Trip recorder operation and memory retention extension through multiple battery backup and a load shedding strategy triggered by a primary power interruption

• US 5,191,529 A
• Filed: 10/01/1990
• Issued: 03/02/1993
• Est. Priority Date: 10/01/1990
• Status: Expired due to Term

• Current Assignee: MiX Telematics North America, Inc. (MiX Telematics Limited)
• Original Assignee: Rockwell International Corporation
• Inventors: Janos, Paul E., Ramsey, Reno V.
• Primary Examiner(s): Black, Thomas G.
• Application Number:
  US07/591,163
• Time in Patent Office: 883 Days
• Field of Search: 364/483, 364/492, 364/424.04, 320/6, 365/229, 346/33 D, 346/33 R
• US Class Current: 701/35
• CPC Class Codes: B60R 16/03 for supply of electrical power to vehicle subsystems or for circuit arrangements for charging batteries H02J7/00
• CPC Class Codes: H02J 2310/46 for ICE-powered road vehicles
• CPC Class Codes: H02J 9/061 for DC powered loads

Abstract

A dual battery backup system which provides power to selected portions of a trip recorder according to a load shedding strategy to maximize duration of operation and data retention in the event of interruption of primary power supply. The trip recorder is divided into three subsystems; a central processing unit, input/output and memory/clock subsystems. In the event of interruption of power from the vehicle battery, backup power is supplied to all systems according to a load shedding strategy. Power supplied to the input/output subsystem and the central processing unit are interrupted after the passage of predetermined amounts of time. The memory subsystem receives power after all other subsystems have been shed enabling memory retention for a period of up to ten years.

Claims

1. A power backup system for providing backup power which provides power to selected portions of a trip recorder having a microcontroller with subsystems capable of independent operation with separate power application including input/output, memory and a central processing unit, said power backup being provided according to a load shedding strategy which seeks to maximize duration of operation and data retention in the event of interruption of primary power supply comprising:

a first power storage device;

a second power storage device;

said primary power supply and said first power storage device are each input to a first OR gate;

said first OR gate having an output connected to said input/output and said central processing unit;

an output of said first OR gate and said second power storage device are each input to a second OR gate;

said second OR gate having an output connected to said memory;

said first OR gate providing power from either said primary power supply or said first power storage device whichever offers the greatest voltage;

said second OR gate providing power from either said first or said second power storage device whichever offers the greatest voltage; and

said first and second OR gate comprising a diode in series with each of said primary power supply, and said first and said second power storage devices.

2. The invention of claim 1 wherein said first power supply is nickel cadmium storage battery.

3. The invention of claim 1 wherein said second power supply is lithium battery.

4. The invention of claim 1 further comprising a first switch means capable of interrupting power supplied to said input/output and a second switch means capable of interrupting power supplied to said memory.

5. The invention of claim 4 wherein said first switch interrupts power supplied to said input/output after the passage of a first predetermined amount of time from said interruption of said primary power supply.

6. The invention of claim 4 wherein said second switch interrupts power supplied to said central processing unit after the passage of a second predetermined amount of time from said interruption of primary power supply.

7. The invention of claim 4 wherein said first switch interrupts power supplied to said input/output after the passage of a first predetermined amount of time from interruption of said primary power supply and after passage of a second predetermined period of time said second switch interrupts power supplied to said central processing unit.

8. A power backup system which provides power to selected portions of a trip recorder having a microcontroller with subsystems capable of independent operation with separate power application including input/output, memory and a central processing unit, said backup power being provided according to a load shedding strategy which seeks to maximize duration of operation and data retention in the event of interruption of primary power supply comprising:

a first OR gate having a pair of inputs including a first backup power storage device and said primary power supply;

a second OR gate having a pair of inputs including a second backup power storage device and an output of said first OR gate;

a first switch means for selectably providing power to said central processing unit from said first OR gate;

a second switch means for selectably providing power to said input/output from said first OR gate;

output of said second OR gate connected to said memory; and

means for controlling said first and second switch to open said first switch after passage of a first predetermined amount of time from interruption of said primary power supply and open said second switch after passage of a second predetermined amount of time.

9. The invention of claim 8 wherein said first power storage means is nickel cadmium storage battery.

10. The invention of claim 8 wherein said second power storage means is lithium storage battery.