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 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 the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered. 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: [email protected] 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 <100mW@no 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