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

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Figure 5.26: Equivalence between the input impedance of a converter and the input impedanceof a LRC network.L is unchanged. C was 20µF (C1) and becomes 40µF (C2).1γ= 20/40 = −6dB.Figures 5.22 to 5.25 show the results of translating the “old” magnitude curves to theirnew positions.Figure 5.27: ‖Z in ‖ of old (blue) and new(red) 3.3V converter with V in = 2.5V .Figure 5.28: ‖Z in ‖ of old (blue) and new(red) 3.3V converter with V in = 4.2V .5.3.6 Frequency design of the filtersThe same filter will be used for the three converters. The filter must be designed so that itsoutput impedance is lower than the input impedance of the converters. The 7.2V converterhas the lowest ‖Z in (s)‖ . The filter can be designed from the ‖Z in (s)‖ curve of the 7.2Vconverter.A second-order low-pass filter is composed of a capacitor C f and an inductor L f connectedas shown in Fig. 5.31. The output impedance of this filter is Z out (s) = Z Lf (s)//Z Cf (s). Theshape of ‖Z out ‖ is shown on Fig. 5.32. It is characterized by the resonant frequency f f , thecharacteristic impedance R 0f , and the quality factor Q f (infinite on this ideal case).The values of f f and R 0f are given by ([16])f f =12π √ L f C f76
Figure 5.29: ‖Z in ‖ of old (blue) and new Figure 5.30: ‖Z in ‖ of old (blue) and new(red) 5V converter with V in = 2.5V . (red) 7.2V converter with V in = 3V .Figure 5.31: Schematics of a basic secondorderlow-pass filter.Figure 5.32: Output impedance of a basicsecond-order low-pass filter.R 0f =√LfC fThe design of the input filter can be seen as the placement of f f and R 0f on the Bodediagram. A higher f f corresponds to smaller electronic components, which is in our interest(but we must keep an eye on the desired attenuation at the switching frequency). R 0f cannotbe too low otherwise the size of the capacitor becomes a concern.There is a last obstacle to the good design of an input filter. As seen on Fig. 5.32, thereis a peak at the resonant frequency, due to the high quality factor Q f . Z out can thus exceedthe input impedance of the converter at f f . To reduce Q f , the filter must be damped. Thedamping can be done using a capacitor C fd with a series resistance R fd in parallel with thefilter capacitor. Formulas to compute the optimal C fd and R fd can be found in [16]. A goodvalue for C fd is generally around 2.5 × C f . In our case, R fd will be found by looking at theBode diagram of Z out in Matlab.From the Fig. 5.30, convenient (f f ; R 0f ) pairs can be found. The criterion used is R 0f =Z in (f f ) − 15dBΩ, so that the output impedance of the filter is negligible compared to theinput impedance of the converters. In Table 5.1, three (f f ; R 0f ) pairs are compared. Theattenuation at 1MHz corresponds to −40 log 10 (f f /1MHz). The corresponding L f and C fare given by77
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 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 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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