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 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. Title Revision History: Previous Version: Page 13 8 August 2011 V1.0 Subjects (major changes since last revision) Revise typo 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 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] 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 4 8 August 2011 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 5 8 August 2011 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 <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 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 6 8 August 2011 EVALQRC-12W5V-ICE2QR4765 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 7 8 August 2011 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 8 8 August 2011 EVALQRC-12W5V-ICE2QR4765 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 9 8 August 2011 EVALQRC-12W5V-ICE2QR4765 8.1 PCB Top overlayer Figure 3 –Component Legend – View from topside Application Note 10 8 August 2011 EVALQRC-12W5V-ICE2QR4765 8.2 PCB Bottom Layer Figure 4 Solder side copper – View from bottom side Application Note 11 8 August 2011 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 12 8 August 2011 EVALQRC-12W5V-ICE2QR4765 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 8 August 2011 EVALQRC-12W5V-ICE2QR4765 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 14 8 August 2011 EVALQRC-12W5V-ICE2QR4765 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 15 8 August 2011 EVALQRC-12W5V-ICE2QR4765 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 16 8 August 2011 EVALQRC-12W5V-ICE2QR4765 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 17 8 August 2011