0618 Page 1 of 24
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/ Data and specifications subject to change without notice.







10 Ang Mo Kio Street 65, #03-18 TechPoint, Singapore 569059


Reference Design # 0618


IRAC1166-100W


+16V Low-side Smart Rectification
100W Flyback Demo Board
Users Guide



by

ISRAEL SERRANO

18 August 2006

Rev.1A 18 August 2006
RD#0618 Page 2 of 24
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105
http://www.irf.com
/ Data and specifications subject to change without notice.


























Page(s)
Table of Contents

2

1.0 INTRODUCTION

3

2.0 GENERAL DESCRIPTION

3

2.1 IRAC1166-100W +16V Demo Board Schematic Diagram

4

2.2 IRAC1166-100W +16V Demo Board Pictures

5

2.3 IRAC1166-100W +16V Demo Board PCB Layout

6

3.0 Circuit Description

7

4.0 Test Connection and Set up Pictures

8

5.0 Circuit Features

9

5.1 OVT Setting
9
5.2 ENABLE Setting
9
5.3 MOT Setting
9
5.4 Mosfet Selection Design Tips
10
6.0 Test Waveforms
11-18
6.1.1 Transient Load Test
11-13
6.1.2 Static Load Test
14-15
6.1.3 Ripple And Noise Measurement
16
6.1.4 Dynamic load Test
17
6.4 Startup & UVLO Test
18
7.0 Line / Load Regulation Test
19
7.1 IR1166 Demo Board V-I Characteristics Curve
19
7.2 System Efficiency Test
20
7.3 Thermal Verification
20
8.0 Summary
21
9.0 Appendix
21-25
9.1 Transformer turns ratio, Duty Cycle and Secondary Current Relationship
Chart
21
9.2 IR1166 100W +16V SR Demo Board Power Transformer Specs
22
10.0 IRAC1166-100W +16V Demo Board Bill of Materials (BOM)
23-24

Rev.1A 18 August 2006
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WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105
http://www.irf.com
/ Data and specifications subject to change without notice.




1.0 INTRODUCTION

Generally, Schottky diodes are traditional devices use in passive rectification in order to
have low conduction loss in secondary side for switching power supplies. The
proliferations of synchronous rectification (SR) idea - which is mostly use in buck-derive
topologies - have reached the domain of flyback application in recent years. The use of
low-voltage-low-Rdson mosfet has become so attractive to replace the Schottky rectifiers
in high current applications because it offers several system advantages such as
dramatic decrease in conduction loss and better thermal management of the whole
system by reducing the cost investment in heat sink and PCB space.


A number of techniques in the implementation of SR in flyback converters are
continuously growing from a simple self-driven (secondary winding voltage detection) to
a more complex solution using current transformer sensing or combinations of both to
improve the existing technology. The idea has become quite complicated though and
additional discrete devices have made the cost and part counts issue even worse.
Moreover, the issue of reverse current conduction (-due to the delay in sensing the sharp
drop of secondary current during turn-off phase of the SR) still lingers on in different input
line/ output load conditions. The use of a simple fast-rate-direct-sensing of voltage drop
across the mosfet (Vsd) using integrated solution has pave the way for a much simpler
and effective means of controlling the SR mosfets as well as alleviating the reverse
current and multiple-pulse gate turn-ON issues.

The objective of this user guide is to show the advantages of SR application using
integrated IC approach and study the practical limits of the efficiency improvements vs.
the normal rectification method.


2.0 GENERAL
DESCRIPTION

The IRAC1166-100W demo board is a universal-input flyback converter with single DC
output capable of delivering continuous 100W (@ +16V x 6.25A) during active
rectification mode. This demo board is primarily designed to study synchronous
rectification using IR1166 in low-side configuration to take advantage of simpler
derivation of Vcc supply from converters output. It is equipped with necessary jumpers to
ease exploring the conduction behavior of synchronous rectifiers SRs in quasi-resonant
mode, so discussion would be confined to variable frequency switching in Critical
Conduction Mode.

It features the fast Vsd sensing of the IR1166 Smart Rectifier Control IC with gate output
drive capability of 1.5Apk. It drives 2 pcs. of SRs in parallel (100V N-ch mosfet IRF7853
in SO-8 package with very low Rdson in its class : 18 m max). This had greatly
simplified the overall mechanical design for not having those bulky and heavy heat sinks
normally seen in high current flyback design using passive rectification.



Rev.1A 18 August 2006
RD#0618 Page 4 of 24
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105
http://www.irf.com
/ Data and specifications subject to change without notice.




FIGURE 1. IRAC1166-100W SCHEMATIC DIAGRAM


#
Vout-tp
Rs20
47K
Rs21
10K
Cs22
*10nF
Cs21
1nf
Rs1
5
10R
1
2
Dp
5
LS
4148
Rs23
430R
LED
Rp2 47K 2W
Cs20
47nF
Cp
4
4N
7/
1k
V
Rp
3
22R
Vcc-
P
TP
Cp
7
470pF 1k
V
1
2
J5
1
2
CS1
8
100N
F
1
2
10K
Rs1
8
1
2
J1
1
3
2
J3
6
1
4
10
12
5
2
9
8
7
11
3
T1
P
Q3535
Vd
-
P
1
2
Rp
6
910K
16Vout
G-TP
C
p13
1n 5
Tit
l
e
S
i
z
e
D
o
c
u
ment
N
u
mber
R
e
v
D
at
e:
S
heet
of
1950-0808
1A
IRAC1166-100W
Schematic Diagram
11
Tues
day
,
A
ugus
t
01,
2006
+
CS1
7
22U
F/
35V
1
2
Rp
5
0R
Vcc
1
OV
T
2
MOT
3
EN
4
Vd
5
Vs
6
GN
D
7
V
gat
e
8
U1
IR1166
Cs1
9
$
0
Rs1
4
$
1
2
Dp
2
B
A
V
103/
200V
Rs1
6
5K
0
1
2
J2
16Vout
1
2
Dp
3
Ls
4148
0
Rs1
3
2K
2
V
d1-P
+
Cs1
6
1500UF/25V
+
Cs1
4
1500UF/25V
+
Cs1
5
1000UF/25V
Rp
4
3K
3
1
FB
2
GND
3
COMP
4
CS
5
VCC
U4
AS4305 or AQ105
Vs
C
p12
22pf
R
s
17
10R
C
p10
10nf
Vo
u
ttp
TP
Cp
9
22pf
VdTP
G
NDS
Vs1
Cp
6
100nF
0
+
Cp
5
100UF/35V
2
1
L1
1uH
8A
1
2
R
p11
280k
+
Cs2
3
1000U
F/
25V
2
1
L3
10uH
U3
SFH615A2
4
1
2
3
5
6
7
8
I
R
F7853
SR1
VCC
1
CT
RL
3
DRAIN
8
GN
D
2
HVS
7
DRIVER
6
Isn
s
5
DEM
4
U
2
TE
A
1507
Rp12 1k
1
3
2
4
L2
40uH
R
p9A
12K
C
p11
4n7
Cp
8
220nf
Ch
ecked
:
ISRAEL
SERRANO
Gat
edr
Rp
9
1K
Cs24
100nF
4
1
2
3
5
6
7
8
I
R
F7853
SR2
1
3
CO
N1
2
1
3
4
-+
DB1
6GB
U
06
1
2
Rp
7
5
K1
1
2
Rp
1
10R NTC Thermi
st
or
1
2
Cp
1
220NF/
275V
2
1
R
p10
0R
1 3W
F1
FU
SE
1
2
Ds5
Ls
4148
LGND
3
1
2
Q1
I
R
FP
22N
60K
1
2
Dp
1
U
F
5407
VCC
1
1
2
2
3
3
4
4
CO
N2
Rs25
30m
1
2
J4
Rs26
$
Cp
2
4N
7/
1k
V
1
2
+
Cp
3
330U
F/
400V
1
2
Rp
8
22R
optoA
Opt
oA
optoK
+
-
Cs25
10nf
Rs24
5.6K
V
out
-TP
optoK
Rs22
1K
16Vout
optoK
Note:
* Optional
$ Unstuffed
# Trimming

Rev.1A 18 August 2006
RD#0618 Page 5 of 24
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105
http://www.irf.com
/ Data and specifications subject to change without notice.





2.1 IRAC1166-100W Demo Board Pictures

Figure 2A. Top side of the IRAC1166-100W Demo Board





Figure 2B. Bottom side of the IRAC1166-100W Demo Board

AC Input
+16 V x 6.25A
Output

- - ++

Rev.1A 18 August 2006
RD#0618 Page 6 of 24
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105
http://www.irf.com
/ Data and specifications subject to change without notice.




2.2 PCB Layout for IRAC1166-100W

Figure 3A. Top layer etch with silkscreen print





Figure 3B. Bottom layer etch with silkscreen print.




Rev.1A 18 August 2006
RD#0618 Page 7 of 24
WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245 Tel: (310) 252-7105
http://www.irf.com
/ Data and specifications subject to change without notice.




3.0 CIRCUIT DESCRIPTION

The PCB design is basically optimized as a test platform to evaluate of active rectification
using Smart synchronous rectification and as well as basic features of flyback converter
operating in quasi-resonant mode.

This demo board has 2-pin connector ( CON1 ) for AC input and a time-lag type 3.5A fuse
for input current overload protection. Minimum input filtering is provided (Cp1-Xcap) before
AC input voltage (90-264VAC) is routed to a 6Amp-bridge rectifier (DB1).

Primary side controller (U2) basically drives the primary Mosfet Q1 to operate in Critical-
Conduction mode to eliminate turn-ON switching loss thru ZVS (zero voltage switching only
occurs when NVsec > Vdcin ) or thru LVS ( low-voltage switching when nVsec< Vdcin) to
reduce capacitive losses of Q1 especially at high line condition. The switching frequency F
sw

at full load varies from ~38 to ~76kHz typically from low to high input condition and falls back
to minimum value (fixed ~ 6 -10kHz) to reduce input power during light load condition.

Auxiliary winding is loosely monitored by demagnetization pin4 of U2 through Dp3, Rp5 and
Rp11 network that sets the OV