FAN7631 — Advanced PFM Controller for Half-Bridge Resonant Converters
April 2012
FAN7631
Advanced Pulse Frequency Modulation (PFM)
Controller for Half-Bridge Resonant Converters
Features
Variable Frequency Control with 50% Duty Cycle
for Half-Bridge Resonant Converter Topologies
High Efficiency with Zero-Voltage-Switching (ZVS)
Up to 600kHz Operating Frequency
Built-in High-Side Gate Driver
High Gate-Driving Current: +500mA/-1000mA
Programmable Dead Time with a Resistor
Pulse Skipping and Burst Operation for Frequency
Limit (Programmable) at Light-Load Condition
Simple Remote On/Off Control with Latch or
Auto-Restart (A/R) Using FI or LS Pin
Protection Functions: Over-Voltage Protection
(OVP), Overload Protection (OLP), Over-Current
Protection (OCP), Abnormal Over-Current Protection
(AOCP), Internal Thermal Shutdown (TSD), and
High Precise Line Under-Voltage Lockout (LUVLO)
Level-Change OCP Function During Startup
Description
The FAN7631 is a pulse-frequency modulation controller
for high-efficiency half-bridge resonant converters that
includes a high-side gate drive circuit, an accurate
current-controlled oscillator, and various protection
functions. The FAN7631 features include variable dead
time, operating frequency up to 600kHz, protections such
as LUVLO, and a selectable latch or A/R protection using
the LS pin for user convenience.
The Zero-Voltage-Switching (ZVS) technique reduces the
switching losses and improves the efficiency significantly.
ZVS also reduces the switching noise noticeably, which
allows a small Electromagnetic Interference (EMI) filter.
Offering everything necessary to build a reliable and
robust resonant converter, the FAN7631 simplifies
designs and improves productivity and performance. The
FAN7631 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
Using FSFR-Series Fairchild Power Switch (FPS™)
Applications
PDP and LCD TVs
Desktop PCs and Servers
Video Game Consoles
Adapters
Telecom Power Supplies
Ordering Information
Part Number
FAN7631SJ
FAN7631SJX
Operating Junction
Temperature
-40C ~ 130C
Package
16-Lead, Small-Outline Package (SOP)
Packaging
Method
Tube
Tape & Reel
© 2011 Fairchild Semiconductor Corporation
FAN7631 • 1.0.2
www.fairchildsemi.com
FAN7631 — Advanced PFM Controller for Half-Bridge Resonant Converters
Application Circuit Diagram
Figure 1.
Typical Application Circuit (Resonant Half-Bridge Converter)
Block Diagram
Figure 2.
Internal Block Diagram
© 2011 Fairchild Semiconductor Corporation
FAN7631 • 1.0.2
www.fairchildsemi.com
2
FAN7631 — Advanced PFM Controller for Half-Bridge Resonant Converters
Pin Configuration
Figure 3.
Package Pin Assignments (16SOP)
Pin Definitions
Pin #
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
Name
CON
RT
SS
DT
NC
FI
SG
LS
CS
PG
LO
LV
CC
NC
CTR
HO
HV
CC
Description
This pin is used to enable / disable the gate drive outputs for pulse-skipping operation. When the
voltage of this pin is above 0.6V, the gate drive outputs are enabled. When the voltage of this pin
drops below 0.4V, gate drive signals for both MOSFETs are disabled.
This pin programs the switching frequency. Typically, an opto-coupler is connected to this pin to
control the switching frequency for the output voltage regulation.
This pin is used to program the soft-start time and overload protection delay. It also programs the
restart delay when the converter auto recovers from the protection states. Typically, a small
capacitor is connected on this pin.
This pin is to adjust the dead time using an external resistor.
No connection
User protection function / fault input. This pin can be used as a latch protection, which is
operated when a voltage applied to this pin is higher than 4V
DC
.
This pin is the ground of the control part.
This pin senses the line voltage for line under-voltage lockout (LUVLO).
This pin senses the current flowing through the main MOSFET. Typically, negative voltage is
applied on this pin.
This pin is the power ground. This pin typically connects to the source of the low-side MOSFET.
This pin is used for the low-side gate-driving signal.
This pin is for the supply voltage of the control IC and low-side gate-driving circuit.
No connection
This pin is connected to the drain of the low-side MOSFET. Typically, a transformer is connected
to this pin.
This pin is used for the high-side gate-driving signal.
This pin is used for the supply voltage of the high-side gate-driving circuit.
© 2011 Fairchild Semiconductor Corporation
FAN7631 • 1.0.2
www.fairchildsemi.com
3
FAN7631 — Advanced PFM Controller for Half-Bridge Resonant Converters
Absolute Maximum Ratings
Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be
operable above the recommended operating conditions. Extended exposure to stresses above the recommended
operating conditions may affect device reliability so that any test which is stressing the parts to these levels is not
recommended. The absolute maximum ratings are stress ratings only. T
A
=25C unless otherwise specified.
Symbol
HV
CC
V
HO
V
CTR
LV
CC
V
LO
V
CON
V
CS
V
RT
f
sw
V
LS
V
FI
V
SS
V
DT
dV
CTR
/dt
P
D
T
J
T
STG
Parameter
High-Side Floating Supply Voltage
High-Side Gate\-Driving Voltage
High-Side Offset Voltage
Allowable Negative V
CTR
at 15V
DC
Applied HV
CC
to CTR Pin
Low-Side Supply Voltage
Low-Side Gate Driving Voltage
Control Pin Input Voltage
Current Sense (CS) Pin Input Voltage
RT Pin Input Voltage
Recommended Switching Frequency
LS Pin Input Voltage
FI Pin Input Voltage
SS Pin Input Voltage
DT Pin Input Voltage
Allowable CTR Voltage Slew Rate
Total Power Dissipation
Maximum Junction Temperature
(2)
Recommended Operating Junction Temperature
(2)
Storage Temperature Range
Min.
-0.3
-0.3
V
CTR
-0.3
HV
CC
-25
-9.8
-0.3
-0.3
-0.3
-5.0
-0.3
10
-0.3
-0.3
-0.3
-0.3
Max.
25.0
625.0
HV
CC
+0.3
HV
CC
+0.3
-7.0
25.0
LV
CC
LV
CC
1.0
5.0
600
LV
CC
LV
CC
Internally
(1)
Clamped
Internally
(1)
Clamped
50
1.24
+150
Unit
V
V
V
V
V
V
V
V
V
V
kHz
V
V
V
V
V/ns
W
C
C
HV
CC
to V
CTR
High-Side V
CC
Pin to Center Voltage
-40
-55
+130
+150
Notes:
1. V
SS
and V
DT
are internally clamped at 5.0V, which has a tolerance between 4.75V and 5.25V.
2. The maximum value of the recommended operating junction temperature is limited by thermal shutdown.
Thermal Impedance
Symbol
θ
JA
Parameter
Junction-to-Ambient Thermal Impedance
Value
102
Unit
ºC/W
© 2011 Fairchild Semiconductor Corporation
FAN7631 • 1.0.2
www.fairchildsemi.com
4
FAN7631 — Advanced PFM Controller for Half-Bridge Resonant Converters
Electrical Characteristics
T
A
=25C and LV
CC
=17V unless otherwise specified.
Symbol
Supply Section
I
LK
I
Q
HV
CC
I
Q
LV
CC
Parameter
Offset Supply Leakage Current
Quiescent HV
CC
Supply Current
Quiescent LV
CC
Supply Current
Condition
HV
CC
=V
CTR
HV
CC,START
- 0.1V, V
CTR
=0V
LV
CC
,
START
- 0.1V, V
CTR
=0V
f
OSC
=100kHz, C
Load
=1nF,
V
CON
> 0.6V, V
CTR
=0V
Min.
Typ.
Max.
50
Unit
μA
μA
μA
mA
mA
μA
mA
mA
mA
50
100
3.0
8
100
5
10
2.6
120
200
4.5
10
200
7
14
3.5
I
O
HV
CC
Operating HV
CC
Supply Current
(3)
(RMS Value)
f
OSC
=300kHz, C
Load
=1nF,
V
CON
> 0.6V, V
CTR
=0V
f
OSC
=300kHz, V
CON
< 0.4V,
V
CTR
=0V (No Switching)
f
OSC
=100kHz, C
Load
=1nF
V
CON
> 0.6V, V
CTR
=0V
I
O
LV
CC
Operating LV
CC
Supply Current
(3)
(RMS Value)
f
OSC
=300kHz, C
Load
=1nF,
V
CON
> 0.6V, V
CTR
=0V
f
OSC
=300kHz, V
CON
< 0.4V,
V
CTR
=0V (No Switching)
UVLO Section
LV
CC,START
LV
CC,STOP
LV
CC,HYS
HV
CC,START
HV
CC,STOP
HV
CC,HYS
V
BH
V
BL
V
RT
f
OSC
DC
LV
CC
UVLO Turn-On Threshold
LV
CC
UVLO Turn-Off Threshold
LV
CC
UVLO Hysteresis
HV
CC
UVLO Turn-On Threshold
HV
CC
UVLO Turn-Off Threshold
HV
CC
UVLO Hysteresis
Pulse Skip Disable Threshold Voltage
Pulse Skip Enable Threshold Voltage
Regulated RT Voltage
Output Oscillation Frequency
Output Duty Cycle
R
T
=11.6kΩ, C
SS
=1nF
R
T
=2.7kΩ, C
SS
=1nF
R
T
=11.6kΩ, C
Load
=100pF
R
T
=2.7kΩ, C
Load
=100pF
V
CSS
=0V, LV
CC
=17V
V
CSS
=1.6V, LV
CC
=17V
C
SS
=1nF, V
CON
=3V
C
SS
=1nF, V
CON
=3V
C
SS
=1nF, V
CON
=3V
R
T
=11.6kΩV
CSS
=1.6V
R
T
=5.8kΩ
R
T
=2.7kΩ
V
RT-CON
RT-CON Voltage for Startup
600
60
120
mV
0.54
0.36
1.5
48
188
49
48
3
25
1.5
4.0
4.75
30
1.6
4.2
5.00
300
530
kHz
35
1.7
4.4
5.25
8.2
7.8
11.2
8.9
12.5
10.0
2.5
9.2
8.7
0.5
0.60
0.40
2.0
50
200
50
50
0.66
0.44
2.5
52
212
51
52
10.2
9.6
13.8
11.1
V
V
V
V
V
V
V
V
V
kHz
%
Oscillator & Feedback Section
Soft-Start and Restart Section
I
SS1
I
SS2
V
SS_START
V
SS_END
V
SSC
f
OSC_SS
Soft-Start Current 1
Soft-Start Current 2
Soft-Start Start Voltage
Soft-Start End Voltage
Clamped Soft-Start Voltage
Initial Output Oscillation Frequency
During Soft-Start
mA
μA
V
V
V
Continued on the following page…
© 2011 Fairchild Semiconductor Corporation
FAN7631 • 1.0.2
www.fairchildsemi.com
5
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