Patent Application
20110316445
The present invention claims priority under 35 U.S.C. §119 to Japanese Patent Application No 2010-146875 filed on Jun. 28, 2010. The content of the application is incorporated herein by reference in their entirety.
The present invention relates to an LED lamp system including a power source unit for supplying constant current to LED elements.
As disclosed in, for example, Japanese Laid-Open Patent Publication No. 2000-260573, a lamp device using LED elements each having low power consumption and a long life has been generally proposed as a light source usable in place of a straight-tube type or self-ballasted fluorescent lamp.
Recently, for renewal of a lighting fixture, there has been increased demand to attach an LED lamp to an existing lighting fixture. In consideration of lamp replacement caused by a change in lamp light color or a change in lamp output, it is preferable to attach a lamp device using LED elements to an existing fluorescent lamp lighting fixture body. Accordingly, the lamp device is lit in a manner of converting AC output of a commercial AC power supply, a fluorescent lamp lighting device or the like to DC output. Thus, when output current contains a large number of ripple components each having a variation width not smaller than a predetermined width, flickering is recognized. In particular, when a lamp device having a small total luminous flux and low iluminance is used, a user feels discomfort as a result of the flickering, thereby diminishing the function of illumination.
In view of the above problem, the present invention has been made and aims to provide an LED lamp system suppressing flickering of LED elements.
An LED lamp system of the present invention has straight-tube type LED lamps each including LED elements. The LED lamp system has a power source unit which rectifies and smoothes alternating current, supplies constant current having a ripple factor of 1.3 or smaller to the LED elements of the straight-tube type LED lamps and lights the LED elements. Since the constant current having a ripple factor of 1.3 or smaller is supplied from the power source unit to the LED elements. so as to light the LED elements, flickering of the LED elements which is caused by pulsating current contained in output current can be suppressed.
Hereinafter, one embodiment will be described with reference to
In
The LED lamp system 11 of the embodiment is a renewal type that uses the fixture body 13 of the existing lighting fixture using a straight-tube type fluorescent lamp and socket 14 as they are, and the straight-tube type LED lamp 16 and dedicated power source 17. Alternatively, even in the case where the LED lamp system 11 using the straight-tube type LED lamps 16 and the dedicated power source 27 is newly installed, it is installed as the LED lamp system 11 reusing the fixture body 13 and the sockets 14 of an existing lighting fixture structure using straight-tube type fluorescent lamps, and using the straight-tube type LED lamp 16 and dedicated power source 17 for the LED lamp system 11.
The straight-tube type LED lamp 16 includes, for example, a cylindrical straight-tube type tube body 21 having transmittance, a light emitting module 22 housed in the tube body 21 and connection portions 23 provided at both ends of the tube body 21.
The tube body 21 is made of glass or resin having transmittance and diffuseness, and formed in a cylindrical shape having substantially the same tube length, tube diameter and appearance as those of a straight-tube type fluorescent lamp. The connection portions 23 as an attachment portion are provided at both ends of the tube body 21.
The light emitting module 22 includes a slender substrate (not shown) along a tube axial direction of the tube body 21 and a plurality of LED elements 25 as loads mounted along a longitudinal direction of the substrate. Light maybe emitted mainly from a predetermined direction of the tube body 21 by making the substrate of the light emitting module 22 flat and mounting the LED elements 25 on one face of the flat substrate. Alternatively, light may be emitted from the whole circumference of the tube body 21 by forming the substrate in a polygonal cylindrical shape and mounting the LED elements 25 on the peripheral surface of the substrate. In the case of an LED element, for example, in the LED element 25, an LED chip emitting blue light is sealed with transparent resin containing fluorescent matter which is excited by the blue light to emit yellow light, and white light is emitted from a surface of the transparent resin.
The connection portion 23 is connected to the socket 14, made of, for example, insulating synthetic resin, formed in the same shape as that of a cap of a straight-tube type fluorescent lamp, and adhered and fixed to the end of the tube body 21. A pair of lamp pins 26 as a receiving power portion similar to a lamp pin of the straight-tube type lamp is provided in a projecting manner on an end face of the connection portion 23. Moreover, the connection portion 23 is not limited to being constituted by a pair of lamp pins 26, and may be constituted by a single lamp pin or the like. Any constitution is applicable if it can realize electric connection or support of the connection portion 23 with respect to the socket 14. Additionally, the connection portion 23 may he electrically and physically connected to the socket 14 via, for example, an adaptor.
The straight-tube type LED lamp 16 has substantially the same outer diameter and total luminous flux as those of, for example, an existing straight-tube type fluorescent lamp 40V type (FL 40 type, FHF 32 type), a total Length in a tube axial direction. of shorter than 1300 mm and 1000 mm or longer, and rated characteristics that the total luminous flux is 2000 lm or larger.
As shown in
In this case, the dedicated power source 17 includes, for example: a full-wave rectifying element 37 such as a bridge diode for rectifying Ac power from the commercial AC power source e: a (first) smoothing element 38 such as a smoothing capacitor for smoothing output power from the full-wave rectifying element 37; and a DC-DC converter 40 including chopper circuit for converting voltage to desired voltage, etc., converts AC power having an AC sine wave or AC rectangular wave to DC power and supplies the DC power to the lamp pins 26 of the straight-tube type LED lamp 16 through the socket 14. Moreover, the dedicated power source 17 may be connected to, for example, an output side of an AC power supply such as a fluorescent lamp lighting device for outputting AC power as AE power from the commercial AC power source e.
The DC-DC converter 40 has, for example: a series circuit of a switching element 41 electrically connected between both ends of the smoothing element 38 and a diode 42 serving as a flywheel diode; and a series circuit of an inductor 43 electrically connected in parallel to the diode 42 and a (second) smoothing element 44 such as a capacitor. The switching element 41 is switching-controlled by a control unit (not shown) so as to perform step-down operation. Moreover, for example, a switching element such as a MOSFET may be used as the switching element 41.
Here, the dedicated power source 17 outputs, for example, output current (constant current) having a current waveform (lamp current envelope waveform) W shown in
In the dedicated power source 17, when the control unit turns on the switching element 41 in the DC-DC converter 40, increased current flows in the inductor 43 and magnetic energy is accumulated therein, and the switching element 41 is turned off, thereby magnetic energy accumulated in the inductor 43 is discharged via the diode 42, decreased current flows and the smoothing element 44 is charged. By repeating the same circuit operation, in the embodiment, constant current having the current waveform W shown in
Since the ripple factor RI of output current of the dedicated power source 17 is here set to 1.3 or smaller, flickering of the LED element 25, in other words, change in the amount of emitted light visible to a user can be suppressed, and in particular, flickering under an environment of high illuminance can be reduced.
When, in particular, the frequency of pulsating current contained in output current is in a relatively small range, for example, approximately 100 Hz, a user can detect flickering of the LED element 25 by eye and easily sense the flickering. Thus, by setting the ripple factor in the dedicated power source 17, which outputs output current containing pulsating current of 100 Hz or higher, to 1.3 or smaller, even when the LED element 25 is lit by output current containing a pulsating current having a frequency band that a user easily senses the user hardly senses flickering and discomfort caused by the flickering can be reduced.
By controlling the output current of the dedicated power source 17 so that the minimum value Imin does not reach 0 A for each cycle, he period when the LED element 25 temporarily turns off can be, realized, Thus, a user senses flickering of the LED element 25 even less.
With the LED lamp system 11 compatible with the straight-tube type LED lamps 16, the dedicated power source 17 is arranged at the fixture body 13 side, thereby the straight-tube type LED lamp 16 can be constituted at a low cost and can be easily replaced in the same manner as the existing straight-tube type fluorescent lamps. Additionally, cost in replacement of the straight-tube type LED lamp 16 can be reduced, thermal influence of the LED elements 25 on the dedicated power source 17 can be reduced, and the reliability and life of the dedicated power source 17 can be improved.
Moreover, in the embodiment, the dedicated power source 17 can be constituted so that the output voltage (output current) is set to 0V (0 A) for each cycle as long as the ripple factor RE of the current waveform W of the output current is set to 1.3 or smaller. In this case, even when arc is generated in a circuit of the straight-tube type LED lamp 16 due to, for example, detachment, contact failure or disconnection at each connection part in the circuit, output voltage (output current) to be supplied to the straight-tube type LED lamp 16 becomes 0V (0 A) for each cycle and the arc can be prevented from continuing.
As the LED lamp system 11, for example, a single lamp type lighting fixture using one pair of sockets 14 may be used, or a multiple-lamp type lighting fixture using three or more sets of the pair of sockets 14 may be used. Additionally, the LED lamp system 11 is applicable not only to a ceiling direct mounting type lighting fixture hut also to an embedding type lighting fixture, etc.
Power may be supplied to the straight-tube type LED lamp 16 via both pair of sockets 14 or only one of them. When power is supplied via only one of the sockets 14, the other socket 14 may only support an end of the straight-tube type LED lamp. 16. Alternatively, for example, a dimming signal is transmitted from the other socket 14 to the straight-tube type LED lamp 16 so that the lit LED element 25 is dimmed by a dimming circuit built in the straight-tube type LED lamp 16. Additionally, without use of the socket 14, power maybe supplied from a non-contact power supplying portion arranged at the fixture body 13 side to a non-contact power receiving portion. arranged at the straight-tube type LED lamp 16 side by a dielectric coupling method or the like. Additionally the sockets 14 may be used for supporting the straight-tube type LED 16 and another power supplying method may be used for the straight-tube type LED lamp 16.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-146875 | Jun 2010 | JP | national |
