Control of Energy to Fluorescent Lighting

This invention pertains to energy control and, more particularly, to controllably varying the amount of energy transmitted to fluorescent lighting.

For the last several years, the public has become increasingly conscious of the conservation of energy. This has been brought about in view of the increasing costs for the fundamental sources of energy and, particularly, those related to petroleum. Accordingly, there have been proposed steps to control the artificial lighting within confined areas. When one considers incandescent lighting it is only necessary to use wellknown dimmers which, in effect, decrease the amplitude of the voltage applied to the lamps. However, when fluorescent lighting is considered, one cannot use these conventional amplitude control devices. Furthermore, during the start-up of fluorescent lighting it is necessary to insure that the ballast and other components are suitably warmed as soon as possible to insure efficient operation of the device.

It is, accordingly, a general object of the invention to control the energy flow of fluorescent lighting so that on the one hand there is a net overall saving of consumed energy and, on the other hand, there is rapid and efficient startup of the fluorescent devices.

Briefly, the invention contemplates a method of reducing the energy consumption of fluorescent lighting energized by an alternating voltage source. The method further contemplates sensing for a particular amplitude of the alternating voltage and upon the sensing of such voltage amplitude establishing a given time period which is a fraction of a cycle of the alternating voltage. At the end of this given period, the alternating voltage source is actively connected to the fluorescent lighting whereby the lighting is energized for a portion of that cycle. This will now continue from cycle to cycle; however, for a given time interval at the start of operation the alternating voltage source is continuously actively connected to the fluorescent lighting so that the components of the fluorescent lighting can efficiently warm up.

Other aspects of the invention contemplate apparatus for carrying out this method.

Other objects, the features and advantages of the invention will be apparent from the following detailed description when read with the accompanying drawing, whose sole FIGURE shows by way of example and not limitation the presently preferred embodiments of the invention.

In the sole FIGURE, there is shown a power control fluorescent lighting system wherein a fluorescent lighting array 10 is activated by the alternating current source 12 under the control of a controller including a sensing means 14, a timing means 16, an interval generating means 18, and a controlled switching means 20. In summary, when a user closes the switch 22 in the interval generating means 18, the controlled switching means directly connects the alternating voltage across the fluorescent array 10. After a given period of time to permit warmup of the elements in the fluorescent lighting array 10, the remainder of the controller takes hold. Most particularly, the sensing means senses effectively the zero crossings of the alternating voltage in its periodic cycles and emits a signal for each zero crossing to trigger the timing means 16. After a given time delay which is a fraction of the alternating voltage cycle, the timing means 16 energizes the control switching means to connect the alternating voltage directly across the fluorescent lighting array for the remainder of the cycle. By virtue of variable resistor 22 the actual active portion of the cycle can be controlled. Thus, it is possible within reasonable limits to control the energy flow to the lighting array. Similarly, by varying the resistance in the variable resistor 24 one can control the time interval of warmup at the start of operation.

Each of the elements will now be described in greater detail. The alternating voltage source 12 includes the mains 26 to which is connected the primary winding of the transformer 28. Connected to the secondary windings of the transformer 28 are the rectifier and filter array 30 which provide the operating voltage for the remainder of the system. In addition, coupled to the secondary windings of the transformer are the diodes 32 and 34. These diodes are connected in such a way that a full wave rectified AC signal is fed to one input of the analog comparator 36. To the other input of the comparator 36 is connected a reference voltage source 38. The reference voltage is ideally fixed at a value fairly close to ground voltage so that as the half-cycles of the alternating voltage start increasing, the analog comparator emits a signal on line 40 to the trigger input of variable one-shot 42. The variable one-shot 42 is a conventional monostable multivibrator having a resistor in its timing circuit. This is resistor 22. This resistor can be a manually controlled resistor whereby an operator can decide on the point in the alternating voltage cycle where the fluorescents receive voltage or can also be a light-sensitive resistor or the like which controls the amount of dimming of the fluorescent as a function of the ambient light in the region. In any event, the trailing edge of the signal from the variable one-shot 42 is fed to the triggering input of the fixed one-shot 44. The fixed one-shot 44 is used primarily to provide a well-defined uniform width pulse to the controlled switching means 20. The controlled switching means 20 includes the transistor Q1 and a similar transistor Q2. The transistors are, in a sense, connected in parallel, i.e., the collector terminals of the transistors are connected to the operating voltage Plus B whereas their emitter terminals are connected in parallel to the input of a triac switch 50. The base terminal of the transistor Q1 receives a signal from the fixed one-shot 44 and the base electrode of the transistor Q2 receives a signal from the variable monostable 52. The triac switch 50 is a conventional triac having one terminal connected to the fluorescent lighting array 10 and the other terminal connected to one terminal of the alternating voltage source 12. Thus, whenever a pulse is present from the fixed one-shot 44, the transistor Q1 is turned on energizing the triac switch 50 causing the alternating voltage to be applied across the lighting array 10.

The interval generator 18 is also a variable monostable multivibrator which is initially triggered at the start of operation by the depression of the switch 18. The duration of the time interval is controlled by variable resistor 24 which can be manually variable giving an operator the option of determining the time of warmup. It is also possible for this resistor to be a temperature sensitive resistor which increases in resistance with decreasing temperature so that as the ambient temperature is colder the warmup period is longer. In any event, at the start of the warmup period the transistor Q2 is turned on so that the controlling via the transistor Q1 is over-ridden. Accordingly, the full cycles of alternating voltage are applied to the fluorescent lighting array 10.

Although only one apparatus embodiment of the invention has been shown and described in detail, there will now be obvious to those skilled in the art many modifications and variations satisfying many or all of the objects of the invention without departing from the spirit thereof.