Patent Application
20100320915
One embodiment of the present invention pertains to methods and apparatus for providing fluorescent lighting. More particularly, one embodiment of the invention comprises a method for stimulating and maintaining the efficient operation of a fluorescent tube.
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Over 500 million fluorescent lamps are sold in the United States every year. Sales of “fluorescent lumiline lamps” commenced in 1938, when four different sizes of tubes were introduced to the market. During the following year, General Electric and Westinghouse publicized the new lights through exhibitions at the New York World's Fair and at the Golden Gate Exposition in San Francisco. Fluorescent lighting systems spread rapidly during World War II, as wartime manufacturing intensified lighting demand. By 1951, more light was produced in the United States by fluorescent lamps than by incandescent lamps.
A generalized pictorial view of a fluorescent lamp is depicted in
A conventional incandescent light is shown in
In a conventional incandescent light bulb, the resistance of a heated filament is relatively constant. In other words, once power is applied to a conventional light bulb, the filament heats up, and the amount of electricity that flows through the bulb remains about the same until the power is switched off.
In a conventional fluorescent lamp, after the power is initially supplied to the electrodes of the fluorescent lamp, the gas inside the tube is excited, and its electrical resistance begins to fall. More electricity flows into the lamp when the resistance drops, and the cycle continues unabated until so much current flows into the lamp, that the lamp is destroyed by excessive heat.
The operation of conventional fluorescent lamps may be controlled by using an external device, called a “ballast,” which limits and regulates the current flow through the tube. The ballast may be a simple electrical component called a “resistor,” which limits the flow of energy into the lamp. A more prevalent form of ballast employs another electrical component called an “inductor,” which generally comprises a coil of wire wrapped around a metal core. Many different circuits have been used to start and run conventional fluorescent lamps. The design of a conventional ballast is based on input power voltage, tube length and size, initial cost, long term cost and other factors. (See Wikipedia).
Conventional fluorescent lamps may be powered by a direct current (DC), which flows in a steady stream, and which does not vary with time. In DC powered fluorescent lamps, the ballast must be resistive, and consumes about as much power as the lamp. Current day fluorescent lamps are almost never powered by direct current. Instead, the vast majority of present day fluorescent lamps run on alternating current (AC), which rises and falls in a regular cycle.
More recent “electronic” ballasts utilize transistors or other semiconductor components to convert household voltage (120 VAC) into high-frequency alternating current.
Beginning in the 1990's, a new type of ballast was introduced to the market. “High frequency” ballasts use high frequency voltage to excite the mercury within the lamp. These newer electronic ballasts convert the 60 Hertz household alternating current to a high frequency signal that can exceed 100 kHz. (See Wikipedia).
Present day conventional ballasts and fluorescent lamps are hampered by serious limitations. First, they consume substantial amounts of power. Second, they are not dimmable over a complete range of brightness. Third, every ballast must be especially configured for the particular fluorescent lamp with which it is to be used.
The development of an energy control device system that overcomes these limitations and that provides a substantial reduction in energy consumption would constitute a major technological advance, and would satisfy long felt needs and aspirations in the lighting industry, and would also satisfy pending and imminent regulatory demands.
One embodiment of the present invention comprises a Fluorescent Lighting System. One embodiment of the invention may be used to control the operation of a fluorescent lamp. One embodiment utilizes a circuit that enables light output dimming to one half of the maximum light output of the lamp, while simultaneously reducing energy consumption by fifty percent.
An appreciation of the other aims and objectives of the present invention and a more complete and comprehensive understanding of this invention may be obtained by studying the following description of a preferred embodiment, and by referring to the accompanying drawings.
The present invention comprises methods and apparatus for operating a highly efficient and dimmable fluorescent illumination device. In general, one embodiment of the invention provides for confining a plasma, and then stimulating the plasma with electrical energy to form a conductive plasma channel. This plasma drives the production of visible light by stimulating a photoluminescent substance surrounding the plasma. The impedance of the plasma channel, which varies with time and with ambient conditions, is then measured, and then the electrical input which maintains the plasma channel is adjusted to optimize its electrical impedance to provide efficient illumination. In another optional step, the polarity of the input waveform to the lamp is periodically reversed to eliminate any artifacts.
In accordance with one of the methods of the present invention, a first electrical signal is applied across the electrodes of the enclosure, as shown in
In the second phase of operation, which occurs between times T1 and T2, and which is labeled “Blending,” the first DC signal is blended with an AC signal.
In the third phase of operation, which occurs between times T2 and T3, and which is labeled “Monitoring,” the sensor inside the enclosure monitors the impedance of the plasma. When the conditions are correct, the source is switched from high impedance to low impedance.
In the fourth phase of operation, which occurs after time T3, and which is labeled “Stabilizing & Maintaining Operation,” an adjusted blend of DC and AC input signals are applied to the electrodes of the enclosure to maintain the optimal operation of the fluorescent device.
In an optional fifth phase of operation, which is labeled “Optional Polarity Reversal,” which may occur after time T4 the polarity of the waveform may be reversed to eliminate artifacts.
In one embodiment, the first signal is a relatively high voltage, constant direct current. In one embodiment, this first signal may range from 625 to 700 VDC. In one embodiment, the second signal is a mix of a constant direct current, and an alternating current. In one embodiment, the alternating current may range from 50 to 90 volts, and from 65,000 to 90,000 cycles per second. In an alternative embodiment, a series of direct current pulses may be substituted for the alternating current. In one embodiment, the second electrical signal ranges from 120 to 150 VDC.
In yet another embodiment of the invention, a radio may be attached to or installed inside the enclosure. This radio may be used to communicate to a remote transceiver to optimize the operation of the fluorescent device. A number of fluorescent devices, such as some or all of the bulbs on the floor of an office building, may use these radios to coordinate and control the operation of this group of fluorescent devices. In particular, these radios may be used for automatic dimming. In one embodiment, the radio operates in the Wi-Fi frequency band, and is used to create a Wi-Fi hotspot for telecommunications.
In another embodiment, the power supply for the fluorescent device is built into the enclosure, and the invention operates without an external ballast.
In another embodiment, the interior surface of said enclosure also includes a partially mirrored surface to further enhance the optimization of the production of visible light from the light emitting substance on said interior surface of the enclosure.
In yet another embodiment of the present invention, priori knowledge of the characteristics of the enclosure are used to optimize the production of visible light from the fluorescent device.
The current through the lamp is monitored by the microcontroller when it interprets the frequency of the voltage pulse output from the optical isolator U-1 which is shown in
From these monitored quantities, the microcontroller calculates the lamp mean impedance characteristic. With this characteristic and the measured lamp mean current value, the microcontroller initiates the appropriate action by altering the voltage parameters applied to the lamp. For example, an F32T8 lamp operating at 100% illumination exhibits high efficiency when the measured mean current value is 0.180 ampere and the calculated mean impedance characteristic is 685 ohms. If the ambient temperature decreases, the lamp mean impedance characteristic will increase and the lamp efficiency will decrease. The microcontroller will react by adjusting the D.C. plus A.C. voltage amplitude and blend, applied to the lamp, to maintain 0.180 amperes and manage the impedance back to 685 ohms. High efficiency operation is restored.
The ballast microcontroller is also capable of dimming the light output. For example, the F32T8 lamp operates at high efficiency, at an illumination level of 37.5%, if the lamp means current value is 0.06 ampere and the calculated mean impedance characteristic is 2500 ohms. This is accomplished and maintained, by the microcontroller adjusting the D.C. plus A.C. voltage amplitude and blend applied to the lamp.
One embodiment of the invention includes a microcontroller and firmware combination, a power supply, an electrical switch, a switchable resistance, a switchable filter and one or more relays that are used to reverse the polarity of the input applied to the lamp. Each component is described below.
In one embodiment, the present invention works in combination with a power supply that converts incoming power line voltage, typically 110 VAC RMS, to an adjustable 100 VDC to 700 VDC at 100 watts. The power supply accomplishes this conversion from alternating to direct current while always making itself appearing as a resistive load to the incoming power line. This ability is called power factor correction (PFC). The circuit which accomplishes this task is readily available from a range of manufacturers. In one embodiment of the invention, a Fairchild model FAN7529 is employed as the power supply. See application note AN-6026. the output voltage is controlled by the microcontroller.
In one embodiment, the present invention also works in combination with a one input electrical. switch, which is used to control power fed to the lamp. When turned on its resistance should be less 0.3 ohms. When turned off, the break down voltage of the switch must be greater than 800 Volts. The switch is controlled by applying a voltage level shift which is supplied to a third connection on the switch. One embodiment of the invention utilizes a model FQP7N80 made by Fairchild. The electrical switch must be fast, making the transitions between states in less than 200 nanoseconds (200×10−9 seconds).
In one embodiment, the present invention is also used in combination with a microcontroller and firmware. The microcontroller converts analog to digital and digital to analog, and must operate fast enough to perform calculations and run the ballast circuitry. A clock frequency of 20 MegaHertz is recommended. The recommended microcontroller family for one embodiment is the Zilog Z8 encore line.
The firmware monitors the amount of voltage and current that crosses and runs through the fluorescent lamp. The firmware must be capable of receiving an energy level instruction from an operator using the standard lighting industry communication protocols. The microcontroller may also be used to analyze the fluorescent lamp's condition, communicate the lamp type, and communicate that condition to the operator.
In one embodiment, the present invention is also used in combination with a switchable filter. The filter resides in series between the power supply and the electrical switch, and it parallels the lamp and works with the switch to control the makeup (the alternating and direct current levels) of energy that powers the lamp. The fluorescent lamp performs best when the energy fed to lamp is filtered to be a mixture of 96-98% DC current and 2-4% AC current. The filter is switchable because its characteristics change depending on the level to which the lamp is being driven.
In one embodiment, the present invention includes a switchable resistance. The switchable resistance resides in series with the power supply. The resistance is used to limit energy transfer to the lamp during the excitation and blending phases of operation. This occurs between T0 and T2, as shown in
In one embodiment, the present invention includes an output relay. The output relay resides between the switchable filter and the lamp. The relay is used to reverse the polarity of the electrical energy driving the lamp. Polarity reversal is utilized during the excitation phase of operation, T0 to T1, as shown in
Although the present invention has been described in detail with reference to one or more preferred embodiments, persons possessing ordinary skill in the art to which this invention pertains will appreciate that various modifications and enhancements may be made without departing from the spirit and scope of the Claims that follow. The various alternatives that have been disclosed above are intended to educate the reader about preferred embodiments ofthe invention, and are not intended to constrain the limits of the invention or the scope of Claims.
