This application is based upon and claims the benefit of priority from prior Japanese Patent Applications No. 2008-232619, filed Sep. 10, 2008; and No. 2009-191891, filed Aug. 21, 2009, the entire contents of both of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a power supply unit having a dimmer function for driving a semiconductor light emitting module so as to light the semiconductor light emitting module at suitably dimmed brightness, and a lighting unit having this power supply unit.
2. Description of the Related Art
Recently, from a viewpoint of energy saving, semiconductor light emitting modules such as light-emitting diodes are used as light sources for lighting units, and DC power supply units into which switching elements are incorporated are developed as power supplies which drive the semiconductor light emitting modules such as the light-emitting diodes. As these power supply units, it is known that they have a dimmer function for adjusting brightness of the light-emitting diodes according to a dimmer signal given from the outside.
Conventionally, the power supply unit having such a dimmer function is disclosed in, for example, JP-A 2003-157986 (KOKAI). The power supply unit disclosed in this publication has a voltage dimmer circuit which controls an applied voltage to light-emitting diodes, and a duty dimmer circuit which switching-controls an applied voltage to the light-emitting diodes. The voltage dimmer circuit and the duty dimmer circuit are changed over to be controlled according to a dimmer control signal.
In the power supply unit disclosed in JP-A 2003-157986 (KOKAI), a DC voltage given to the light-emitting diodes is adjusted according to a pulse width of the dimmer signal, and an applied voltage to the light-emitting diodes is switched so that the light-emitting diodes are controlled to be dimmed. Therefore, output light from the light-emitting diodes has a problem that flicker easily occurs. In addition to a current limiting function for controlling an output current according to the pulse width of the dimmer signal, a switching element which is in series or in parallel with the light-emitting diodes is necessary, and thus the number of parts increases and circuit efficiency is deteriorated. Since the pulse width is controlled, when a switching frequency for this control is in an audible area, a noise might be generated.
On the other hand, since the light-emitting diodes have an approximately constant voltage characteristic, a part or a device having the current limiting element is necessary for stable lighting. In order to control an electric power in a power supply unit using a switching element, current control is generally used. In the current control, an element temperature of the light-emitting diodes is determined by a value of an electric current flowing in the light-emitting diodes, and the element temperature influences an element life. Therefore, in the current control, the flowing electric current is the important control element due to design of the lighting unit.
The dimming of the light-emitting diodes can be realized comparatively more easily than a discharge lamp lighting unit. The light-emitting diodes as a load have stable electric characteristics, and fluctuation in the brightness of the light-emitting diodes due to an external factor such as temperature is small. For this reason, the dimming of the light-emitting diodes can be easily realized. In the application of deep dimmer control, namely, brightness control where a brightness control rate or a dimmer rate is set large and thus brightness of the light-emitting diodes is greatly reduced, the constant current control is adopted to the light-emitting diodes. In this constant current control system, the light-emitting diodes can be lighted stably in a control area where lighting current is high for full-emission lighting. In this system, however, the lighting current supplied to the light-emitting diodes is lowered in the deep dimmer control area, and a current detecting signal becomes minute according to the lowering of the lighting current, and a reference current for controlling the lighting current is a minute signal. Therefore, in a constant current control circuit, accuracy of a detecting circuit or a comparator requires high performance, and the control circuit is easily influenced by a noise, so that a stable operation becomes difficult. It is thus considered that a signal voltage for control is increased. However, the current detecting signal is generally detected by a resistor inserted in series into the light-emitting diodes, and resistance of the resistor should be increased in order to increase the detecting signal. As a result, in the control area where the electric current flowing in the light-emitting diodes is high, the electric power is greatly consumed by the detection resistor, or heat is generated from the detection resistor, and a countermeasure against this heat inhibits developments of products.
As a control system which solves these problems, a constant voltage control system which constantly controls an output voltage is also proposed. A voltage for turning on the light-emitting diodes is higher than that for a general. silicon diode. For example in a GaN type diode represented by blue one, an electric current starts to flow at about 2.5 V, and about 3.5 to 4.5 V in the full-emission lighting, and the brightness of the light-emitting diodes can be controlled comparatively stably without being influenced by the performance of the light-emitting diodes or a noise generated on the light-emitting diodes even in the deep dimmer control. However, a forward voltage of the light-emitting diodes has a negative temperature characteristic, and the forward voltage is decreased due to self heat generation at the time of applying an electric current to the light-emitting diodes, and the electric current increases. As a result, heat generation becomes large, and thus thermo-runaway might occur. The forward voltage of the light-emitting diodes greatly varies, and even if an output from the lighting unit is adjusted, output currents vary due to a individual difference of respective light-emitting diodes.
The above-mentioned problem arises not only in the semiconductor light emitting modules such as the light-emitting diodes but also in the power supply units which light a light source such as an organic EL light source or an inorganic EL light source developed in recent years, and this problem still remains unsolved.
The power supply unit and the lighting unit having the power supply unit which can realize the stable dimmer control are already proposed as a prior application in International Application No. PCT/JP2009/055871 filed on Mar. 24, 2009 by the same assignee. In the power supply unit of the International Application, first and second reference signals, which change according to a dimmer rate of a dimmer signal, namely, a dimmer level, are prepared. In the almost full-emission lighting control area where the dimmer rate is small, the first reference signal is selected, and light-emitting diodes are controlled with constant current with reference to the first signal. In a lighting control area where the dimmer rate is large and the brightness is reduced, the second reference signal is selected, and the light-emitting diodes are controlled with constant voltage with reference to the second reference signal. Since the first and second reference signals are selected so that the light emission from the light-emitting diodes is controlled, the stable dimmer control can be realized.
An object of the present invention is to provide a power supply unit and a lighting unit which can realize stable dimmer control.
According to a first aspect of the present invention, there is provided a power supply unit comprising:
a semiconductor light emitting moudule;
a power supply part which lights the semiconductor light emitting moudule in accordance with one of load characteristics, wherein the load characteristics have inclination lines extending from a base point, whose inclinations are changed depending on dimmer rates, respectively;
a voltage detecting part which detects a load voltage applied to the semiconductor light emitting moudule to generate a voltage detection signal;
a current detecting part which detects an electric current supplied to the semiconductor light emitting moudule to generate a current detection signal; and
a control part which controls the power supply part depending on the voltage detect-ion signal, the current detection signal, and a dimmer signal having one of the dimmer rates, to adjust a power supplied to the semiconductor light emitting moudule from the power supply part and the power is set depending on one of the inclination lines of the load characteristic which is set in accordance with the dimmer rate.
According to a second aspect of the present invention, there is provided the power supply unit according to the first aspect, wherein the inclination lines of the load characteristics are radially extended from the base point DIa (constant value) depending on the dimmer rates, and each of the load characteristics is substantially expressed by a function formula of {I+k(V)=Dia}, where I represents the electric current flowing in the semiconductor light emitting moudule, V represents the load voltage applied to the semiconductor light emitting moudule, and k represents one of the dimmer rates.
According to a third aspect of the present invention, there is provided the power supply unit according to the first or second aspect, wherein the control part controls the power supply part depending on a constant current characteristic, a constant voltage characteristic, and a combination of a constant current characteristic and a constant voltage characteristic, if the dimmer rate is smaller than a predetermined rate, the current detection signal is weighted and thus a tendency of a constant current characteristic is strengthened, and if the dimmer rate is not smaller than the predetermined rate, the voltage detection signal is weighted and thus a tendency of a constant voltage characteristic is strengthened.
According to a fourth aspect of the present invention, there is provided a lighting unit comprising:
the power supply unit according to any one of the first to third aspects; and
a unit main body having the power supply unit.
A power supply unit and a lighting unit according to embodiments of the present invention will be described below with reference to the drawings.
First, an operation principle of a dimmer function for dimming light-emitting diodes in the power supply unit of the present invention will be simply described.
The light-emitting diodes as semiconductor light emitting modules, as is well known, has a V-I characteristic shown in
If the light-emitting diodes are controlled so that a constant current flows in the light-emitting diodes, in a range where an increase of the electric current ΔI (ΔI/ΔV) with respect to an increase of the voltage ΔV is small, a voltage varies with respect to a certain electric current within an operation area B11. On the contrary, in a range where the increase of the electric current ΔI (ΔI/ΔV) with respect to the increase of the voltage ΔV is large, the voltage varies with respect to a certain electric current within an operation area B12. The operation area B12 where the voltage varies becomes smaller than the operation area B11 where the voltage varies. Therefore, when a constant current control mode is applied in an operation area where a dimmer level is shallow and a comparatively large current flows in the light-emitting diodes, namely, in a control area where a dimmer rate is small and the comparatively large current flows in the light-emitting diodes and the light-emitting diodes emit light at comparatively high brightness, variation of dimmer brightness can be decreased. As a result, in the dimmer control of the light-emitting diodes, a fluctuation in light output can be effectively suppressed.
On the other hand, when the light-emitting diodes are controlled by a constant voltage, in the range where the increase of the electric current ΔI (ΔI/ΔV) with respect to the increase of the voltage ΔV is large, the electric current varies with respect to a certain constant voltage within an operation area B21. On the contrary, in the range where the increase of the electric current ΔI (ΔI/ΔV) with respect to the increase of the voltage ΔV is small, the electric current varies with respect to a certain constant voltage within an operation area B22. The variation operation area B22 can be smaller than the variation operation area B21. Therefore, the constant voltage control mode is applied in an operation area where the dimmer level is deep and a comparatively small current flows in the light-emitting diodes, namely, in a control area where the dimmer rate is large and the comparatively small current flows in the light-emitting diodes and the light-emitting diodes emit light at comparatively low brightness, variation of the dimmer brightness can be decreased. As a result, in the dimmer control of the light-emitting diodes, a fluctuation in light output from the light-emitting diodes can be effectively suppressed.
According to the above characteristic, in the power supply unit of the present invention, in the operation area where the dimmer rate is small (the dimmer level is shallow) and a large electric current flows in the light-emitting diodes, the light-emitting diodes are controlled in the constant current control mode, and in the area where the dimmer rate is large (the dimmer level is deep) and a small electric current flows in the light-emitting diodes, the light-emitting diodes are controlled in the constant voltage control mode. As the power supply unit which realizes such an operation, the power supply unit is operated by load characteristic (V-I characteristic) which varies according to the dimmer rate k1, k2, . . . k7 of the dimmer signal k as shown in
The load characteristics with respect to the dimmer rates k1, k2, . . . k7 can be expressed by a linear function of I=DIa . . . k(V). That is, the above formula is I+k(V)=DIa . . . (1), and a relationship holds as follows. The load, namely, a value, which is obtained by adding a current detected value in the light-emitting diodes and a load voltage detected value and an operated result of a dimmer signal voltage, becomes a constant current value DIa. The power supply unit according to first to third embodiments described below is constituted so that this relational expression holds.
From another viewpoint, the load characteristics with respect to the dimmer rates k1, k2, . . . k7 can be expressed by a linear function of V=DVb−k(I). That is, this formula is V+k(I)=DVb . . . (2), and a relationship holds as follows. The load, namely, the value, which is obtained by adding the operated result of the dimmer signal voltage to the load voltage detected value and the current detected value in the light-emitting diodes, becomes a constant voltage value DVb.
The power supply unit according to the embodiments of the present invention based on such an operation principle is realized as follows.
The lighting unit to which the power supply unit of the present invention is applied will be simply described. In
A space in the middle between the partition members 1a and 1b of the unit main body 1 is allocated to a power supply chamber 3. In the power supply chamber 3, a wiring substrate 3a is arranged on the partition member 1a. The wiring substrate 3a is provided with electronic parts composing the power supply unit for driving the plurality of LEDs 2a. The power supply unit and the plurality of LEDs 2a are connected by a lead wire 4.
An upper space between the partition member 1b of the unit main body 1 and an upper opening is allocated to a power supply terminal chamber 5. In the power supply terminal chamber 5, a power supply terminal table 6 is provided to the partition member 1b. The power supply terminal table 6 is provided in order to supply an AC power of a commercial power to the power supply unit in the power supply chamber 3. The power supply terminal table 6 has a box 6a made of insulating synthetic resin, and an outlet 6b to be a power supply cable terminal section is provided to both surfaces of the box 6a. An outlet 6c to be a feed cable terminal section and a release button 6d which disconnects a power supply line and a feed line are provided to the box 6a.
In
As the DC power supply, a circuit which rectifies and smoothens an AC voltage from the commercial power supply is used, but a power factor improving converter which improves a power factor may be used.
The smoothening capacitor 13 is connected to a DC-DC converter 10. The DC-DC converter 10 is composed of a switching transformer 14 as a flyback transformer and a switching transistor 15 which switches an output voltage from the smoothening capacitor 13. The switching transformer 14 has a primary winding 14a and a secondary winding 14b which is magnetically coupled with the primary winding 14a. A primary side of the switching transformer 14 is connected to the smoothening capacitor 13 via the switching transistor 15. That is, both ends of the smoothening capacitor 13 are connected to the primary winding 14a of the switching transformer 14 and a series circuit of the switching transistor 15.
The DC-DC converter 10 includes a rectifying smoothening circuit 18 composed of a diode 16 which rectifies a voltage generated on the secondary side of the switching transformer 14 and a smoothening capacitor 17 for smoothening a rectified voltage, and a control circuit 30. The secondary winding 14b of the switching transformer 14 is connected to the rectifying smoothening circuit 18 composed of the diode 16 of polarity shown in the drawing and the smoothening capacitor 17. The rectifying smoothening circuit 18 as well as the switching transistor 15 and the switching transformer 14 composes a converter circuit which generates and output a DC output. In the converter circuit, an alternating voltage obtained by switching (on/off) the DC voltage by the switching transistor 15 is applied to the primary winding 14a of the switching transformer 14. An alternating output is generated on the secondary winding 14b of the switching transformer 14. This alternating output is rectified by the diode 16, and the rectified output is smoothened by the smoothening capacitor 17 so as to be output as the DC output.
In addition, in the embodiment described above, a power supply part which control the brightness of the light emitting diodes is composed of the AC power supply 11, the full-wave rectifying circuit 12, the smoothing capacitor 13, the DC-DC converter 10, and the rectifying smoothening circuit 18.
In the first embodiment, the flyback converter is used as the DC-DC converter 10. Instead of the flyback converter, when the voltage on the load side is lower than the power supply voltage, a step-down converter may be used as the DC-DC converter 10. When the voltage on the load side is higher than the power supply voltage, a step-up converter or a step-up/step-down converter may be used as the DC-DC converter 10. The converter 10 may be realized by any circuit configuration as long as an output can be varied according to a state of the load or an external signal.
A plurality of light-emitting diodes 19 to 21 (in this example, three) is connected in series as semiconductor light emitting modules of the load to both the ends of the smoothening capacitor 17 of the rectifying smoothening circuit 18 composing the DC-DC converter 10. The light-emitting diodes 19 to 21 correspond to the LED 2a shown in
The series circuit of the light-emitting diodes 19 to 21 is connected to a current detecting circuit 22 in series. The current detecting circuit 22 is composed of a resistor 221 as an impedance element, and detects an electric current (load current) flowing in the light-emitting diodes 19 to 21 so as to output a current detected signal I. The series circuit of the light-emitting diodes 19 to 21 is connected to a load voltage detecting circuit 23 in parallel. The load voltage detecting circuit 23 is composed of a series circuit of resistors 231 and 232 as impedance elements, and detects a load voltage to be applied to the light-emitting diodes 19 to 21, so as to output the load voltage V as a load voltage signal.
The current detected signal I and the load voltage signal V are input into the current detecting circuit 22 and the load voltage detecting circuit 23, respectively, and a signal control section 24 which outputs a control signal according to these input signals is connected thereto. The signal control section 24 is composed of a multiplier 26, an adder 27, and a comparator 28. The load voltage signal V from the load voltage detecting circuit 23 and a dimmer signal k from a dimmer signal generator 31 are input into the multiplier 26. The multiplier 26 outputs a multiplied signal obtained by multiplying the load voltage signal V by the dimmer signal k. Details of the multiplier 26 will be described later. The adder 27 adds the multiplied signal output from the multiplier 26 to the current detected signal I from the current detecting circuit 22 so as to generate an added output DIa. The comparator 28 compares the output DIa from the adder 27 with a constant reference value 29, so as to output a compared result as a control signal.
The dimmer signal generator 31 generates the dimmer signal k based on an external dimmer operation signal. The dimmer signal k is generated as a PWM signal which is selected according to a dimmer rate (dimmer level) and has a different duty ratio. The duty ratio is defined as a value obtained by dividing the pulse width of the PWM signal by a pulse cycle as is well known. The external dimmer operation signal is input as a signal for specifying the dimmer level, namely, the dimmer rate into the dimmer signal generator 31. The dimmer signal generator 31 has a table where the dimmer rate and the duty ratio have a correlation with each other, this table is seen as to the dimmer rate specified by the dimmer operation signal so that a duty ratio is determined, and a PWM signal having this duty ratio is output from the dimmer signal generator 31 to the multiplier 26.
The dimmer signal k is varied within a duty ratio range of 0 to 100% in such a manner that an upper limit of dimmer corresponding to the smallest dimmer rate k1 in the full-emission state is set at the duty ratio of 0%, and the brightness is the lowest and a lower limit of dimmer corresponding to the largest dimmer rate k7 is set at the duty ratio of 100%. The dimmer signal k whose duty ratio is 0% corresponds to a low-level DC signal, and the dimmer signal k whose duty ratio is 100% corresponds to a high-level DC voltage. The dimmer signal is generated at the duty ratio depending on the dimmer rates k1, k2, . . . k7 (k1<k2, . . . <k7).
In the multiplier 26, as shown in
In the multiplier 26 constituted in such a manner, the transistor 261 is turned on/off by the dimmer signal k. Therefore, the capacitor 263 is charged with the output voltage (load voltage V) from the resistor 232 of the load voltage detecting circuit 23 according to the duty ratio of the dimmer signal k, and the charged voltage is generated as an output voltage from the multiplier 26. More concretely, the PWM signal of the dimmer signal k is set to a dimmer upper limit (full-emission state) at the duty ratio of 0%, and set to a dimmer lower limit at the duty ratio of 100%. In the circuit shown in
In the circuit shown in
The control circuit 30 has a memory (not shown), and a table in the memory is referred to by the output voltage of the comparator 28. A switching waveform of the switching control signal, namely, the duty ratio of the PWM control signal is selected, and the switching control signal having the selected duty ratio is applied to the gate of the switching transistor 15.
The dimmer operation in the power supply circuit shown in
The load characteristics corresponding to the dimmer rates k1, k2, . . . k7 of the power supply unit and the V-I characteristic A of the light-emitting diodes 19 to 21 establish a relationship shown in
At first, when the dimmer signal generator 31 outputs the dimmer signal k of the upper limit (all-optic) at the duty ratio of 0% based on an external dimmer operation signal, a load characteristic corresponding to the dimmer rate k1 shown in
In the lighting control according to the constant current characteristic, when the control circuit 30 turns on/off the switching transistor 15, the switching of the switching transformer 14 is driven. When the switching transistor 15 is turned on, an electric current flows in the primary winding 14a of the switching transformer 14 and energy is accumulated, and when the switching transistor 15 is turned off, the energy accumulated on the primary winding 14a is discharged through the secondary winding 14b. The discharge of the energy generates a DC output in the rectifying smoothening circuit 18, and the light-emitting diodes 19 to 21 are lighted by the DC output.
When the dimmer rate of the dimmer signal k is changed and the duty ratio is set large, any one of the load characteristics corresponding to the dimmer rates k2 to k6 shown in
Thereafter, the dimmer signal generator 31 outputs the dimmer signal k of the lower limit at the duty ratio of 100%, the load characteristic corresponding to the dimmer rate k7 shown in
In this setting, duty ratio of 100% is given to the dimmer signal k, and the transistor 261 of the multiplier 26 is maintained off in the control section 24. Therefore, the entire output voltage (load voltage V) from the resistor 232 of the load voltage detecting circuit 23 is applied to the capacitor 263, and the capacitor 263 is charged. A voltage with a large charging value is generated as the output voltage of the multiplier 26 from the capacitor 263. As a result, the output value DIa from the adder 27 is influenced only by the output voltage (load voltage V) of the load voltage detecting circuit 23, and the control circuit 30 generates a switching signal so as to control the light-emitting diodes 19 to 21 based on the output signal from the comparator 28. As a result, the control circuit 30 controls the light-emitting diodes 19 to 21 under the constant voltage control such that the voltages to be applied to the light-emitting diodes 19 to 21 are approximately constant. That is, since the k (V) component for determining DIa are mostly present and the I component is approximately 0 in the formula (1), the lighting of the light-emitting diodes 19 to 21 is controlled by the constant voltage characteristic.
In the above control system, when the dimmer signal k of the dimmer signal generator 31 is change within the range of the dimmer rates k1, k2, . . . k7, in the operation area where the dimmer rate is small, the lighting of the light-emitting diodes 19 to 21 is controlled by the constant current characteristic according to the load characteristics corresponding to the dimmer rates k1, k2, . . . k7. As the dimmer rate becomes larger, the tendency for the constant voltage characteristic becomes gradually stronger than the constant current characteristic, so that the lighting of the light-emitting diodes 19 to 21 is controlled. The transition of the dimmer control system by means of the constant current characteristic and the constant voltage characteristic can be performed only by changing the dimmer rate (dimmer level) of the dimmer signal k, and thus the stable dimmer control can be realized within the wide range of the operation area of the small dimmer rate to the operation area of the large dimmer rate.
Since the dimmer control does not use a control system for directly controlling a pulse width, flicker can be prevented from occurring on the light outputs from the light-emitting diodes in the light supply unit unlike the power supply unit which makes the dimmer control according to a pulse width disclosed in JP-A 2003-157986 (KOKAI). Further, since a switching element is not necessary for the dimmer control, the circuit configuration of the power supply unit is simplified so that the number of parts can be reduced, miniaturization and lower price of the power supply unit can be realized, and deterioration of the circuit efficiency can be suppressed.
As described above with reference to
If the number of the connected light-emitting diodes composed of the semiconductor light emitting modules as a load is increased or decreased or different types of light-emitting diodes are used, the electric current flowing in the light-emitting diodes is changed so that the light output (brightness) occasionally changes. It is assumed that a certain light-emitting diode has a V-I characteristic A shown in
In the power supply unit according to the second embodiment, the constant light outputs (brightness) can be always maintained at the set dimmer rate regardless of the changes in the number and the type of the connected light-emitting diodes.
In the unit shown in
As a result, in a state that all the light-emitting diodes 19 to 21 are connected, an intersection between the V-I characteristic A of the light-emitting diodes and a voltage axis (V) is at a point DVb as shown in
Therefore, also in the power supply unit according to the second embodiment, the similar effect to that of the first embodiment can be obtained, and even when the V-I characteristic changes due to the change in the number and the type of connected light-emitting diodes, the electric current flowing in the light-emitting diodes can be corrected to be constant, so that the constant light output can be always obtained.
Also in the power supply unit according to a third embodiment, similarly to the second embodiment, the constant light output (brightness) can be obtained according to the dimmer rate regardless of the change in the number and the type of connected light-emitting diodes.
In this power supply unit, as shown in
More concretely, in the state that all the light-emitting diodes 19 to 21 are connected, as shown in
As described above, the load characteristics corresponding to the dimmer rates k1, k2, . . . k7 can be expressed by a liner function of V=DVb−k(I). A relationship: V+k(I)DVb(2) holds, and the load, namely, a value, which is obtained by adding an operated result of the dimmer signal voltage to the load voltage detected value and the current detected value in the light-emitting diodes, becomes a constant voltage value DVb.
The relationship in which the value, which is obtained by adding the operated result of the dimmer signal voltage to the load voltage detected value and the current detected value in the light-emitting diodes becomes the constant voltage value DVb can be realized by a circuit shown in
Also in the circuit shown in
Therefore, also in the power supply unit according to the fourth embodiment, the similar effect to that of the first embodiment can be obtained, and even if the V-I characteristic changes due to the change in the number and type of connected light-emitting diodes, the electric current flowing in the light-emitting diodes can be corrected into a constant state, so that the constant light output can be always obtained.
The present invention is not limited to the above embodiment, and at the stage of practicing the present invention, the present invention can be modified variously within a range where the gist is not changed. The above embodiments describe the example of the analog circuit, but control systems using a microcomputer and a digital process can be adopted. Further, the changing-over of the dimmer rate includes continuous dimmer and gradual dimmer, and phase control in which a conducting period of a power supply voltage is controlled and an effective voltage to the load is varied may be adopted. A dedicated signal line is used for the dimmer signal, or a power-line signal which is obtained by superimposing a dimmer signal on a power supply electric wire can be used.
In the embodiments described above, the power supply unit which lights the light emitting diodes 19 to 21 is comprised of the AC power supply 11, the full-wave rectifying circuit 12, the smoothening capacitor 13, the DC-DC converter 10, and the rectifying smoothening circuit 18, and the signal control section 24 is independent from the power supply unit. However, the signal control section 24 may be incorporated in the power supply unit, or a part of the the power supply unit and the signal control section 24 may be formed in a single circuit module.
The above embodiments describe the power supply unit and the lighting unit for lighting the semiconductor light emitting modules such as the light-emitting diodes. In the embodiments, a category of the semiconductor light emitting modules may include EL light source devices such as an organic EL light source and an inorganic EL light source. Thus, the technical concept of the invention can be applied to the power supply unit and the lighting unit for the EL light source devices such as an organic EL light source and an inorganic EL light source.
In addition, in the power supply unit shown in
According to the present invention, the power supply unit and the lighting unit which can realize stable dimmer control can be provided.
According to the embodiments of the present invention, there can be provided the power supply unit and the lighting unit, which select the load characteristic having the tendency of the constant current characteristic or the load characteristic having the tendency of the constant voltage characteristic according to the dimmer rate so as to realize the dimmer control. In the power supply unit and the lighting unit, smooth transition between the control having the strong tendency for the constant current characteristic and the control having the strong tendency for the constant voltage control characteristic can be realized according to the dimmer rate.
There can be provided the power supply unit and the lighting unit, which change over the dimmer control system smoothly from the constant current characteristic into the constant voltage characteristic or from the constant voltage characteristic into the constant current characteristic only by means of the change in the dimmer rate so as to enable the stable dimmer control over a wide rage covering from the small dimmer rate area to the large dimmer rate area.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
---|---|---|---|
2008-232619 | Sep 2008 | JP | national |
2009-191891 | Aug 2009 | JP | national |