20W 5V Evaluation Board using ICE2QR2280Z

Application Note, V1.1, 3 August 2012
A pp l i c at i o n N ot e
AN- EVAL-2QR2280Z-20W
20W 5V E valuati on Board wi th Quasi Resonant CoolSET® ICE2QR2280Z
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
© 2010 Infineon Technologies AG
All Rights Reserved.
Legal Disclaimer
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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,
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including without limitation, warranties of non-infringement of intellectual property rights
of any third party.
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For further information on technology, delivery terms and conditions and prices, please
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on the types in question, please contact the nearest Infineon Technologies Office.
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AN-EVAL-2QR2280Z-20W
Revision History:
3 Aug 2012
V1.1
Previous Version:
Page
V1.0
Subjects (major changes since last revision)
11, 19
Revise BOM and reference
®
20W5V Evaluation Board with Quasi-Resonant CooLSET ICE2QR2280Z
License to Infineon Technologies Asia Pacific Pte Ltd
Wong Siew Teng Winson
[email protected]
Kok Siu Kam Eric
[email protected]
Wang Zan
[email protected]
We Listen to Your Comments
Any information within this document that you feel is wrong, unclear or missing at all?
Your feedback will help us to continuously improve the quality of this document.
Please send your proposal (including a reference to this document) to:
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AN-PS0055
EVAL-2QR2280Z-20W
Table of Contents
1
2
3
4
5
Content ............................................................................................................... 5
Evaluation Board ............................................................................................... 5
List of Features .................................................................................................. 5
Technical Specifications ................................................................................... 6
Circuit Description............................................................................................. 6
5.1
5.2
5.3
5.4
Mains Input and Rectification..................................................................................................6
Integrated MOSFET and PWM Control ....................................................................................6
Output Stage ............................................................................................................................6
Feedback Loop.........................................................................................................................6
6
Circuit Operation ............................................................................................... 6
6.1
6.2
6.3
6.4
6.5
Startup Operation.....................................................................................................................6
Normal Mode Operation...........................................................................................................6
Primary side peak current control...........................................................................................7
Digital Frequency Reduction ...................................................................................................7
Burst Mode Operation..............................................................................................................7
7
Protection Features ........................................................................................... 7
7.1
7.2
7.3
7.4
7.5
7.6
Vcc under voltage and over voltage protection......................................................................7
Foldback point protection........................................................................................................7
Open loop/over load protection...............................................................................................8
Adjustable output overvoltage protection ..............................................................................8
Short winding protection .........................................................................................................8
Auto restart for over temperature protection..........................................................................8
8
Circuit diagram .................................................................................................. 9
8.1
8.2
PCB Top overlayer .................................................................................................................10
PCB Bottom Layer .................................................................................................................10
9
10
11
Component List ............................................................................................... 11
Transformer Construction .............................................................................. 12
Test Results ..................................................................................................... 13
11.1
Efficiency and standby performance ....................................................................................13
12
Waveforms and scope plots ........................................................................... 16
12.1
12.2
12.3
12.4
12.5
Startup at 85Vac and 20W load..............................................................................................16
Zero Crossing Points during normal operation ....................................................................16
Load Transient Response......................................................................................................17
Burst Mode Operation............................................................................................................17
Protection modes...................................................................................................................18
13
References ....................................................................................................... 19
Application Note
4
3 August 2012
EVAL-2QR2280Z-20W
1
Content
This application note is a description of 20W switching mode power supply evaluation board designed in a
®
quasi resonant flyback converter topology using ICE2QR2280Z Quasi-resonant CoolSET .The target
application of ICE2QR2280Z 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 ICE2QR2280Z 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-by-cycle 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-20W-ICE2QR2280Z
3
List of Features
®
800V 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
5
3 August 2012
EVAL-2QR2280Z-20W
4
Technical Specifications
Input voltage
Input frequency
Output voltage and current
Output power
Average Efficiency
Standby power
Minimum switching frequency at full load,
minimum input voltage
5
85Vac~265Vac
50Hz, 60Hz
5V 4.0A
20W
>80% 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
ICE2QR2280Z 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. ICE2QR2280Z also performs all
necessary protection functions in flyback converters. Details about the information mentioned above are
illustrated in the product datasheet.
5.3
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 capacitor 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.
5.4
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.
6
Circuit Operation
6.1
Startup Operation
Since there is a built-in startup cell in the ICE2QR2280Z, 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 ICE2QR2280Z 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
Application Note
6
3 August 2012
EVAL-2QR2280Z-20W
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 ICE2QR2280Z 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 ICE2QR2280Z 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 nth.
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:
1. 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;
2. the up/down counter is 7;
3. and a certain blanking time, 24ms (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 switching frequency is set to a fix frequency of 52kHz.
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.
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.
Application Note
7
3 August 2012
EVAL-2QR2280Z-20W
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 R4 and R4A 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
8
3 August 2012
EVAL-2QR2280Z-20W
8
Circuit diagram
Figure 2 – Schematics
Application Note
9
3 August 2012
EVAL-2QR2280Z-20W
8.1
PCB Top overlayer
Figure 3 –Component Legend – View from topside
8.2
PCB Bottom Layer
Figure 4 Solder side copper – View from bottom side
Application Note
10
3 August 2012
EVAL-2QR2280Z-20W
9
Component List
Items
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Designator
F1
L1
BR1
ZD1
D1
D2
D3
IC1
IC2
IC3
C1
C3
C4
C5
C6
C7
C8
C9
C10
20
C11
21
C12
22
23
24
C14
C15
C17
25
C18
26
27
28
29
30
31
32
33
34
35
36
37
38
39
R1
R3
R5
R5P
R5A
R6
R7
R8
R10
R12
R13
R14
R15
L2
Descriptions
Fuse
Com-Choke
Bridge Rectifier
Zener Diode
Ultra Fast Diode
Diode
45V Schottky Diode
800V QR Coolset
Optp-coupler
2.5 Reference
0.22uF / 275V X Cap
68uF / 400V Bulk Cap
2.2nF / 630V
2.2nF/ 250V, Y Cap
33uF / 35V
0.1uF SMD
100pF SMD
1nF SMD
47pF / 1kV
2200uF / 25V, 105°C, low
ESR, 12.5x25 mm
220uF / 25V, 105°C, low
ESR, 10x13 mm
1nF
1uF
0.1uF / 50V
2200uF / 25V, 105°C, low
ESR, 12.5x25 mm
150K / 2W
200 SMD
2.4R / 1W
2.4R / 1W
3.3R / 1W
470 SMD
1.2K SMD
6.8K SMD
22K SMD
22K SMD
OPEN
39K SMD
6.82K SMD
1.5uH
Part No.
1.6A
2x47mH, 0.4A
2KBB80R
22V
UF4005
1N486B
STPS30L45CT
ICE2Q2280Z
SFH617A-3
TL431
B32922 X2 MKP/SH
B43501A9686M00
MKP 2.2nF / 630V
2.2nF/ 250V, Y1
33uF / 35V
0.1uF SMD
100pF SMD
1nF SMD
47pF / 1kV
Manufacturer
Epcos
Infineon
Epcos
Epcos
Epcos
2200uF / 25V
220uF / 25V
1nF
1uF
0.1uF / 50V
2200uF / 25V
150K / 2W
200 SMD
2.4R / 1W
2.4R / 1W
3.3R / 1W
470 SMD
1.2K SMD
6.8K SMD
22K SMD
22K SMD
OPEN
39K SMD
6.82K SMD
1.5uH
Table 1– Component List
Application Note
11
3 August 2012
EVAL-2QR2280Z-20W
10
Transformer Construction
Core and material :EPCOS(N87)or TDK PC40 EF25/13/7
Bobbin: Vertical Version
Primary Inductance, Lp=829μH(±3%), measured between pin 3 and pin 5 (Gapped to Inductance)
Air Gap in center leg
Figure 5 – Transformer structure
Figure 6 – Transformer complete – top view
Table 2 wire gauge used of the transformer windings
Application Note
12
3 August 2012
EVAL-2QR2280Z-20W
11
Test Results
11.1
Efficiency and standby performance
Table 3 – Efficiency vs. Load
Vin (Vac)
85
115
150
180
230
282
Application Note
Pin (W)
Vo(Vdc)
Io(A)
Po(W)
η(%)
6.17
5.01
0.9975
4.997475
80.9964
12.57
5.004
2.0025
10.02051
79.7177
19.1
4.997
3.0075
15.02848
78.6831
26.38
4.99
4.0106
20.01289
75.8639
6.09
5.01
0.9975
4.997475
82.0603
12.04
5.003
2.0025
10.01851
83.2102
18.35
4.997
3.0075
15.02848
81.8991
25
4.99
4.0106
20.01289
80.0516
6.08
5.01
0.9975
4.997475
82.1953
12.05
5.003
2.0025
10.01851
83.1411
18.15
4.997
3.0075
15.02848
82.8015
24.55
4.99
4.0106
20.01289
81.5189
5.89
5.01
0.9975
4.997475
84.8468
12.06
5.003
2.0025
10.01851
83.0722
18
4.996
3.0075
15.02547
83.4748
24.3
4.989
4.0106
20.00888
82.3411
6.25
5.01
0.9975
4.997475
79.9596
12.05
5.003
2.0025
10.01851
83.1411
18.05
4.996
3.0075
15.02547
83.2436
24.2
4.989
4.0106
20.00888
82.6813
6.43
5.01
0.9975
4.997475
77.7212
12.3
5.004
2.0025
10.02051
81.4676
18.35
4.997
3.0075
15.02848
81.8991
24.25
4.99
4.0106
20.01289
82.5274
13
Avg η(%)
78.8153
81.8053
82.4142
83.4337
82.2564
80.9038
3 August 2012
EVAL-2QR2280Z-20W
Efficiency vs Output Load
90.0000
88.0000
86.0000
Efficiency (%)
84.0000
82.0000
82.5274
80.9964
79.7177
81.4676
80.0000
78.0000
85Vac
81.8991
78.6831
282Vac
77.7212
76.0000
75.8639
74.0000
72.0000
70.0000
25
50
75
100
Load (%)
Efficiency vs Output Load
90.0000
88.0000
86.0000
Efficiency (%)
84.0000
83.2102
82.0603
82.0000
81.8991
83.1411
80.0000
82.6813
83.2436
80.0516
79.9596
115Vac
230Vac
78.0000
76.0000
74.0000
72.0000
70.0000
25
50
75
100
Load (%)
Figure 7 – Efficiency vs. Output Load
Application Note
14
3 August 2012
EVAL-2QR2280Z-20W
Efficiency vs AC Line Input Voltage
84.0000
83.4337
83.0000
82.4142
Efficiency (%)
82.0000
82.3411
82.6813
82.2564
81.8053
82.5274
81.5189
81.0000
80.9038
80.0000
Average Efficiency
80.0516
79.0000
Full Load Efficiency
78.8153
78.0000
77.0000
76.0000
75.8639
75.0000
85
115
150
180
230
282
AC Input Voltage (V)
Figure 8 Efficiency vs AC line voltage
Standby Power at No Load versus Input Voltage (AC)
1600
1358
1302
1318
1034
1030
1010
660
663
667
672
294
298
304
20.2
20.99
23.92
24.7
34.06
85
115
150
180
230
Output Power (mW)
1400
1200
1400
1307
1033
1308
1070
1120
1000
800
700
725
330
334
600
400
307
200
0
49.6
282
AC Input Voltage
0W
0.2W
0.5W
0.8w
1W
Figure 9 Standby input power vs AC line voltage
Application Note
15
3 August 2012
EVAL-2QR2280Z-20W
12
Waveforms and scope plots
12.1
Startup at 85Vac and 20W load
Figure 10 Constant Charging VCC @ startup
Ch1 Current Sense Voltage, VCS
Ch2 VCC Supply Voltage
Ch3 Feedback Voltage, VFB
Ch4 Zero Crossing Voltage, VZC
Test Condition: 85Vac input, 4A Load
12.2
Figure 11 Four steps softstarts
Ch1 Current Sense Voltage, VCS
Ch2 VCC Supply Voltage
Ch3 Feedback Voltage, VFB
Ch4 Zero Crossing Voltage, VZC
Test Condition: 85Vac input, 4A Load
Zero Crossing Points during normal operation
st
nd
Figure 12 Working at the 1 Zero Crossing
Ch1 Current Sense Voltage, VCS
Ch2 Drain Voltage
Ch3 Feedback Voltage, VFB
Ch4 Zero Crossing Voltage, VZC
Test Condition: 85Vac input
Application Note
Figure 13 Working at the 2 Zero Crossing
Ch1 Current Sense Voltage, VCS
Ch2 Drain Voltage
Ch3 Feedback Voltage, VFB
Ch4 Zero Crossing Voltage, VZC
Test Condition: 85Vac input
16
3 August 2012
EVAL-2QR2280Z-20W
12.3
Load Transient Response
Figure 14 AC output ripple overshoot
Ch1 Output Current, Iout
Ch2 Feedback Voltage, VFB
Test Condition: Load 3A to 0A
Measured with decouple capacitor 0.1uF, and 10uF
12.4
Figure 15 AC output ripple undershoot
Ch1 Output Current, Iout
Ch2 Feedback Voltage, VFB
Test Condition: Load 0A to 3A
Measured with decouple capacitor 0.1uF, and 10uF
Burst Mode Operation
Figure 16 Entering Burst Mode Operation
Ch1 Current Sense Voltage, VCS
Ch2 Drain Voltage
Ch3 Feedback Voltage, VFB
th
Test Condition: 85Vac, Load changed fr. 6 ZC to 0.2A
Application Note
17
Figure 17 Leaving Burst Mode Operation
Ch1 Current Sense Voltage, VCS
Ch2 Drain Voltage
Ch3 Feedback Voltage, VFB
th
Test Condition: Load changed fr. 6 ZC to 0.2A
3 August 2012
EVAL-2QR2280Z-20W
Figure 18 Active Burst Mode Operation
Ch1 Current Sense Voltage, VCS
Ch2 Drain Voltage
Ch3 Feedback Voltage, VFB
Test Condition: 85Vac, under BMO
12.5
Figure 19 Active Burst Mode Operation
Ch1 Current Sense Voltage, VCS
Ch2 Drain Voltage
Ch3 Feedback Voltage, VFB
Test Condition: 282Vac, under BMO
Protection modes
Figure 20 VCC Over-voltage Protection
Ch2 VCC Supply Voltage
Ch3 Feedback Voltage, VFB
Test Condition: open the zener clamping with
overload at high-line
Application Note
Figure 21 Over Load/ Open Loop Protection
Ch1 Output Voltage, Vo
Ch2 VCC Supply Voltage
Ch3 Feedback Voltage, VFB
Ch4 Zero Crossing Voltage. VZC
Test Condition: Load change from 1A to 5A
18
3 August 2012
EVAL-2QR2280Z-20W
Figure 22 Output Over-voltage Protection
Ch1 Current Sense Voltage, VCS
Ch2 VCC Supply Voltage
Ch3 Feedback Voltage, VFB
Ch4 Zero Crossing Voltage. VZC
Test Condition: change the ZC resistor divider ratio,
Apply 230Vac, Load 1A
13
[1]
[2]
[3]
[4]
[5]
Figure 23 Output Short Circuit Protection
Ch1 Output Voltage, Vo
Ch2 VCC Supply Voltage
Ch3 Feedback Voltage, VFB
Ch4 Zero Crossing Voltage. VZC
Test Condition: Shorted output terminal
References
ICE2QR2280Z datasheet, Infineon Technologies AG, 2010
ICE2Qxx65/80x Quasi Resonance CoolSET Design Guide (ANPS0053), Infineon Technologies AG,
2010
Design Tips for flyback converters using the Quasi-Resonant (ANPS0005), Infineon Technologies
AG, 2006
Converter Design Using the Quasi-Resonant PWM Controller ICE2QS01 (ANPS0003), Infineon
Technologies AG, 2006
Determine the Switching Frequency of Quasi-Resonant Flyback Converters Designed with
ICE2QS01 (ANPS0004), Infineon Technologies AG, 2006
Application Note
19
3 August 2012
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