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

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Figure 2.6: Top view of the PC104 card for the EPS [5].2.3.3 Power conditionningThe EPS has to provide several stabilized voltage power outputs. Figure 2.7 shows thedifferent power buses and the subsystems. The maximum current from each output hasto be known before we can design the power conditioning unit. The exact consumptions ofsubsystems were not available during the work on this thesis, so that the following estimationswere made:• The OBC1 consumes 10mW at 5V. The current is thus 2mA [22].• The OBC2 consumes 10mW at 3.3V. The current is thus 3mA.• The Beacon uses one ADF7021, supplied in 3.3V. The maximum current consumed byan ADF is 25mA [8].• The COM can use two ADF at a time. The maximum consumption is 50mA with 3.5V[8].• Measurement systems are supplied with 3.3V. It is reasonable to think that the consumptionwill stay under 50mA.• There will be one or two amplifier(s) for radio transmission, supplied with 7.2V. Thedesired RF power transmitted by the Beacon is 100mW. The desired RF power emittedby D-STAR and AX.25 is around 750mW. Assuming the amplifier has an efficiency of30% (it should be higher), the maximum consumed power would be close to 3000mW.This corresponds to a current of 417mA [8].18
Figure 2.7: OUFTI-1 subsystems and power buses.The requirements for the power conditioning unit are based on the above assumptions.The maximum current of the 3.3V and 5V outputs is higher than computed above, to letsome flexibility.Requirements for the power conditioning unit:• One output at 3.3V with un maximum current of 200mA.• One output at 5V with un maximum current of 200mA.• One output at 7.2V with un maximum current of 420mA.These requirements should be reviewed each time changes are made to the architecture ofthe cubesat.2.3.4 Housekeeping parametersThere are important values on the EPS, like solar panels currents, batteries voltages, batteriestemperature, and power bus voltage, that must be measured and transmitted to the ground,to know the state of the CubeSat and to verify that everything works fine. The EPS willinclude the measurement circuits, sensors, and ADC’s. There must be an interface with theOBC to command the measurement circuits and to transmit data. An I 2 C bus has beenchosen as an interface.A current-limiting protection circuit must also be included on the EPS for the measurementcircuits.2.3.5 Antennas Deployment SystemDuring the launch, antennas are wound. They are held back by a string. To release theantennas, the string is cut by a thermal cutter. It is a resistor crossed by an importantcurrent (the exact current value is still unknown but its order of magnitude is around 1A).The antenna deployment is controlled by the OBC, but the OBC cannot deliver such acurrent. A power switch will be used and it will be located on the EPS card. The switch willbe designed to withstand a current of 3A.19
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 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 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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