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

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R KR >1.45V100mA − 1.3A35= 23.07Ω.The minimum cathode current for regulation is 1mA. When the regulation starts, theEmitter-Base voltage of the transistor V EB is around 0.6V. If there is no base current (I B = 0),the TL1431 is supplied through resistor KR:I KR > 1mA,The chosen value for R KR is 560Ω.R KR < V EB1mA = 600Ω.SCRA and SCRBThe intern reference of the TL1431 V I (ref) is equal to 2.5V.The ratio SCRB/SCRA is given by:V I (ref)4.2V − V I (ref) = 1.47.The resistances must not be too high or the reference input current (up to 3µA) can diruptthe regulation voltage. If they are too low, some power will be dissipated in the scaler.The chosen values are SCRA = 10kΩ and SCRB = 14.7kΩ.SHRFor the regulation, the transistor must be in linear mode. The Emitter-Collector voltagemust be superior to the Emitter-Collector saturation voltage (V E C(sat) = 0.75V when I C =2.5A, it will be less when I C = 1.3A ). We haveV E C = 4.2V − I C R S HR > V E C(sat),R S HR
Figure 5.40: Dissipated power in the transistor and in the resistor.5.5 Design of the protection circuits5.5.1 DescriptionThe protection circuit was chosen in [3]. It is the MAX890L. It can operate with an inputvoltage of 2.7 to 5.5V. It can thus be used for all systems supplied by 3.3V and 5V busses.It is a current-limiting circuit. A threshold current (I thr ) can be chosen between 240mAand 1,200mA. The threshold depends on the value of the resistor R set . It is possible to choosea threshold under 240mA, but the circuit will operate with less precision. When the currentat the output becomes higher than the threshold, the MAX890L starts to decrease the outputvoltage. The voltage falls to zero when the output current reach 1.5 times the threshold.The circuit has a thermal shut-down. When the junction temperature exceeds 135 ◦ C, theswitch turns off. It turns back on at 125 ◦ C. In case of high dV DSdton the output (short-circuit),the switch turns off too. It is then slowly tuned back on with the output current limited to1.5 × I thr .The circuit provides a “F AULT ′′ signal. It is an open-drain output that goes low whenI thr is reached or when the thermal shut-down is activated. There is a “ON/OF F ′′ input.When this input is set to high, the power output is disconnected from the power input.5.5.2 ComponentsThe value of R set depends on the desired I thr . Here is the formula to choose R set : R set =1,380I thr. The protection circuit of the EPS has a R set of 10kΩ (I thr = 138mA). It protects themeasurement system and their total consumption is very low (less than 10mA).A capacitor of 1µF is used on the input of the circuit and a capacitor of 0.1µF on theoutput. A pull-up resistor of 100kΩ and a decoupling capacitor of 100pF are used on the“ON/OF F ′′ input.83
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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 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 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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