FSFR-XS Series — Fairchild Power Switch (FPS™)
for Half-Bridge Resonant Converters
Features
Description
Variable Frequency Control with 50% Duty Cycle
for Half-Bridge Resonant Converter Topology
High Efficiency through Zero Voltage Switching (ZVS)
Internal UniFET™ with Fast-Recovery Body Diode
Fixed Dead Time (350ns) Optimized for MOSFETs
Up to 300kHz Operating Frequency
Auto-Restart Operation for All Protections with
External LVCC
Protection Functions: Over-Voltage Protection
(OVP), Over-Current Protection (OCP), Abnormal
Over-Current Protection (AOCP), Internal Thermal
Shutdown (TSD)
Applications
PDP and LCD TVs
Desktop PCs and Servers
Adapters
Telecom Power Supplies
The FSFR-XS series includes highly integrated power
switches designed for high-efficiency half-bridge
resonant converters. Offering everything necessary to
build a reliable and robust resonant converter, the FSFRXS series simplifies designs while improving productivity
and performance. The FSFR-XS series combines power
MOSFETs with fast-recovery type body diodes, a highside gate-drive circuit, an accurate current controlled
oscillator, frequency limit circuit, soft-start, and built-in
protection functions. The high-side gate-drive circuit has
common-mode noise cancellation capability, which
guarantees stable operation with excellent noise
immunity. The fast-recovery body diode of the MOSFETs
improves reliability against abnormal operation
conditions, while minimizing the effect of reverse
recovery. Using the zero-voltage-switching (ZVS)
technique dramatically reduces the switching losses and
significantly improves efficiency. The ZVS also reduces
the switching noise noticeably, which allows a smallsized Electromagnetic Interference (EMI) filter.
The FSFR-XS series can be applied to resonant
converter topologies such as series resonant, parallel
resonant, and LLC resonant converters.
Related Resources
AN4151 — Half-bridge LLC Resonant Converter Design
TM
Using FSFR-Series Fairchild Power Switch (FPS )
Ordering Information
Part Number
Package
Operating
Junction
Temperature
FSFR2100XS
FSFR1800XS
FSFR1700XS
9-SIP
FSFR1600XS
-40 to +130°C
FSFR2100XSL
FSFR1800XSL
FSFR1700XSL
9-SIP
L-Forming
FSFR1600XSL
RDS(ON_MAX)
Maximum Output Power
without Heatsink
(1,2)
(VIN=350~400V)
Maximum Output
Power with Heatsink
(1,2)
(VIN=350~400V)
0.51Ω
180W
400W
0.95Ω
120W
260W
1.25Ω
100W
200W
1.55Ω
80W
160W
0.51Ω
180W
400W
0.95Ω
120W
260W
1.25Ω
100W
200W
1.55Ω
80W
160W
Notes:
1. The junction temperature can limit the maximum output power.
2. Maximum practical continuous power in an open-frame design at 50°C ambient.
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
October 2010
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
Application Circuit Diagram
Figure 1. Typical Application Circuit (LLC Resonant Half-Bridge Converter)
Block Diagram
Figure 2. Internal Block Diagram
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
2
Figure 3. Package Diagram
Pin Definitions
Pin #
Name
Description
1
VDL
This is the drain of the high-side MOSFET, typically connected to the input DC link voltage.
2
AR
This pin is for discharging the external soft-start capacitor when any protections are
triggered. When the voltage of this pin drops to 0.2V, all protections are reset and the
controller starts to operate again.
3
RT
This pin programs the switching frequency. Typically, an opto-coupler is connected to control
the switching frequency for the output voltage regulation.
4
CS
This pin senses the current flowing through the low-side MOSFET. Typically, negative
voltage is applied on this pin.
5
SG
This pin is the control ground.
6
PG
This pin is the power ground. This pin is connected to the source of the low-side MOSFET.
7
LVCC
This pin is the supply voltage of the control IC.
8
NC
9
HVCC
No connection.
This is the supply voltage of the high-side gate-drive circuit IC.
10
VCTR
This is the drain of the low-side MOSFET. Typically, a transformer is connected to this pin.
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
3
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
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
VDS
LVCC
Parameter
Min.
Maximum Drain-to-Source Voltage (VDL-VCTR and VCTR-PG)
Low-Side Supply Voltage
Max.
Unit
500
V
-0.3
25.0
V
-0.3
25.0
V
High-Side Floating Supply Voltage
-0.3
525.0
V
VAR
Auto-Restart Pin Input Voltage
-0.3
LVCC
V
VCS
Current-Sense (CS) Pin Input Voltage
-5.0
1.0
V
VRT
RT Pin Input Voltage
-0.3
5.0
V
50
V/ns
HVCC to VCTR High-Side VCC Pin to Low-Side Drain Voltage
HVCC
dVCTR/dt
PD
TJ
TSTG
Allowable Low-Side MOSFET Drain Voltage Slew Rate
Total Power Dissipation
(3)
Maximum Junction Temperature
FSFR2100XS/L
12.0
FSFR1800XS/L
11.7
FSFR1700XS/L
11.6
FSFR1600XS/L
11.5
(4)
W
+150
(4)
Recommended Operating Junction Temperature
-40
+130
Storage Temperature Range
-55
+150
°C
°C
MOSFET Section
VDGR
Drain Gate Voltage (RGS=1MΩ)
VGS
Gate Source (GND) Voltage
IDM
Drain Current Pulsed
(5)
500
±30
FSFR2100XS/L
32
FSFR1800XS/L
23
FSFR1700XS/L
20
FSFR1600XS/L
18
FSFR2100XS/L
FSFR1800XS/L
ID
V
Continuous Drain Current
FSFR1700XS/L
FSFR1600XS/L
TC=25°C
10.5
TC=100°C
6.5
TC=25°C
7.0
TC=100°C
4.5
TC=25°C
6.0
TC=100°C
3.9
TC=25°C
4.5
TC=100°C
2.7
V
A
A
Package Section
Torque
Recommended Screw Torque
5~7
kgf·cm
Notes:
3. Per MOSFET when both MOSFETs are conducting.
4. The maximum value of the recommended operating junction temperature is limited by thermal shutdown.
5. Pulse width is limited by maximum junction temperature.
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
4
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
Absolute Maximum Ratings
TA=25°C unless otherwise specified.
Symbol
θJC
Parameter
Value
Junction-to-Case Center Thermal Impedance
(Both MOSFETs Conducting)
FSFR2100XS/L
10.44
FSFR1800XS/L
10.68
FSFR1700XS/L
10.79
FSFR1600XS/L
10.89
Unit
ºC/W
Electrical Characteristics
TA=25°C unless otherwise specified.
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
MOSFET Section
BVDSS
RDS(ON)
trr
Drain-to-Source Breakdown Voltage
On-State Resistance
Body Diode Reverse
(6)
Recovery Time
ID=200μA, TA=25°C
ID=200μA, TA=125°C
500
V
540
FSFR2100XS/L VGS=10V, ID=6.0A
0.41
0.51
FSFR1800XS/L VGS=10V, ID=3.0A
0.77
0.95
FSFR1700XS/L VGS=10V, ID=2.0A
1.00
1.25
FSFR1600XS/L VGS=10V, ID=2.25A
1.25
1.55
FSFR2100XS/L
VGS=0V, IDiode=10.5A,
dIDiode/dt=100A/μs
120
FSFR1800XS/L
VGS=0V, IDiode=7.0A,
dIDiode/dt=100A/μs
160
FSFR1700XS/L
VGS=0V, IDiode=6.0A,
dIDiode/dt=100A/μs
160
FSFR1600XS/L
VGS=0V, IDiode=4.5A,
dIDiode/dt=100A/μs
90
Ω
ns
Supply Section
ILK
Offset Supply Leakage Current
HVCC=VCTR=500V
50
μA
IQHVCC
Quiescent HVCC Supply Current
(HVCCUV+) - 0.1V
50
120
μA
IQLVCC
Quiescent LVCC Supply Current
(LVCCUV+) - 0.1V
100
200
μA
IOHVCC
Operating HVCC Supply Current
(RMS Value)
fOSC=100KHz
6
9
mA
No Switching
100
200
μA
IOLVCC
Operating LVCC Supply Current
(RMS Value)
fOSC=100KHz
7
11
mA
No Switching
2
4
mA
Continued on the following page…
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
5
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
Thermal Impedance
TA=25°C unless otherwise specified.
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
UVLO Section
LVCCUV+
LVCC Supply Under-Voltage Positive Going Threshold (LVCC Start)
11.2
12.5
13.8
V
LVCCUV-
LVCC Supply Under-Voltage Negative Going Threshold (LVCC Stop)
8.9
10.0
11.1
V
LVCCUVH
LVCC Supply Under-Voltage Hysteresis
HVCCUV+
HVCC Supply Under-Voltage Positive Going Threshold (HVCC Start)
8.2
9.2
10.2
V
HVCCUV-
HVCC Supply Under-Voltage Negative Going Threshold (HVCC Stop)
7.8
8.7
9.6
V
HVCCUVH
HVCC Supply Under-Voltage Hysteresis
2.50
V
0.5
V
Oscillator & Feedback Section
VRT
V-I Converter Threshold Voltage
fOSC
Output Oscillation Frequency
DC
Output Duty Cycle
fSS
Internal Soft-Start Initial Frequency
tSS
Internal Soft-Start Time
RT=5.2KΩ
1.5
2.0
2.5
V
94
100
106
KHz
48
50
52
%
fSS=fOSC+40kHz,
RT=5.2KΩ
140
KHz
2
3
4
ms
Protection Section
VCssH
Beginning Voltage to Discharge CSS
0.9
1.0
1.1
V
VCssL
Beginning Voltage to Charge CSS and
Restart
0.16
0.20
0.24
V
VOVP
LVCC Over-Voltage Protection
21
23
25
V
VAOCP
AOCP Threshold Voltage
-1.0
-0.9
-0.8
V
LVCC > 21V
(6)
tBAO
AOCP Blanking Time
VOCP
OCP Threshold Voltage
VCS < VAOCP
(6)
tBO
OCP Blanking Time
VCS < VOCP
tDA
Delay Time (Low Side) Detecting from
(6)
VAOCP to Switch Off
TSD
Thermal Shutdown Temperature
(6)
50
ns
-0.64
-0.58
-0.52
V
1.0
1.5
2.0
μs
250
400
ns
135
150
°C
120
Dead-Time Control Section
DT
(7)
Dead Time
350
ns
Notes:
6. This parameter, although guaranteed, is not tested in production.
7. These parameters, although guaranteed, are tested only in EDS (wafer test) process.
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
6
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
Electrical Characteristics (Continued)
1.1
1.1
1.05
1.05
Normalized at 25OC
Normalized at 25OC
These characteristic graphs are normalized at TA=25ºC.
1
0.95
1
0.95
0.9
0.9
-50
-25
0
25
50
75
-50
100
-25
0
Temp (OC)
50
75
100
Figure 5. Switching Frequency vs. Temperature
1.1
1.1
1.05
1.05
Normalized at 25OC
Normalized at 25OC
Figure 4. Low-Side MOSFET Duty Cycle
vs. Temperature
1
0.95
0.9
1
0.95
0.9
-50
-25
0
25
50
75
100
-50
-25
0
25
50
75
100
Temp (OC)
Temp (OC)
Figure 6. High-Side VCC (HVCC) Start vs. Temperature
Figure 7. High-Side VCC (HVCC) Stop vs. Temperature
1.1
1.1
1.05
1.05
Normalized at 25OC
Normalized at 25OC
25
Temp (OC)
1
0.95
1
0.95
0.9
0.9
-50
-25
0
25
50
75
-50
100
Figure 8. Low-Side VCC (LVCC) Start vs. Temperature
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
-25
0
25
50
75
100
Temp (OC)
Temp (OC)
Figure 9. Low-Side VCC (LVCC) Stop vs. Temperature
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7
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
Typical Performance Characteristics
1.1
1.1
1.05
1.05
Normalized at 25OC
Normalized at 25OC
These characteristic graphs are normalized at TA=25ºC.
1
0.95
0.9
1
0.95
0.9
-50
-25
0
25
50
75
100
-50
-25
0
Temp (OC)
Figure 10. LVCC OVP Voltage vs. Temperature
50
75
100
Figure 11. RT Voltage vs. Temperature
1.1
1.1
1.05
1.05
Normalized at 25℃
Normalized at 25℃
25
Temp (OC)
1
0.95
0.9
1
0.95
0.9
-50
-25
0
25
50
75
100
-50
Temp(℃)
-25
0
25
50
75
100
Temp(℃)
Figure 12. VCssL vs. Temperature
Figure 13. VCssH vs. Temperature
1.1
Normalized at 25OC
1.05
1
0.95
0.9
-50
-25
0
25
50
75
100
Temp (OC)
Figure 14. OCP Voltage vs. Temperature
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
8
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
Typical Performance Characteristics (Continued)
1. Basic Operation. FSFR-XS series is designed to
drive high-side and low-side MOSFETs complementarily
with 50% duty cycle. A fixed dead time of 350ns is
introduced between consecutive transitions, as shown in
Figure 15.
Figure 15. MOSFETs Gate Drive Signal
2. Internal Oscillator: FSFR-XS series employs a
current-controlled oscillator, as shown in Figure 16.
Internally, the voltage of RT pin is regulated at 2V and the
charging / discharging current for the oscillator capacitor,
CT, is obtained by copying the current flowing out of the
RT pin (ICTC) using a current mirror. Therefore, the
switching frequency increases as ICTC increases.
Figure 17. Resonant Converter Typical Gain Curve
LVCC
VDL
RT
Rmax
Rmin
Rss
AR
Css
CS
PG
SG
Figure 16. Current-Controlled Oscillator
Figure 18. Frequency Control Circuit
3. Frequency Setting: Figure 17 shows the typical
voltage gain curve of a resonant converter, where the
gain is inversely proportional to the switching frequency
in the ZVS region. The output voltage can be regulated
by modulating the switching frequency. Figure 18 shows
the typical circuit configuration for the RT pin, where the
opto-coupler transistor is connected to the RT pin to
modulate the switching frequency.
To prevent excessive inrush current and overshoot of
output voltage during startup, increase the voltage gain
of the resonant converter progressively. Since the
voltage gain of the resonant converter is inversely
proportional to the switching frequency, the soft-start is
implemented by sweeping down the switching frequency
ISS
from an initial high frequency (f ) until the output
voltage is established. The soft-start circuit is made by
connecting R-C series network on the RT pin, as shown
in Figure 18. FSFR-XS series also has a 3ms internal
soft-start to reduce the current overshoot during the initial
cycles, which adds 40kHz to the initial frequency of the
external soft-start circuit, as shown in Figure 19. The
initial frequency of the soft-start is given as:
The minimum switching frequency is determined as:
f min =
5.2k Ω
× 100(kHz )
Rmin
(1)
Assuming the saturation voltage of opto-coupler
transistor is 0.2V, the maximum switching frequency is
determined as:
f max = (
5.2k Ω 4.68k Ω
+
) × 100( kHz )
Rmin
Rmax
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
f ISS = (
5.2k Ω 5.2k Ω
+
) × 100 + 40 (kHz )
Rmin
RSS
(3)
(2)
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9
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
Functional Description
τ = RSS • CSS
(a )
(b )
( a)
(b ) (a )
(b )
L V CC
V AR
V C ssH
V C ssL
(4)
ICr
t stop
tS /S
(a ) P r o te ction s a r e tr igge r e d, ( b ) F S F R- U S r e sta r ts
Figure 21. Self Auto-Restart Operation
5. Protection Circuits: The FSFR-XS series has several
self-protective functions, such as Over-Current Protection
(OCP), Abnormal Over-Current Protection (AOCP), OverVoltage Protection (OVP), and Thermal Shutdown (TSD).
These protections are auto-restart mode protections, as
shown in Figure 22.
Figure 19. Frequency Sweeping of Soft-Start
4. Self Auto-Restart: The FSFR-XS series can restart
automatically even though any built-in protections are
triggered with external supply voltage. As can be seen in
Figure 20 and Figure 21, once any protections are
triggered, the M1 switch turns on and the V-I converter is
disabled. CSS starts to discharge until VCss across CSS
drops to VCssL. Then, all protections are reset, M1 turns
off, and the V-I converter resumes at the same time. The
FSFR-XS starts switching again with soft-start. If the
protections occur while VCss is under VCssL and VCssH
level, the switching is terminated immediately, VCss
continues to increase until reaching VCssH, then CSS is
discharged by M1.
Once a fault condition is detected, switching is terminated
and the MOSFETs remain off. When LVCC falls to the LVCC
stop voltage of 10V or AR signal is HIGH, the protection is
reset. The FSFR-XS resumes normal operation when
LVCC reaches the start voltage of 12.5V.
Figure 22. Protection Blocks
5.1 Over-Current Protection (OCP): When the
sensing pin voltage drops below -0.58V, OCP is
triggered and the MOSFETs remain off. This protection
has a shutdown time delay of 1.5µs to prevent
premature shutdown during startup.
Figure 20. Internal Block of AR Pin
5.2 Abnormal Over-Current Protection (AOCP): If
the secondary rectifier diodes are shorted, large
current with extremely high di/dt can flow through the
MOSFET before OCP is triggered. AOCP is triggered
without shutdown delay if the sensing pin voltage
drops below -0.9V.
After protections trigger, FSFR-XS is disabled during the
stop-time, tstop, where VCss decreases and reaches to
VCssL. The stop-time of FSFR-XS can be estimated as:
t STOP = C SS • {(RSS + RMIN ) || 5kΩ}
(5)
The soft-start time, ts/s can be set as Equation (4).
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
10
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
It is typical to set the initial frequency of soft-start two to
three times the resonant frequency (fO) of the resonant
network. The soft-start time is three to four times the RC
time constant. The RC time constant is:
7. PCB Layout Guidelines: Duty imbalance problems
may occur due to the radiated noise from the main
transformer, the inequality of the secondary side leakage
inductances of main transformer, and so on. This is one
of the reasons that the control components in the vicinity
of RT pin are enclosed by the primary current flow pattern
on PCB layout. The direction of the magnetic field on the
components caused by the primary current flow is
changed when the high- and low-side MOSFET turn on
by turns. The magnetic fields with opposite directions
induce a current through, into, or out of the RT pin, which
makes the turn-on duration of each MOSFET different. It
is strongly recommended to separate the control
components in the vicinity of RT pin from the primary
current flow pattern on PCB layout. Figure 25 shows an
example for the duty-balanced case.
5.4 Thermal Shutdown (TSD): The MOSFETs and
the control IC in one package makes it easier for the
control IC to detect the abnormal over-temperature of
the MOSFETs. If the temperature exceeds
approximately 130°C, thermal shutdown triggers.
6. Current Sensing Using a Resistor: FSFR-XS series
senses drain current as a negative voltage, as shown in
Figure 23 and Figure 24. Half-wave sensing allows low
power dissipation in the sensing resistor, while full-wave
sensing has less switching noise in the sensing signal.
Cr
Np
Ns
Ns
Control
IC
VCS
Ids
CS
SG
PG
Rsense
VCS
Ids
Figure 25. Example for Duty Balancing
Figure 23. Half-Wave Sensing
Ids
VCS
Cr
Control
IC
VCS
Np
CS
PG
SG
Rsense
Ns
Ns
Ids
Figure 24. Full-Wave Sensing
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
11
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
5.3 Over-Voltage Protection (OVP): When the LVCC
reaches 23V, OVP is triggered. This protection is used
when auxiliary winding of the transformer to supply VCC
to the FPS™ is utilized.
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
Physical Dimensions
Figure 26. 9-Lead Single Inline Package (SIP)
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions,
specifically the warranty therein, which covers Fairchild products.
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
12
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
Physical Dimensions
Figure 27. 9-Lead Single Inline Package (SIP) L-Forming
Package drawings are provided as a service to customers considering Fairchild components. Drawings may change in any manner
without notice. Please note the revision and/or date on the drawing and contact a Fairchild Semiconductor representative to verify or
obtain the most recent revision. Package specifications do not expand the terms of Fairchild’s worldwide terms and conditions,
specifically the warranty therein, which covers Fairchild products.
Always visit Fairchild Semiconductor’s online packaging area for the most recent package drawings:
http://www.fairchildsemi.com/packaging/.
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
13
FSFR-XS Series — Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter
© 2010 Fairchild Semiconductor Corporation
FSFR-XS Series • Rev.1.0.1
www.fairchildsemi.com
14