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Titus Chow

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DRAFT

DescriptionAnalog precharge/discharge for motor controllers
Target release
EpicDocument status
Status
title
Jira Legacy
serverJIRA (uwmidsun.atlassian.net)
columnskey,summary,type,created,updated,due,assignee,reporter,priority,status,resolution
serverId6df7ba0d-c6df-39f5-b19f-bb96d235af5f
keyELEC-35

Document owner

Taiping Li

DesignerProject leads

Taiping Li

DevelopersQATeam members


Goals

  • Safely pre-charge the motor controller by applying 12V to the pre-charge relay
  • Discharge the motor controller to ground whenever 12V is not applied

Background and strategic fit

The pre-charge and discharge controllers will each be responsible for one motor controller. It's job is to safely charge the motor controller up to the same voltage as the battery before allowing the main relay to connect; and to discharge the motor controller to ground whenever power is not being applied. This allows the main relay to connect without arcing, and de-energize the motor controller when the vehicle is not running. 

Based on the requirements, it was determined that the high voltage from the battery would be reduced to 5-12V using two resistors in series, and an instrumentation amplifier would measure the difference in voltage across the pre-charge resistor. Once the differential is minimum, the main relay would then be closed with a MOSFET. The discharge portion of the circuit would simply be a normally closed relay that would open when the vehicle is in it's run state. 


Requirements

#TitleUser StoryImportanceNotes
1Voltage IsolationHigh voltages must be isolated from the 12V rail of the vehicle, so in case of a failure in the resistors, HV will not go into the 12V railMust Have
  • Looking into Optoisolators or Digital Isolators with a isolated power supply
2    

...


Questions

Below is a list of questions to be addressed as a result of this requirements document:

...

Part NumberDescriptionLinkPurpose
LM311MNS/NOPB-NDComparator General Purpose DTL, MOS, Open-Collector, Open-Emitter, RTL, TTL 8-SOIChttp://www.digikey.ca/product-detail/en/texas-instruments/LM311M-NOPB/LM311MNS-NOPB-ND/32589
P16919CTP470KBYCT-NDRES SMD 680K 470K OHM 1% 1/2W 08054W 0603http://www.digikey.ca/product-detail/en/panasonic-electronic-components/ERJ-P6WF6803VPA3F4703V/P16919CTP470KBYCT-ND/49649585036197Voltage Divider R1
P16901CTP33KBYCT-NDRES SMD 22K 33K OHM 1% 1/2W 08054W 0603http://www.digikey.ca/product-detail/en/panasonic-electronic-components/ERJ-P6WF2202VPA3F3302V/P16901CTP33KBYCT-ND/49649405036176Voltage Divider R2
PB1248CT-NDTelecom Relay SPST-NO (1 Form A) Surface Mounthttp://www.digikey.ca/product-detail/en/te-connectivity-potter-brumfield-relays/1462041-3/PB1248CT-ND/2126954Pre-Charge
PB1250PB1250CT-NDTelecom Relay SPDT (1 Form C) Through HoleSurface Mounthttp://www.digikey.ca/product-detail/en/te-connectivity-potter-brumfield-relays/1462042-69/PB1250PB1250CT-ND/21269482126956DisCharge
945-1209-NDIsolated Module DC DC Converter 1 Output 12V 21mA 10.8V - 13.2V Inputhttp://www.digikey.ca/product-detail/en/recom-power/RM-1212S/945-1209-ND/2256389DCDC
1080-1201-1-NDLogic Output Optoisolator 1MHz Open Collector 5000Vrms 1 Channel 6-SMD

http://www.digikey.ca/product-search/en?keywords=1080-1201-1-ND


Voltage Isolation
497-15521-1-NDMOSFET P-CH 30V 4A SOT23-6http://www.digikey.ca/product-detail/en/stmicroelectronics/STT4P3LLH6/497-15521-1-ND/5244878Main Relay
BSS138-FDICT-NDMOSFET N-CH 50V 200MA SOT23-3http://www.digikey.ca/product-detail/en/diodes-incorporated/BSS138-7-F/BSS138-FDICT-ND/7178432* for Pre-Charge Relay & DCDC
296-1858814106-1-NDDS-Type Transparent R Latch 1 4 Channel 1:1 IC Tri-State SOT16-23-6TSSOPhttp://www.digikey.ca/product-detail/en/texas-instruments/SN74LVC1G373DBVRCD4043BPWR/296-1858814106-1-ND/857357525904Latch Output
WM2282CT-ND4 Position Receptacle Connector 0.079" (2.00mm) Surface Mount, Right Angle Tinhttp://www.digikey.ca/product-detail/en/molex-llc/5024940470/WM2282CT-ND/2380440HV & Power to Board
WM2274-ND4 Position Rectangular Housing Connector Plug White 0.079" (2.00mm)http://www.digikey.ca/product-detail/en/molex-llc/5024390400/WM2274-ND/2380424
WM3978CT-NDContact Crimp Non-Gendered 22-26 AWG Tinhttp://www.digikey.ca/product-detail/en/molex-llc/5024380000/WM3978CT-ND/2421937
WM9812CT-ND2 Position Receptacle Connector 0.059" (1.50mm) Surface Mount, Right Angle Tinhttp://www.digikey.ca/product-detail/en/molex-llc/5025850270/WM9812CT-ND/4176661To Main Relay
WM11189-ND2 Position Rectangular Housing Connector Plug Beige 0.059" (1.50mm)http://www.digikey.ca/product-detail/en/molex-llc/5025780200/WM11189-ND/2818998
311-15KGRCT-NDRES SMD 15K OHM 5% 1/10W 0603http://www.digikey.ca/product-detail/en/yageo/RC0603JR-0715KL/311-15KGRCT-ND/7296642* Pull up Resistor
490-10731-1-ND2.2µF ±10% 25V Ceramic Capacitor X5R 0603 (1608 Metric)http://www.digikey.ca/product-detail/en/murata-electronics-north-america/GRM188R61E225KA12D/490-10731-1-ND/5251369RC delay for DCDC_IN

987-1016-1-ND

20k Ohm 0.25W, 1/4W Gull Wing Surface Mount Trimmer Potentiometer Cermet 1 Turn Top Adjustmenthttp://www.digikey.ca/product-detail/en/tt-electronics-bi/23BR20KLFTR/987-1016-1-ND/2409027Adjustment for voltage divider



Changes:

  • Look at Chaos MOSFETS 
  • Change to N channel mosfets, standardize 


http://mustcalculate.com/electronics/capacitorchargeanddischarge.php?vfrom=0&vto=10.8&vs=12&r=120&time=1m