ICE2QR4765 application note

Application Note, V1.1, 8 August 2011
Application Note
AN- EVALQRC-ICE2QR4765
12W5V Evaluation Board with QuasiResonant CoolSET® ICE2QR4765
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
© 2007 Infineon Technologies AG
All Rights Reserved.
Legal Disclaimer
The information given in this document shall in no event be regarded as a guarantee of
conditions or characteristics. With respect to any examples or hints given herein, any typical
values stated herein and/or any information regarding the application of the device,
Infineon Technologies hereby disclaims any and all warranties and liabilities of any kind,
including without limitation, warranties of non-infringement of intellectual property rights
of any third party.
Information
For further information on technology, delivery terms and conditions and prices, please
contact the nearest Infineon Technologies Office (www.infineon.com).
Warnings
Due to technical requirements, components may contain dangerous substances. For information
on the types in question, please contact the nearest Infineon Technologies Office.
Infineon Technologies components may be used in life-support devices or systems only with
the express written approval of Infineon Technologies, if a failure of such components can
reasonably be expected to cause the failure of that life-support device or system or to affect
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Title
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8 August 2011
V1.0
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12W5V Evaluation Board with Quasi-Resonant CooLSET® ICE2QR4765
License to Infineon Technologies Asia Pacific Pte Ltd
Eric Kok
[email protected]
Wang Zan
[email protected]
He Yi
[email protected]
Jeoh Meng kiat
[email protected]
We Listen to Your Comments
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V1.1
AN-PS0039
EVALQRC-12W5V-ICE2QR4765
Table of Contents
1
Content ............................................................................................................... 5
2
Evaluation Board ............................................................................................... 5
3
List of Features .................................................................................................. 5
4
Technical Specifications ................................................................................... 6
5
Circuit Description............................................................................................. 6
5.1
Mains Input and Rectification ......................................................................................................6
5.2
Integrated MOSFET and PWM Control........................................................................................6
5.3
Snubber Network ..........................................................................................................................6
5.4
Output Stage..................................................................................................................................6
5.5
Feedback Loop..............................................................................................................................6
6
Circuit Operation ............................................................................................... 7
6.1
Startup Operation..........................................................................................................................7
6.2
Normal Mode Operation ...............................................................................................................7
6.3
Primary side peak current control...............................................................................................7
6.4
Digital Frequency Reduction .......................................................................................................7
6.5
Burst Mode Operation ..................................................................................................................7
7
Protection Features ........................................................................................... 8
7.1
Vcc under voltage and over voltage protection.........................................................................8
7.2
Foldback point protection ............................................................................................................8
7.3
Open loop/over load protection...................................................................................................8
7.4
Adjustable output overvoltage protection..................................................................................8
7.5
Short winding protection..............................................................................................................8
7.6
Auto restart for over temperature protection.............................................................................8
8
Circuit diagram .................................................................................................. 9
8.1
PCB Top overlayer ......................................................................................................................10
8.2
PCB Bottom Layer ......................................................................................................................11
9
Component List ............................................................................................... 12
10
Transformer Construction .............................................................................. 13
11
Test Results ..................................................................................................... 14
11.1
Efficiency and standby performance ........................................................................................14
12
Waveform and scope plots ............................................................................. 15
12.1
Startup @85Vac and 12W load ..................................................................................................15
12.2
Working at different zero crossing point..................................................................................15
12.3
Load transient response ............................................................................................................16
12.4
AC Output ripple during full load ..............................................................................................16
12.5
Burst mode operation.................................................................................................................17
13
References ....................................................................................................... 17
Application Note
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EVALQRC-12W5V-ICE2QR4765
1
Content
This application note is a description of 12W switching mode power supply evaluation board designed in a
quasi resonant flyback converter topology using ICE2QR4765 Quasi-resonant CoolSET ®.The target
application of ICE2QR4765 are for set-top box, portable game controller, DVD player, netbook adapter and
auxiliary power supply for LCD TV, etc. With the CoolMOS® integrated in this IC, it greatly simplifies the
design and layout of the PCB. Due to valley switching, the turn on voltage is reduced and this offers higher
conversion efficiency comparing to hard-switching flyback converter. With the DCM mode control, the
reverse recovery problem of secondary rectify diode is relieved. And for its natural frequency jittering with
line voltage, the EMI performance is better. Infineon’s digital frequency reduction technology enables a
quasi-resonant operation till very low load. As a result, the system efficiency, over the entire load range, is
significantly improved compared to conventional free running quasi resonant converter implemented with
only maximum switching frequency limitation at light load. In addition, numerous adjustable protection
functions have been implemented in ICE2QR4765 to protect the system and customize the IC for the chosen
application. In case of failure modes, like open control-loop/over load, output overvoltage, and transformer
short winding, the device switches into Auto Restart Mode or Latch-off Mode. By means of the cycle-bycycle peak current limitation plus foldback point correction, the dimension of the transformer and current
rating of the secondary diode can both be optimized.Thus, a cost effective solution can be easily achieved.
2
Evaluation Board
Figure 1-EVALQR-12W-ICE2QR4765
3
List of Features
650V avalanche rugged CoolMOS® with built in depletion startup cell
Quasi-resonant operation
Digital frequency reduction with decreasing load
Cycle-by-cycle peak current limitation with foldback point correction
Built-in digital soft-start
Direct current sensing with internal Leading Edge Blanking Time
VCC under voltage protection: IC stop operation, recover with softstart
VCC over voltage protection: IC stop operation, recover with softstart
Openloop/Overload protection: Auto Restart
Output overvoltage protection: Latch-off with adjustable threshold
Short-winding protection: Latch-off
Over temperature protection: Autorestart
Application Note
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EVALQRC-12W5V-ICE2QR4765
4
Technical Specifications
Input voltage
Input frequency
Output voltage and current
Output power
Efficiency
Standby power
Minimum switching frequency at full load,
minimum input voltage
5
85Vac~265Vac
50Hz, 60Hz
5V 2.4A
12W
>78% at full load
<[email protected] load
65kHz
Circuit Description
5.1
Mains Input and Rectification
The AC line input side comprises the input fuse F1 as overcurrent protection. The X2 Capacitors C1 and
Choke L1 form a main filter to minimize the feedback of RFI into the main supply. After the bridge rectifier
BR1, together with a smoothing capacitor C2, provide a voltage of 70VDC to 380 VDC depending on mains
input voltage.
5.2
Integrated MOSFET and PWM Control
ICE2QR4765 is comprised of a power MOSFET and the quasi-resonant controller; this integrated solution
greatly simplifies the circuit layout and reduces the cost of PCB manufacturing. The PWM switch-on is
determined by the zero-crossing input signal and the value of the up/down counter. The PWM switch-off is
determined by the feedback signal VFB and the current sensing signal VCS. ICE2QR4765 also performs all
necessary protection functions in flyback converters. Details about the information mentioned above are
illustrated in the product datasheet.
5.3
Snubber Network
A snubber network R1, C3 and D1 dissipate the energy of the leakage inductance and suppress ringing on
the SMPS transformer.
5.4
Output Stage
On the secondary side, 5V output, the power is coupled out via a schottky diode D21. The capacitors C21
provides energy buffering followed by the L-C filters L21 and C22 to reduce the output ripple and prevent
interference between SMPS switching frequency and line frequency considerably. Storage capacitors C21 is
designed to have an internal resistance (ESR) as small as possible. This is to minimize the output voltage
ripple caused by the triangular current.
5.5
Feedback Loop
For feedback, the output is sensed by the voltage divider of Rc1 and Rc3 and compared to TL431 internal
reference voltage. Cc1, Cc2 and Rc4 comprise the compensation network. The output voltage of TL431 is
converted to the current signal via optocoupler IC2 and two resistors Rc5 and Rc6 for regulation control.
Application Note
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6
Circuit Operation
6.1
Startup Operation
Since there is a built-in startup cell in the ICE2QR4765, there is no need for external start up resistor, which
can improve standby performance significantly.
When VCC reaches the turn on voltage threshold 18V, the IC begins with a soft start. The soft-start
implemented in ICE2QR4765 is a digital time-based function. The preset soft-start time is 12ms with 4 steps.
If not limited by other functions, the peak voltageon CS pin will increase step by step from 0.32V to 1V finally.
After IC turns on, the Vcc voltage is supplied by auxiliary windings of the transformer.
6.2
Normal Mode Operation
The secondary output voltage is built up after startup. The secondary regulation control is adopted with
TL431 and optocoupler. The compensation network Cc1, Cc2 and Rc4 constitute the external circuitry of the
error amplifier of TL431. This circuitry allows the feedback to be precisely controlled with respect to
dynamically varying load conditions, therefore providing stable control.
6.3
Primary side peak current control
The MOSFET drain source current is sensed via external resistor R4 and R4A. Since ICE2QR4765 is a
current mode controller, it would have a cycle-by-cycle primary current and feedback voltage control which
can make sure the maximum power of the converter is controlled in every switching cycle.
6.4
Digital Frequency Reduction
During normal operation, the switching frequency for ICE2QR4765 is digitally reduced with decreasing load.
At light load, the MOSFET will be turned on not at the first minimum drain-source voltage time, but on the n th.
The counter is in range of 1 to 7, which depends on feedback voltage in a time-base. The feedback voltage
decreases when the output power requirement decreases, and vice versa. Therefore, the counter is set by
monitoring voltage VFB. The counter will be increased with low VFB and decreased with high VFB. The
thresholds are preset inside the IC.
6.5
Burst Mode Operation
At light load condition, the SMPS enters into Active Burst Mode. At this stage, the controller is always active
but the Vcc must be kept above the switch off threshold. During active burst mode, the efficiency increase
significantly and at the same time it supports low ripple on Vout and fast response on load jump.
For determination of entering Active Burst Mode operation, three conditions apply:
.the feedback voltage is lower than the threshold of VFBEB(1.25V). Accordingly, the peak current sense
voltage across the shunt resistor is 0.18;
.the up/down counter is 7;
.and a certain blanking time (tBEB).
Once all of these conditions are fulfilled, the Active Burst Mode flip-flop is set and the controller enters Active
Burst Mode operation. This multi-condition determination for entering Active Burst Mode operation prevents
mistriggering of entering Active Burst Mode operation, so that the controller enters Active Burst Mode
operation only when the output power is really low during the preset blanking time .
During active burst mode, the maximum current sense voltage is reduced from 1V to 0.34V so as to reduce
the conduction loss and the audible noise. At the burst mode, the FB voltage is changing like a sawtooth
between 3.0 and 3.6V.
The feedback voltage immediately increases if there is a high load jump. This is observed by one comparator.
As the current limit is 34% during Active Burst Mode a certain load is needed so that feedback voltage can
exceed VLB (4.5V). After leaving active busrt mode, maximum current can now be provided to stabilize V O.
Application Note
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EVALQRC-12W5V-ICE2QR4765
In addition, the up/down counter will be set to 1 immediately after leaving Active Burst Mode. This is helpful
to decrease the output voltage undershoot
7
Protection Features
7.1
Vcc under voltage and over voltage protection
During normal operation, the VCC voltage is continuously monitored. When the Vcc voltage falls below the
under voltage lock out level (VCCoff) or the Vcc voltage increases up to VCCovp, the IC will enter into
autorestart mode.
7.2
Foldback point protection
For a quasi-resonant flyback converter, the maximum possible output power is increased when a constant current
limit value is used for all the mains input voltage range. This is usually not desired as this will increase additional
cost on transformer and output diode in case of output over power conditions.
The internal fold back protection is implemented to adjust the VCS voltage limit according to the bus voltage. Here,
the input line voltage is sensed using the current flowing out of ZC pin, during the MOSFET on-time. As the result,
the maximum current limit will be lower at high input voltage and the maximum output power can be well limited
versus the input voltage.
7.3
Open loop/over load protection
In case of open control loop, feedback voltage is pulled up with internally block. After a fixed blanking time
30ms, the IC enters into auto restart mode. In case of secondary short-circuit or overload, regulation voltage
VFB will also be pulled up, same protection is applied and IC will auto restart.
7.4
Adjustable output overvoltage protection
During off-time of the power switch, the voltage at the zero-crossing pin ZC is monitored for output
overvoltage detection. If the voltage is higher than the preset threshold 3.7V for a preset period 100μs, the
IC is latched off.
7.5
Short winding protection
The source current of the MOSFET is sensed via two shunt resistors R5 and R5A in parallel. If the voltage at
the current sensing pin is higher than the preset threshold VCSSW of 1.68V during the on-time of the power
switch, the IC is latched off. This constitutes a short winding protection. To avoid an accidental latch off, a
spike blanking time of 190ns is integrated in the output of internal comparator.
7.6
Auto restart for over temperature protection
The IC has a built-in over temperature protection function. When the controller’s temperature reaches 140 °C,
the IC will shut down switch and enters into autorestart. This can protect power MOSFET from overheated.
Application Note
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8
Circuit diagram
C23 *
BR1
+
*S G 1
F1
L
1.6A
85V - 265Vac
C1
0.1uF/275V
L1
Lp= 707uH
C2
47uF/400V
2KBB80R
R1
150k/2W
EMI
5
L21
1.5uH
D21
6
5V/2.4A
C3
2.2nF/400V
*L2
IR90SQ045
3
2 x 47mH, 0.4A
D1
UF4005
N
R21 *
C21
1800uF/25V
4
C22
220uF/25V
+
+
C13
0.1uF/50V
9
COM
*S G 2
R4
1.5R
2
R4A
20R
C5 22uF/50V
4
CS
C7
68pF
1
5
GND FB
8
D2
R2
2R
1N4148
TR1 1370uH
Vcc
2
7
R5
51k
1
DRAIN
IC1
ICE2QR4765
ZC
Text
+
3
C8
1nF
R3
6.8k
4
1
3
2
Rc6
470R
Rc1
10k
Rc5
2.2K
Cc2
1nF
Cc1
0.1uF
Rc4
22k
IC2
SFH617A-3
C6
0.1uF
ZD1
22V
IC3
TL431
Rc3
10k
12W 5V SMPS Demoboard with ICE2QR4765
C4
1nF/250V,Y1
Figure 2 – Schematics
Application Note
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EVALQRC-12W5V-ICE2QR4765
8.1
PCB Top overlayer
Figure 3 –Component Legend – View from topside
Application Note
10
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EVALQRC-12W5V-ICE2QR4765
8.2
PCB Bottom Layer
Figure 4 Solder side copper – View from bottom side
Application Note
11
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EVALQRC-12W5V-ICE2QR4765
9
Component List
Items
Designator
Part Type
Part No.
Manufacturer
1
BR1
2KBB80R
2
C1
0.1uF/305V
B32922C3104K000
Epcos
3
C13
0.1uF/50V
RPER71H104K2K1A03B
Murata
4
C2
47uF/400V
B43504A9476M
Epcos
5
C21
1800uF/25V
6
C22
220uF/25V
7
C3
2.2nF/630V
8
C4
1nF/250V,Y1
DE1E3KX102MA4BL01
Murata
9
C5
22uF/50V
B41851A6226M000
Epcos
10
C6
0.1uF, SMD
11
C7
68pF
12
C8
1nF
13
Cc1
0.1uF
RPER71H104K2K1A03B
Murata
14
Cc2
1nF
15
D1
UF4005
UF4005
Vishay
16
D2
1N4148
17
D21
IR90SQ045
18
F1
1.6A/250Vac
19
IC1
ICE2QR4765
ICE2QR4765
Infineon
20
IC2
SFH617A-3
21
IC3
TL431
22
L1
2 x 47mH, 0.4A
23
L2
Jumper
24
L21
1.5uH
25
R1
150k/2W
26
R2
2R, SMD
27
R3
6.8k, SMD
28
R4
1.5R
29
R4A
20R, SMD
30
R5
51k, SMD
31
Rc1
10k, SMD
32
Rc3
10k, SMD
33
Rc4
22k
34
Rc5
2.2K
35
Rc6
470R
36
TR1
Lp=707uH
37
ZD1
22V zenor diode
B82731R2401A30
Epcos
EF20/10/6, N87
Epcos
Table 1– Component List
Application Note
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10
Transformer Construction
Core and material: EF20/10/6, EPCOS N87
Bobbin: Horizontal Version
Primary Inductance, Lp=707μH, measured between pin 5 and pin 4 (Gapped to Inductance)
Figure 5 – Transformer structure
Figure 6 – Transformer complete – top view
Table 2 wire gauge used of the transformer windings
Application Note
Start
1
Stop
2
No. of turns
15
Wire size
1XAWG#29
3
6
5
9
30(15+15)
5
1XAWG#27
2XAWG#25
/2 Primary
Secondary
4
3
30(15+15)
1XAWG#27
1
13
Layer
Auxiliary
1
/2 Primary
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11
11.1
Test Results
Efficiency and standby performance
Input voltage(Vac)
115
115
115
115
230
230
230
230
Input power(W)
3.7367
7.5648
11.3124
15.2544
3.7785
7.4424
11.1366
14.7858
Vo(V)
4.9983
4.9978
4.9973
4.9966
4.9983
4.9979
4.9975
4.9971
Io(A)
0.6
1.2
1.8
2.4
0.6
1.2
1.8
2.4
Po(W)
2.99898
5.99736
8.99514
11.99184
2.99898
5.99748
8.9955
11.99304
Efficiency
80.26%
79.28%
79.52%
78.61%
79.37%
80.59%
80.77%
81.11%
Table 3 – Efficiency vs. Load
Efficiency versus Load
81.50%
81.11%
80.77%
81.00%
80.50%
80.59%
80.26%
Efficiency
80.00%
79.52%
79.37%
79.28%
79.50%
79.00%
78.61%
78.50%
78.00%
115V 60Hz
77.50%
230V 50Hz
77.00%
25%
50%
75%
100%
Load
Figure 7 – Efficiency vs. AC line voltage
Input Power VS Line Voltage
800
700
664.2
688.6
685.4
664.5
Input Power(mW)
600
500
400
300
No Load
0.5W load
200
100
18.6
18.8
20.9
26.2
85
115
230
264
0
Line Voltage(Vac)
Figure 8 Standby input power vs AC line voltage
Application Note
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12
Waveform and scope plots
All waveform and scope were recorded with LeCroy 44Xi oscilloscope.
12.1
Startup @85Vac and 12W load
Figure 9 Constant charging VCC during startup
Figure 10 Softstart of current in 4 steps
Ch1 Drain source voltage ; Ch2 VCC supply voltage ;
Ch1 Drain source voltage ; Ch2 VCC supply voltage ;
Ch3 Zero crossing voltage ; Ch4 Current sense voltage
Ch3 Zero crossing voltage ; Ch4 Current sense voltage
Test condition: input 85Vac output 2.4A load
Test condition: input 85Vac output 2.4A load
12.2
Working at different zero crossing point
Figure 11 Working at first ZC point
Figure 12 Working at 7th ZC point
Ch1 Drain source voltage ; Ch2 VCC supply voltage ;
Ch1 Drain source voltage ; Ch2 VCC supply voltage ;
Ch3 Zero crossing voltage ; Ch4 Current sense voltage
Ch3 Zero crossing voltage ; Ch4 Current sense voltage
Test condition:5V/2.4A @85Vac
Test condition:5V/0.5A @85Vac
Application Note
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12.3
Load transient response
Figure 13 AC output ripple undershoot
Figure 14 AC output ripple overshoot
Ch1 Output ripple voltage div 100mv
Ch1 Output ripple voltage div 110mv
Ch4 Output current
Ch4 Output current
Measured with decouple capacitor 0.1uF+10uF, scope
bandwidth 20MHz
Measured with decouple capacitor 0.1uF+10uF, scope
bandwidth 20MHz
Test condition:0A to 2.4A
Test condition:2.4A to 0A
12.4
AC Output ripple during full load
Figure 15 AC output ripple at 85 Vac input
Figure 16 AC output ripple at 265 Vac input
Ch1 Output ripple voltage div 20mV
Ch1 Output ripple voltage div 20mV
Measured with decouple capacitor 0.1uF+10uF, scope
bandwidth 20MHz
Measured with decouple capacitor 0.1uF+10uF, scope
bandwidth 20MHz
Test condition: 85V 5V/2.4A
Test condition: 265V 5V/2.4A
Application Note
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12.5
Burst mode operation
Figure 17 Entering burst mode
Figure 18 Leaving burst mode
Ch1 Drain source voltage ; Ch2 Supply voltage VCC ;
Ch1 Drain source voltage ; Ch2 Supply voltage VCC ;
Ch3 Feedback voltage Vfb ; Ch4 Current sense voltage
Ch3 Feedback voltage Vfb ; Ch4 Current sense voltage
Test condition: load jump from 2.4A to 0.1A at 85Vac line
Test condition: load jump from 0A to 2.4A at 85Vac line
Figure 19 AC output ripple during 85Vac
Figure 20 AC output ripple during 265V
Ch1 AC output ripple 50mV/ div; Ch2 Supply voltage VCC ;
Ch1 AC output ripple 50mV/ div; Ch2 Supply voltage VCC;
Ch3 Feed back voltage Vfb ; Ch4 Current sense voltage
Ch3 Feed back voltage Vfb ; Ch4 Current sense voltage
Measured with decouple capacitor 0.1uF+10uF, scope
bandwidth 20MHz
Measured with decouple capacitor 0.1uF+10uF, scope
bandwidth 20MHz
Test condition : 85V ac line, 5V/0.1A
Test condition : 265V ac line, 5V/0.1A
13
References
[1]
ICE2QR4765 datasheet Infineon Technologies AG,2009
[2]
ICE2QRxx65/80x Quasi Resonance CoolSET Design Guide, Infineon Technologies, 2010. [ANPS0053]
[3]
Design tips for flyback converters using the Quasi-Resonant PWM controller ICE2QS01, Infineon
Technologies, 2006. [ANPS0005]
[4]
Converter design using the quasi-resonant PWM controller ICE2QS01, application notes, Infineon
Technologies, 2006. [ANPS0003]
[5]
Determine the switching frequency of Quasi-Resonant flyback converters designed with ICE2QS01,
Infineon Technologies, 2006. [ANPS0004]
Application Note
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8 August 2011