TA
Normalized
Normalized
Figure 4. Operating Supply Current (IOP) vs. TA
0.0
-25
25
Temperature [°C]
www.fairchildsemi.com
9
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Typical Performance Characteristics
1.2
Normalized
Normalized
These characteristic graphs are normalized at TA= 25°C.
1.0
0.8
1.2
1.0
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
-25
0
25
50
75
100
0.0
-25
125
0
1.2
1.0
0.8
0.4
0.2
0.2
75
100
0.0
-25
125
0
1.2
1.0
0.8
125
0.8
0.4
0.4
0.2
0.2
75
100
0.0
-25
125
Temperature [°C]
0
25
50
75
100
125
Temperature [°C]
Figure 14. Burst-Mode Low Threshold Voltage
(Vburl) vs. TA |
Figure 15. Peak Current Limit (ILIM) vs. TA
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
100
1.0
0.6
50
75
1.2
0.6
25
50
Figure 13. Burst-Mode High Threshold Voltage
(Vburh) vs. TA
Normalized
Normalized
Figure 12. Shutdown Delay Current (IDELAY) vs. TA
0
25
Temperature [°C]
Temperature [°C]
0.0
-25
125
0.8
0.4
50
100
1.0
0.6
25
75
1.2
0.6
0
50
Figure 11. Feedback Source Current (IFB) vs. TA
Normalized
Normalized
Figure 10. Blanking Time (tB) vs. TA
0.0
-25
25
Temperature [°C]
Temperature [°C]
www.fairchildsemi.com
10
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Typical Performance Characteristics (Continued)
1.2
Normalized
Normalized
These characteristic graphs are normalized at TA= 25°C.
1.0
0.8
1.2
1.0
0.8
0.6
0.6
0.4
0.4
0.2
0.2
0.0
-25
0
25
50
75
100
0.0
-25
125
0
1.2
1.0
0.8
0.4
0.2
0.2
75
100
0.0
-25
125
0
1.2
1.0
0.8
125
0.8
0.4
0.4
0.2
0.2
75
100
0.0
-25
125
Temperature [°C]
0
25
50
75
100
125
Temperature [°C]
Figure 20. Sync High Threshold Voltage 2
(VSH2) vs. TA
Figure 21. Sync Low Threshold Voltage 2
(VSL2) vs. TA
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
100
1.0
0.6
50
75
1.2
0.6
25
50
Figure 19. Over-Voltage Protection (VOV) vs. TA
Normalized
Normalized
Figure 18. Shutdown Feedback Voltage (VSD) vs. TA
0
25
Temperature [°C]
Temperature [°C]
0.0
-25
125
0.8
0.4
50
100
1.0
0.6
25
75
1.2
0.6
0
50
Figure 17. Sync Low Threshold Voltage 1
(VSL1) vs. TA
Normalized
Normalized
Figure 16. Sync High Threshold Voltage 1
(VSH1) vs. TA
0.0
-25
25
Temperature [°C]
Temperature [°C]
www.fairchildsemi.com
11
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Typical Performance Characteristics (Continued)
2.1 Pulse-by-Pulse Current Limit: Because currentmode control is employed, the peak current through the
SenseFET is limited by the inverting input of PWM
comparator (VFB*), as shown in Figure 23. Assuming
that the 0.9mA current source flows only through the
internal resistor (3R + R = 2.8k), the cathode voltage of
diode D2 is about 2.5V. Since D1 is blocked when the
feedback voltage (VFB) exceeds 2.5V, the maximum
voltage of the cathode of D2 is clamped at this voltage,
clamping VFB*. Therefore, the peak value of the current
through the SenseFET is limited.
1. Startup: At startup, an internal high-voltage current
source supplies the internal bias and charges the
external capacitor (Ca) connected to the VCC pin, as
illustrated in Figure 22. When VCC reaches 12V, the
FPS™ begins switching and the internal high-voltage
current source is disabled. The FPS continues its normal
switching operation and the power is supplied from the
auxiliary transformer winding unless VCC goes below the
stop voltage of 8V.
VDC
2.2 Leading-Edge Blanking (LEB): At the instant the
internal SenseFET is turned on, a high-current spike
usually occurs through the SenseFET, caused by
primary-side capacitance and secondary-side rectifier
reverse recovery. Excessive voltage across the Rsense
resistor would lead to incorrect feedback operation in the
current-mode PWM control. To counter this effect, the
FPS employs a leading-edge blanking (LEB) circuit. This
circuit inhibits the PWM comparator for a short time
(tLEB) after the SenseFET is turned on Pulse-WidthModulation (PWM) Circuit
CVCC
VCC
3
VSTR
6
Istart
VREF
8V/12V
Vcc good
Internal
Bias
3. Synchronization: The FSQ-series employs a quasiresonant switching technique to minimize the switching
noise and loss. The basic waveforms of the quasiresonant converter are shown in Figure 25. To minimize
the MOSFET's switching loss, the MOSFET should be
turned on when the drain voltage reaches its minimum
value, which is indirectly detected by monitoring the VCC
winding voltage, as shown in Figure 24.
FSQ0465 Rev.00
Figure 22. Startup Circuit
2. Feedback Control: FPS employs current-mode
control, as shown in Figure 23. An opto-coupler (such as
the FOD817A) and shunt regulator (such as the KA431)
are typically used to implement the feedback network.
Comparing the feedback voltage with the voltage across
the Rsense resistor makes it possible to control the
switching duty cycle. When the reference pin voltage of
the shunt regulator exceeds the internal reference
voltage of 2.5V, the opto-coupler LED current increases,
pulling down the feedback voltage and reducing the duty
cycle. This typically happens when the input voltage is
increased or the output load is decreased.
Vds
V RO
VRO
V DC
TF
Vsync
V ovp (8V)
VCC
VREF
Idelay
VFB
VO
IFB
4
H11A817A
D2
+
VFB*
KA431
1.2V
SenseFET
OSC
D1
CB
1.0V
3R
230ns Delay
Gate
driver
R
MOSFET Gate
-
VSD
OLP
ON
Rsense
ON
FSQ0465 Rev.00
FSQ0465 Rev.00
Figure 24. Quasi-Resonant Switching Waveforms
Figure 23. Pulse-Width-Modulation (PWM) Circuit
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
12
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
Functional Description
ID S
I DS
ingnore
4.4V
V sync
FS Q 0465 R ev.00
Figure 27. After Vsync Finds First Valley
4. Protection Circuits: The FSQ-series has several
self-protective functions, such as Overload Protection
(OLP), Abnormal Over-Current Protection (AOCP),
Over-Voltage Protection (OVP), and Thermal Shutdown
(TSD). All the protections are implemented as autorestart mode. Once the fault condition is detected,
switching is terminated and the SenseFET remains off.
This causes VCC to fall. When VCC falls down to the
Under-Voltage Lockout (UVLO) stop voltage of 8V, the
protection is reset and the startup circuit charges the
VCC capacitor. When the VCC reaches the start voltage
of 12V, normal operation resumes. If the fault condition is
not removed, the SenseFET remains off and VCC drops
to stop voltage again. In this manner, the auto-restart can
alternately enable and disable the switching of the power
SenseFET until the fault condition is eliminated.
Because these protection circuits are fully integrated into
the IC without external components, reliability is
improved without increasing cost.
V DS
4.4V
V sync
1.2V
1.0V
FSQ 0465 Rev.00
internal delay
Figure 25. Vsync > 4.4V at tX
tX
IDS
1.2V
1.0V
internal delay
I DS
tB=15µs
I DS
V DS
tX
t B =15µs
tX
t B =15µs
IDS
V DS
Power
on
Fault
occurs
Fault
rem oved
VDS
Vsync
4.4V
V CC
1.2V
1.0V
12V
8V
FSQ0465 Rev.00
internal delay
t
Figure 26. Vsync < 4.4V at tX
FSQ0465 Rev.00
Norm al
operation
Fault
situation
Norm al
operation
Figure 28. Auto Restart Protection Waveforms
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
13
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
The switching frequency is the combination of blank time
(tB) and detection time window (tW). In case of a heavy
load, the sync voltage remains flat after tB and waits for
valley detection during tW. This leads to a low switching
frequency not suitable for heavy loads. To correct this
drawback, additional timing is used. The timing
conditions are described in Figures 25, 26, and 27. When
the Vsync remains flat higher than 4.4V at the end of tB
which is instant tX, the next switching cycle starts after
internal delay time from tX. In the second case, the next
switching occurs on the valley when the Vsync goes below
4.4V within tB. Once Vsync detects the first valley in tB, the
other switching cycle follows classical QRC operation.
3R
LEB
200ns
S
Q
R
Q
Gate
driver
R
Rsense
2
GND
+
AOCP
-
FSQ0465 Rev.00
VOCP
Figure 30. Abnormal Over-Current Protection
4.3 Output-Short Protection (OSP): If the output is
shorted, steep current with extremely high di/dt can flow
through the SenseFET during the LEB time. Such a
steep current brings high voltage stress on the drain of
SenseFET when turned off. To protect the device from
such an abnormal condition, OSP is included in the FSQseries. It is comprised of detecting VFB and SenseFET
turn-on time. When the VFB is higher than 2V and the
SenseFET turn-on time is lower than 1.2µs, the FPS
recognizes this condition as an abnormal error and shuts
down PWM switching until VCC reaches Vstart again. An
abnormal condition output short is shown in Figure 31.
Rectifier
Diode
Current
MOSFET
Drain
Current
F S Q 0 4 6 5 R e v .0 0
V FB
OSC
PWM
Turn-off delay
ILIM
O ve rlo a d p ro te c tio n
VFB
6 .0 V
0
Minimum turn-on time
Vo
2 .5 V
D
1.2µs
output short occurs
t 1 2 = C fb *(6 .0 -2 .5 )/I d e la y
T1
0
T2
Io
t
FSQ0465 Rev. 00
Figure 29. Overload Protection
0
Figure 31. Output Short Waveforms
4.2 Abnormal Over-Current Protection (AOCP): When
the secondary rectifier diodes or the transformer pins are
shorted, a steep current with extremely high di/dt can
flow through the SenseFET during the LEB time. Even
though the FSQ-series has overload protection, it is not
enough to protect the FSQ-series in that abnormal case,
since severe current stress is imposed on the SenseFET
until OLP triggers. The FSQ-series has an internal
AOCP circuit shown in Figure 30. When the gate turn-on
signal is applied to the power SenseFET, the AOCP
block is enabled and monitors the current through the
sensing resistor. The voltage across the resistor is
compared with a preset AOCP level. If the sensing
resistor voltage is greater than the AOCP level, the set
signal is applied to the latch, resulting in the shutdown of
the SMPS.
4.4 Over-Voltage Protection (OVP): If the secondary
side feedback circuit malfunctions or a solder defect
causes an opening in the feedback path, the current
through the opto-coupler transistor becomes almost
zero. Then, Vfb climbs up in a similar manner to the
overload situation, forcing the preset maximum current
to be supplied to the SMPS until overload protection is
activated. Because more energy than required is
provided to the output, the output voltage may exceed
the rated voltage before overload protection is activated,
resulting in the breakdown of the devices in the
secondary side. To prevent this situation, an over-voltage
protection (OVP) circuit is employed. In general, VCC is
proportional to the output voltage and the FSQ-series
uses VCC instead of directly monitoring the output
voltage. If VCC exceeds 19V, an OVP circuit is activated,
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
14
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
4.1 Overload Protection (OLP): Overload is defined as
the load current exceeding its normal level due to an
unexpected abnormal event. In this situation, the
protection circuit should trigger to protect the SMPS.
However, even when the SMPS is in the normal
operation, the overload protection circuit can be
triggered during the load transition. To avoid this
undesired operation, the overload protection circuit is
designed to trigger only after a specified time to
determine whether it is a transient situation or a true
overload situation. Because of the pulse-by-pulse
current limit capability, the maximum peak current
through the SenseFET is limited, and therefore the
maximum input power is restricted with a given input
voltage. If the output consumes more than this maximum
power, the output voltage (VO) decreases below the set
voltage. This reduces the current through the optocoupler LED, which also reduces the opto-coupler
transistor current, thus increasing the feedback voltage
(VFB). If VFB exceeds 2.5V, D1 is blocked and the 5µA
current source starts to charge CB slowly up to VCC. In
this condition, VFB continues increasing until it reaches
6V, when the switching operation is terminated, as
shown in Figure 29. The delay time for shutdown is the
time required to charge CFB from 2.5V to 6V with 5µA. A
20 ~ 50ms delay time is typical for most applications.
VO
Voset
VFB
4.5 Thermal Shutdown with Hysteresis (TSD): The
SenseFET and the control IC are built in one package.
This enables the control IC to detect the abnormally high
temperature of the SenseFET. If the temperature
exceeds approximately 140°C, the thermal shutdown
triggers IC shutdown. The IC recovers its operation when
the junction temperature decreases 60°C from TSD
temperature and VCC reaches startup voltage (Vstart).
0.55V
0.35V
IDS
5. Soft-Start: The FPS has an internal soft-start circuit
that increases PWM comparator inverting input voltage
with the SenseFET current slowly after it starts up. The
typical soft-start time is 17.5ms. The pulse width to the
power switching device is progressively increased to
establish the correct working conditions for transformers,
inductors, and capacitors. The voltage on the output
capacitors is progressively increased with the intention of
smoothly establishing the required output voltage. This
mode helps prevent transformer saturation and reduces
stress on the secondary diode during startup.
VDS
t1
Switching
disabled
t2
t3
Switching
disabled
t4
Figure 32. Waveforms of Burst Operation
7. Switching Frequency Limit: To minimize switching
loss and Electromagnetic Interference (EMI), the
MOSFET turns on when the drain voltage reaches its
minimum value in quasi-resonant operation. However,
this causes switching frequency to increases at light load
conditions. As the load decreases or input voltage
increases, the peak drain current diminishes and the
switching frequency increases. This results in severe
switching losses at light-load condition, as well as
intermittent switching and audible noise. These problems
create limitations for the quasi-resonant converter
topology in a wide range of applications.
6. Burst Operation: To minimize power dissipation in
standby mode, the FPS enters burst-mode operation. As
the load decreases, the feedback voltage decreases. As
shown in Figure 32, the device automatically enters
burst-mode when the feedback voltage drops below
VBURL (350mV). At this point, switching stops and the
output voltages start to drop at a rate dependent on
standby current load. This causes the feedback voltage
to rise. Once it passes VBURH (550mV), switching
resumes. The feedback voltage then falls and the
process repeats. Burst-mode operation alternately
enables and disables switching of the power SenseFET,
thereby reducing switching loss in standby mode.
To overcome these problems, FSQ-series employs a
frequency-limit function, as shown in Figures 33 and
Figure 34. Once the SenseFET is turned on, the next
turn-on is prohibited during the blanking time (tB). After
the blanking time, the controller finds the valley within
the detection time window (tW) and turns on the
MOSFET, as shown in Figures 33 and Figure 34 (Cases
A, B, and C). If no valley is found during tW, the internal
SenseFET is forced to turn on at the end of tW (Case D).
Therefore, the devices have a minimum switching
frequency of 48kHz and a maximum switching frequency
of 67kHz.
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
time
FSQ0465 Rev. 00
www.fairchildsemi.com
15
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
resulting in the termination of the switching operation. To
avoid undesired activation of OVP during normal
operation, VCC should be designed below 19V.
IDS
IDS
A
VDS
tB=15μs
ts
IDS
Internally, quasi-resonant operation is divided into two
categories; one is first-valley switching and the other is
second-valley switching after blanking time. In AVS, two
successive occurrences of first-valley switching and the
other two successive occurrences of second-valley
switching is alternatively selected to maximize frequency
modulation. As depicted in Figure 34, the switching
frequency hops when the input voltage is high. The
internal timing diagram of AVS is described in Figure 35.
IDS
B
tB=15μs
VDS
ts
IDS
IDS
fs
C
VDS
1
15μs
1
17 μs
Assume the resonant period is 2 μ s
67kHz
59kHz
tB=15μs
53kHz
48kHz
ts
1
19 μs
AVS trigger point
Constant
frequency
CCM
IDS
IDS
1
21μs
Variable frequency within limited range
DCM
AVS region
VDS
tB=15μs
tW=6μs
D
D
C
B
A
VIN
FSQ0465 Rev.00
tsmax=21μs
FSQ0465 Rev. 00
Figure 34. Switching Frequency Range
Figure 33. QRC Operation with Limited Frequency
Vgate
AVS
Synchronize
One-shot
Synchronize
GateX2
triggering
1st or 2nd is depend on GateX2
tB
Vgate continued 2 pulses
Vgate continued another 2 pulses
1st valley switching
2nd valley switching
fixed
fixed
fixed
VDS
Vgate continued 2 pulses
fixed
de-triggering triggering
tB
1st valley switching
tB
GateX2: Counting Vgate every 2 pulses independent on other signals .
fixed
fixed
1st or 2nd is dependent on GateX2
tB
tB
tB
1st valley- 2nd valley frequency modulation.
Modulation frequency is approximately 17kHz.
FSQ0465 Rev. 00
Figure 35. Alternating Valley Switching (AVS)
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
16
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
8. AVS (Alternating Valley Switching): Due to the
quasi-resonant operation with limited frequency, the
switching frequency varies depending on input voltage,
load transition, and so on. At high input voltage, the
switching on time is relatively small compared to low
input voltage. The input voltage variance is small and the
switching frequency modulation width becomes small. To
improve the EMI performance, AVS is enabled when
input voltage is high and the switching on time is small.
tsmax=21μs
Due to the combined scheme, FPS shows better noise
immunity than conventional PWM controller and
MOSFET discrete solutions. Furthermore, internal drain
current sense eliminates noise generation caused by a
sensing resistor. There are some recommendations for
PCB layout to enhance noise immunity and suppress the
noise inevitable in power-handling components.
There are typically two grounds in the conventional
SMPS: power ground and signal ground. The power
ground is the ground for primary input voltage and
power, while the signal ground is ground for PWM
controller. In FPS, those two grounds share the same
pin, GND. Normally the separate grounds do not share
the same trace and meet only at one point, the GND pin.
More, wider patterns for both grounds are good for large
currents by decreasing resistance.
Capacitors at the VCC and FB pins should be as close as
possible to the corresponding pins to avoid noise from
the switching device. Sometimes Mylar® or ceramic
capacitors with electrolytic for VCC is better for smooth
operation. The ground of these capacitors needs to
connect to the signal ground (not power ground).
Figure 36. Recommended PCB Layout
The cathode of the snubber diode should be close to the
Drain pin to minimize stray inductance. The Y-capacitor
between primary and secondary should be directly
connected to the power ground of DC link to maximize
surge immunity.
Because the voltage range of feedback and sync line is
small, it is affected by the noise of the drain pin. Those
traces should not draw across or close to the drain line.
When the heat sink is connected to the ground, it should
be connected to the power ground. If possible, avoid
using jumper wires for power ground and drain.
Mylar® is a registered trademark of DuPont Teijin Films.
© 2008 Fairchild Semiconductor Corporation
FSQ0465RS/RB Rev. 1.0.1
www.fairchildsemi.com
17
FSQ0465RS/RB — Green-Mode Farichild Power Switch (FPS™) for Quasi-Resonant Operation
PCB Layout Guide
Application
FPS™ Device
Input Voltage
Range
Rated Output Power
Output Voltage
(Maximum Current)
LCD Monitor
Power Supply
FSQ0465RS
85-265VAC
40W
5.0V (2.0A)
13V (2.3A)
Features
! Average efficiency of 25%, 50%, 75%, and 100% load conditions is higher than 80% at universal input
! Low standby mode power consumption (
工商网监
湘ICP备2023018690号
