AN-PS0019-FF PWM controller ICE3XS03LJG

Application Note, V1.1, December 2011
ICE3xS03LJG
F3 Fixed Frequency PWM Controller (Latch
& Jitter version) Design Guide
Power Management & Supply
N e v e r
s t o p
t h i n k i n g .
Published by
Infineon Technologies AG
81726 Munich, Germany
© 2011 Infineon Technologies AG
All Rights Reserved.
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ICE3xS03LJG
Revision History:
Previous Version:
Page
5
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25
2011-12
V1.0
Subjects (major changes since last revision)
Add 130kHz
Add block diagram of ICE3GS03LJG
Add schematic of ICE3GS03LJG
Update equation (1)
Add 130kHz
Update table (1) Protection functions and failure conditions
Update product portfolio
Update references
ICE3XS03LJG F3 FF PWM controller (Latch & Jitter version) Design Guide:
License to Infineon Technologies Asia Pacific Pte Ltd
Kyaw Zin Min
Kok Siu Kam Eric
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V1.1
AN-PS0019
ICE3xS03LJG
Table of Contents
Page
1 Introduction ................................................................................................................................... 5 2 List of Features ............................................................................................................................. 5 3 Package .......................................................................................................................................... 6 4 Block Diagram ............................................................................................................................... 7 5 Typical Application Circuit ......................................................................................................... 10 6 6.1 6.1.1 6.2 6.3 6.3.1 6.3.2 6.3.3 6.3.4 6.4 6.4.1 6.4.2 6.4.3 6.5 6.6 6.7 6.7.1 6.7.2 6.7.3 6.7.4 Functional description and component design ....................................................................... 13 Startup time ................................................................................................................................... 13 Vcc capacitor ................................................................................................................................. 13 Soft Start ....................................................................................................................................... 14 Low standby power - Active Burst Mode....................................................................................... 14 Entering Active Burst Mode........................................................................................................... 14 Working in Active Burst Mode ....................................................................................................... 15 Leaving Active Burst Mode ........................................................................................................... 16 Minimum VCC supply voltage during burst mode........................................................................... 17 Low EMI noise ............................................................................................................................... 17 Frequency jittering ......................................................................................................................... 17 Soft gate drive ............................................................................................................................... 18 Other suggestions to solve EMI issue........................................................................................... 19 Gate drive capability...................................................................................................................... 19 Tight control in maximum power - Propagation delay compensation ........................................... 20 Protection Features ....................................................................................................................... 20 Auto Restart Protection Mode ....................................................................................................... 21 Latch off Protection Mode ............................................................................................................. 22 Blanking Time for over load protection ......................................................................................... 22 User defined protections by external protection enable pin .......................................................... 24 7 Layout Recommendation ........................................................................................................... 24 8 FF PWM controller F3 version 3 (S03) portfolio ....................................................................... 24 9 Useful formula for the SMPS design ......................................................................................... 25 10 References ................................................................................................................................... 26 Application Note
4
2011-12-15
ICE3xS03LJG
1
Introduction
The ICE3xS03LJG is the latest development of the F3 fixed frequency PWM controller IC with latch and jitter
features. It is a current mode PWM controller with startup cell in a DSO-8 package. The switching frequency
is running at 65/100/130 kHz and it is suitable for AC/DC power supply such as LCD monitors, adapters for
printers and notebook computers, DVD players and recorder, Blue-Ray DVD player and recorder, set-top
boxes and industrial auxiliary power supplies. It is a current mode PWM controller and provides a cycle-bycycle peak current control which can provide extended protection for the risk of transformer saturation.
The ICE3xS03LJG adopts the BICMOS technology and provides a wider Vcc operating range up to 24.5V. It
inherits the proven good features of F3 FF PWM controller such as the active burst mode achieving the
lowest standby power, the propagation delay compensation making the most precise current limit control in
wide input voltage range, etc. In addition, it also adds on some useful features such as built-in soft start time,
built-in basic with extendable blanking time for over load protection and built-in switching frequency
modulation ( frequency jittering ), latch off protection enable pin, etc.
2
List of Features
500V Startup Cell switched off after Start Up
Active Burst Mode for lowest Standby Power
Fast load jump response in Active Burst Mode
65/100/130 kHz internally fixed switching frequency
Built-in Latched Off Protection Mode for Over-temperature, Overvoltage & Short Winding
Auto Restart Protection Mode for Overload, Open Loop, VCC Under-voltage & Short Optocoupler
Built-in Soft Start
Built-in blanking window with extendable blanking time for short duration high current
External latch off enable function
Max Duty Cycle 75%
Overall tolerance of Current Limiting < ±5%
Internal PWM Leading Edge Blanking
BiCMOS technology provide wide VCC range
Frequency jitter and soft gate driving for low EMI
Application Note
5
2011-12-15
ICE3xS03LJG
3
Package
The package for F3 ICE3xS03LJG latch & Jitter mode product is DSO-8.
Figure 1
Application Note
Pin assignment
Pin
Name
Description
1
BL
extended Blanking & Latch off enable
2
FB
FeedBack
3
CS
Current Sense
4
Gate
5
HV
6
N.C.
Not Connected
7
VCC
Controller supply voltage
8
GND
Controller GrouND
Gate driver output
High Voltage input of startup cell
6
2011-12-15
ICE3XS03LJG
4
Block Diagram
Figure 2
Application Note
Block Diagram of ICE3BS03LJG
7
2011-12-15
ICE3XS03LJG
Figure 3
Application Note
Block Diagram of ICE3AS03LJG
8
2011-12-15
ICE3XS03LJG
Figure 4
Application Note
Block Diagram of ICE3GS03LJG
9
2011-12-15
Application Note
Figure 5
AC
VAR1
0.25W
275V
10
39mH 1.4A
L1
C13
100pF
C12
0.1uF
0.22uF
275V
C2
1
24V
7
HV
5
FB
2
8
C15
220pF
ICE3BS03LJG
GND
BL
IC1
R11
47 R10 100
VCC
2A 800V
BR1
ZD1
NTC 2.5Ohm
RT1
Gate
3
CS
0.5W
0.56
R8
4
R14
0R
R8A
0.56 0.5W
C11
22uF
50V
D3
1N4148
400V
150uF
C3
R9
3R3
2W
33k
R1
3
2
1
10
11
IC2
ER28L/N87/154uH
T1
6
5
Q1
SPA07N60C3
D1
UF4006
400V
10n
C4
Demo board 60W, 16V SMPS using ICE3BS03LJG and SPA07N60C3
R25
1M
C1
1M 275V
R24 0.22uF
R7
750
IC3
TL431
D2
MUR1520
R6
1K
C6
35V
1000uF
R5
10K
C10
2.7nF
C7
1000uF
35V
L2
1uH
R4
4.3K, 1%
C9
0.68uF
R3
1.2K, 1%
R2
22K, 1%
C8
220uF
25V
Gnd
16V/3.75A
5
85V - 265V
AC
FUSE1
2A
C5
2.2nF
Y1
ICE3XS03LJG
Typical Application Circuit
Typical application circuit with ICE3BS03LJG 60W 16V
2011-12-15
8 5V ~ 26 5V
2A
#VAR
Q2
C18
100k 0.1uF
R8
R7
27k(1% )
R6
110k(1% )
Q3
R25
0R
L2
3.3mH 1.8A
#SG 2
L1
27mH 1.7A
OTP
#C19
R9
62k(1% )
#R13
C1
#SG 1
C2
0.1uF
100nF
C10
C9
24V
ZD1
#NTC 1
10R
R4
IC1
100R
R3
5 HV
8 Gnd
1nF
C11
2 FB
3 CS
1 BL ICE3AS03LJG
7 Vcc
BR1
4A 600V
#C7
4 Gate
10uF
35V
C8
R23
0R
R5
9R1
0R
R2
R10
0.47R/0.5W
R14
0R
R24
0R
1N4148
D4
D3
C6
3 3k /2W
3
4
1N4148
R1
D1
UF4006
C4
10nF/400V
SPA07N60C3
Q1
R11
0.51R/0.5W
C3
120uF
400V
65W(19.5V X 3.34A) SMPS Demo Board using ICE3AS03LJG and SPA07N60C3(V 1.1)
Kyaw Zin Min, Eric Kok/ 30 Apr 2009
N
L
0 .47 uF
3 05 V
#R12
BC8 07 -2 5
F1
4 70 k(B5 78 91 M 04 74 +0 00 )
NTC 2
11
BC8 17 -2 5
3 05 V
Application Note
0 .33 uF
Figure 6
3
2
1
5
6
4 7pF/1 kV
IC2 SFH617A-3
2
1
IC3
TL431
R22
820R
R21
1.2k
R20
39k
470pF
*R19
220uF
25V
2200uF
25V
R18
3.6k, 1%
C13
68nF
R17
470R, 1%
R16
24k, 1%
C14
C17
L3
1.5uH
C12
#C15
MBR20H150CT
D2
#R15
T1
ER28,98uH(P=24,S=5,A=4)
11
12
C5 2.2nF
#C16
#L4
Com
19.5V/3.34A
ICE3XS03LJG
Typical application circuit with ICE3AS03LJG 65W 19.5V
2011-12-15
ICE3XS03LJG
Figure 7
Application Note
Typical application circuit with ICE3GS03LJG 65W 19.5V
12
2011-12-15
ICE3XS03LJG
6
Functional description and component design
6.1
Startup time
Startup time is counted from applying input voltage to IC turn on. ICE3xS03LJG has a startup cell which is
connected to input bulk capacitor. When there is input voltage, the startup cell will act as a constant current
source to charge up the Vcc capacitor and supply energy to the IC. When the Vcc capacitor reaches the
Vcc_on threshold 18V, the IC turns on. Then the startup cell is turned off and the Vcc is supplied by the
auxiliary winding. The startup time formula is expressed in equation (1).
t STARTUP =
VVCCon ⋅ CVcc
IVCCCh arg e
(1)
where, IVCCCharge : average of Vcc charge current of IVCCCharge2 and IVCCCharge3 ( 0.8mA ),
VVCCon : IC turns on threshold ( 18V ), CVCC : Vcc capacitor
Pls refer to the datasheet for the symbol used in the equation.
6.1.1
Vcc capacitor
The minimum value of the Vcc capacitor is determined by voltage drop during the soft start time. The formula
is expressed in equation (2).
CVCC =
I VCC sup 2 ⋅ t soft 2
⋅
VCCHY
3
(2)
where, IVCCCsup2 : IC consumption current ( 4.2mA ), tsoft : soft start time ( 20(ICE3BS03LJG) or 10ms(ICE3AS03LJG &
ICE3GS03LJG ) ),
VCCHY : Vcc turn-on/off hysteresis voltage ( 7.5V )
Therefore, the minimum Vcc capacitance can be 7.4µF(ICE3BS03LJG) and 3.7µF(ICE3AS03LJG). In order to give
more margins, 22µF(ICE3BS03LJG) and 10µF(ICE3AS03LJG) is taken for the design. The startup time tSTARTUP is
then 0.6/0.3s. The measured start up time is 0.54/0.23 s (Figure 6). A 0.1uF filtering capacitor is always
needed to add as near as possible to the Vcc pin to filter the high frequency noise.
ICE3BS03LJG
ICE3AS03LJG/ICE3GS03LJG
0.54s
Figure 8
0.23s
The startup delay time at AC line input voltage of 85Vac
Precaution : For a typical application, start up should be VCC ramps up first, other pin (such as FB pin)
voltage will follow VCC voltage to ramp up. It is recommended not to have any voltage on other
pins (such as FB; BA and CS) before VCC ramps up.
Application Note
13
2011-12-15
ICE3XS03LJG
6.2
Soft Start
When the IC is turned on after the Startup time, a digital soft start circuit is activated. A gradually increased
soft start voltage is emitted by the digital soft start circuit, which in turn releases the duty cycle gradually from
0. The duty cycle increases to maximum (which is limited by the transformer design) at the end of the soft
start period. When the soft start time ends, IC goes into normal mode and the duty cycle is controlled by the
FB signal. The soft start time is set at 20ms (ICE3BS03LJG) and 10ms (ICE3AS03LJG/ICE3GS03LJG) for
maximum load. The soft start time is load dependent; shorter soft start time with lighter load.
Figure 9 shows the soft start behavior at 85Vac input. The primary peak current increases slowly to the
maximum in the soft start period.
ICE3BS03LJG
ICE3AS03LJG/ICE3GS03LJG
1V
1V
Vcs
Vcs
Vcc
Vcc
Vfb
19.2ms
Vfb
9.9ms
Vbl
Vbl
Figure 9
6.3
Soft start at AC line input voltage of 85Vac
Low standby power - Active Burst Mode
The IC will enter Active Burst Mode function at light load condition which enables the system to achieve the
lowest standby power requirement of less than 100mW. Active Burst Mode means the IC is always in the
active state and can therefore immediately response to any changes on the FB signal, VFB.
6.3.1
Entering Active Burst Mode
Because of the current mode control scheme, the feedback voltage VFB actually controls the power delivery
to output. An important relationship between the VCS and the VFB is expressed in equation (3).
VFB = VCS ⋅ AV + VOffset − Ramp
(3)
where, VFB:feedback voltage, VCS:current sense voltage, AV:PWM OP gain, VOffset-Ramp:voltage ramp offset
When the output load reduces, the feedback voltage VFB drops. If the VFB stays below 1.23V for 20ms, the IC
enters into the Active Burst Mode. The threshold power to enter burst mode is expressed in equation (4).
PBURST _ enter =
VFB _ enter − VOffset − Ramp 2
V
1
1
1
⋅ LP ⋅ Ip 2 ⋅ f SW = ⋅ LP ⋅ ( CS ) 2 ⋅ f SW = ⋅ LP ⋅ (
) ⋅ f SW
2
2
Rsense
2
Rsense ⋅ AV
(4)
where, Lp : transformer primary inductance
Rsense:current sense resistance, fsw:switching frequency, VFB_enter:Feedback level to enter burst mode
Figure 8 shows the waveform with the load drops from nominal load to light load. After the 20ms blanking
time IC goes into burst mode.
Application Note
14
2011-12-15
ICE3XS03LJG
Vds
Vcc
20ms
Vfb
Vbl
Figure 10
6.3.2
Entering Active Burst Mode
Working in Active Burst Mode
In the active burst mode, the IC is constantly monitoring the output voltage by feedback pin, VFB, which
controls burst duty cycle and burst frequency. The burst “ON” starts when VFB reaches 3.5V and it stops
when VFB is dropped to 3.0V. During burst “ON”, the primary current limit is set to 25% of maximum peak
current (VCS=0.25V) to reduce the conduction losses and to avoid audible noise. The FB voltage is changing
like a saw tooth between 3.0V and 3.5V. The corresponding secondary output ripple (peak to peak) is
controlled to be small. It can be calculated by equation (5).
Vout _ ripple _ pp =
Ropto
RFB ⋅ Gopto ⋅ GTL 431
⋅ ΔVFB
(5)
where, Ropto : series resistor with opto-coupler at secondary side (e.g. R7 in Figure 4)
RFB : IC internal pull up resistor connected to FB pin (RFB=15.4KΩ)
Gopto : current transfer gain of opto-coupler
GTL431 : voltage transfer gain of the loop compensation network (e.g. R2, R3,R4,R5,R6,R7,C9 & C10
in figure 5)
ΔVFB : feedback voltage change (0.5V)
Usually there is a noise coupling capacitor at the FB pin to filter the switching noise and spike (e.g. C15 in
Figure 4). However, if this capacitor is too large (>10nF), it would affect the normal operation of the
controller. This capacitor should be as small as possible (without the capacitor is the best). In the mean time,
it is found that this filter capacitor will also affect the output ripple voltage during burst mode; larger
capacitance will get larger ripple voltage and smaller capacitance get lower ripple voltage.
Figure 11 is the output ripple waveform of the 60W demo board. The burst ripple voltage is about 50mV
(exclude switching spikes).
Application Note
15
2011-12-15
ICE3XS03LJG
48mV
Figure 11
6.3.3
Output ripple during Active Burst Mode at light load
Leaving Active Burst Mode
When the output load increases to be higher than the maximum burst power, Pburst_max, Vout will drop a little bit
and VFB will rise up fast to exceed 4.0V(ICE3BS03LJG) & 4.2V(ICE3AS03LJG/ ICE3GS03LJG). The system
leaves burst mode immediately when VFB reaches respective threshold voltage. Once system leaves burst
mode, the current sense voltage limit, VCS_MAX, is released to 1V, the feedback voltage VFB swings back to
the normal control level.
The leaving burst power threshold is (i.e. maximum power to be handled during burst operation) is expressed
in equation (6).
Pburst _ max = 0.5 ⋅ LP ⋅ (0.25 ⋅ i peak _ max ) 2 ⋅ f SW = 0.5 ⋅ LP ⋅ (0.25 ⋅
VCS _ max
Rsense
) 2 ⋅ f SW = 0.0625 ⋅ Pmax
(6)
where, ipeak_max : maximum primary peak current, VCS_max : current limit threshold at CS pin,
Pmax : maximum output power
The calculated maximum power in burst mode is around 6.25% of Pmax. However, the actual power can be
higher as it would include propagation delay time.
The leave burst mode timing diagram is shown in Figure 10.
The maximum output drop during the transition can be estimated in equation (7).
Vout _ drop _ max =
Ropto
RFB ⋅ Gopto ⋅ GTL 431
Application Note
⋅ (VFBC 4 −
3 .0 + 3 .5
)
2
(7)
16
2011-12-15
ICE3XS03LJG
VFBC 4
3.5V
VFB
3.0V
Vout
Vout_AV
Vout_drop_max
1V
VCS
0.25V
Figure 12
Timing diagram of leaving burst mode
Figure 13 is the captured waveform when there is a load jump from light load to full load. The output ripple
drop during the transition is about 141mV (Figure 13 right).
Vcs
Vo_ripple
141mV
Vo
Vfb
Figure 13
6.3.4
Leaving burst mode waveform; Vfb, Vcs and Vo (left); Vo_ripple (right)
Minimum VCC supply voltage during burst mode
It is particularly important that the Vcc voltage must stay above VVCCoff (i.e. 10.5V). Otherwise, the expected
low standby power cannot be achieved. The IC will go into auto-restart mode instead of Active Burst Mode. A
reference Vcc circuit is presented in Figure 5, 6 & 7. This is for a low cost transformer design where the
transformer coupling is not too good. Thus the circuit(Fig. 5) R11 and ZD1 is added to clamp the Vcc voltage
exceeding 25.5V in extreme case such as high load and the Vcc OVP protection is triggered. If the
transformer coupling is good, this circuit is not needed.
6.4
Low EMI noise
6.4.1
Frequency jittering
The IC is running at a fixed frequency of 65/100/130 kHz with jittering frequency at ±2.6/±4/±5.2 kHz in a
switching modulation period of 4ms. This kind of frequency modulation can effectively help to obtain a low
EMI noise level particularly for conducted EMI. The jittering frequency measured is shown in the Fig.14.
Application Note
17
2011-12-15
ICE3XS03LJG
ICE3BS03LJG
ICE3AS03LJG
62.7kHz
96kHz
67.2kHz
104kHz
ICE3GS03LJG
130kHz
138kHz
Figure 14
6.4.2
Switching frequency jittering ( Vds )
Soft gate drive
The gate soft driving is to split the gate driving slope into 2 so that the MOSFET turns on speed is relatively
slower comparing to a single slope drive (see Figure 15). In this way, the high ∆I/∆t noise is greatly reduced
and the noise signal reflected in the EMI spectrum is also reduced.
Figure 15
Application Note
Soft gate drive waveform
18
2011-12-15
ICE3XS03LJG
6.4.3
Other suggestions to solve EMI issue
Some more suggestions to improve the EMI performance and is listed below.
1. Add capacitor (Cds) at the drain source pin (refer to Figure 16): it can slow down the turn off speed
of the MOSFET and the high ∆V/∆t noise will be reduced and so is the EMI noise. The drawback is
more energy will be dissipated due to slower turn off speed of MOSFET.
2. Adjust the turn on (R9) and turn off (R13 and D4) gate series resistor (refer to figure 16) : it can fine
tune the turn on and turn off speed of the MOSFET so that the EMI noise in some particular
frequency can be reduced. The drawback is it would dissipate more energy with slower turn on/off
speed of MOSFET.
3. Add snubber circuit to the output rectifier : Most of the radiated EMI noise comes out from the output
of the system esp. for a system with output cable. Adding snubber circuit (Rs and Cs) to the output
rectifier is a more direct way to suppress those EMI noise (refer to Figure 17).
4. Add output common mode choke (L3) to the output : similar to item 3, adding the output common
mode choke can help to reduce the noise of the radiated EMI emission (refer to Figure 17).
7
5
VCC
1
Figure 16
Q1
R9
4
Gate
ICE3BS03LJG
BL
R13
GND
FB
CS
8
2
3
Cds
D4
Drain-source capacitor and turn on/off drive resistor
Rs
Cs
T1
HV
IC1
11
L3
L2
D2
C6
16V/3. 75A
C8
C7
10
Gnd
Figure 17
6.5
Output rectifier snubber and output common mode choke
Gate drive capability
Vcc
The IC is designed for medium power supply. The target gate drive capability is 680pF. For higher power
application or larger input capacitance MOSFET, a drive buffer circuit (Qb1, Qb2, Rb1 and Rb2) should be
added. It is showed in Figure 18.
7
VCC
1
BL
IC1
Rb1
HV
Gate
ICE3BS03LJG
GND
FB
CS
8
2
3
Figure 18
Application Note
Qb1
5
4
Q1
Rb2
Qb2
Gate drive buffer for larger MOSFET
19
2011-12-15
ICE3XS03LJG
6.6
Tight control in maximum power - Propagation delay compensation
The maximum power of the system is changed with the input voltage; higher voltage got higher maximum
power. This is due to the propagation delay of the IC and the different rise time of the primary current under
different input voltage. The propagation delay time is around 200ns. But if the primary current rise time is
faster, the maximum power will increase. The power difference can be as high as >14% between high line
and low line. In order to make the maximum power control become tight, a propagation delay compensation
network is implemented so that the power difference is greatly reduced to best around 2%. Figure 19 shows
the compensation scheme of the IC. The equation (8) explains the rate of change of the current sense
voltage is directly proportional to the input voltage and current sense resistor. For a DCM operation, the
operating range for the dVsense/dt is from 0.1 to 0.7. It can show in Figure 15 that higher dVsense/dt will give
more compensation; i.e. lower value of Vsense.
Vin
Vin
dVsense
dIp
dIp Vin
=
⇒ Rsense ⋅
= Rsense ⋅
⇒
= Rsense ⋅
Lp
Lp
dt
dt
dt Lp
(8)
where, Ip : primary peak current, Vin : input voltage, Lp : primary inductance of the transformer,
Vsense : current sense voltage, Rsense : current sense resistor
The measured maximum power for the 60W demo boards shows an output power difference of around +/3% between 85Vac and 265Vac input. This function is limited to discontinuous conduction mode flyback
converter only.
w itho ut co m pe nsa tio n
w ith co m pe nsa tion
V
1,3
1,25
VSense
1,2
1,15
1,1
1,05
1
0,95
0,9
0
0,2
0,4
0,6
0,8
1
1,2
dV Sense
dt
Figure 19
6.7
1,4
1,6
1,8
2
V
μs
Propagation delay compensation curve
Protection Features
ICE3xS03LJG provides all the necessary protections to ensure the system is operating safely. Two kinds of
protection are provided; auto-restart and latch off. The auto restart protections include over-load, open loop,
Vcc under-voltage, short opto-coupler, etc. For those more severe faults such as Vcc over-voltage, overtemperature, short winding, etc., it goes into latch off protection. Once it enters the latch off protection, the
Vcc voltage needs to drop below 6.23V before it can be reset to normal operation. There is a flexible
protection enable pin which can fulfill the custom-made protections requirement such as output over voltage,
MOSFET over temperature, etc. The protection is simply triggered by pulling down the BL pin to be < VLE
and the IC will go into latch off mode. A list of protections and the failure conditions is showed in Table 1.
Application Note
20
2011-12-15
ICE3XS03LJG
Protection function
Vcc
Overvoltage
Failure condition
Protection Mode
ICE3AS03LJG
VCC > 25.5V & last for (120+25)μs (both normal & burst
mode)
ICE3BS03LJG
VCC > 25.5V & last for (120+25)μs (normal mode only)
ICE3GS03LJG
VCC > 25.5V & last for (120+30)μs (both normal & burst
mode)
Latch Off
Over-temperature
(controller junction)
TJ > 130°C
Latch Off
Short Winding/Short Diode
VCS > 1.66V & last for 190ns
Latch Off
Latch enable
Over-load /
Open loop
ICE3AS03LJG
VBL < 0.33V & last for 25μs
ICE3BS03LJG
VBL < 0.25V & last for 30μs
ICE3GS03LJG
ICE3AS03LJG
ICE3GS03LJG
VBL < 0.33V & last for 30μs
VFB > 4.2V and VBK > 4.0V
(Blanking time counted from charging VBK from 0.9V to 4.0V )
VFB > 4.0V and VBK > 4.0V
(Blanking time counted from charging VBK from 0.9V to 4.0V )
ICE3BS03LJG
Vcc Under-voltage / short Optocoupler
VCC < 10.5V
Table 1
6.7.1
Latch Off
Auto Restart
Auto Restart
Protection functions and failure conditions
Auto Restart Protection Mode
When the failure condition meets the auto restart protection mode, the IC will go into auto-restart. The
switching pulse will stop. Then the Vcc voltage will drop. When the Vcc voltage drops to 10.5V, the startup
cell will turn on again. The Vcc voltage is then charged up. When it hits 18V, the IC will turn on and the
startup cell will turn off. It would then start the startup phase with soft start. After the startup phase the failure
condition is checked to determine whether the fault persists. If the fault is removed, it will go to normal
operation. Otherwise, the IC will repeat the auto restart protection and the switching pulse stop again.
Figure 20 shows the switching waveform of the VCC and the feedback voltage VFB when the output is
overloaded by shorting the outputs. The IC is turned on at VCC = 18V. After going through the startup phase,
IC is off again due to the presence of the fault. VCC is discharged until 10.5V. Then, the Startup Cell is
activated again to charge up capacitor at VCC that initiates another restart cycle.
Vds
Vcc
Vfb
Vbl
Figure 20
Application Note
Auto Restart Mode ( without extended blanking time )
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2011-12-15
ICE3XS03LJG
6.7.2
Latch off Protection Mode
In case of Latched Off Protection Mode, there is no new startup phase any more. Once Latched Off Mode is
entered, the internal Voltage Reference is switched off in order to reduce the current consumption of the IC.
In this stage only the UVLO is working which switches on/off the startup cell at VCCoff/VCCon. Latched Off
Mode can only be reset when AC line input is plugged out and VCC is discharged to be lower than 6.23V.
Figure 21 shows the Vcc waveform during latch off mode.
Vds
Vcc
Vfb
Vbl
Vbl
Figure 21
6.7.3
Latch off Mode ( VBL < VLE)
Blanking Time for over load protection
The IC controller provides a blanking window before entering into the auto restart mode due to output
overload/short circuit. The purpose is to ensure that the system will not enter protection mode unintentionally.
There are 2 kinds of the blanking time; basic and the extendable. The basic one is a built-in feature which is
set at 20ms. The extendable one is to extend the basic one with a user defined additional blanking time. The
extendable blanking time can be achieved by adding a capacitor, CBK to the BL pin. When there is over load
occurred ( VFB > VFBC4), the CBK capacitor will be charged up by an constant current source, IBK ( 13uA ) from
0.9V to 4.0V. Then the auto restart protection will be activated. The charging time from 0.9V to 4.0V to the
CBK capacitor is the extended blanking time. The total blanking time is the addition of the basic and the
extended blanking time.
Tblanking = Basic + Extended = 20 ms +
( 4.0 − 0.9) * CBK
= 20 ms + 238461 .5 * CBK
IBK
(9)
The measured total blanking time showing in Figure 23 is 42ms using CBK=0.1uF.
In case of output overload or short circuit, the transferred power during the blanking period is limited to the
maximum power defined by the value of the sense resistor Rsense.
The noise level in BL pin can be quite high particularly in some high power application. In order to avoid mistriggering of other protection features, it is recommended to add a minimum 100pF filter capacitor at BL pin
to filter the noise.
Application Note
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2011-12-15
ICE3XS03LJG
Vds
Vcc
Vfb
19.5ms
Vbl
Figure 22
blanking window for output over load protection ( basic blanking time )
Vds
Vcc
Vfb
20ms 24ms
Vbl
Figure 23
blanking window for output overload protection ( extended blanking time=24ms with
CBK=0.1uF )
Application Note
23
2011-12-15
ICE3XS03LJG
6.7.4
User defined protections by external protection enable pin
7
5
VCC
Gate
IC1
HV
GND
FB
CS
8
2
3
Figure 24
7
1
External OTP
HV
Gate
ICE3BS03LJG
R9
62k(1% )
4
R7
27k(1% )
8
FB
2
Q2
CS
3
BC807
GND
Rt2
Figure 25
100k
C18
0.1uF
5 HV
IC1
Q3
R8
NTC 2
t
7 Vcc
R25
0R
C10
100nF
#C19
THERMISTOR
7
R6
110k(1% )
470k
5V
Output OVP circuit
Q8
Rt1
ZD6
BL
IC1
ZD2
IC4
5
VCC
Rz
1
BL
ICE3BS03LJG
1 BL ICE3AS03LJG
8 Gnd
2 FB
4 Gate
3 CS
BC817
4
Vo
Although there are lots of protection conditions defined in the IC, customer still can have some tailor-made
protection for the application needs. Some suggested protection circuits are recommended below.
1. Output over voltage : Figure 24 shows the output OVP latch circuit.
2. MOSFET over temperature : Figure 25 is an over temperature latch circuit. The thermistor Rt2 is
glued to the hot component such as MOSFET to protect the device to be over heated.
OTP circuit
Layout Recommendation
In order to get the optimized performance of the fixed frequency PWM controller ICE3GS03LJG, the
grounding of the PCB layout must be connected carefully. From the circuit diagram in Figure 7, it indicates
that the grounding for the controller can be split into several groups; signal ground, Vcc ground, Current
sense resistor ground and EMI return ground. All the split grounds should be “star” connected to the bulk
capacitor ground directly. The split grounds are described as below.
•
Signal ground includes all small signal grounds connecting to the controller GND pin such as filter
capacitor ground C17, C18, C19, C110 and opto-coupler ground.
•
Vcc ground includes the Vcc capacitor ground C16 and the auxiliary winding ground, pin 5 of the power
transformer.
•
Current Sense resistor ground includes current sense resistor R14 and R15.
•
EMI return ground includes Y capacitor C12.
8
FF PWM controller F3 version 3 (S03) portfolio
Device
Application Note
Package
HV
Frequency / kHz
ICE3BS03LJG
PG-DSO-8
500V
65
ICE3AS03LJG
PG-DSO-8
500V
100
ICE3GS03LJG
PG-DSO-8
500V
130
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ICE3XS03LJG
9
Useful formula for the SMPS design
Transformer calculation ( DCM flyback)
Input data
Vin_min = 90Vdc, Vin_max = 380Vdc,
Vds_max = 470V for 600V MOSFET,
Vds_max = 650V for 800V MOSFET,
Dmax ≤ 50%
Turn ratio
Nratio =
Vds _ max − Vin _ max
Vout + Vdiode
Maximum Duty ratio
D max =
(Vout + Vdiode) ⋅ Nratio
Vin _ min+ (Vout + Vdiode) ⋅ Nratio
Primary Inductance
(Vin _ min ⋅ D max) 2
Lp ≤
2 ⋅ Pin ⋅ fsw
Primary peak current
Ip _ max =
Primary turns
Np ≥
Ip _ max ⋅ Lp
B max ⋅ A min
Secondary turns
Ns =
Np
Nratio
Auxiliary turns
Naux =
Vin _ min⋅ D max
Lp ⋅ fsw
Vcc + Vdiode
⋅ Ns
Vout + Vdiode
ICE3xS03LJG external component design
Current sense resistor
Soft start time
Rsense ≤
Vcsth _ max
Ip _ max
tsoft = 20ms (ICE3BS03LJG) & 10ms (ICE3AS03LJG/
ICE3GS03LJG)
I VCC sup 2 ⋅ t soft 2
⋅
VCCHY
3
Vcc capacitor
CVCC =
Startup time
t STARTUP =
Enter burst mode power
Pburst _ enter =
Leave burst mode power
Pburst _ max = 0.0625 ⋅ Pmax
Application Note
25
VVCCon ⋅ CVcc
IVcc _ Ch arg e − IVcc _ Start
VFB _ enter − VOffset − Ramp 2
1
⋅ LP ⋅ (
) ⋅ f SW
2
Rsense ⋅ AV
2011-12-15
ICE3XS03LJG
Ropto
Output ripple during burst mode
Vout _ ripple _ pp =
Voltage drop when leave burst mode
Vout _ drop _ max =
Total blanking time for over load
protection
Tblanking = 20ms + 238461.5 * CBK
10
RFB ⋅ Gopto ⋅ GTL 431
⋅ ΔVFB
1.25 ⋅ Ropto
RFB ⋅ Gopto ⋅ GTL 431
References
[1]
Infineon Technologies, Datasheet “F3 PWM controller ICE3BS03LJG Off-Line SMPS Current Mode
Controller with integrated 500V Startup Cell ( Latched and frequency Jitter Mode )”
[2]
Infineon Technologies, Datasheet “F3 PWM controller ICE3AS03LJG Off-Line SMPS Current Mode
Controller with integrated 500V Startup Cell ( Latched and frequency Jitter Mode )”
[3]
Infineon Technologies, Datasheet “F3 PWM controller ICE3GS03LJG Off-Line SMPS Current Mode
Controller with integrated 500V Startup Cell ( Latched and frequency Jitter Mode )”
[4]
Kyaw Zin Min, Eric Kok Siu Kam, Infineon Technologies, Application Note “AN-EVAL3BS03LJG, 60W
16V SMPS Evaluation Board with F3 controller ICE3BS03LJG “
[5]
Kyaw Zin Min, Eric Kok Siu Kam, Infineon Technologies, Application Note “AN-EVAL3AS03LJG, 65W
19.5V SMPS Evaluation Board with F3 controller ICE3AS03LJG “
[6]
Kyaw Zin Min, Eric Kok Siu Kam, Infineon Technologies, Application Note “AN-EVAL3GS03LJG, 65W
19.5V SMPS Evaluation Board with F3 controller ICE3GS03LJG “
[7]
Harald Zoellinger, Rainer Kling, Infineon Technologies, Application Note “AN-SMPS-ICE2xXXX-1,
CoolSET® ICE2xXXXX for Off-Line Switching Mode Power supply (SMPS )”
Application Note
26
2011-12-15
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