Design and Implementation of On-board Electrical Power ... - OUFTI-1
Design and Implementation of On-board Electrical Power ... - OUFTI-1 Design and Implementation of On-board Electrical Power ... - OUFTI-1
A commercial model meets all requirements, the ROHM - RTR040N03TL. The quadmountsolution is thus adopted. It is a discrete component (if we use several transistors onone chip, there is a risk that a trouble affect all transistors).Characteristics:Gate-source threshold voltage (V gs (th)): between 0.5 and 1.5V.Drain-source on-state resistance: max. 66mohm (V gs = 2.5V).Total power dissipation: 1W (on a ceramic board).Occupied Surface: 10mm 2 .V gs (max): 12V.V ds (max): 30.The decoupling capacitors will be ceramic 100pF capacitors and the resistors will be 100kresistors.5.7 Design of the battery heaterThe function of the heater is to prevent the temperature of the batteries to drop under adetermined temperature (0 ◦ C). A simple and convenient heater consists in a heating resistorin contact with the batteries, in which the current flows when the temperature of the batteriesdrops under a chosen threshold (T th ).As said in chapter 3, the system will be supplied by the batteries bus. A special attentionmust thus be given to the reliability.The “switch” controlling this current can be a FET transistor. The transistor can becontrolled by the OBC or by an independent system. In either case, the control voltagewould be quite low (down to around 2.7V). We saw while designing the antennas deploymentsystem that the available low V gs (th) MOSFET’s were commercial models. Then, the samesolution is adopted to have a good reliability. Four transistors are mounted so that if one ofthem fails (stay opened or closed), the system is still operational.5.7.1 Control by the OBCIf the system is controlled by the OBC, a PIN of the batteries connector (connector betweenthe EPS and the batteries card) and a PIN of the PC104 port must be dedicated to the controlsignal (“BattH”) of the batteries heater. There is a temperature sensor on the batteries in themeasurement system of the EPS. The OBC can retrieve the measurement of the temperatureof the batteries through the I 2 C data bus. The schematics of the circuit is shown on figure5.43.5.7.2 Independent controlThe heater can also be controlled by an independent system. This solution was chosen onSwisscube because a failure of the OBC does not influence the heater. This is also the chosensolution for OUFTI-1, as explained in chapter 3.86
Figure 5.43: Schematics of the batteries heater circuit with a control by the OBC.Here, an independent temperature probe is used. The same probe as in the measurementsystem can be used (LM94022). There are two logical inputs on the LM94022 that have tobe set to chose the desired output voltage level, as shown on figure 5.44.Figure 5.44: Output voltage of LM94022 as a function of T ◦ and logical inputs.The switch will be driven by a logical comparator that compares the output of theLM94022 with a voltage reference. A circuit using a logical comparator and where thereis a feed-back loop is liable to enter in oscillation. The parry to this problem is to add anhysteresis. If there is enough distance between the heater and the temperature probe, thesystem will have an intrinsic hysteresis. A small electronical hysteresis will be added anyway.The IC MAX9015 contains a logical comparator with hysteresis and a voltage reference(Vref). Its output is a push-pull and thus able to drive the MOSFET’s. The reference has avalue of 1,236mV. The output voltage of the LM94022 has to be scaled. The schematics ofthe heater circuit with independent control is shown on figure 5.45.The temperature threshold to activate the heater as well as the amount of dissipatedpower in the heater must be determined by thermal studies. Thermal simulations about theheater were done in [7] and the following values were chosen:87
- 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 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
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- 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
A commercial model meets all requirements, the ROHM - RTR040N03TL. The quadmountsolution is thus adopted. It is a discrete component (if we use several transistors onone chip, there is a risk that a trouble affect all transistors).Characteristics:Gate-source threshold voltage (V gs (th)): between 0.5 <strong>and</strong> 1.5V.Drain-source on-state resistance: max. 66mohm (V gs = 2.5V).Total power dissipation: 1W (on a ceramic <strong>board</strong>).Occupied Surface: 10mm 2 .V gs (max): 12V.V ds (max): 30.The decoupling capacitors will be ceramic 100pF capacitors <strong>and</strong> the resistors will be 100kresistors.5.7 <strong>Design</strong> <strong>of</strong> the battery heaterThe function <strong>of</strong> the heater is to prevent the temperature <strong>of</strong> the batteries to drop under adetermined temperature (0 ◦ C). A simple <strong>and</strong> convenient heater consists in a heating resistorin contact with the batteries, in which the current flows when the temperature <strong>of</strong> the batteriesdrops under a chosen threshold (T th ).As said in chapter 3, the system will be supplied by the batteries bus. A special attentionmust thus be given to the reliability.The “switch” controlling this current can be a FET transistor. The transistor can becontrolled by the OBC or by an independent system. In either case, the control voltagewould be quite low (down to around 2.7V). We saw while designing the antennas deploymentsystem that the available low V gs (th) MOSFET’s were commercial models. Then, the samesolution is adopted to have a good reliability. Four transistors are mounted so that if one <strong>of</strong>them fails (stay opened or closed), the system is still operational.5.7.1 Control by the OBCIf the system is controlled by the OBC, a PIN <strong>of</strong> the batteries connector (connector betweenthe EPS <strong>and</strong> the batteries card) <strong>and</strong> a PIN <strong>of</strong> the PC104 port must be dedicated to the controlsignal (“BattH”) <strong>of</strong> the batteries heater. There is a temperature sensor on the batteries in themeasurement system <strong>of</strong> the EPS. The OBC can retrieve the measurement <strong>of</strong> the temperature<strong>of</strong> the batteries through the I 2 C data bus. The schematics <strong>of</strong> the circuit is shown on figure5.43.5.7.2 Independent controlThe heater can also be controlled by an independent system. This solution was chosen onSwisscube because a failure <strong>of</strong> the OBC does not influence the heater. This is also the chosensolution for <strong>OUFTI</strong>-1, as explained in chapter 3.86
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