Digital control of electronic ballasts using AC power lines as a communication medium

• US 7,391,168 B1
• Filed: 01/13/2006
• Issued: 06/24/2008
• Est. Priority Date: 01/13/2005
• Status: Expired due to Fees

• Current Assignee: Universal Lighting Technologies Incorporated (Panasonic Holdings Corporation)
• Original Assignee: Universal Lighting Technologies Incorporated (Panasonic Holdings Corporation)
• Inventors: Bell, Brett, Shet, Deepak, Dernovsek, John Jay
• Primary Examiner(s): TRAN, THUY V
• Application Number:
  US11/332,503
• Time in Patent Office: 893 Days
• Field of Search: 315/200.R, 315/224, 315/246, 315/289, 315/290, 315/291, 315/362, 340/310.11, 340/310.13, 340/310.14, 340/870.3, 340/870.4, 340/870.39, 375/259
• US Class Current: 315/291
• CPC Class Codes: H02J 13/00009 using pulsed signals
• CPC Class Codes: H02J 13/0001 using modification of a parameter of the network power signal
• CPC Class Codes: H05B 47/185 via power line carrier transmission
• CPC Class Codes: Y02B 70/30 Systems integrating technologies related to power network operation and communication or information technologies for improving the carbon footprint of the management of residential or tertiary loads, i.e. smart grids as climate change mitigation technology in the buildings sector, including also the last stages of power distribution and the control, monitoring or operating management systems at local level
• CPC Class Codes: Y02B 90/20 Smart grids as enabling technology in buildings sector smart grids supporting the management or operation of end-user stationary applications in general, or like technologies with no associated climate change mitigation effect Y04S20/00
• CPC Class Codes: Y02E 60/00 Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
• CPC Class Codes: Y04S 10/52 Outage or fault management, e.g. fault detection or location
• CPC Class Codes: Y04S 20/246 the system involving the remote operation of lamps or lighting equipment
• CPC Class Codes: Y04S 40/121 using the power network as support for the transmission

Abstract

A system for establishing communications between a central lighting controller and a series of electronic dimming ballasts uses an AC power supply line as a communication medium. A MOSFET switched by a control circuit selectively shorts the AC power lines when a rectified version of the power line signal indicates that the power line signal is nearing a zero crossing to create notches in the AC power signal. A simple receiver in each of the ballasts detects the presence or absence of notches in the power signal and interprets the results as digital data indicating a desired dimming level for each of the ballast. The ballasts then adjust their light output accordingly.

Claims

1. A method of enabling communications between a controller and at least one electronic ballast on an AC power line supplying power to said at least one electronic ballast, said method comprising:

rectifying an AC power signal on the AC power line thereby creating a rectified power line signal;

sending the rectified power line signal to the controller which can activate a switch which shorts the AC power line;

using said controller to activate the switch whenever the rectified power line signal approaches a zero crossing for the rectified power line signal thereby extending a zero crossing that occurs when the AC power signal on said AC power line either transitions from a positive to a negative polarity or from a negative to a positive polarity; and

detecting a presence or absence of a zero crossing extension when said AC power line signal changes polarity with said at least one electronic ballast and interpreting said presence or absence of said zero crossing extensions in accordance with a predetermined code to thereby enable communications between said controller and said at least one electronic ballast.

2. The method of claim 1 further comprising the step of rectifying said power signal and using said rectified power signal to control production of said zero crossing extensions.

3. The method of claim 1 wherein said zero crossing extensions are created by selectively shorting said AC power line.

4. The method of claim 3 wherein said selective shorting occurs immediately prior to a change in polarity of said AC power signal.

5. The method of claim 1 further comprising using said zero crossing extensions to communicate a desired dimming amount to said at least one electronic ballast.

6. The method of claim 1 wherein selectively extending said zero crossing further comprises shorting said AC power line with a MOSFET.

7. The method of claim 1 further comprising using a ratio between extended zero crossings and non-extended zero-crossings to communicate information from said controller to said at least one electronic ballast.

8. A system for creating notches in an AC power line signal propagating over an AC power line in order to communicate over the AC power line, the system comprising:

a rectifier for rectifying the AC power line signal on the AC power line to produce a rectified power line signal;

a switch device connected to the AC power line so that activating the switch device shorts the AC power line; and

control circuitry connected to the rectifier wherein the control circuitry is adapted to activate the switch device whenever the rectified power line signal reaches a reference voltage thereby creating a notch in the AC power line signal.

9. The system of claim 8 wherein the system further comprises a receiver for detecting the notches in the AC power signal.

10. The system of claim 8 wherein said switch device is a MOSFET.

11. The system of claim 8 wherein the reference voltage is less than 10% of a maximum voltage potential of said power line signal.

12. The system of claim 8 wherein the rectified signal reaches the reference voltage immediately prior to a zero crossing by said power line signal.

13. The system of claim 8 wherein said control circuitry further comprises a phase detection circuit for monitoring the rectified signal to determine when the rectified signal reaches the reference voltage.

14. The apparatus of claim 13, further comprising a rectifier connected to the phase detection circuit so that the phase detection circuit can determine a change in polarity in the power signal.

15. The system of claim 8, further comprising at least one electronic ballast connected to the AC power line wherein a dimming function of the electronic ballast is controlled by the notches in the AC power line signal.

16. The system of claim 8, further comprising:

AC input terminals for receiving the AC power line signal;

load output terminals for delivering the AC power line signal to the load;

a first circuit path coupled to the AC input terminals and having the rectifier, the switch, and the control circuitry; and

a second circuit path coupled to the AC input terminals and to the load output terminals.