Vehicle locating unit with input voltage protection

• US 7,511,606 B2
• Filed: 05/18/2005
• Issued: 03/31/2009
• Est. Priority Date: 05/18/2005
• Status: Active Grant

• Current Assignee: Calamp Wireless Networks Inc. (CalAmp Corporation)
• Original Assignee: LoJack Operating Company, LP (Solera Holdings Incorporated)
• Inventors: Smithers, Colin Richard, Finchley Cletheroe, Daniel Jonathan, Nguyen, Son, Rhodes, Jesse, Stroud, Ian Christopher, Howe, Timothy David, Smith, Gerard Edward, Watson, Nigel James, Krishna, Sampath, Romano, Frank, Greendale, Steven Walter, Crewe, Philip Grahame, Marsden, Mark
• Primary Examiner(s): Wu; Daniel
• Assistant Examiner(s): Lu; Shirley
• Application Number:
  US11/131,846
• Publication Number:
  US 20060261934A1
• Time in Patent Office: 1,413 Days
• Field of Search: 340/428, 340/426, 340/933, 340/988, 342/357.07, 342/357.09, 342/357.04, 327/310
• US Class Current: 340/428
• CPC Class Codes: B60R 25/102 a signal being sent to a remote location, e.g. a radio signal being transmitted to a police station, a security company or the owner
• CPC Class Codes: B60R 25/33 of global position, e.g. by providing GPS coordinates

Abstract

A vehicle locating unit with a receiver for receiving a signal from a network of communication sources, a transponder activated when a communication source sends a message to the receiver, and a power supply regulating circuit for regulating a nominal input voltage and powering the receiver and the transponder. A protection circuit is responsive to an injected input voltage and configured to clamp the injected (high level) input voltage at a predetermined maximum voltage.

Claims

1. A vehicle locating unit comprising:

a receiver for receiving a signal from a network of communication sources;

a transponder activated when a communication source sends a message to the receiver;

a power supply regulating circuit for regulating a nominal vehicle input voltage and powering said receiver and said transponder; and

a protection circuit responsive to an injected input voltage at least an order of magnitude higher than the vehicle input voltage and configured to clamp the injected input voltage at a predetermined maximum voltage the same as or approximately the same as the vehicle input voltage, the protection circuit comprising;

a filtering circuit with at least one voltage protection device having a breakdown voltage at least as high as the injected input voltage, and

a voltage regulating circuit including at least one voltage protection device having a breakdown voltage at least as high as the injected input voltage.

2. The vehicle locating unit of claim 1 in which every component of the protection circuit is selected to withstand an injected input voltage greater than said nominal input voltage.

3. The vehicle locating unit of claim 1 in which the protection circuit includes a voltage limiting diode which clamps the injected input voltage at the predetermined maximum voltage.

4. The vehicle locating unit of claim 1 in which the protection circuit is integrated with the power supply regulating circuit.

5. The vehicle locating unit of claim 1 in which the power supply circuit further includes a second stage voltage regulating circuit connected to the first stage voltage regulating circuit and configured to provide the appropriate voltage levels to the receiver and transponder.