60W Auxiliary Power Supply Demonstration board 1. DEMONSTRATION BOARD SUMMARY The CRD-060DD12P is a Cree demonstration board for a single-end Flyback converter design with a commercially available 1700V Silicon Carbide (SiC) MOSFET to replace conventional two-switch Flyback converter for high voltage input auxiliary power supply of three phase applications. The demonstration board is not designed to be a product and is to be only used as a tool to evaluate the performance Cree switching devices. 2. INTRODUCTION VCPWR-AN14, RE o board wer Supply Dem Po ry lia xi Au W 60 Three-phase applications, such as motor drive, UPS and PV inverter, have a front end AC/DC or DC/DC converter to boost the DC link voltage up to 600Vdc to 800Vdc. Factoring in a design margin, the maximum DC link voltage is up to 1000V. To support such systems in practice, an auxiliary power supply is used to generate power for cooling fans, displays, control logic and system protection functions with the DC link voltage as its input. For such low power applications, Flyback topology is the most common type in the industry; however, the conventional single end Flyback topology has difficulty in meeting high input voltage. The first difficulty is caused by the high input voltage (1000Vdc); the singleend Flyback topology would require high blocking voltage switching devices. Currently, the Silicon MOSFET only has 1500V blocking voltage, which has low voltage stress design margin and thus affects the reliability of the power supply. The second challenge is that most of the 1500V Si MOSFETs have very large on-state resistance, and this will lead to higher losses, higher thermal and lower efficiency, especially when the whole three-phase system is operating at light output load and auxiliary power losses occupy most of total system losses. Lastly, to support a wide input voltage range, a pure resistance start up circuit is normally used. However, the start-up resistance will lead to losses at high input voltage. Larger start-up resistance will have less losses but lead to long start-up time at low input voltage. In order to overcome these auxiliary power supply design challenges to supply high input voltage, twoswitch Flyback converter was proposed to use high side and low side 800V Si MOSFETs as shown in Fig.1, but it has the additional isolation gate drive circuit which increases component counts and complicates the design. This application note proposes a single-end Flyback converter to replace complicated two-switch Flyback converter by using 1700V SiC MOSFET. An active start-up circuit is also introduced to achieve less start-up losses with faster start up time. The 60W experimental reference design demonstrates that the 1700V SiC MOSFET can reduce total cost and simplify the design of auxiliary power supply. Figure 1: A conventional two-switch Flyback converter with 800V Si MOSFET Subject to change without notice. www.cree.com 1 3. Cree 1700V SiC MOSFET Today, SiC devices are characterized by a number of promising properties like high rating voltages, low switching losses, low on-state resistance, higher operating temperature, and high radiation hardness. A commercially available 1700V TO-247 packaged SiC MOSFET, C2M1000170D, from Cree Inc is used for a wide input auxiliary power supply application. The table compares the key parameters between SiC MOSFET and Si MOSFET with common TO-247 package. From this comparison, SiC MOSFET can support much higher blocking voltage to 1700V and avalanche voltage above 1800V, while Si MOSFET only has 1500V blocking voltage with lower avalanche voltage. For the on-state resistance and parasitic capacitance, the SiC MOSFET has lower value than Si MOSFET to have low conduction losses and low switching losses. This key difference will value 1700V SiC MOSFET to have high efficiency and high reliability replacing 1500V Si MOSFET. Table 1: Parameter comparisons of 1700V SiC MOSFET and 1500V Si MOSFET Parameters SiC MOSFET Si MOS Si MOS C2M1000170D STW4N150 2SK2225DS V(BR)DSS 1700V 1500V 1500V Avalanche >1800V N/A N/A Id @ Tc=25°C 5A 4A 2A Rdson @150°C 2ohm 9ohm 20ohm Coss 14pF 120pF 60pF Tjmax >150°C 150°C 150°C Package TO-247 TO-220, TO-247 TO-3PF 4. ACTIVE START-UP CIRCUIT In this design, a non-dissipative, active start-up circuit has been implemented to optimize converter efficiency and fast start-up time. The alternative is to use a pure resistive start-up circuit which significantly affects converter efficiency and start up times at low input voltages in a negative way. Figure 2 shows the proposed active start-up circuit. When input voltage is increasing, Q6 is turned on by Vbase from path R31 to R36. The VCC voltage comes from path R22 to R25 when U1 (UCC28C44) is turning on. Once U1 starts operating, the VCC supply comes from the primary auxiliary winding. When VCC reaches the startup threshold of U1, the VREF (+5V) goes to high and Q7 is turned on. And then Q6 is turned off, which disconnects the start-up current path to VCC. The R31 to R36 resistors with large value are used as the voltage balancing for input capacitors C1 to C3. The startup resistors R22 to R25 feeds the PWM controller of U1 until the auxiliary supply voltage rises and is disconnected from VCC of U1 and then there are no more losses from start-up resistors. So the active start-up circuit can reduce the start up power dissipation, especially at high line input voltage and improve the efficiency. The additional power dissipation under such normal steady state conditions is due to the balance resistances, and they can be set at very high values (>6Mohm). More importantly, due to low resistance values for this active start-up circuit, the start-up time will be short and can be trimmed to meet targeting start-up time. If assuming minimum start-up time 1s, the VCC capacitance can be calculated as follows: C start up CPWR-AN14, REV 2 60W Auxiliary Power Supply Demo board IUCC 28C 44 startupTstart up VUVLO _ on VUVLO _ off (1) This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Cree Sales at [email protected]. From datasheet of UCC28C44: I UCC 28C 44 start up 0.1mA ; VUVLO _ on 14.5V ; VUVLO _ off 9.0V . If C Start up 18F , it can select the VCC capacitance is 22uF. The total start-up current may then be calculated using the below equation: I start up C start upVUVLO _ on Tstart up 22F 14.5V 0.319mA 1S (2) Hence, the total start-up resistors (R22 to R25) may be calculated as: Rstart up VDC min VUVLO _ off I start up 200V 9V 600 K 0.319mA (3) Assuming worse darlington gain hFE is 500, the total balance resistance (R31-R36) may be calculated as: RBalance VDC min VUVLO _ off I startup / hFE 200V 9V 300M 0.319mA (4) By using much higher balance resistance, total additional losses can be seen to have no negative impact on total losses. HV_DC J1 1 HV_DC C1 10uF 450V R22 150k R32 1M5 I/P: 200V to 1000V R23 150k VCC R33 1M5 C2 10uF 450V J2 R31 1M5 Q5 PBSS4240T R24 150k R47 4.7k R34 1M5 + C12 22uF R25 150k + C36 NC + C10 10uF C11 0.1uF 1 ZD3 18V P_GND C3 10uF 450V R35 R36 1M5 1M5 Q6 STP03D200 Q7 MMBT2222A R30 510k 1 2 3 4 U1 COMP VREF FB VCC CS OUT RC GND 8 7 6 C13 0.1uF 5 UCC28C44 Figure 2: The proposed active start-up circuit CPWR-AN14, REV 3 60W Auxiliary Power Supply Demo board This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Cree Sales at [email protected]. 5. EXPERIMENTAL RESULTS To demonstrate high performance of 1700V SiC MOSFET, a 60W single-end end Flyback auxiliary power supply with proposed active start-up start circuit is developed as shown in Figure 3. Table 2: 60W auxiliary SMPS prototype design specification with 1700V SiC MOSFET 200Vdc to 1000Vdc Input Voltage Output Voltage +12Vdc +5Vdc -12Vdc Output Current 4.5A 0.5A 0.25A Frequency 75KHz Efficiency >83% Figure 3:: Photo of 60W auxiliary SMPS with 1700V SiC MOSFET 85.0% 84.0% 83.0% Efficiency (%) 82.0% 81.0% 80.0% 79.0% 78.0% CREE C2M1000170D ST STW4N150 77.0% 76.0% 75.0% 200v 400v 600v 800v 1000V Vin (Vdc) Figure 4:: 60W auxiliary SMPS efficiency with 1700V SiC MOSFET CPWR-AN14, REV 4 60W Auxiliary Power Supply Demo board This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Cree Sales at [email protected]. Figure 4 compares measured efficiency at full load with input voltage varying from 200V to 1000V using different Si and SiC devices. Due to lower on-state resistance and parasitic capacitance, the 1700V SiC MOSFET can achieve a higher efficiency when compared to other 1500V Si MOSFET competitors. Thermal comparison at full load with the same heat sink is shown in Fig.5, SiC MOSFET clearly shows a lower operating temperature at 45.9°C when compared to Si 1500V MOS at 60°C and 99.9°C. It shows that 1700V SiC MOSFET can achieve higher reliability. Use of the 1700V SiC MOSFET also allows us to use a small low cost heat sink due to the fact that a smaller amount of heat needs to be dissipated as shown in Figure 6. This can save the auxiliary power board size and improve power density. STW4N150 with large heat sink C2M1000170D with large heat sink (a) SiC MOS C2M1000170D (b) Si MOS STW4N150 2SK2225 with large heat sink (c) Si MOS 2SK2225 Figure 5: Thermal comparison with same large heat sink and input voltage is 1000Vdc C2M1000170D with small heat sink Figure 6: SiC MOSFET Thermal with small low cost heatsink and input voltage is 1000Vdc Figure 7 shows the start up waveform with the proposed active start-up circuit. At 1000Vdc input, start up time is less 100ms and at 200Vdc input, start up time is less than 1s. Meanwhile, by trimming the start-up resistor R22 to R25, it can achieve faster start up time smoothly without sacrificing efficiency. (a) 1000V input full load (b) 200V input full load Figure 7: Start-up sequence waveforms C2 (pink): Vin, 350V/Div; C3 (blue): Vcc, 10V/Div; C4 (green):Vgs, 20V/Div CPWR-AN14, REV 5 60W Auxiliary Power Supply Demo board This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Cree Sales at [email protected]. Figure 8 shows the Vgs and Vds waveforms at difference input voltage and output loading (full load and light load). It shows that 1700V SiC MOSFET Vgs and Vds waveforms are very clean with fast switching at 200Vdc and 1000Vdc inputs. (a) Input: 200Vdc, Light load (b) Input: 200Vdc, Full load (c) Input: 1000Vdc, Light load (d) Input: DC 1000V, Full load Figure 8: Vgs and Vds waveforms of 1700V SiC MOSFET C1(yellow): Vgs, 10V/div; C4 (green): Vds, 500V/div REFERENCES [1] [2] [3] [4] [5] C2M1000170D 1700V SiC MOSFET datasheet, Cree InC. JinBin Zhao, and FengZhi Dai, “Soft-switching two-switch flyback converter with wide range,” in Industrial Electronics and Application, 2008. ICIEA 2008. Robert W, Dragan M, Fundamentals of Power Electronics, Boulder Colorado, 2002. Lloyd H. Dixon, “Magnetics Design for Switching Power Supplies,” in Unitrode Magnetics Design Handbook, 1990. Bob Callanan. Application Considerations for Silicon Carbide MOSFETs, Cree InC. CPWR-AN14, REV 6 60W Auxiliary Power Supply Demo board This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Cree Sales at [email protected]. Appendix A – Schematic CPWR-AN14, REV 7 60W Auxiliary Power Supply Demo board This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Cree Sales at [email protected]. Appendix B - BOM Part no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 C16 C17 C18 C19 C20 C21 C22 C23 C24 C25 C26 C27 C28 C29 C30 C31 C32 C33 C34 C35 C36 C37 C38 C39 C40 C41 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10 J1 J2 J3 J4 J5 L1 L2 L3 Q1 Q4 Value 10uF 10uF 10uF 0.1uF 680uF 0.1uF 1.2nF 100pF 1uF 10uF 0.1uF 22uF 0.1uF 22nF 1nF 0.1uF NC 10nF 680uF 100nF 100uF 1uF 100nF 220uF 0.1uF 1uF 47uF 1uF 0.22uF 220uF 0.1uF 0.1uF 47uF 1uF 100pF NC 10nF 1uF 100pF 33pF 33pF HV_DC P_GND CON2 CON2 CON2 3.5uH 2.7uH 2.7uH 1000mohm, 1700V Manufacturer Part no. Manufacturer name B32794D2106K B32794D2106K B32794D2106K EPCOS EPCOS EPCOS EEU-HD1V681 Panasonic ECW-H16122JV Panasonic Description MKP, 5% MKP, 5% MKP, 5% CAP CER 100V 10% X7R 0603 CAP CER 100V 10% X7R 0603 CAP CER 100V 10% X7R 0603 CAP CER 100V 10% X7R 1206 ECEA1HKS100 Panasonic EEA-GA1V220 Panasonic CAP CER 100V 10% X7R 1206 CAP CER 100V 10% X7R 0603 CAP CER 100V 10% X7R 0603 CAP CER 100V 10% C0G 0603 CAP CER 100V 10% X7R 0603 CAP CER 100V 10% X7R 0603 EEU-HD1V681 Panasonic UPB1V101MPD Nichicon CAP CER 100V 10% X7R 0603 CAP CER 50V 10% X7R 0603 CAP CER 100V 10% X7R 0603 EEU-EB1V221 Panasonic CAP CER 100V 10% X7R 0603 CAP CER 50V 10% X7R 0603 EEA-GA1V470 Panasonic R76TR3220SE30K EEU-EB1V221 Kamet Panasonic CAP CER 50V 10% X7R 0603 CAP CER 100V 10% X7R 0603 CAP CER 100V 10% X7R 0603 EEA-GA1V470 Panasonic CAP CER 50V 10% X7R 0603 CAP CER 100V 10% X7R 0603 CAP CER 100V 10% X7R 0603 CAP CER 50V 10% X7R 0603 CAP CER 100V 10% C0G 1206 CAP CER 100V 10% C0G 1206 CAP CER 100V 10% C0G 1206 RS1M-13-F STTH1R02A 1N4148 VB30100S-E3/8W STPS3H100U STPS3H100U RS1M-13-F 1N4148 1N4148 1N4148 2 pin, P:5.08mm 2 pin, P:5.08mm 282837-2 282837-2 282837-2 744771003 SWPA5020S2R7NT SWPA5020S2R2NT C2M1000170D PBSS4240T CPWR-AN14, REV 8 60W Auxiliary Power Supply Demo board Diodes ST Vishay ST ST Diodes TE TE TE Wurth Sunlord Sunlord CREE NXP HV tips terminal HV tips terminal Horizontal, P:5.08mm Horizontal, P:5.08mm Horizontal, P:5.08mm 1700V, 1000mohm, SiC MOSFET This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Cree Sales at [email protected]. 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 Q5 Q6 Q7 R1 R2 R3 R4 R5 R6 R7 R8 R9 R12 R13 R14 R15 R16 R17 R18 R19 R20 R21 R22 R23 R24 R25 R26 R27 R28 R29 R30 R31 R32 R33 R34 R35 R36 R37 R38 R39 R40 R41 R42 R43 R44 R45 R46 R47 R50 R51 R52 R53 T1 U1 U2 U3 ZD1 ZD2 ZD3 HS1 PBSS4240T STP03D200 MMBT2222A 220K 10R 2k2 1R3 1R3 220K 1R NC 11k 0 10k 0 NC 1k 33k 39k 10k 2K 10k 150k 150k 150k 150k 0R 0R 0R 0R 510K 1M5 1M5 1M5 1M5 1M5 1M5 10k 10k 2.4k 5.6k NC 220K 220K 33 10k 0 4.7k 51R 36R 36R 10R PQ26/25 UCC28C44 FOD817A TL431A 22V 5.6V 18V CRCW25121R30FP CRCW25121R30FP NXP ST Vishay Vishay 1W, 1% RES, 0.25W, 1%, 1206 RES, 0.25W, 1%, 1206 1W, 1% 1W, 1% 1W, 1% RES, 0.25W, 1%, 1206 RES, 0.1W, 1%, 0603 RES, 0.1W, 1%, 0603 RES, 0.1W, 1%, 0603 RES, 0.1W, 1%, 0603 RES, 0.1W, 1%, 0603 RES, 0.1W, 1%, 0603 RES, 0.1W, 1%, 0603 RES, 0.1W, 1%, 0603 RES, 0.1W, 1%, 0603 RES, 0.25W, 1%, 1206 RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.25W, 1%, 1206 RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.5W, 200V, 1% RES, 0.25W, 1%, 1206 RES, 0.25W, 1%, 1206 RES, 0.1W, 1%, 0603 RES, 0.1W, 1%, 0603 750341672 UCC28C44D FOD817ASD TL431AIDBZ MMSZ5251 MMSZ5232 MMSZ5248 RA-T2X-38E CPWR-AN14, REV 9 60W Auxiliary Power Supply Demo board Würth-midcom TI Fairchild TI Vishay Vishay Vishay Ohmite 1W, 1% 1W, 1% RES, 0.5W, 200V, 1% RES, 0.1W, 1%, 0603 RES, 0.5W, 100V, 1% RES, 0.1W, 1%, 0603 RES, 0.25W, 1%, 1206 RES, 0.25W, 1%, 1206 RES, 0.25W, 1%, 1206 RES, 0.25W, 1%, 1206 PQ2625 transformer 0.5W 0.5W 0.5W Heatsink This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Cree Sales at [email protected]. Appendix C – PCB layout Top side PCB layout Bottom side PCB layout CPWR-AN14, REV 10 60W Auxiliary Power Supply Demo board This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com/power. For warranty information, please contact Cree Sales at [email protected].