Voltage regulator for merchandise display security device

• US 8,558,414 B2
• Filed: 08/11/2010
• Issued: 10/15/2013
• Est. Priority Date: 08/11/2010
• Status: Active Grant

• Current Assignee: InVue Security Products Incorporated
• Original Assignee: InVue Security Products Incorporated
• Inventors: Warren, William M., Christianson, David P.
• Primary Examiner(s): AMAYA, CARLOS DAVID
• Application Number:
  US12/854,246
• Publication Number:
  US 20120038342A1
• Time in Patent Office: 1,161 Days
• Field of Search: 307/20, 307/28, 307/154, 340/568.2, 340/568.3
• US Class Current: 307/154
• CPC Class Codes: H02M 1/00 Details of apparatus for conversion

Abstract

A voltage regulator for a merchandise display security device provides an appropriate operating voltage through a power cable electrically connected between an alarm sensor and an item of merchandise. The voltage regulator utilizes a feedback signal from a power conversion chip and data from a microprocessor look-up table to adjust the input power to the merchandise. The look-up table stores appropriate operating voltage requirements for each power cable used for different types and brands of merchandise. The type and brand of merchandise is identified by the resistance of the power cable and the feedback signal is modified continuously to maintain power to the merchandise at an appropriate operating voltage.

Claims

1. A voltage regulator for an alarm sensor configured to provide power to an item of merchandise via a power cable having an identifying resistor, the voltage regulator comprising:

a reference voltage source in electronic communication with the identifying resistor and producing a voltage drop across the identifying resistor;

a microprocessor measuring the voltage drop across the identifying resistor and calculating a resistance value of the identifying resistor; and

a power conversion chip in electronic communication with the microprocessor and providing an operating voltage to the power cable;

wherein a first feedback signal is transmitted from the power cable back to the power conversion chip; and

wherein a correction signal generated by the microprocessor encodes the first feedback signal to provide power to the item of merchandise according to the resistance value of the identifying resistor.

2. A voltage regulator according to claim 1, further comprising:

a means for varying the voltage of the first feedback signal in response to the correction signal generated by the microprocessor.

3. A voltage regulator according to claim 2, wherein the means for varying the voltage of the first feedback signal comprises a pulse width modulation signal.

4. A voltage regulator according to claim 3, further comprising a summation node connecting the pulse width modulation signal to the first feedback signal.

5. A voltage regulator according to claim 3, wherein the microprocessor comprises a computer readable medium storing a first look-up table that correlates the resistance value of the identifying resistor in the power cable with an operating voltage requirement of the item of merchandise.

6. A voltage regulator according to claim 5, wherein the microprocessor comprises a computer readable medium storing a second look-up table that correlates the duty cycle of the pulse width modulation signal with an operating voltage requirement of the item of merchandise.

7. A voltage regulator according to claim 1, further comprising a second feedback signal between an operating voltage node and the microprocessor.

8. A system for digitally controlling power to an item of merchandise electrically connected to an alarm sensor, the system comprising:

a power cable extending between the alarm sensor and the item of merchandise;

a regulated voltage source in electrical communication with the power cable;

a reference resistor connected to the regulated voltage source and generating a reference voltage;

a microprocessor in electrical communication with the power cable and the reference resistor, wherein the microprocessor identifies the power cable by measuring the reference voltage and calculating a corresponding resistance of the power cable;

a power conversion chip electrically connected between the microprocessor and the power cable configured to provide an operating voltage to the item of merchandise;

a first feedback signal transmitted from the power cable to the power conversion chip; and

a correction signal generated by the microprocessor for encoding the voltage of the first feedback signal to provide power to the item of merchandise according to the corresponding resistance of the power cable.

9. A system according to claim 8, wherein the microprocessor comprises a computer readable medium storing a first look-up table that lists a plurality of the power cables by corresponding resistance values and further lists a plurality of output voltage requirements by corresponding resistance values.

10. A system according to claim 8, wherein the correction signal is a pulse width modulation signal.

11. A system according to claim 10, wherein the microprocessor comprises a computer readable medium storing a second look-up table that lists a plurality of output voltage requirements by corresponding duty cycle adjustments to the pulse width modulation signal.

12. A system for digitally controlling power to an item of merchandise electrically connected to an alarm sensor, the system comprising:

a power cable extending between the alarm sensor and the item of merchandise;

a microprocessor in electrical communication with the power cable;

a regulated voltage source in electrical communication with the microprocessor;

wherein the microprocessor is configured to;

(i) calculate a voltage drop across the power cable;

(ii) access a look-up table of power cable identifying information stored on the microprocessor; and

(iii) continuously maintain the appropriate power to the item of merchandise according to an identified one of a plurality of the power cables.

13. A system according to claim 12, further comprising

a power conversion chip in electrical communication with the microprocessor and the power cable;

and

a pulse width modulation signal transmitted from the microprocessor to the power conversion chip for continuously adjusting an operating voltage from the power conversion chip.

14. A system according to claim 13, further comprising a summation node connecting the pulse width modulation signal to a first feedback signal from the power cable.

15. A system according to claim 14, wherein pulse width modulation data is adjusted in the microprocessor via a second feedback signal configured for monitoring the operating voltage of the power conversion chip.

16. A system according to claim 12, wherein the power conversion chip provides a constant operating voltage within a predetermined range of a voltage drop across the power cable.

21. A system according to claim 12, wherein the microprocessor comprises a computer readable medium storing the first look-up table, the first look-up table listing a plurality of the power cables by corresponding resistance values and a plurality of output voltage requirements by corresponding resistance values.

17. A method for regulating an operating voltage in a power circuit providing power to an item of merchandise electrically connected to a security device, the method comprising:

identifying an operating voltage set point for the item of merchandise;

measuring a real time operating voltage via a feedback loop;

generating a correction signal that is correlated to the operating voltage set point and the real time operating voltage;

adjusting an input to the feedback loop with the correction signal.

18. A method according to claim 17, wherein the correction signal is a pulse width modulation signal.

19. A method according to claim 17, further comprising identifying the operating voltage set point by identifying an input resistance of a load powering the item of merchandise.

20. A method according to claim 19, further comprising associating the input resistance of the load powering the item of merchandise with the correction signal that adjusts the input to the feedback loop.

22. A method according to claim 17, further comprising continuously monitoring the operating voltage via a second feedback loop, wherein generating the correction signal comprises generating the correction signal based on the operating voltage monitored via the second feedback loop.

23. A method according to claim 17, further comprising identifying an input resistance of a load powering the item of merchandise, wherein generating a correction signal comprises accessing a look-up table comprising a plurality of correction signals and operating voltages for each input resistance of a load powering the item of merchandise.