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

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C f =12πf f R 0f,L f = R 2 0f C f .(f f ; R 0f ) pair C f L f Attenuation at 1MHz(10kHz; −18dBΩ) 79.6µF 3.18µH 80dB(20kHz; −20dBΩ) 72.3µF 0.875µH 68dB(30kHz; −22dBΩ) 66.3µF 0.424µH 61dBTable 5.1: Comparison of three possible filters.The filter with f f = 30kHz has the smallest components and offers an attenuation of61dB. This filter was chosen.The values of the real components will be C f = 66µF (three ceramic capacitors of 22µF inparallel), L f = 0.47µH, C fd = 150µF (tantalum capacitor), and R df = 0.1Ω (series resistanceof the tantalum capacitor). The schematics of this filter is shown in figure 5.33 and the Bodediagram of its output impedance is shown in figure 5.34.Figure 5.33: Schematics of the input filtersof the converters of the EPS.Figure 5.34: Output impedance of the inputfilters of the converters of the EPS.5.4 Design of the dissipation system (shunt regulator)The dissipation system must prevent the voltage on the batteries bus to get over 4.2V.5.4.1 Choice of DesignTwo kinds of solution were envisaged: a series regulator or a shunt regulator.Series RegulatorA series regulator is inserted between the solar panels and the batteries bus (figure 5.35).The drawbacks of this solution are:78
Figure 5.35: Series Regulator.• There is always a voltage drop between the base and the emitter of the transistor. Therewill be power losses even if the batteries voltage is under 4.2V.• All the exceeding power must be dissipated in the transistor.Shunt RegulatorA shunt regulator is used in parallel with the solar panels.Figure 5.36: Shunt Regulator.This solution does not suffer the same drawbacks. There is practically no power losseswhen the voltage of the bus is lower than 4.2V. A resistor can be inserted between the emitterand the ground and take a portion of the power to dissipate. This was the chosen solution.5.4.2 First versionA first version of dissipation system was designed in [3]. The transistor was a field effecttransistor. It was controlled by a logical comparator. The voltage on one input of thecomparator was imposed by a reference. The other input was connected to a voltage scaler,measuring the bus voltage (figure 5.37).79
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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
Page 18 and 19:
Figure 2.6: Top view of the PC104 c
Page 20 and 21:
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
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 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 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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