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| Front | Rear |
|---|---|
Peripheral Displays & Cameras (Use a simple circuit to distribute the current) | Solar Master (Front) |
| Steering Board | Solar Master (Rear) |
| Pedal Board | Rear View Camera |
| Fan | Fan |
| Spare | Telemetry |
| Spare | Charger Interface |
Potential Parts
| Part Number | Load Current | Rds On | Number of Outputs | Analog Current Sense |
|---|---|---|---|---|
| TPS2H160BQPWPRQ1 | 2.5A | 155mOhm | 2 | |
| BTS71202EPAXUMA1 | 2A | 61mOhm | 2 | +/-30% @ 50mA, +/-11% @ 500mA |
| AUIPS7091GTR | 1.5A | 80mOhm | 1 | +/-8% @ 50mA, +/-3% @ 500mA |
| AUIPS7081RTRL | 2A | 55mOhm | 1 |
Medium-Current HSD
Current Limit: < 6-8A @ 12-13.5V
| Front | Rear |
|---|---|
| Front Lights Board | Motor Interface |
| Center Console | Rear Lights Board |
| Horn? (8A) | Spare |
Potential Parts
| Part Number | Load Current | Rds On |
|---|---|---|
| BTS70401EPAXUMA1 | 4.5A | 19mOhm |
| BTS70081EPPXUMA1 | 11A | 8.8mOhm |
| BTS70061EPPXUMA1 | 12A | 6.6mOhm |
High-Current HSD
Current Limit: < 20A @ 12-13.5V
| Front | Rear |
|---|---|
Spare | Front Power Distribution (around 16A at the maximum) |
| Spare | BMS Carrier (Master & Slave) (due to high inrush current to the relays) |
Potential Parts
| Part Number | Load Current | Rds On | Current Mirror Error |
|---|---|---|---|
| BTS70041EPPXUMA1 | 15A | 4.4mOhm | ± 8% @ 10 - 15A |
| AUIR3313STRL | 23A (Adjustable) | 5.5mOhm | ± 5% |
| BTS70021EPPXUMA1 | 21A (Fixed) |
Front Power Distribution
(around 16A at the maximum)| 2.6mOhm | ± 5% |
Medium-High-Current HSD
Current Limit: 6 - 20A @ 12-13.5V
Potential Parts
| Part Number | Load Current | Rds On | Analog Current Sense | Note |
|---|---|---|---|---|
| TPS2HB08BQPWPRQ1 | 6.4A - 70A (Adjustable) | 8mOhm | ±15% @ > 0.5A | Found on Mouser |
Supplemental Battery
MS12 use a 12 V 10-cell? NiMH battery as the supplemental battery. It is used to power the minimal necessary systems to check the battery system and the reset of the car before closing the main battery relays.
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Since the loads are parallel, they should operate at the same voltage. The PWR board only needs to measure the output voltage of the supplemental battery and the DC-DC converters
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Current Sensing
Accuracy
The main benefit purpose of high-side current sensing is the ability to detect a short circuit in the load or the harness. There are few solutions to current sensing:
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the current sensing is understanding how much power is being used by each system while the car is driving/racing. The data will be used to identify systems with high power usage for future optimization. It is more meaningful to track the power consumption of each system relative to the total power rather than the absolute value.
The target power consumption of MSXIV's LV system is 20 W. A reasonable accuracy will be the +/- 0.1% of the total power. Given the supply voltage will be 12-13.5 V, the current sensing circuit should be more accurate than +/- 1.5 mA.
Locations
Given the HSD will be responsible for disconnecting the load when it is shorted to ground, there is no safety advantage for high side current sensing. There are three locations for the current sense resistor:
- Low-Side
- Easier to implement
- Requires a 100 mOhms current sense resistor which consumes some power
- High-Side
- High immunity to ground disturbance
- The common-mode voltage tolerance of the differential op-amp must be greater than 12V
- HSD Current Mirror
- A HSD built-in current mirror with high gain plus a current sense resistor should use less power than the low-side sensing (needs proof)
- The accuracy is around +/- 30% for low current (< 100 mA)
Block Diagram
Ports
Front
| Board | Nom. Current (A) | Max. Current (A) | Connector | HSD |
|---|---|---|---|---|
| Peripheral Displays & Cameras | 0.278 | 0.329 | Light | |
| Front Lights Board | 1.889 | 4.163 | Heavy | |
| Steering Board | 0.017 | 0.071 | Light | |
| Pedal Board | 0.013 | 0.067 | Light | |
| Center Console | 0.952 | 2.146 | Light | |
| Horn | 0 | 8 | Heavy |
Rear
| Board | Nom. Current (A) | Max. Current (A) | Connector | HSD |
|---|---|---|---|---|
| Motor Interface | 0.179 | 4.958 | Light | |
| BMS Carrier (Master & Slave) | 0.814 | 19.800 | Heavy | |
| Solar Master | 0.150 | 0.482 | Light | |
| Rear Lights Board | 0.022 | 2.879 | Heavy | |
| Rear View Camera | 0.5 | 0.5 | Light | |
| Charging Interface | 0.026 | 0.133 | Light | |
| Front Power Distribution | 3.250 | 15.97 | Heavy |