LED lamp system
Disclosed is an LED lamp system designed to fit into a fluorescent lamp fixture and to utilize a fluorescent lamp power supply contained in the fixture and receiving power from AC mains. The LED lamp system includes an LED driver which comprises a power factor corrected driver circuit for achieving a power factor of at least about 0.8. The LED driver further comprises a current control circuit, responsive to the presence of a three-wire magnetic ballast in the fluorescent lamp power supply, for increasing the LED operating current above the nominal rated LED operating current and to a level sufficient to achieve power factor of the LED driver of at least about 0.8.
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The present invention relates to an LED lamp system designed to fit into a fluorescent lamp fixture. More particularly, the invention relates to an LED driver for the LED lamp system that results in a power factor presented to AC mains of at least about 0.8 when the fluorescent lamp fixture includes a three-wire magnetic ballast.
BACKGROUND OF THE INVENTIONLED lamps are being developed by various companies for replacing fluorescent lamps in fluorescent lamp fixtures (“FLFs”). In many cases, the fluorescent lamp ballasts are removed or disconnected from a FLF, and additional wiring is provided to drive (or power) the LED lamps. In some cases, the LED lamps can be made to accept the electrical power input from a specific type of existing fluorescent tube ballast in the FLF. An economical option for fluorescent lamp replacement by an LED lamp is to leave the existing fluorescent lamp ballast in the FLF and to utilize such ballast for powering the LED lamps without any rewiring of the FLF.
As discovered by the present inventor, current LED lamp drive circuitry encounters a problem with three-wire magnetic ballasts used in fluorescent lamp fixtures (“FLFs”). Three-wire magnetic ballasts exhibit a high power factor when powering fluorescent lamps, but when powering LED lamps with a power factor corrected LED driver, the present inventor discovered that power factor substantially decreases to about 0.63, for instance. As is known, the power factor of an electrical circuit is the ratio of the real power flowing to the circuit to the apparent power in the circuit.
Accordingly, it would be desirable to provide an LED lamp system designed to fit into a fluorescent lamp fixture and which can utilize an existing three-wire magnetic fluorescent lamp ballast already present in the fluorescent lamp fixture, while presenting a power factor to AC mains of at least about 0.8.
BRIEF SUMMARY OF THE INVENTIONIn accordance with a preferred aspect of the invention, an LED lamp system is provided. The LED lamp system is designed to fit into a fluorescent lamp fixture and to utilize a fluorescent lamp power supply contained in the fixture and receiving power from AC mains. The LED lamp system includes an LED driver which comprises a power factor corrected driver circuit for presenting a power factor to the AC mains of at least about 0.8. The LED driver further comprises a current control circuit, responsive to the presence of a three-wire magnetic ballast in the fluorescent lamp power supply, for increasing the LED operating current above the nominal rated LED operating current and to a level sufficient to present a power factor to the AC mains of at least about 0.9. Preferably, the presence of the three-wire magnetic ballast is automatically detected by the LED lamp system.
Beneficially, the foregoing LED lamp system can utilize an existing three-wire magnetic fluorescent lamp ballast already present in a fluorescent lamp fixture, while presenting a power factor to AC mains of at least about 0.8.
Further features and advantages of the invention will become apparent from reading the following detailed description in conjunction with the following drawings, in which like reference numbers refer to like parts.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTLED lamp driver arrangement 12 includes a suitably conventional full-wave rectifier and filter 28 for receiving power from fluorescent lamp ballast 18. A Power Factor Corrected (PFC) driver circuit 30 is used to present to the AC mains 20 and 22 a power factor of at least about 0.8, 0.9 and 0.95, with 1.0 being a perfect power factor. More preferably, such power factor is at least 0.99. As is known, the power factor of an electrical circuit is the ratio of the real power flowing to the circuit to the apparent power in the circuit. A suitable PFC driver circuit 30 may be a Model L6562AT chip sold by STMicroelectronics whose headquarters is in Geneva, Switzerland. Other suitable PFC circuits include a Model MC33368 chip sold by Freescale Semiconductor Inc. of Austin, Tex. U.S.A.
In a preferred embodiment, an electrical condition sensor 33 monitors input voltage and current from the rectifier and filter 28 and also output current supplied to the one or more LEDs on the LED board 14. A logic and electrical condition control circuit 36, typically carried out with a microprocessor, determines whether the fluorescent lamp fixture 16 contains a ballast 18 and whether such ballast 18 is a three-wire magnetic ballast, such as shown in
In response to the electrical condition sensor 33, the logic and electrical condition control circuit 36 sets an appropriate level of current for the one or more LEDs on the LED board 14, and also may adjust the input voltage and current to the LED driver 16 so as to properly interact with the fluorescent lamp ballast 18.
In the event that a determination is made that the fluorescent lamp ballast 18 is a three-wire magnetic ballast, which may be done manually or more preferably via the logic and electrical condition control circuit 36, such circuit 36 will increase the current supplied to the LED board 14 sufficiently above the nominal current rating of the one or more LEDs on the board 14 to assure that the power factor presented to the AC mains 20 and 22 can be maintained at least about 0.8. This is in accordance with experimentation and discovery by the present inventor, which found that, despite using a PFC driver circuit 30 that normally results in a power factor of at least about 0.99 with a two-wire magnetic ballast, for example, considerably lower power factors, such as 0.83, were obtained when the fluorescent lamp fixture 16 contained a three-wire magnetic ballast and nominal rated current was supplied to the one or more LEDs on the LED board 14. Ironically, three-wire magnetic ballasts, when powering fluorescent lamps, typically achieved, without a separate power factor correction circuit, a power factor that could typically reach in excess of about 0.97. Beneficially, when the current level is increased to the LED board 14 to no more than about 318 ma, the efficiency of electricity-to-lumen conversion of the LEDs on the LED board 14 does not decrease because the lumen output of the LED board increases.
In order to determine an appropriate increase in current supplied to the one or more LEDs on LED board 14,
As can be seen in
For high power factor, it is preferred that the current supplied to the LED driver arrangement 12 is greater than 200 milliamps, or, stated differently, that such current is within about five percent of 270 ma.
It would be a matter of routine skill, based on the present specification, for a person of ordinary skill in the art to prepare a graph similar to graph 45 of
If the mentioned comparison of voltages in connection with the voltage-comparison step 58 indicates that the difference in voltages is greater than about five volts, for instance, a determination is made that FLF 16 contains a magnetic ballast. The flow chart then proceeds to step 64, wherein detection is made between a two-wire magnetic ballast and a three-wire magnetic ballast in FLF 16. Based on the detection between two-wire and three-wire magnetic ballasts of step 64, which is further detailed below, a selection of either a two-wire magnetic ballast or a three-wire magnetic ballast in made in step 66; such selection is carried out by the logic and electrical condition circuit 36 of
The various measurements made in connection with the flow charts of
Although the flow charts of
The following is a list of reference numerals and associated parts as used in this specification and drawings:
The foregoing describes an LED lamp system designed to fit into a fluorescent lamp fixture, and which increases the current supplied to one or more LED lamps, upon determination that the fluorescent lamp fixture contains a three-wire magnetic ballast, so that the power factor presented to AC mains is at least about 0.8.
While the invention has been described with respect to specific embodiments by way of illustration, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true scope and spirit of the invention.
Claims
1. An LED lamp system designed to fit into a fluorescent lamp fixture and to utilize a fluorescent lamp power supply contained in the fluorescent lamp fixture; the fluorescent lamp power supply receiving power from AC mains and having a ballast condition that can be at least either a two-wire magnetic ballast or a three-wire magnetic ballast; the LED lamp system including an LED driver arrangement which comprises:
- a) a power factor corrected driver circuit for presenting a power factor to the AC mains of at least about 0.8 when either a two-wire magnetic ballast or a three-wire magnetic ballast is present in the fluorescent lamp power supply; and
- b) a logic and electrical condition current control circuit, responsive to the presence of a three-wire magnetic ballast in the fluorescent lamp power supply for increasing an LED operating current above a nominal rated LED operating current and to a level sufficient to achieve power factor of the LED driver arrangement of at least about 0.8;
- c) wherein the two-wire magnetic ballast is configured so that: i) first and second conductors from a power source applying a potential therebetween are respectively coupled directly to a first end of said LED lamp system and to a first terminal of the two-wire magnetic ballast; ii) said LED lamp system receives power from said first conductor and from a third conductor connected between a second terminal of the two-wire magnetic ballast and a second end of said LED system; and iii) said lamp system has a power factor greater than 0.8 when operated from a two-wire magnetic ballast; and
- d) wherein the three-wire magnetic ballast is configured so that: i) first and second conductors from a power source applying a voltage potential therebetween are respectively coupled directly to two terminals of the three-wire magnetic ballast; ii) said LED lamp system receives power from said first conductor at a first end of said LED lamp system and from a third conductor at a second end of said LED lamp system connected to a further terminal of the three-wire magnetic ballast; iii) when powering a fluorescent lamp, said three-wire ballast attains a power factor of greater than 0.8; and iv) said lamp system has a power factor below 0.8 when the LED operating current is at the nominal rated LED operating current.
2. The LED lamp system of claim 1, wherein the current supplied to the LED driver arrangement is greater than 200 milliamps.
3. The LED lamp system of claim 1, wherein the current supplied to the LED driver arrangement is within about five percent of 270 ma.
4. The LED lamp system of claim 1, wherein the power factor presented to the AC mains with the three-wire ballast is at least about 0.9.
5. The LED lamp system of claim 1, wherein the power factor presented to the AC mains with the three-wire ballast at least about 0.95.
6. The LED lamp system of claim 1, wherein the power factor presented to the AC mains with the three-wire ballast is at least 0.99.
7. The LED lamp system of claim 1, wherein the LED driver arrangement is electrically connected between the fluorescent lamp power supply and LEDs of the LED lamp system and is separate from the fluorescent lamp fixture.
8. The LED lamp system of claim 7 1, wherein said logic and electrical condition current control circuit is configured:
- a) to cause the LED driver arrangement to achieve a first impedance by selection of level of current drawn by the LED driver from the fluorescent lamp power supply;
- b) to determine a first power level used by the LED driver arrangement when the LED driver is at said first impedance;
- c) to cause the LED driver arrangement to thereafter achieve a second impedance, greater than the first impedance, by selection of the level of current drawn by the LED driver from the fluorescent lamp power supply; and
- d) to determine a second power level used by the LED driver arrangement when the LED driver is at said second impedance; and
- e) a three-wire magnetic ballast being indicated if the second power level exceeds the first power level, and a two-wire magnetic ballast being indicated if the first power level exceeds the second power level.
9. The LED lamp system of claim 1, wherein the ballast condition is absence of a magnetic ballast.
10. The LED lamp system of claim 1, wherein the ballast condition is a NEALS U.S. Navy Military No. M16377/77-001 ballast.
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Type: Grant
Filed: Nov 30, 2017
Date of Patent: May 21, 2019
Assignee: ENERGY FOCUS, INC. (Solon, OH)
Inventors: Laszlo A. Takacs (Lakewood, OH), Roger F. Buelow (Pepper Pike, OH), Tomislav Kralj (Chardon, OH)
Primary Examiner: Angela M Lie
Application Number: 15/827,385
International Classification: H05B 37/02 (20060101); H05B 33/08 (20060101);