Methods and apparatus for controlling a notification appliance circuit

• US 8,373,571 B2
• Filed: 02/06/2009
• Issued: 02/12/2013
• Est. Priority Date: 02/08/2008
• Status: Active Grant

• Current Assignee: Siemens Industry Incorporated (Siemens AG)
• Original Assignee: Siemens Industry Incorporated (Siemens AG)
• Inventors: Henson, James C., Lontka, Karen D.
• Primary Examiner(s): Lee, Benjamin C
• Assistant Examiner(s): PHAM, QUANG
• Application Number:
  US12/322,839
• Publication Number:
  US 20100066557A1
• Time in Patent Office: 1,467 Days
• Field of Search: 340/693.1, 340/635, 340/652, 340/657, 340/664, 340/501, 361/58, 713/300, 713/324
• US Class Current: 340/664
• CPC Class Codes: H02H 9/001 limiting speed of change of electric quantities, e.g. soft switching on or off progressive control of electronic switches for eliminating interferences H03K17/16

Abstract

An arrangement for use in a safety notification system includes an alarm signal power source, a first semiconductor device, a current sensing unit, and a controller unit. The alarm signal power source is configured to generate bias power for activating a notification appliance circuit of a notification system. The first semiconductor device has a load path coupled between the alarm signal power source and the notification appliance circuit. The current sensing unit is operably coupled to generate a sensing signal that is dependent on the current in the load path. The controller circuit is operably connected to receive the current sensing signal and to control the first semiconductor device responsive to a current sensing signal that exceeds an in-rush current threshold.

Claims

1. A safety notification system comprising:

a detector device configured to detect an alarm event and to generate an indication of the alarm event;

a fire control panel connected to the detector device and configured to receive the indication from the detector device and to generate a notification signal based on the indication; and

an arrangement connected to the fire control panel and configured to receive the notification signal, the arrangement comprising;

an alarm signal power source, the alarm signal power source configured to generate bias power for activating a notification appliance circuit of a notification extension loop responsive to receiving the notification signal;

at least a first semiconductor device having a load path coupled between the alarm signal power source and the notification appliance circuit to selectively activate the notification appliance circuit;

a current sensing unit operably coupled between the alarm signal power source and the first semiconductor device and configured to generate a current sensing signal that is dependent on the current in the load path, the current sensing signal indicative of whether the current through the load path exceeds an in-rush current threshold;

a processing circuit operably coupled to a current measurement circuit which is coupled to the current sensing unit and configured to generate an overcurrent detection signal, based on the current sensing signal, indicative of whether an average of the current through the load path over a predetermined period of time exceeds a steady state current threshold, the steady state current threshold being different from the in-rush current threshold; and

a controller circuit operably connected to receive the current sensing signal and wherein the controller circuit is configured to control the first semiconductor device responsive to the current sensing signal exceeding the in-rush current threshold and the average of the current over the predetermined period of time being less than or equal to the steady state current threshold;

wherein the processing circuit is configured to cause the controller circuit to control the first semiconductor device such that the first semiconductor device does not conduct the current through the load path responsive to the overcurrent detection signal, different from the current sensing signal, indicating that the average of the current through the load path over the predetermined period of time exceeds the steady state threshold.

2. The safety notification system of claim 1, wherein the first semiconductor device is a MOSFET.

3. The safety notification system of claim 2, wherein the current sensing unit includes a sense resistor and wherein the current sensing signal comprises a voltage level of a terminal of the sense resistor.

4. The safety notification system of claim 1, wherein the controller circuit further comprises an input for receiving the current sensing signal.

5. The safety notification system of claim 2, wherein the controller circuit operably controls the MOSFET to limit the current through the load by changing a gate voltage of the MOSFET.

6. The safety notification system of claim 1, wherein the processing circuit is further configured to generate the overcurrent detection signal indicative of whether the average of the current through the load path over the predetermined period of time exceeds the steady state current threshold.

7. The safety notification system of claim 1, wherein the processing circuit is configured to generate a shutdown signal responsive to the overcurrent detection signal indicating that the average of the current through load path over the predetermined period of time exceeds the steady state threshold, and wherein the processing circuit is configured provide the shutdown signal to a first input of the controller circuit.

8. The safety notification system of claim 1, wherein the controller circuit is configured to limit, but not shut off, the current through the load path when the current exceeds the in-rush current threshold.

9. The safety notification system of claim 1, wherein the controller circuit is configured to shut down the first semiconductor device when the average of the current through the load path over the predetermined period of time exceeds the steady state current threshold.

10. A safety notification system comprising:

a detector device configured to detect an alarm event and to generate an indication of the alarm event;

a fire control panel connected to the detector device and configured to receive the indication from the detector device and to generate a notification signal based on the indication; and

an arrangement connected to the fire control panel and configured to receive the notification signal, the arrangement comprising;

an alarm signal power source, the alarm signal power source configured to generate bias power for activating a notification appliance circuit of a notification extension loop responsive to receiving the notification signal;

at least a first semiconductor device having a load path coupled between the alarm signal power source and the notification appliance circuit to selectively activate the notification appliance circuit;

a current sensing unit operably coupled between the alarm signal power source and the first semiconductor device and configured to generate a current sensing signal that is dependent on the current in the load path, the current sensing signal indicative of whether the current through the load path exceeds an in-rush current threshold;

a processing circuit operably coupled to a current measurement circuit which is coupled to the current sensing unit and configured to generate an overcurrent detection signal, based on the current sensing signal, whether an average of the current through the load path over a predetermined period of time exceeds a steady state current threshold; and

a hot swap controller operably connected to receive the current sensing signal and configured to control the first semiconductor device responsive to the current sensing signal and the overcurrent detection signal indicative of whether the average of the current through the load path over the predetermined period of time exceeds the steady state current threshold, the overcurrent detection signal being different from the current sensing signal, said control including limiting the current through the load path when said current exceeds the in-rush current threshold and the average of the current over the predetermined period of time that is less than or equal to the steady state current threshold;

wherein the processing circuit is configured to cause the hot swap controller to control the first semiconductor device such that the first semiconductor device does not conduct the current through the load path responsive to the overcurrent detection signal indicating that the average of the current through the load path over the predetermined period of time exceeds the steady state threshold.

11. The safety notification system of claim 10, wherein the first semiconductor device is a MOSFET.

12. The safety notification system of claim 11, wherein the current sensing unit includes a sense resistor and wherein the current sensing signal comprises a voltage level of a terminal of the sense resistor.

13. The safety notification system of claim 10, wherein the hot swap controller further comprises an input for receiving the current sensing signal.

14. The safety notification system of claim 11, wherein the hot swap controller operably controls the MOSFET to limit the current through the load by changing a gate voltage of the MOSFET.

15. The safety notification system of claim 10, wherein the processing circuit is further configured to generate the overcurrent detection signal indicative of whether the average of the current through the load path over the predetermined period of time exceeds the steady state current threshold.

16. The safety notification system of claim 10, wherein the processing circuit is configured to generate a shutdown signal responsive to the overcurrent detection signal indicating that the average of the current through the load path over the predetermined period of time exceeds the steady state threshold, and wherein the processing circuit is configured provide the shutdown signal to a first input of the hot swap controller.