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

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Figure 5.45: Schematics of the heater with independent control.• Temperature threshold: 0 ◦ C.• Dissipated power: 2 × 250mW at 2.5V (there are two heaters of 250Ω in parallel).At 0 ◦ C, the output of LM94022 is 1567mV (for GS = 01). The scaler ratio R1/R2 is then331/1236.The scaler resistors R1 and R2 are chosen so that the input current of the comparator(± 2nA) is negligible compared to the current passing through the resistances. The currentflowing through the resistance must itself be less than 30µA to have a good precision on theoutput of the LM94022. The precision of the resistors must be good (1% or better), and thesize should be large enough to easily replace them (for calibrating). Suitable values for R1and R2 are 42.2k and 158k.Chosen models:R1: TYCO ELECTRONICS RP73D2B42K2BTG. R2: TYCO ELECTRONICS RP73D2B158KBTG.Size: “1206”. Precision: 0.1%. Temperature coefficient: ±15ppm/ ◦ C.A decoupling capacitor of 100pF is used in parallel with R2.The output of the MAX9015 must be high when the temperature of batteries is underT th . The output of the LM94022 is decreasing with temperature. As a consequence, it mustbe connected to the “+” input of the comparator while the reference is connected to the “-”input.A decoupling capacitor of 100pF is connected on the V c c of the MAX9015.5.8 Design of the measurement systemThe design of the measurement circuits is the subject of the master thesis “Développementde l’infrastructure de mesure du nanosatellite OUFTI-1.” [10].88
5.9 Components selectionThis section explains some considerations that guided the choice of components.5.9.1 FormatsMost components will be Surface Mounted Devices (SMD). There is a standard for the sizesof SMD resistors and capacitors. Most used values are show in the table 5.2.0201 0.60mm × 0.30mm0201 0.60mm × 0.30mm0402 1.00mm × 0.50mm0603 1.60mm × 0.80mm0805 2.00mm × 1.25mm1206 3.20mm × 1.60mm1210 3.20mm × 2.50mmTable 5.2: Examples of standard SMD formats.For the realization of a PCB, formats of resistors and capacitors are generally harmonized:only one or two formats are used. In our case, the used formats are 0805 and 1210. Mostof high-capacity ceramic capacitors are available in the 1210 format. The 0805 format isused for smaller components, but is still large enough to allow manual modifications on theprototypes.5.9.2 CapacitorsIn most systems, the capacitors are the components with the higher failure rate. The choiceof reliable capacitors is thus especially important.5.9.3 DielectricCapacitor dielectrics were classified by the Electronic Industries Association (EIA) in functionof the relative variation of their capacity in a given temperature range. Most used capacitorclasses are shown in the table 5.3. It is composed of a prefix, indicating the temperaturerange, and of a suffix, indicating the relative variation of capacity in this range.Most popular dielectrics are X5R and X7R. On the EPS of OUFTI-1, X7R capacitorswill be chosen (this corresponds to a variation of 15% of capacity in the temperature range of-55 ◦ C to 125 ◦ C). They not only have one of the lowest variation of capacity with temperature,but the parasitic inductance of the capacitor is very low (The inductance has no influenceunder 10MHz).89
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AcknowledgementsI want to thank the
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Contents1 Introduction 91.1 Cubesat
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4.4.2 Mean case . . . . . . . . . .
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B Power budget worksheet 106C Pictu
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design and the tests are delegated
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Chapter 2Requirements of the EPS2.1
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• The Single-Event Upset (SEU)Thi
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the P-POD. RBF pins must fit within
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Figure 2.6: Top view of the PC104 c
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Chapter 3Design of EPS architecture
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• Voltage (4) and current (5) at
Page 24 and 25:
Figure 3.6: The equivalent circuit
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of our Lithium-Polymer batteries va
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Figure 3.12: I-V curve of a solar p
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3.3.3 CapacityA important value to
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Parameter SLPB723870H4 SLPB554374HN
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of the batteries is kept between -2
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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 66 and 67: Figure 5.14: Simplified schematics
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 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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