Design and Implementation of On-board Electrical Power ... - OUFTI-1

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Figure 5.14: Simplified schematics of the 3.3V converter.2. Switches are included.3. High expected efficiency (more than 90%).4. Power PAD and thermal shutdown.5. There is a soft-start.The choice of the control IC mainly depends on the properties of its internal switch. Thisswitch must be able to:1. withstand a current equal to I max .2. withstand a voltage of V out + V diode (in boost mode).3. dissipate the heat due to switching losses and ohmic resistance.This is verified below.Maximum current in the switch:The switches are able to withstand 1.6A.Maximum voltage on the switch:The TPS61001 is designed for an output voltage of 3.3V.Heat dissipation:The junction to air thermal resistance R θJA of the TPS63001 is equal to 48.7 ◦ C/W whenthe power PAD is soldered. The maximum operating junction temperature is 150 ◦ C. A marginof 25 ◦ C is taken. The converter is designed to work with a PCB temperature of -40 ◦ C to85 ◦ C. The maximum dissipated power isP D = T J − T A 125 − 85= = 0.82W.R ϑJA 45.766
Switching frequencyThe switching frequency of the TPS63001 is between 1,250 and 1,500 kHz.Design of inductor and capacitorThe components of the 3.3V converter must suit for the two operation modes, buck and boost.Two worksheets were used, one for the design of the boost mode (it is the same worksheet asfor the other converters), and one for the design of the buck mode (it is a new worksheet).For the buck mode, the inductance is computed using Eq. 5.9. The peak inductor currentis found with Eq. 5.7. The desired series resistance and the output capacitor are alsodetermined with Eqs. 5.10 and 5.13.The inputs are V in,Min , V in,Max , V out , I out,Max , the expected efficiency η, the switchingfrequency f s , k (∆i L /I av max), and ∆v max .The V in,Min for the buck mode is equal to the V in,Max for the boost mode but it is notnecessarily 3.3V. For a buck converter with an efficiency of η, the V inMin is equal to Voutη .Similarly, for a boost converter with a efficiency of η, the V in,Max is equal to Voutη .Inductor selectionThe chosen inductor is the EPCOS B82472P6472M000. It is the same model as for the5V converter. The inductance is 4.7µH. With this value, the k is equal to 0.429 in the boostmode and equal to 0.633 in the buck mode. Once again, the k is quite high but the converterworks fine with a high k (the recommended value for L in the datasheet is 2.2µH).Capacitor selectionOne 10µF ceramic capacitor will be used at the output.The maximum inductor current is 0.34A. This current is acceptable for the switch, whichis able to withstand 1.6A.Design of other componentsC by and R byR by and C by are decoupling components. Values of respectively 100Ω and 0.1µF arerecommended by the datasheet of the TPS63001.Schottky diodeThe present 3.3V converter and the EPS2 [2] will have to work in parallel. The behaviorof these system must be studied. The engineering model will be equipped of a Schottky diodeon the output of the 3.3V converter, before the feedback loop. A jumper will be placed inparallel to short-circuit the diode if needed. The same model of diode as in the 7.2V converteris used.67
Page 2 and 3:
AcknowledgementsI want to thank the
Page 4 and 5:
Contents1 Introduction 91.1 Cubesat
Page 6 and 7:
4.4.2 Mean case . . . . . . . . . .
Page 8 and 9:
B Power budget worksheet 106C Pictu
Page 10 and 11:
design and the tests are delegated
Page 12 and 13:
Chapter 2Requirements of the EPS2.1
Page 14 and 15:
• The Single-Event Upset (SEU)Thi
Page 16 and 17: the P-POD. RBF pins must fit within
Page 18 and 19: Figure 2.6: Top view of the PC104 c
Page 20 and 21: Chapter 3Design of EPS architecture
Page 22 and 23: • Voltage (4) and current (5) at
Page 24 and 25: Figure 3.6: The equivalent circuit
Page 26 and 27: of our Lithium-Polymer batteries va
Page 28 and 29: Figure 3.12: I-V curve of a solar p
Page 30 and 31: 3.3.3 CapacityA important value to
Page 32 and 33: Parameter SLPB723870H4 SLPB554374HN
Page 34 and 35: of the batteries is kept between -2
Page 36 and 37: Over Charge Prohibition 4.275 ± 0.
Page 38 and 39: supplied in 5V. The circuit will be
Page 40 and 41: Chapter 4The Power Budget4.1 Introd
Page 42 and 43: Figure 4.1: P-V curve of a solar pa
Page 44 and 45: 4.3.2 Efficiency of convertersTo at
Page 46 and 47: Figure 4.3: Consumptions in % in me
Page 48 and 49: Chapter 5Electrical Design of EPS5.
Page 50 and 51: V outV in= D. (5.1)Since D ≤ 1, t
Page 52 and 53: The power losses in the inductor ar
Page 54 and 55: ∆i L,1 + ∆i L,2 = 0, (5.16)V in
Page 56 and 57: Using the value of ∆i L given by
Page 58 and 59: There is no data about the case to
Page 60 and 61: Capacitor selectionFour 10µF ceram
Page 62 and 63: • Output voltage: 5V.• Maximum
Page 64 and 65: Figure 5.12: Burst mode operation (
Page 68 and 69: Figure 5.15: Worksheet for 3.3V con
Page 70 and 71: sequently, the k was chosen above 0
Page 72 and 73: where G 1 is the initial control-to
Page 74 and 75: Figure 5.21: Measured Bode diagram
Page 76 and 77: Figure 5.26: Equivalence between th
Page 78 and 79: C f =12πf f R 0f,L f = R 2 0f C f
Page 80 and 81: Figure 5.37: Schematics of the firs
Page 82 and 83: R KR >1.45V100mA − 1.3A35= 23.07
Page 84 and 85: The schematics is shown on figure 5
Page 86 and 87: A commercial model meets all requir
Page 88 and 89: Figure 5.45: Schematics of the heat
Page 90 and 91: PrefixX7X5Y5Z5SuffixTemperature ran
Page 92 and 93: 6.2.1 The second dissipation system
Page 94 and 95: • The antenna deployment system.
Page 96 and 97: 6.3.3 TestsThe engineering model of
Page 98 and 99: 7.3 ActivitiesAs OUFTI-1 is designe
Page 100 and 101: 8.1.2 DesignA model of Li-Po batter
Page 102 and 103: [15] Fabien Jordan, Phase B Electri
Page 104 and 105: TaK = 273 + TaC;%Photo-current ther
Page 106 and 107: Appendix BPower budget worksheetIn
Page 108 and 109: 108
Page 110 and 111: Appendix CPictures of the prototype
Page 112 and 113: Appendix DSchematics of the enginee
Page 114 and 115: 876543213V3 CONVERTER AND INPUT FIL
Page 116:
87654321ANTENNA DEPLOYMENT CIRCUITB
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Design and Implementation of On-board Electrical Power ... - OUFTI-1

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