Application Note, V1.0, 7 September 2011 Application Note AN- EVAL-2QR0680Z-40W 40W20V Evaluation Board with QuasiResonant CoolSET® ICE2QR0680Z 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. 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. EVAL-2QR0680Z-40W Title Revision History: Previous Version: Page 7 September 2011 none Subjects (major changes since last revision) 40W20V Evaluation Board with Quasi-Resonant CooLSET® ICE2QR0680Z License to Infineon Technologies Asia Pacific Pte Ltd V1.0 AN-PS0066 Wong Siew Teng Winson [email protected] Eric Kok Siu Kam [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] Application Note 4 7 September 2011 EVAL-2QR0680Z-40W Table of Contents 1 2 3 4 5 Content ............................................................................................................... 6 Evaluation Board ............................................................................................... 6 List of Features .................................................................................................. 6 Technical Specifications ................................................................................... 7 Circuit Description............................................................................................. 7 5.1 5.2 5.3 5.4 Mains Input and Rectification ...................................................................................................... 7 Integrated MOSFET and PWM Control........................................................................................ 7 Output Stage .................................................................................................................................. 7 Feedback Loop .............................................................................................................................. 7 6 Circuit Operation ............................................................................................... 7 6.1 6.2 6.3 6.4 6.5 Startup Operation.......................................................................................................................... 7 Normal Mode Operation ............................................................................................................... 8 Primary side peak current control............................................................................................... 8 Digital Frequency Reduction ....................................................................................................... 8 Burst Mode Operation .................................................................................................................. 8 7 Protection Features ........................................................................................... 8 7.1 7.2 7.3 7.4 7.5 7.6 Vcc under voltage and over voltage protection ......................................................................... 8 Foldback point protection ............................................................................................................ 8 Open loop/over load protection ................................................................................................... 9 Adjustable output overvoltage protection.................................................................................. 9 Short winding protection.............................................................................................................. 9 Auto restart for over temperature protection ............................................................................. 9 8 Circuit diagram ................................................................................................ 10 8.1 8.2 PCB Top overlayer ...................................................................................................................... 11 PCB Bottom Layer ...................................................................................................................... 11 9 10 11 Component List ............................................................................................... 12 Transformer Construction .............................................................................. 13 Test Results ..................................................................................................... 14 11.1 Efficiency and standby performance ........................................................................................ 14 12 References ....................................................................................................... 16 Application Note 5 7 September 2011 EVAL-2QR0680Z-40W 1 Content This application note is a description of 40W switching mode power supply evaluation board designed in a quasi resonant flyback converter topology using ICE2QR0680Z Quasi-resonant CoolSET®.The target application of ICE2QR0680Z 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 ICE2QR0680Z 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-40W-ICE2QR0680Z 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 6 7 September 2011 EVAL-2QR0680Z-40W 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~282Vac 50Hz, 60Hz 20V 2.0A 40W >85% 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 ICE2QR0680Z 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. ICE2QR0680Z 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 ICE2QR0680Z, 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 ICE2QR0680Z 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. Application Note 7 7 September 2011 EVAL-2QR0680Z-40W 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 ICE2QR0680Z 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 ICE2QR0680Z 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 VO. 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 Application Note 8 7 September 2011 EVAL-2QR0680Z-40W 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 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 9 7 September 2011 EVAL-2QR0680Z-40W 8 Circuit diagram 40W 20V SMPS Demoboard with ICE2QR0680Z Figure 2 – Schematics Application Note 10 7 September 2011 EVAL-2QR0680Z-40W 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 11 7 September 2011 EVAL-2QR0680Z-40W 9 Component List Items 1 2 Designator F1 Part type 1.0A/250Vac Part No. Manufacturer C1 220nF/275Vac X2 224K/275VAC15MM 3 L1 2 x 27mH, 0.9A B82732R2901B30 Epcos 4 BR1 DB107, 1000V 5 C3 68uF/450V 6 R1 150k/2W 7 D1 UF4007 8 C4 2.2nF/400V 9 TR1 750uH 10 C8 100pF 11 R14 47k 12 R15 8.2K 13 R5 1.8R 14 R5A 0.75R 15 C10 47pF/1kV 16 C9 1nF 17 C7 0.1uF 18 R4 0R 19 R3 0R 20 R2 0R 21 ZD1 22V zener 22 D2 1nN4148 23 IC1 2QR0680Z IFX 24 IC2 EL817 25 D3 STPS20H100CFP 26 C11 1000uF/25V 27 C16 1000uF/25V 28 L2 1.5uH 29 C12 220uF/25V 30 C17 0.1uF/50V 31 R6 680R 32 R7 1.2k 33 C14 100pF 34 R8 22k 35 IC3 TL431 36 R13 510k 37 R12 10k 38 R11 27k 39 R10 43k 40 C15 100nF 41 C5 2.2nF/250V Table 1– Component List Application Note 12 7 September 2011 EVAL-2QR0680Z-40W 10 Transformer Construction Core and material : PQ2620, PC40 Bobbin: Vertical Version Primary Inductance, Lp=750μH±10%, measured between pin 4 and pin 5 (Gapped to Inductance) Air Gap in center leg Figure 5 – Transformer structure Figure 6 – Transformer complete – top view Start Stop No. of turns Wire Size Layer 4 3 19 2UEW,φ0.40mm *1p ½ primary 8 10 5 Triple insulatedφ0.55mm *2p Secondary 3 5 18 2UEW,φ0.37mm *1p ½ primary 1 2 4 2UEW,φ0.40mm *1p Auxiliary Table 2 wire gauge used of the transformer windings Application Note 13 7 September 2011 EVAL-2QR0680Z-40W 11 Test Results 11.1 Efficiency and standby performance Voltage (Vac) 85 85 85 85 115 115 115 115 150 150 150 150 180 180 180 180 230 230 230 230 282 282 282 282 Input Power (W) 11.68 23.46 35.15 47.67 11.56 23.45 34.37 45.93 11.533 22.9 34.01 45.15 11.567 22.83 33.79 45.05 11.67 22.85 33.8 44.87 11.82 22.92 33.89 44.85 Output Voltage (V) 20.26 20.26 20.27 20.27 20.26 20.26 20.27 20.27 20.26 20.26 20.27 20.27 20.26 20.26 20.27 20.27 20.26 20.26 20.27 20.27 20.26 20.26 20.27 20.27 Output Current Output Power (A) (W) 0.5062 10.255612 1.0143 20.549718 1.5075 30.557025 2.0025 40.590675 0.5062 10.255612 1.0143 20.549718 1.5075 30.557025 2.0025 40.590675 0.5062 10.255612 1.0143 20.549718 1.5075 30.557025 2.0025 40.590675 0.5062 10.255612 1.0143 20.549718 1.5075 30.557025 2.0025 40.590675 0.5062 10.255612 1.0143 20.549718 1.5075 30.557025 2.0025 40.590675 0.5062 10.255612 1.0143 20.549718 1.5075 30.557025 2.0025 40.590675 Efficiency (%) 87.80 87.59 86.93 85.15 88.72 87.63 88.91 88.38 88.92 89.74 89.85 89.90 88.66 90.01 90.43 90.10 87.88 89.93 90.41 90.46 86.76 89.66 90.17 90.50 Table 3 – Efficiency vs. Load Application Note 14 7 September 2011 EVAL-2QR0680Z-40W Efficiency vs. Load 91.00 90.17 90.00 90.50 89.66 Efficiency % 89.00 88.00 87.80 87.00 87.59 85Vac 86.93 86.76 282Vac 86.00 85.15 85.00 84.00 25% 50% 75% 100% Load Efficiency vs. Load 91.00 90.50 90.41 Efficiency % 90.00 90.46 89.93 89.50 89.00 88.91 88.72 88.50 115Vac 88.38 88.00 230Vac 87.88 87.63 87.50 87.00 25% 50% 75% 100% Load Figure 7 – Efficiency vs. Output Load Application Note 15 7 September 2011 EVAL-2QR0680Z-40W Efficiency vs. AC Line Voltage 91.00 90.00 89.90 89.60 90.50 90.46 90.10 89.80 89.67 89.27 Efficiency % 89.00 88.41 88.38 88.00 87.00 Full Load 86.87 Average Eff 86.00 85.15 85.00 84.00 85Vac 115Vac 150Vac 180Vac 230Vac 282Vac AC Line Voltage (Vac) Figure 8 Efficiency vs AC line voltage Standby Power 90.0 83.0 80.0 Power (mW) 70.0 66.0 60.0 55.0 50.0 40.0 42.5 44.0 47.0 No Load 30.0 20.0 10.0 0.0 85Vac 115Vac 150Vac 180Vac 230Vac 282Vac AC Line Voltage (Vac) Figure 9 Standby input power vs AC line voltage 12 [1] [2] References ICE2QR0680Z datasheet, Infineon Technologies AG, 2011 ICE2QS03G Design Guide Infineon Technologies AG,2010 Application Note 16 7 September 2011 EVAL-2QR0680Z-40W [3] [4] [5] 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 17 7 September 2011