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

More documents

Recommendations

Info

Chapter 5Electrical Design of EPS5.1 IntroductionIn this chapter, the electrical design of each module of the EPS is explained. The firstand second sections deal with the design of the power conditioning unit. Some theory isgiven about converters and input filters. The design of the dissipation system, the antennasdeployment system, the protection circuit, and the batteries heater is discussed in subsequentsections. Finally, the complete electrical schematics of the EPS is given.5.2 Design of ConvertersThis section describes the design of the three DC/DC converters. The 7.2V and 5V convertersare ”boost” or ”step-up” converters. The 3.3V converter is an hybrid ”buck/boost” converter.This last converter can pass from one operating mode to another depending upon the inputvoltage. First, the theory about switching DC/DC converters is explained (for Buck andBoost) and design rules are deduced. The electrical design of each converter is then presented.Finally, we indicate how the design of the converters could be updated.A first design of the converters was made by Philippe Ledent [3]. The prototypes ofthese converters have been tested [1]. Based on the lessons learned with the tests of the firstdesign, and based on the upgraded requirements of the power conditioning unit, a new designis proposed in this section. Compared to the first design, the control circuits remained thesame, but the passive components were modified.5.2.1 TheoryThe converters of the EPS are output-voltage controled converters. A converter is composedof a power stage and a control (Fig. 5.1). The power stage performs the voltage conversion.We will see below that the power stage contains a switch and that the portion of time duringwhich this switch is closed determines the voltage convertion ratio. The portion of time duringwhich the switch is closed is called the duty cycle (D). The duty cycle is set by the control.By adjusting the duty cycle, the control can maintain an electrical value constant. Here, the48
duty cycle is determined by the output voltage. In other kinds of converters, the duty cyclecan be determined by the input voltage if a stabilized input voltage is needed, by the inputcurrent, or by the output current.Figure 5.1: Block diagram of an output voltage controlled converter.”Buck” converter [16]PrincipleThe power stage of the buck converter is composed of a switch, an inductor, and a capacitor(Fig. 5.2). The switch is in position 1 during a time interval DT s (phase 1), and in position2 during an interval D ′ T s (phase 2), with D ′ = 1 − D. D is called the duty cycle. T s is theswitching period, and f s = 1/T s is the switching frequency. The voltage V s is equal to theinput voltage V in when the switch is in position 1 and equal to zero when the switch is inposition 2.Figure 5.2: Power stage of a buck converter.The DC component of V s is equal to DV in . The inductor and the capacitor form a lowpassfilter. As a consequence, the DC voltage V out on the load R is equal to DV in . The Buckconverter is able to convert a voltage to a lower voltage, with a better efficiency than linearconverters, especially if the difference between V in and V out is important. The ratio betweenthe output voltage and the input voltage is49
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 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
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?