Lighting Device and Illumination Fixture using thereof

Abstract

 [Object] To provide a lighting device which enables a user of an illumination fixture to select any of a fluorescent lamp and a DC lighting light source as represented by a light emitting diode, and further realizes safe use. [Means for Settlement] A lighting device has first control means 11 adapted to output a driving signal to switching elements Q1 and Q2 which are used to drive a discharge lamp La at high frequency via a resonance part 4, and second control means 12 adapted to output a driving signal to a switching element Q3 of a voltage conversion circuit (i.e. DC/DC conversion part 5) which steps down an output of a DC power source circuit 1, and the lighting device includes an inductor (i.e. preheating transformer T1) having secondary windings n2 and n3 for use in supplying a preheating current to a filament of the discharge lamp La, and a rectifier DB for rectifying a voltage in an output end of at least one of the secondary windings n2 and n3 (i.e. secondary winding n2), wherein an output path of the voltage conversion circuit (i.e. DC/DC conversion part 5) is connected in parallel with an output path of the rectifier DB.

Description

[Field of the Invention]

[0001] The present invention relates to a lighting device for applying a high-frequency lighting control to a discharge lamp and a DC lighting control to a light source which is lit by a direct current such as LED, and an illumination fixture using the lighting device.

[Background Art]

[0002] A fluorescent lamp has been used as a mainstream light source for illumination and an illumination fixture to allow high-frequency lighting by using an inverter lighting device has been widely disseminated. The inverter lighting device is generally provided with a series circuit made of two switching elements connected to an output end of a DC power source, and a resonance circuit connected in parallel with one of the switching elements and including a fluorescent lamp. The two switching elements are turned on/off alternately in response to a driving signal outputted from a driving circuit so as to supply high-frequency AC power generated by a resonance action of the resonance circuit to the fluorescent lamp. As a widely known object, in order to allow a delay operation of a switching current in turning on/off the switching elements, by optimizing lighting impedance in a resonance inductor, a resonance capacitor, and a discharge lamp under a frequency at which a lighting operation is performed, it is avoided to apply an excessive stress to the switching elements.

[0003] Meanwhile, as an electric light source other than discharges lamps as represented by the fluorescent lamp, attention has been paid to the light emitting diode in recent years. The light emitting diode is superior to the fluorescent lamp in particular from a viewpoint of its life and expected to exhibit efficiency which exceeds that of the fluorescent lamp resulting from technical improvement in the future. However, the light emitting diode differs from the discharge lamp in that lighting is realized by a lighting circuit which outputs DC power, so that conventional inverter lighting devices cannot be used without making any changes and a DC power source exclusively adjusted to characteristics of light emitting diode needs to be prepared.

[Conventional Technique Literature]

[Patent Literature]

[0004] 

Patent literature 1: JP 2009-272088A

Patent literature 2: JP 2009-87588A

Patent literature 3: JP 2003-264090A

[Disclosure of the Invention]

[Problems to be solved by the Invention]

[0005] Currently, light emitting efficiency of an illumination fixture using a light emitting diode has become substantially the same as that of an illumination fixture using a fluorescent lamp, but the light emitting diode itself is fairly expensive and if it is aimed to output light whose intensity is substantially equivalent to that of a fixture used for two of FLR 40 lamps regarded as a mainstream fluorescent lamp, about 50 to 100 light emitting diodes need to be used and it will result in a very expensive illumination fixture.

[0006] Therefore, a light emitting diode illumination device which can be attached to the illumination fixture and the lighting device for fluorescent lamps is proposed so that a user of an illumination fixture can select any one of a fluorescent lamp and a light emitting diode.

[0007] As disclosed in Patent Literature 1, conventional illumination fixtures using fluorescent lamps are largely classified into a starter type, a rapid start type, and an inverter type, and there is a problem such that slightly different voltages and currents are outputted from ballast even in illumination fixtures of the same type depending on manufacturing companies. A lighting circuit of the inverter type is also set to have completely different operation frequency values in a range exceeding 40kHz depending on the manufacturing company, and accompanied by totally different protection functions in preparation for discharge lamp detachment and lamp life. Furthermore, in lighting circuits of the inverter type, a stress applied to a switching element is reduced by achieving impedance matching among a resonance inductor, a resonance capacitor, and a discharge lamp under a frequency operated as stated above, and if a light emitting diode with a completely different impedance from that of a discharge lamp is connected to such a lighting circuit, there is high danger that the light emitting diode and/or the lighting circuit may be damaged. Connecting the light emitting diode may also possibly cause an unsafe situation because a protection function in lighting circuits of the inverter type fails to operate normally.

[0008] Regarding a combination with ballast of a copper-iron type, copper-iron ballast itself has a simple configuration with a conductive winding wound around an iron core which permits magnetism to pass therethrough, so that there is danger that an excessive stress may be generated to cause application of energy accumulated in an inductor to a load side in response to an external surge voltage, and overheat may occur resulting from deterioration of an insulation property due to deterioration with age after using more than 10 years. By a combination with a light emitting diode, if, by any chance, a short-circuit fault of a light emitting diode is followed by excessive supply of a current, there is danger that an overcurrent may flow in copper-iron ballast. A combination of simply configured copper-iron ballast and a light emitting diode with long life is therefore considered as unpreferable.

[0009] The present invention has an object to provide a lighting device and an illumination fixture which enable a user of an illumination fixture to select any of a fluorescent lamp and a DC lighting light source as represented by light emitting diode and further realizes safe use.

[Means adapted to solve the Problems]

[0010] A lighting device according to a first aspect of the present invention is provided with, in order to solve the above problems, as shown in Figs.1 and 2, a series circuit made of first and second switching elements Q1 and Q2 connected between output ends of a DC power source circuit 1, first control means 11 adapted to output a driving signal for periodically and alternately turning on/off the first and second switching elements Q1 and Q2, a resonance circuit (i.e. a resonance part 4 and a preheating part 3) connected in parallel with any one of the first and second switching elements Q1 and Q2 in order to preheat a filament of a discharge lamp La, generate a high voltage for starting the discharge lamp La and supply high frequency power in lighting, a connection terminal (i.e. terminals a and b of a connector CON1 and terminals c and d of a connector CON2) for electrically connecting the discharge lamp La to the resonance circuit, a voltage conversion circuit (i.e. a DC/DC conversion part 5) connected between the output ends of the DC power source circuit 1 and configured to include a third switching element Q3 to step down an output voltage outputted from the DC power source circuit 1 to a required voltage, and second control means 12 adapted to output a driving signal for turning on/off the third switching element Q3 of the voltage conversion circuit, wherein the resonance circuit is configured to include an inductor (i.e. a preheating transformer T1 or an inductor L1 in Figs.6, 7, and 10) having secondary windings n2 and n3 for supplying a preheating current to the filament, a rectifier DB is provided to rectify a voltage in an output end of at least one of the secondary windings n2 and n3 of the inductor (i.e. the secondary winding n2), and an output path of the voltage conversion circuit (i.e. the DC/DC conversion part 5) and an output part of the rectifier DB are connected in parallel to each other.

[0011] A lighting device according to a second aspect of the present invention is provided with, in order to solve the above problems, as shown in Figs.1 and 2, a series circuit made of first and second switching elements Q1 and Q2 connected between output ends of a DC power source circuit 1, first control means 11 adapted to output a driving signal for periodically and alternately turning on/off the first and second switching elements Q1 and Q2, a resonance circuit (i.e. a resonance part 4 and a preheating part 30a) connected in parallel with any one of the first and second switching elements Q1 and Q2 in order to preheat a filament of a discharge lamp La, generates a high voltage for starting the discharge lamp La, and supplies high frequency power in lighting, a connection terminal (i.e. terminals a and b of a connector CON1 and terminals c and d of a connector CON2) for electrically connecting the discharge lamp La to the resonance circuit, a voltage conversion circuit (i.e. a DC/DC conversion part 50) connected between the output ends of the DC power source circuit 1 and configured to include a third switching element Q30 in order to step down an output voltage outputted from the DC power source circuit 1 to a required voltage, and second control means 12 adapted to output a driving signal for turning on/off the third switching element Q30 of the voltage conversion circuit, wherein an output of the voltage conversion circuit is supplied to a low voltage side of the connection terminal (i.e. the terminal d of the connector CON2).

[0012] According to the above configuration, a discharge lamp can be subjected to high frequency lighting by driving the first and second switching elements using the first control means, and a light source such as LED can be subjected to DC lighting by driving the third switching element of the voltage conversion circuit using the second control means.

[0013] Load determination means (i.e. a load determination part 15 including resistors R1 to R3 in Fig.10) may also be provided to determine a load (i.e. the discharge lamp La or an LED module 7) connected to the connection terminal (i.e. the terminals a and b of the connector CON 1 and the terminals c and d of the connector CON2), so that switching means 13 is arranged to switch an operation state of the first control means 11 or the second control means 12 in accordance with determination results of the load determination means.

[0014] According to the above configuration, a discharge lamp and a light source performing DC lighting such as an LED can be selectively lit by selecting the first control means or the second control means to operate using the load determination means.

[0015] An illumination fixture according to a third embodiment of the present invention has the lighting device according to the first embodiment or the second embodiment, and a socket part connectable to the discharge lamp La, while including the discharge lamp La or the light source module 7 having an electric light source performing DC lighting, each of which is connectable to the socket part. (See Figs.3, 4 and 5).

[0016] According to the above configuration, it is possible to provide an illumination fixture in which any of a discharge lamp subjected to high frequency lighting such as a fluorescent lamp and a light source performing DC lighting such as an LED can be lit.

[Brief Description of the Drawings]

[0017] 

[Fig.1] Fig.1 is a circuit diagram in the case of connecting a discharge lamp to a lighting device according to a first embodiment of the present invention.

[Fig.2] Fig.2 is a circuit diagram in the case of connecting an LED module to the lighting device according to the first embodiment of the present invention.

[Fig.3] Fig.3 is a front view showing an appearance of the lighting device according to the first embodiment of the present invention.

[Fig.4] Fig.4 is a perspective view showing an appearance of an illumination fixture on which the lighting device according to the first embodiment of the present invention is mounted.

[Fig.5] Fig.5 is a perspective view showing through a light emitting part of an LED module connectable to the first embodiment of the present invention.

[Fig.6] Fig.6 is a circuit diagram in the case of connecting the discharge lamp to a lighting device according to a second embodiment of the present invention.

[Fig.7] Fig. 7 is a circuit diagram in the case of connecting the discharge lamp to a lighting device according to a third embodiment of the present invention.

[Fig. 8] Fig.8 is an operation waveform diagram obtained when the discharge lamp is connected according to the third embodiment of the present invention.

[Fig.9] Fig.9 is an operation waveform diagram obtained when the LED module is connected according to the third embodiment of the present invention.

[Fig.10] Fig.10 is a circuit diagram in the case of connecting the discharge lamp to a lighting device according to a fourth embodiment of the present invention.

[Fig.11] Fig.11 is a circuit diagram of an LED module used for the lighting device according to the fourth embodiment of the present invention.

[Fig.12] Fig.12 is a characteristic diagram of the LED module used for the lighting device according to the fourth embodiment of the present invention.

[Fig.13] Fig.13 is a circuit diagram in the case of connecting the discharge lamp to a lighting device according to a fifth embodiment of the present invention.

[Fig.14] Fig.14 is a circuit diagram in the case of connecting the LED module to the lighting device according to the fifth embodiment of the present invention.

[Fig.15] Fig.15 is a circuit diagram in the case of connecting the discharge lamp to a lighting device according to a sixth embodiment of the present invention.

[Fig.16] Fig.16 is a circuit diagram in the case of connecting the discharge lamp to a lighting device according to a seventh embodiment of the present invention.

[Fig.17] Fig.17 is a circuit diagram in the case of connecting the discharge lamp to a lighting device according to an eighth embodiment of the present invention.

[Fig.18] Fig.18 is an operation explanatory diagram obtained when the discharge lamp is connected according to the seventh embodiment of the present invention.

[Fig.19] Fig.19 is an operation explanatory diagram obtained when the LED module is connected according to the seventh embodiment of the present invention.

[Best Mode for Carrying Out the Invention]

(First embodiment)

[0018] Figs.1 and 2 are circuit diagrams according to a first embodiment of the present invention. Fig.1 corresponds to the case of connecting a discharge lamp, and Fig.2 corresponds to the case of connecting an LED module.
A DC power source part 1 outputs a DC voltage obtained by, for example, rectifying and smoothing a commercial AC power source using a full-wave rectifier and a step-up chopper circuit. A high frequency conversion part 2 is configured by connecting a circuit with serially connected switching elements Q1 and Q2 such as MOSFET between output ends of the DC power source part 1. The switching elements Q1 and Q2 are driven to be turned on/off alternately by an inverter driving part 11.

[0019] After the DC power source part 1 starts supplying a predetermined DC voltage, a control power source voltage Vcc is generated in a control power source part 6, and the control power source voltage Vcc is supplied to the inverter driving part 11 and a DC/DC conversion driving part 12. In response to an operation selection signal outputted from an operation switching part 13, each of the inverter driving part 11 and the DC/DC conversion driving part 12 determines an operation state thereof. Detailed operations of the operation switching part 13 will be described later.

[0020] The inverter driving part 11 which is made into, for example, an integrated circuit starts operating in response to an operation selection signal sent from the operation switching part 13, followed by outputting a driving signal to the switching elements Q1 and Q2 of the high frequency conversion part 2 by using output terminals thereof including a Hout terminal and a Lout terminal. In parallel with the switching element Q2 being one of the switching elements, a resonance part 4 which is made of a DC cutting capacitor C2, a resonance inductor L1, and a resonance capacitor C1 is connected. Also connected in parallel with the resonance part 4 is a preheating part 3 which is made of a preheating transformer T1 with secondary windings n2 and n3, a capacitor C3 connected in series to a primary winding of the transformer T1, and a rectifier DB connected to the secondary winding n2 being one of the secondary windings.

[0021] A discharge lamp La is also connected in parallel with the resonance capacitor C1 of the resonance part 4, and connectors CON1 and CON2 which are electrically connectable to the outside of the lighting device are arranged so that a preheating current is supplied from the preheating part 3 to a filament of the discharge lamp La.

[0022] When the discharge lamp La is connected to the connectors CON1 and CON2 and the inverter driving part 11 starts operating in response to an operation selection signal outputted from the operation switching part 13, as known in general, each of precedent preheating, starting, and lighting are controlled by changing a frequency of a driving signal.

[0023] A voltage charged in a capacitor C6 is used as a power source to generate a signal for driving the switching element Q1. Owing to a high frequency generated by alternately turning on/off the switching elements Q1 and Q2, high frequency power is generated in the secondary windings n2 and n3 of the preheating transformer T1. Here, the rectifier DB is connected to an output end of the secondary winding n2 in the preheating part 3. High frequency power generated in the secondary winding n2 of the preheating transformer T1 is rectified to a direct current by the full-wave rectifier DB, whereby the filament of the discharge lamp La connected to the connector CON2 (connection terminals c and d) is preheated by DC power.

[0024] Meanwhile, connected to an output end of the DC power source part 1 is a DC/DC conversion part 5 made of a switching element Q3, diodes D1 and D2, an inductor L2, and a capacitor C4. The DC/DC conversion part 5 has a configuration which is the same as that of a generally known step-down chopper circuit and details thereof will be omitted accordingly. The switching element Q3 is driven by an output of the DC/DC conversion driving part 12. The DC/DC conversion driving part 12 which is also similarly made into an integrated circuit outputs a driving signal from a Hout terminal being an output terminal thereof to the switching element Q3 so as to set a time width to turn on the switching element Q3 to a desired value, whereby a DC voltage generated in the capacitor C4 in an output end can be controlled.

[0025] In the case of the configuration of Fig.1, because the discharge lamp La is connected to the connectors CON1 and CON2, the DC/DC conversion part 5 is assumed to stop in response to an operation selection signal outputted from the operation switching part 13 to the DC/DC conversion driving part 12.

[0026] Although an output end of the DC/DC conversion part 5 is connected to an output end of the rectifier DB via the diode D2, a voltage generated in the capacitor C4 or a potential on an anode side of the diode D2 falls in 0[V] because the DC/DC conversion part 5 is stopped, whereby the filament of the discharge lamp La disposed to the terminals c and d is preheated by an output of the rectifier DB which is connected to the output end of the secondary winding n2 in the preheating part 3.

[0027] Next, Fig.2 shows a case of connecting the LED module 7 made of a plurality of LEDs to the connector CON2. As shown in Fig.2, a cathode side of the LED module 7 is connected to the connection terminal c of the connector CON2 and an anode side thereof is connected to the connection terminal d of the connector CON2.

[0028] In the above case, the inverter driving part 11 is stopped in response to an operation selection signal outputted from the operation switching part 13, and the DC/DC conversion driving part 12 starts operating, whereby DC power is supplied to the LED module 7 from the output end of the DC/DC conversion part 5 (i.e. the capacitor C4) via the diode D2. Here, the inverter driving part 11 is stopped and a voltage in the secondary winding n2 of the preheating part 3 falls in 0[V], whereby appropriate DC power is supplied from the output end of the DC/DC conversion part 5.

[0029] The lighting device of the present invention is configured by mounting the electronic components as shown in Fig.1 at least on one print substrate and storing the mounting substrate in a case 20 as shown in Fig.3. The aforementioned connectors CON1 and CON2 are also arranged so as to be connectable to the discharge lamp La and/or the LED module 7 in the outside of the lighting device. CON3 is a connector arranged on a power source side and connected to a wiring for supplying a commercial AC power source to the DC power source part 1. A screw hole 21 for fixation is arranged in each end of the case 20.

[0030] The lighting device covered by such a case shell is incorporated in a fixture main body 31 of an illumination fixture 30 as shown in Fig.4. Each of the connectors CON1 and CON2 of the lighting device is connected to a socket part 32 to which a base part of the discharge lamp La can be connected and inserted.

[0031] The LED module 7 may be configured as shown in Fig.5 so as to be connectable and insertable to such an illumination fixture, wherein a plurality of LEDs is mounted on a substrate and stored in a translucent case whose shape is substantially the same as that of the discharge lamp and terminals a, b, c, and d having the same shape as the base part of the discharge lamp La may be arranged.

[0032] Note that detailed operations of the operation switching part 13 may be any operations as long as the above operation can be realized. For example, the operation switching part 13 may be composed of a microcomputer so as to output binary signals of "H" and "L" to the inverter driving part 11 and the DC/DC conversion driving part 12 in response to a light source selection signal received by a setting switch or the like not shown, whereby the inverter driving part 11 and the DC/DC conversion driving part 12 are configured to operate when the "H" signal is inputted and stop when the "L" signal is inputted.

[0033] The preheating part 3 is not limited to the configuration of connecting the preheating transformer T1 and the capacitor C3 in series, but may have, for example, a switching element connected in series to the preheating transformer T1 so as to control the switching element to be turned on at least in precedent preheating and turned off in lighting.

[0034] As explained above, by using the lighting device of the present embodiment, without increasing the number of connection terminals and sockets in the lighting device as required in illumination fixtures for discharge lamp, a discharge lamp and an LED module can be freely selected to use and the illumination fixture can be assembled inexpensively by using facilities to manufacture illumination fixtures for discharge lamp.

[0035] Furthermore, the terminals a and b of the LED module 7 shown in the present embodiment are electrically insulated from the terminals c and d thereof, so that there is no danger of unsafe phenomena even if it is attached to conventional illumination fixtures.

(Second embodiment)

[0036] Fig.6 is a circuit diagram according to a second embodiment of the present invention. Here is shown a configuration in the case of connecting the discharge lamp La. The first embodiment preheats the filament of the discharge lamp La by using the rectifier DB which rectifies high frequency power generated in the secondary winding n2 of the preheating transformer T1 to a direct current, while the present embodiment preheats the filament of the discharge lamp La by arranging the secondary winding n2 in the resonance inductor L1 of the resonance part 4 and using the rectifier DB which similarly rectifies high frequency power generated in the secondary winding n2 to a direct current. Also, as shown in Fig.6, in order to prevent the secondary windings n2 and n3 from being short-circuited due to filament abnormalities of the discharge lamp La or any other reasons, a capacitor may be connected between the secondary windings n2 and n3 and the filament.

[0037] The DC/DC conversion part 5 also has a configuration which is, similar to the first embodiment, a step-down chopper configuration, wherein an output end of the DC/DC conversion part 5 is connected to an output end of the rectifier DB (the terminal d side) via the diode D2.

[0038] The preheating part is simplified in the present example, whereby the number of components is reduced and the lighting device can be therefore configured inexpensively.

(Third embodiment)

[0039] Fig. 7 is a circuit diagram according to a third embodiment of the present invention. Here is shown a configuration in the case of connecting the discharge lamp La. In the present embodiment, the filament of the discharge lamp La is preheated by preheating power which is supplied by arranging, similarly to the second embodiment, the secondary winding n2 in the resonance inductor L1. The resonance capacitor C1 is also connected between the connection terminals b and d so as to be connected via the filament of the discharge lamp La, and a current is not supplied to the resonance part 4 if the discharge lamp La is removed.

[0040] A basic configuration of the DC/DC conversion part 5 is, similarly to the first and second embodiments, a step-down chopper configuration including a switching element and other components, wherein the switching element Q1 which constitutes the high frequency conversion part 2 is shared as a switching element to constitute the DC/DC conversion part 5 so as to reduce the number of components. An output end of the DC/DC conversion part 5 is connected to an output end of the rectifier DB (the terminal d side) via a switching element Q4.

[0041] The operation switching part 13 outputs an operation selection signal to a driving control part 14 which has a function to enable switching between a driving signal for alternately turning on/off the switching elements Q1 and Q2 and a driving signal for turning on/off only the switching element Q1, and further outputs a driving signal to the switching element Q4 which is connected to the output end of the above DC/DC conversion part 5.

[0042] Detailed operations in the operation switching part 13 and the driving control part 14 according to the present embodiment are shown in timing charts of Figs.8 and 9. Fig.8 shows operations in the case of connecting the discharge lamp La. When the discharge lamp La is connected, an operation selection signal outputted from a load determination part (refer to Fig.10) to the operation switching part 13 is assumed to have a predetermined voltage which is lower than a threshold value Vref2 as shown in Fig.8a. At this time, driving signals Hout and Lout outputted from the driving control part 14 to the switching elements Q1 and Q2 are a signal of a cycle To with a quiescent period t1 detected in rising and falling of the driving signals as shown in Figs.8b and 8c, and switching currents flowing in the switching elements Q1 and Q2 exhibit delay waveforms as shown in Figs.8d and 8e due to a resonance action. In order to control precedent preheating, starting, and lighting of the discharge lamp La, the driving control part 14 may be configured to control a frequency so that the cycle To of the driving signals Hout and Lout is rendered variable and a constant value is maintained in the quiescent period t1.

[0043] A signal of substantially 0[V] as shown in Fig.8f is also outputted from the operation switching part 13 to the switching element Q4 which is connected to the output end of the DC/DC conversion part 5, whereby the switching element Q4 is turned off. By turning on/off the switching element Q1, a voltage is generated in the output end of the DC/DC conversion part 5 (i.e. the capacitor C4), but DC power is not supplied to the connection terminal d of the connector CON2 because the switching element Q4 is turned off, so that DC power outputted from the rectifier DB is used to preheat the filament of the discharge lamp La which is connected between the terminals c and d.

[0044] Next, Fig.9 shows operations in the case of connecting the LED module 7. An operation selection signal in this case is assumed to have a predetermined voltage which is lower than a threshold value Vref1 and higher than the threshold value Vref2 as shown in Fig.9a.

[0045] At this time, the driving signals Hout and Lout outputted from the driving control part 14 to the switching elements Q1 and Q2 are as shown in Figs.9b and 9c respectively, wherein the driving signal Lout maintains 0[V] and the driving signal Hout is turned on/off repeatedly with a cycle T2. Accordingly, switching currents flowing in the switching elements Q1 and Q2 are as shown in Figs.9d and 9e respectively, wherein current waveforms of a saw-wave are observed because energy is accumulated in the inductor L2 when the switching element Q1 is turned on, and energy of the inductor L2 is discharged when the switching element Q1 is turned off, so that a discharged current is made to flow via a diode parasitized in anti-parallel with the switching element Q2. More specifically, the switching element Q1 functions as a switching element of a step-down chopper circuit and a diode provided in anti-parallel with the switching element Q2 functions as a diode used for regenerative current supply in a step-down chopper circuit. In order to realize a step-down chopper control for adjustment of a voltage in the capacitor C4, the driving control part 14 may be configured to carry out a duty control by which at least one of the period to turn on the switching element Q1 and the on/off cycle T2 is rendered variable.

[0046] Furthermore, because of an "H" signal outputted at this time as shown in Fig.9f from the operation switching part 13 to the switching element Q4 which is connected to the output end of the DC/DC conversion part 5, the switching element Q4 is turned on and DC power generated in the output end of the DC/DC conversion part 5 is supplied to the terminal d of the connector CON2. The driving control part 14 may have any configurations as long as it is configured to select any one of a frequency control and a duty control in response to an operation selection signal as stated above.

[0047] Although the driving signal Lout is assumed to maintain 0[V] in the case of connecting the LED module 7, in order to stably ensure a charge voltage of the capacitor C6 which serves as a power source to generate a signal for driving the switching element Q1, it may be configured such that the driving signal Lout is brought into "H" in an "L" period of the driving signal Hout.

[0048] Also, as a further concrete example of the duty control, because a current which falls in substantially 0[A] in energy discharge of the inductor L2 can be determined by detecting a source voltage of the switching element Q1 and/or arranging a secondary winding in the inductor L2 and detecting a voltage in the secondary winding, the driving control part 14 may have control means adapted to turn on the switching element Q1 at timing at which a current in the inductor L2 is determined to be 0[A].

[0049] In the present embodiment, the switching element which constitutes the high frequency conversion part 2 is used in common as a switching element to configure the DC/DC conversion part 5, and the control circuit to output a driving signal to these switching elements can also be shared, whereby the driving control part 14 can be made into an integrated circuit and the number of components can be therefore reduced substantially.

(Fourth embodiment)

[0050] Fig.10 is a circuit diagram according to a fourth embodiment of the present invention. Here is shown a configuration in the case of connecting the discharge lamp La. The configuration is substantially the same as that of the second embodiment, but a load determination part 15 is added to detect whether a load connected to the connector CON2 is the discharge lamp La or the LED module 7 which is shown in Fig.11, wherein an operation state is determined by the operation switching part 13 in response to a determination signal outputted from the load determination part 15.

[0051] Voltage - current characteristics of the LED module 7 shown in Fig.11A include the presence of a predetermined threshold value Vth similarly to a normal diode as shown in Fig.12. The load determination part 15 includes, for example, a plurality of serially connected resistors R1, R2, and R3 as shown in Fig.10, wherein a voltage generated in a connection point of the resistors R1 and R2 is set to be higher than the threshold voltage Vth of the above LED module 7.

[0052] When the LED module 7 is connected between the connection terminals d and c of the connector CON2, a minute current flows in the LED module 7 and a determination signal which is determined at this time by an equivalent impedance of the LED module 7 and the resistors R1, R2, and R3 is generated in a connection point of the resistors R2 and R3 (refer to Fig.9a).

[0053] In the case of connecting the discharge lamp La, the filament of the discharge lamp La is connected between the connection terminals d and c of the connector CON2. Since the filament of the discharge lamp La has equivalent impedance of around 10[Ω], a voltage generated in the connection point of the resistors R1 and R2 is substantially equivalent to 0[V] and a determination signal generated in the connection point of the resistors R2 and R3 also falls in substantially 0[V] (refer to Fig.8a).

[0054] If neither the discharge lamp La nor the LED module 7 is connected, a determination signal corresponds to a voltage determined by the resistors R1, R2, and R3 (a voltage higher than Vref1 as shown in Fig.8 and Fig.9).

[0055] By determining a load with a method as stated above, as explained in the second embodiment, a predetermined operation can be carried out in connecting the discharge lamp and/or the LED module and it is further possible to stop the lighting device to operate if neither the discharge lamp nor the LED module is connected. Accordingly, even after the illumination fixture is installed, a user can freely select the discharge lamp or the LED module to use.

[0056] There are variations in voltage - current characteristics of the LED chip and some of a plurality of LED chips included in the LED module 7 may or may not emit light when a minute current is made to flow, but if a high resistance is connected in parallel with the series circuit made of LED chips as shown in Fig.11B, it is possible to determine a load without taking light emitting variations into consideration.

[0057] Note that, in the present embodiment, the circuit configuration remains substantially the same as that of the second embodiment, but similar effects can also be realized even in the circuit configuration of the first or third embodiment.

(Fifth embodiment)

[0058] Figs.13 and 14 are circuit diagrams according to a fifth embodiment of the present invention. Fig.13 corresponds to the case of connecting the discharge lamp and Fig.14 corresponds to the case of connecting the LED module.

[0059] The present embodiment has a configuration which is substantially the same with that of the first embodiment. Explained below will be an aspect which differs from the configuration of the first embodiment, wherein the same component numbers are used in the same configuration and explanation thereof will be omitted.
In the above first embodiment, the preheating part 3 is configured to have the preheating transformer T1 provided with the secondary windings n2 and n3 and the primary winding of the preheating transformer T1 being connected to the capacitor C3 while the secondary winding n2 being one of the secondary windings to the rectifier DB, in a state of being connected in parallel with the resonance part 4, whereas a preheating part 30a of the fifth embodiment includes a preheating transformer T10 having a secondary winding n20 and a capacitor C30 connected in series to a primary winding of the preheating transformer T10, in a state of being connected in parallel with the resonance part 4.

[0060] In such a configuration, a voltage charged in the capacitor C6 is used as a power source to generate a signal for driving the switching element Q1. Owing to high frequency generated by alternately turning on/off the switching elements Q1 and Q2, high frequency power is generated in the secondary winding n20 of the preheating transformer T10. By providing such a configuration, the filament of the discharge lamp La which is connected between the terminals a and b of the connector CON1 is preheated by high frequency power.

[0061] Meanwhile, the DC/DC conversion part 50 includes a switching element Q30, a diode D10, an inductor L20, and a capacitor C40, and connected to the output end of the DC power source part 1. By providing such a configuration, the filament of the discharge lamp La which is connected between the terminals c and d of the connector CON2 is preheated by DC power.

[0062] In the case of the configuration of Fig.13, the discharge lamp La is connected to the connectors CON1 and CON2, and the DC/DC conversion part 50 is therefore assumed to operate in response to an operation selection signal outputted from the operation switching part 13 to the DC/DC conversion driving part 12.

[0063] At this time, the DC/DC conversion part 50 is controlled to operate at least in precedent preheating of the discharge lamp La and stop in lighting of the discharge lamp La, whereby wasted power can be reduced.

[0064] Next, Fig.14 shows the case of connecting the LED module 7 made of a plurality of LEDs to the connector CON2. As shown in Fig.14, a cathode of the LED module 7 is connected to the connection terminal c of the connector CON2 and an anode thereof is connected to the connection terminal d of the connector CON2.

[0065] In the above case, the inverter driving part 11 is stopped in response to an operation selection signal outputted from the operation switching part 13 and the DC/DC conversion driving part 12 starts operating, whereby appropriate DC power is supplied from an output end of the DC/DC conversion part 50 (i.e. the capacitor C40) to the LED module 7. At this time, the inverter driving part 11 is stopped in response to an operation selection signal outputted from the operation switching part 13, whereby enabling reduction of wasted power.

[0066] Note that detailed operations of the operation switching part 13 in the fifth embodiment may be any operations as long as the above operation can be realized. For example, the operation switching part 13 may include a microcomputer so that binary signals of "H" and "L" are outputted to the inverter driving part 11 and the DC/DC conversion driving part 12 in response to a light source selection signal received by a setting switch or the like not shown, or load determination means which is capable of differentiating the discharge lamp La and the LED module 7 may be arranged so as to determine an operation state of the inverter driving part 11 and the DC/DC conversion driving part 12.
The inverter driving part 11 may also be configured to operate when the "H" signal is inputted and stop when the "L" signal is inputted. The DC/DC conversion driving part 12 may also be configured to operate so as to supply preheating power to the discharge lamp La when the "H" signal is inputted and supply appropriate DC power to the LED module 7 when the "L" signal is inputted.

[0067] Moreover, the configuration of the preheating part 30a is not limited to serial connection of the preheating transformer T10 and the capacitor C30, and for example, a switching element may be connected in series to the preheating transformer T10 so that the switching element is controlled to be turned on at least in precedent preheating of the discharge lamp La and turned off in lighting of the discharge lamp La.

[0068] As explained above, by using the lighting device according to the present embodiment, the discharge lamp and the LED module can be freely selected to use without increasing the number of connection terminals and sockets in the lighting device as required in illumination fixtures for discharge lamp, and the illumination fixture can be assembled inexpensively by using facilities to manufacture illumination fixtures for discharge lamp.

[0069] Furthermore, the terminals a and b of the LED module 7 shown in the present embodiment are electrically insulated from the terminals c and d thereof, and there is no danger of unsafe phenomena even if it is attached to conventional illumination fixtures.

(Sixth embodiment)

[0070] Fig.15 is a circuit diagram according to a sixth embodiment of the present invention. Here is shown a configuration in the case of connecting the discharge lamp La. The fifth embodiment preheats the filament of the discharge lamp La by high frequency power generated in the secondary winding n20 of the preheating transformer T1, while the present embodiment preheats the filament of the discharge lamp La by arranging the secondary winding n20 in the resonance inductor L1 of the resonance part 4 and similarly using high frequency power generated in the secondary winding n20. Also, as shown in Fig.15, a capacitor may also be connected between the secondary winding n20 and the filament to prevent the secondary winding n20 from being short-circuited due to filament abnormalities of the discharge lamp La or any other reasons.

[0071] The DC/DC conversion part 50 has, similarly to the fifth embodiment, a step-down chopper configuration, and an output end of the DC/DC conversion part 50 is connected to the filament of the discharge lamp La (or the terminal d side).

[0072] The preheating part is simplified in the present embodiment, whereby the number of components is reduced and the lighting device can be therefore configured inexpensively.

(Seventh embodiment)

[0073] Fig.16 is a circuit diagram according to a seventh embodiment of the present invention. Here is shown a configuration in the case of connecting the discharge lamp La. In the present embodiment, the filament of the discharge lamp La is preheated by, different from the fifth and sixth embodiments, supplying preheating power through a preheating current path which is arranged via the resonance capacitor C1. It is also configured to connect the resonance capacitor C1 between the connection terminals b and d so as to be connected via the filament of the discharge lamp La, wherein a current is not supplied to the resonance part 4 if the discharge lamp La is removed.

[0074]  A basic configuration of the DC/DC conversion part 50 is, similarly to the fifth and sixth embodiments, a step-down chopper configuration including a switching element and other components, and the switching element Q1 to constitute the high frequency conversion part 2 is used in common as a switching element to configure the DC/DC conversion part 50, whereby the number of components is reduced. An output end of the DC/DC conversion part 50 is connected to the discharge lamp La via a switching element Q40.

[0075] The operation switching part 13 outputs an operation selection signal to the driving control part 14 which has a function to enable switching between a driving signal for alternately turning on/off the switching elements Q1 and Q2 and a driving signal for turning on/off only the switching element Q1, and further outputs a driving signal to the switching element Q40 which is connected to the output end of the DC/DC conversion part 50. On/off state of the switching element Q40, an output of the DC/DC conversion part 50, and an output voltage of the capacitor C40 at the start of operation in the present embodiment are shown in timing charts of Figs.18 and 19. Fig.18 shows operations in connecting the discharge lamp La and Fig.19 shows operations in connecting the LED module 7.

[0076] Detailed operations in the operation switching part 13 and the driving control part 14 according to the seventh embodiment are the same as those shown in the above timing charts of Figs.8a to 8e and Figs.9a to 9e.

[0077]  Fig.18 shows operational changes due to switching from a preheating/starting mode to a lighting mode in the case of connecting the discharge lamp La. When the discharge lamp La is connected, in precedent preheating, the switching element Q40 is turned on at the start and the filament of the discharge lamp La which is connected between the terminals c and d is preheated by DC power. The switching element Q40 is turned off in lighting, whereby a space between the terminals c and d is not preheated excessively. Thus controlling the operation switching part 13 makes it possible to reduce wasted power.

(Eighth embodiment)

[0078] Fig.17 is a circuit diagram according to an eighth embodiment of the present invention. Here is shown a configuration in the case of connecting the discharge lamp La. The configuration remains substantially the same as that of the sixth embodiment, but the load determination part 15 is added to detect whether a load connected to the connector CON2 is the discharge lamp La or the LED module 7 which is shown in Fig.11, wherein an operation state is determined by the0 operation switching part 13 in response to a determination signal outputted from the load determination part 15.

[0079] Note that, in the present embodiment, the circuit configuration remains substantially the same as that of the sixth embodiment, but similar effects can also be realized even in the circuit configuration of the fifth or seventh embodiment.

[0080] Although explanation was made in the first to eighth embodiments by using the light emitting diode as a representative light source performing DC lighting, an organic EL may also be used.

[Description of Reference Numerals]

[0081] 

1

DC power source part

2

High frequency conversion part

3, 30a

Preheating part

4

Resonance part

5, 50

DC/DC conversion part

7

LED module

11

Inverter driving part (first control means)

12

DC/DC conversion driving part (second control means)

13

Operation switching part

T1, T10

Preheating transformer

n2, n20

Secondary winding

La

Discharge lamp

Q1 to Q3, Q30

Switching element

CON1, CON2

Connector

Claims

1. A lighting device comprising: a series circuit made of first and second switching elements connected between output ends of a DC power source circuit; first control means adapted to output a driving signal for periodically and alternately turning on/off the first and second switching elements; a resonance circuit connected in parallel with any one of the first and second switching elements to preheat a filament of a discharge lamp, generate a high voltage for starting the discharge lamp, and supply high frequency power in lighting; and a connection terminal for electrically connecting the discharge lamp to the resonance circuit, wherein: the lighting device includes a voltage conversion circuit connected between the output ends of the DC power source circuit and configured to include a third switching element in order to step down an output voltage outputted from the DC power source circuit to a required voltage, and second control means adapted to output a driving signal for turning on/off the third switching element of the voltage conversion circuit; the resonance circuit is configured to include an inductor having a secondary winding for supplying a preheating current to the filament; a rectifier is provided to rectify a voltage of at least one of output ends of the secondary winding of the inductor; and an output path of the voltage conversion circuit is connected in parallel with an output path of the rectifier.

2. The lighting device according to claim 1, comprising load determination means adapted to determine a load connected to the connection terminal and switching means adapted to switch an operation state of the first control means or the second control means in accordance with determination results of the load determination means.

3. An illumination fixture comprising: the lighting device according to any one of claims 1 and 2; and a socket part connectable to the discharge lamp, wherein a discharge lamp or a light source module with an electric light source performing DC lighting, each being connectable to the socket part, is included.

4. A lighting device comprising: a series circuit made of first and second switching elements connected between output ends of a DC power source circuit; first control means adapted to output a driving signal for periodically and alternately turning on/off the first and second switching elements; a resonance circuit connected in parallel with any one of the first and second switching elements to preheat a filament of a discharge lamp, generate a high voltage for starting the discharge lamp, and supply high frequency power in lighting; and a connection terminal for electrically connecting the discharge lamp to the resonance circuit, wherein: the lighting device includes a voltage conversion circuit connected between the output ends of the DC power source circuit and configured to include a third switching element to step down an output voltage outputted from the DC power source circuit to a required voltage, and second control means adapted to output a driving signal for turning on/off the third switching element of the voltage conversion circuit; and an output of the voltage conversion circuit is supplied to a low voltage side of the connection terminal.

5. The lighting device according to claim 4, comprising: load determination means adapted to determine a load connected to the connection terminal; and switching means adapted to switch an operation state of at least the second control means in accordance with determination results of the load determination means.

6. An illumination fixture comprising: the lighting device according to any one of claims 4 and 5; and a socket part connectable to the discharge lamp, wherein a discharge lamp or a light source module with an electric light source performing DC lighting, each being connectable to the socket part, is included.

Drawing