Digital current limiter

• US 20050078024A1
• Filed: 10/08/2004
• Published: 04/14/2005
• Est. Priority Date: 10/09/2003
• Status: Abandoned Application

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Harrington, James B.
• Application Number:
  US10/961,339
• Publication Number:
  US 20050078024A1
• Time in Patent Office: Days
• US Class Current: 341/155
• CPC Class Codes: H02J 1/08 Three-wire systems; Systems having more than three wires
• CPC Class Codes: H02J 1/14 Balancing the load in a network
• CPC Class Codes: H02J 7/00304 Overcurrent protection
• CPC Class Codes: H02J 7/0031 using battery or load disconnect circuits H02J9/002 takes precedence

Abstract

A digital current limiter is provided. The digital current limiter includes a microprocessor that is capable of monitoring and controlling multiple current flows concurrently. The microprocessor can be programmed with various current limits and current control functions than can be set and modified in software. In addition, by including a serial communication interface, the current limits and current control functions of the digital current limiter can be modified remotely.

Claims

1. A digital current limiter, comprising:

one or more switches, wherein each respective switch is serially coupled to a respective current sensing circuit, and wherein the respective current sensing circuit senses current flowing at the respective switch and responsively produces an indication of a magnitude of the current; and

a digital controller electrically coupled to the respective current sensing circuit, the digital controller configured to receive the indication of the magnitude of the current and control the respective switch according to the magnitude of the current.

2. The digital current limiter of claim 1 adapted for performing digital power control.

3. The digital current limiter of claim 1, wherein the one or more switches is a plurality of switches.

4. The digital current limiter of claim 3, wherein the digital controller concurrently controls each of the plurality of switches.

5. The digital current limiter of claim 1, wherein the digital controller controls the respective switch via a respective control circuit electrically coupled to the digital controller.

6. The digital current limiter of claim 5, wherein the respective control circuit is a gate drive circuit.

7. The digital current limiter of claim 5, wherein the digital controller generates control signals to the respective control circuit to turn the respective switch on or off based on the magnitude of the current.

8. The digital current limiter of claim 1, wherein the respective switch is a FET, a BJT, an IGBT, or a relay.

9. The digital current limiter of claim 1, wherein the indication of the magnitude of the current is an analog voltage directly proportional to the magnitude of the current, and wherein the digital controller includes an analog-to-digital converter to convert the analog voltage to a digital signal.

10. The digital current limiter of claim 1, wherein the respective current sensing circuit includes a current sense resistor and a differential amplifier, and wherein the differential amplifier is an instrumentation amplifier.

11. The digital current limiter of claim 1, wherein the digital controller is microprocessor or a microcontroller.

12. The digital current limiter of claim 1, wherein the digital controller compares the magnitude of the current to a predetermined current limit and causes the switch to switch to an on state or an off state based on whether the magnitude of the current exceeds the current limit.

13. The digital current limiter of claim 1, wherein the digital controller causes the switch to switch to an on state or an off state in a pulsing manner when the magnitude of the current exceeds the current limit.

14. The digital current limiter of claim 1, wherein the digital controller includes a communication interface.

15. The digital current limiter of claim 14, wherein the communication interface is a serial port.

16. The digital current limiter of claim 14, wherein the communication interface is a wireless link.

17. The digital current limiter of claim 12, wherein the digital controller includes a communication interface, and wherein the predetermined current limit can be modified remotely via the communication interface.

18. The digital current limiter of claim 14 adapted for use in an electric system, wherein the communication interface is serially connected to a host system, and wherein the digital controller provides the host system with information related to the electric system.

19. The digital current limiter of claim 18, wherein the host system reviews the information related to the electric system to determine a health status of the electric system.

20. The digital current limiter of claim 1, wherein the respective switch and the respective current sensing circuit are serially coupled between a power source and a load, and wherein the respective switch functions (i) to electrically couple the power source and the load when the switch is an on state and (ii) to electrically isolate the power source and the load when the switch is an off state.

21. The digital current limiter of claim 20, wherein the current flows via the respective switch when the switch is the on state, electrically coupling the power source and the load.

22. The digital current limiter of claim 20, wherein the power source is selected from the group consisting of (i) a power supply, (ii) a battery, and (iii) a voltage regulator.

23. The digital current limiter of claim 20, wherein when the digital controller determines that the magnitude of the current indicates an over-current condition, the digital controller responsively causes the respective switch to switch to the off state to electrically isolate the power source and the load.

24. The digital current limiter of claim 23, wherein the over-current condition is caused by an overload condition, and wherein the digital controller responsively causes the respective switch to switch to the off state to electrically isolate the power source and the load in response to the overload condition.

25. The digital current limiter of claim 20, wherein when the digital controller determines that the magnitude of the current and an input voltage from the power source indicates an over-power condition, the digital controller responsively causes the respective switch to switch to the off state to electrically isolate the power source and the load.

26. The digital current limiter of claim 25, wherein the over-power condition is caused by an overload condition, and wherein the digital controller responsively causes the respective switch to switch to the off state to electrically isolate the power source and the load in response to the overload condition.

27. The digital current limiter of claim 20, wherein the digital controller includes a communication interface, the communication interface being serially connected to a master controller that controls a power switch electrically coupled to the load.

28. The digital current limiter of claim 27, wherein the master controller is capable of turning the power switch to the load on or off.

29. A method for controlling current flow, comprising:

determining a level of a given current flow on a circuit;

comparing the level of the given current flow to a first predetermined level;

(i) if the level of the current flow is greater than the first predetermined level,

incrementing a digital counter,

comparing the digital counter to a predefined counter value,

if the digital counter is equal to the predefined counter value, responsively interrupting the given current flow on the circuit, otherwise,

comparing the level of the given current flow to a second predetermined level,

if the level of the current flow is greater than the second predetermined level, responsively interrupting the given current flow on the circuit, otherwise,

returning to the step of determining the level of the given current flow on a circuit; and

(ii) if the level of the current flow is greater than the first predetermined level,

decrementing the digital counter,

determining if the digital counter is less than zero,

if the digital counter is less than zero, resetting the digital counter and advancing to the step of determining the level of the given current flow on a circuit the digital counter to a predefined counter value, otherwise,

returning to the step of determining the level of the given current flow on a circuit the predetermined counter value.

30. The method of claim 29, wherein the first predetermined level is an over-current limit level, and wherein the second predetermined level is a critical-current limit level.

31. The method of claim 29, wherein each of the first predetermined level, the second predetermined level, and the predefined counter value can be modified.

32. The method of claim 29, wherein interrupting the given current flow on the circuit includes turning off a switch.

33. A digital circuit breaker comprising a microprocessor executing the method of claim 29.

34. The digital circuit breaker of claim 33, wherein the microprocessor is capable of executing the method of claim 29 for each of multiple current flows on the circuit.

35. A method for limiting current to a plurality of circuits, comprising:

determining at a digital controller whether current through at least one of the plurality of circuits exceeds a predetermined threshold condition; and

upon determining that the threshold condition has been exceeded, pulsing a switch on and off to limit current to the at least one circuit.