JP2017107777A - Lighting device and luminaire having the same - Google Patents

Abstract

A lighting device capable of realizing downsizing and reduction in manufacturing cost while performing stable dimming from a high dimming level to a low dimming level by switching between a switching operation and a linear operation, and a lighting device therefor Provided lighting equipment provided. A lighting device 2 uses a switching element 54 to convert an input DC voltage into a DC voltage to be applied to a light emitting element 3, and a switching operation according to a dimming level of the switching element 54. A first control circuit 60 that performs the linear operation according to the dimming level, and the first control circuit 60 and the second control circuit when the dimming level is equal to or higher than a predetermined value. A switching unit 81 that operates only the first control circuit 60 out of 70 and operates only the second control circuit 70 out of the first control circuit 60 and the second control circuit 70 when the dimming level is less than a predetermined value; I have. [Selection] Figure 1

Description

  The present invention relates to a lighting device for a light emitting element such as a light emitting diode (LED) and a lighting fixture including the same.

  Conventionally, an LED lighting apparatus is known as an example of a lighting fixture that performs lighting and dimming of LED lighting using a light emitting diode (see, for example, Patent Document 1). The LED drive circuit used in this LED lighting device performs light control by increasing or decreasing the current value output to the light emitting element that operates at a constant current. As a driving method of the DC / DC converter configured in the LED lighting device, there are a switching operation (PWM control) and a linear operation (also called a linear driving method or a DC driving method).

  In the switching operation, the average current value output from the DC / DC converter is varied by varying the pulse width of the dimming signal. The advantage of this method is that the LED lighting device can be operated with energy saving because the on / off operation by the switching element is repeated. On the other hand, the disadvantage is that if the on-time Ton, which is a period during which the switching element is on, becomes too short, the switching element cannot perform normal on / off operation, and the light emitting element cannot be normally lit. It is. Further, there is a problem that noise is generated by switching the switching element at high speed.

  In the linear operation, the voltage applied to the light emitting element is converted by a variable resistor or the like to generate a constant voltage, and the current flowing through the light emitting element is varied. The advantage of this method is circuit simplification and cost reduction. On the other hand, the disadvantage is that a power loss proportional to the current flowing through the variable resistor occurs.

  Therefore, in this LED drive circuit, the first control unit performs a switching operation with a high dimming level, and the second control unit performs a linear operation with a low dimming level.

Japanese Unexamined Patent Publication No. 2014-7078

  However, in the LED drive circuit described in Patent Document 1, the first control unit performs a switching operation at a high dimming level, and the second control unit performs a linear operation at a low dimming level. That is, in this LED drive circuit, the switching element that performs the switching operation and the switching element that performs the linear operation are controlled using different switching elements. For this reason, in this LED drive circuit, an increase in the number of parts causes an increase in running cost due to an increase in manufacturing cost, an increase in size, and an increase in power energy.

  The present invention has been made to solve such a problem, and by switching between a switching operation and a linear operation, while performing stable dimming from a high dimming level to a low dimming level, downsizing and It is an object of the present invention to provide a lighting device that can realize a reduction in manufacturing cost and a lighting fixture including the lighting device.

  In order to solve the above-described problem, one aspect of a lighting device according to the present invention is a lighting device that allows a current to flow through a light-emitting element in accordance with a dimming level that is instructed from the outside. A DC / DC converter that converts an input DC voltage into a DC voltage to be applied to the light emitting element, and the switching element is controlled so that the switching element performs a switching operation according to the dimming level. A first control circuit that controls the switching element so that the switching element performs a linear operation according to the dimming level, and the first control circuit when the dimming level is a predetermined value or more. Of the control circuit and the second control circuit, only the first control circuit is operated, and when the dimming level is less than a predetermined value, the first control circuit and the second control circuit And a switching circuit for operating only said second control circuit of the two control circuits.

  According to the present invention, it is possible to realize downsizing and reduction in manufacturing cost while performing stable dimming from a high dimming level to a low dimming level by switching between a switching operation and a linear operation.

It is a circuit diagram which shows the structure of the lighting device in Embodiment 1, and a lighting fixture provided with the same. FIG. 3 is a circuit diagram illustrating a configuration of a control unit and a DC / DC converter of the lighting device in the first embodiment. (A) is a timing chart which shows operation | movement of the switching element of the lighting device in Embodiment 1. FIG. (B) is a timing chart showing the operation of the inductor of the lighting device in the first embodiment. (C) is a timing chart showing the operation of the diode of the lighting device in the first embodiment. (A) is a timing diagram which shows the relationship between the voltage of the switching element of the lighting device in Embodiment 1, and a light control level. (B) is a timing chart showing the relationship between the current of the switching element of the lighting device and the dimming level in the first embodiment. (A) is a timing chart showing the relationship between the voltage of the switching element of the lighting device and the dimming level in Modification 1 of Embodiment 1. FIG. (B) is a timing chart showing the relationship between the current of the switching element of the lighting device and the dimming level in Modification 1 of Embodiment 1. FIG. (A) is a timing diagram which shows the relationship between the voltage of the switching element of the lighting device in the modification 2 of Embodiment 1, and a light control level. (B) is a timing chart showing the relationship between the current of the switching element of the lighting device and the dimming level in Modification 2 of Embodiment 1. FIG. FIG. 6 is a circuit diagram illustrating a partial configuration of a lighting device according to Embodiment 2. 6 is a graph showing the operation of the lighting device in the second embodiment. FIG. 6 is a circuit diagram illustrating a configuration of a control unit and a DC / DC converter of a lighting device in a third embodiment. 14 is an external view of a lighting fixture in Embodiment 4. FIG. 14 is an external view of a lighting fixture in Embodiment 4. FIG. 14 is an external view of a lighting fixture in Embodiment 4. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each of the embodiments described below shows a preferred specific example of the present invention. Therefore, the numerical values, shapes, materials, components, arrangement positions and connection forms of the components shown in the following embodiments are merely examples, and are not intended to limit the present invention. Therefore, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims showing the highest concept of the present invention are described as optional constituent elements.

  Each figure is a schematic diagram and is not necessarily illustrated strictly. Moreover, in each figure, the same code | symbol is attached | subjected to the substantially same structure, The overlapping description is abbreviate | omitted or simplified.

(Embodiment 1)
[Constitution]
Hereinafter, the structure of the lighting device according to Embodiment 1 of the present invention will be described with reference to FIG.

  1 is a circuit diagram illustrating a configuration of a lighting device and a lighting fixture including the lighting device according to Embodiment 1. FIG.

  As illustrated in FIG. 1, the lighting fixture 1 includes a lighting device 2 and a light emitting element 3.

  The lighting device 2 supplies a current to the light emitting element 3 in accordance with a dimming level (light output) instructed from the outside. The lighting device 2 includes a DC power supply circuit 4, a step-down converter 5 (an example of a DC / DC converter), a control circuit 6, a switching circuit 8, and a dimming circuit 9. Note that the dimming level is a variable for adjusting the brightness of the light-emitting element 3, and the brightness of the light-emitting element 3 can be increased as the numerical value increases (the maximum value is 100%). The dimming level may be expressed as a dimming rate, a dimming ratio, or the like, for example.

  The DC power supply circuit 4 generates a DC voltage that is input to the step-down converter 5. The DC power supply circuit 4 includes an AC power supply 41, a diode bridge 42, and a capacitor 43.

  The AC power supply 41 is a power supply that outputs an AC voltage to the diode bridge 42, and is a system power supply such as a commercial AC power supply.

  The diode bridge 42 and the capacitor 43 are a rectifying / smoothing circuit that rectifies and smoothes an AC voltage supplied from an AC power source 41 such as a commercial AC power source, and converts the DC voltage into a DC voltage. The DC voltage is input to the step-down converter 5. An AC power supply 41 is connected between the input terminals of the diode bridge 42. A smoothing capacitor 43 is connected between the output terminals of the diode bridge 42.

  The step-down converter 5 is a circuit that converts the DC voltage input from the rectifying and smoothing circuit into a predetermined DC voltage using the switching element 54 and applies it to the light emitting element 3. The step-down converter 5 constitutes a chopper circuit that chops the input DC voltage. The step-down converter 5 includes a diode 51, an inductor 52, a capacitor 53, and a switching element 54.

  The diode 51 regenerates energy stored in the inductor 52. The anode electrode of the diode 51 is connected to the terminal on one end side of the inductor 52 and the drain electrode of the switching element 54. The cathode electrode of the diode 51 is connected to the output terminal on the high potential side of the rectifying / smoothing circuit including the diode bridge 42 and the capacitor 43, the terminal on one end side of the capacitor 53, and the anode electrode of the light emitting element 3. .

  A terminal on one end side of the inductor 52 is also connected to the drain electrode of the switching element 54. The terminal on the other end side of the inductor 52 is connected to the terminal on the other end side of the capacitor 53 and the cathode electrode of the light emitting element 3.

  The capacitor 53 is connected in parallel with the light emitting element 3. Capacitor 53 smoothes the output voltage and output current generated in the lighting circuit composed of diode 51, inductor 52, and capacitor 53.

  The switching element 54 is an element such as a MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor). In the present embodiment, the switching element 54 is an n-channel MOSFET. A terminal on one end side of the resistor 11 and the control circuit 6 are connected to the source electrode of the switching element 54. A control circuit 6 is connected to the gate electrode of the switching element 54. The switching element 54 turns on and off between the diode 51 and the inductor 52 and the resistor 11 based on the control signal output from the control circuit 6.

  The resistor 11 is a current detection resistor that is connected in series with the switching element 54 and detects a current flowing through the switching element 54. The terminal on the other end side of the resistor 11 is connected to the ground. This resistor 11 detects the output current of the switching element 54. The detected current value is input to the control circuit 6.

  The dimming circuit 9 is a circuit that inputs a dimming signal to the control circuit 6 via the switching circuit 8. The dimming circuit 9 receives a signal from the outside, for example, by a remote controller (not shown), and calculates a dimming signal so that the light emitting element 3 can output a desired light. That is, the dimming circuit 9 determines the dimming signal according to the dimming level.

  The dimming signal is a signal that specifies the dimming level of the light emitting element 3, and is, for example, a DC voltage or a PWM signal. In the present embodiment, the dimming signal is described as being a PWM signal. The PWM signal is a signal having a rectangular wave voltage waveform for driving the switching element 54 by PWM control.

  The switching circuit 8 includes a switching unit 81 and a switch 82. The input side of the switching unit 81 is connected to the dimming circuit 9. The output side of the switching unit 81 is connected to the switch 82. The switching unit 81 switches the switch 82 to a first control circuit 60 described later or a second control circuit 70 described later according to the dimming level.

  The switching circuit 8 inputs the dimming signal output from the dimming circuit 9 to the control circuit 6. The switching circuit 8 operates only the first control circuit 60 out of the first control circuit 60 and the second control circuit 70 when the dimming level is equal to or higher than a predetermined value, and first when the dimming level is lower than the predetermined value. Of the control circuit 60 and the second control circuit 70, only the second control circuit 70 is operated. That is, the switching unit 81 determines whether the on-time Ton corresponding to the dimming level is equal to or longer than the predetermined time, thereby switching the switch 82 and only one of the first control circuit 60 and the second control circuit 70. To work. In the present embodiment, the switching circuit 8 has a low-pass filter for DC voltage, and smoothes and outputs the dimming signal (PWM signal) input from the dimming circuit 9.

  The control circuit 6 supplies the dimming signal output from the dimming circuit 9 via the switching circuit 8 to the gate electrode of the switching element 54. The control circuit 6 includes a first control circuit 60 and a second control circuit 70.

  FIG. 2 is a circuit diagram showing a configuration of a control unit and a step-down converter of the lighting device in the first embodiment.

  As shown in FIG. 2, the first control circuit 60 of the control circuit 6 performs switching so that the current flowing through the light emitting element 3 changes according to the dimming signal input from the dimming circuit 9 via the switching circuit 8. The on / off or conduction resistance of the element 54 is controlled. The first control circuit 60 controls the switching element 54 so that the switching element 54 performs a switching operation according to the dimming level. The first control circuit 60 includes a pulse power supply 61 and a resistor 62.

  The pulse power supply 61 is connected to the gate electrode of the switching element 54 via the resistor 62. The pulse power supply 61 changes the on time Ton or the off time Toff or changes the frequency of the dimming signal input from the dimming circuit 9 via the switching circuit 8 according to the dimming signal. A rectangular wave-shaped dimming signal is output to the gate electrode of the switching element 54.

  Specifically, the dimming signal output from the dimming circuit 9 is smoothed by the switching circuit 8, and the smoothed signal (DC voltage) is input to the pulse power supply 61. In response to the dimming signal input from the dimming circuit 9, the pulse power supply 61 emits a dimming signal to the gate electrode of the switching element 54 so that the current (drain current) flowing through the light emitting element 3 is constant. Adjust the width. Here, when the width of the dimming signal is changed, the ratio (on duty) of the on time Ton when the switching element 54 is repeatedly turned on and off changes. That is, the on / off timing of the switching element 54 is determined by the dimming signal.

  The second control circuit 70 controls the switching element 54 so that the switching element 54 performs a linear operation according to the dimming level. The second control circuit 70 includes an operational amplifier 71, resistors 72 and 73, and a capacitor 74.

  The voltage smoothed by the switching circuit 8 is input to the non-inverting input terminal of the operational amplifier 71, and the voltage applied to the resistor 73 is input to the inverting input terminal. The output terminal of the operational amplifier 71 is connected to the gate electrode of the switching element 54 via the resistor 72. Further, the output terminal of the operational amplifier 71 and the non-inverting input terminal are connected via a capacitor 74. That is, the operational amplifier 71 constitutes a voltage follower in which the resistor 72, the switching element 54, and the resistor 73 are connected to the feedback path (path from the source electrode of the switching element 54 to the control circuit 6). In other words, when the dimming signal (DC voltage) is input to the non-inverting input terminal, the operational amplifier 71 drives the switching element 54 so that the non-inverting input terminal and the inverting input terminal are short-circuited (conduction resistance). Control).

  The light emitting element 3 is an element to which a direct current is input from the lighting circuit, and emits light by a direct current voltage supplied from the step-down converter 5. The light emitting element 3 is, for example, an LED or an organic EL (Electro-Luminescence). In addition, the light emitting element 3 may be comprised from several LED connected in series. The number of light emitting elements 3 is not limited to one and may be two or more.

[Operation]
Next, the operation of the lighting device 2 according to Embodiment 1 of the present invention will be described.

  FIG. 3A is a timing chart showing the operation of the switching element of the lighting device in the first embodiment. FIG. 3B is a timing chart showing the operation of the inductor of the lighting device in the first embodiment. FIG. 3C is a timing chart showing the operation of the diode of the lighting device in the first embodiment.

  FIG. 3A shows the relationship between the voltage applied to the switching element 54 and time. FIG. 3B shows the relationship between the current flowing through the inductor 52 and time. FIG. 3C shows the relationship between the voltage applied to the diode 51 and time. The thick solid line shown in FIG. 3 is a voltage applied to the switching element 54 in FIG. 3A, a current flowing through the inductor 52 in FIG. 3B, and input to the step-down converter 5 in FIG. This shows the voltage waveform. 3 indicates the output current output from the inductor 52 in FIG. 3B and the output voltage output from the diode 51 in FIG. 3C. The output current output from the inductor 52 is obtained by a value that is ½ of the peak value of the current shown in the triangular wave shape. The output voltage output from the diode 51 can be expressed by the following expression using the ON time Ton, one period T, and the input voltage Ei that is the peak value of the voltage of the diode 51.

  Diode output voltage = (Ton / T) × Ei

  As shown in FIG. 2 and FIG. 3A, the pulse power supply 61 inputs the dimming signal input from the dimming circuit 9 through the switching circuit 8 to the step-down converter 5. Here, an on / off operation performed once by the switching element 54 is defined as one cycle. In FIG. 3A, the dimming signal includes an on-time Ton indicating a duty ratio and an off-time Toff. For example, a dimming signal having a duty ratio of 50% is generated. Here, the duty ratio is a ratio of the on-time Ton occupying one cycle in the dimming signal.

  Next, the operation of the lighting device 2 when the first control circuit 60 of the control circuit 6 performs a switching operation will be described.

  As shown in FIG. 2 and FIG. 3A, the switching operation of the first control circuit 60 is when the on-time Ton is longer than a predetermined time (driving in a high luminance region). When the dimming signal generated by the dimming circuit 9 is input via the switching circuit 8, the first control circuit 60 pulses the current input to the step-down converter 5. That is, the switching element 54 is repeatedly turned on and off by the input dimming signal. When the switching element 54 is in the on-time Ton, a current that has been changed to direct current by the AC power supply 41 by the DC power supply circuit 4 flows to the light emitting element 3. On the other hand, when the switching element 54 is off time Toff, the energy accumulated in the inductor 52 becomes a regenerative current and flows to the light emitting element 3 through the diode 51. Such an operation generates a voltage having a waveform as shown in FIG.

  As shown in FIGS. 1 and 3B, the current flowing through the inductor 52 has a waveform corresponding to the waveform of the dimming signal shown in FIG. The current flowing through the inductor 52 includes a rising period in which the height gradually increases when the switching element 54 is on-time Ton, and a falling period in which the height gradually decreases when the switching element 54 is off-time Toff. Consists of. Specifically, when the switching element 54 is on-time Ton, a current flows through the light emitting element 3, the inductor 52, the switching element 54 and the resistor 11, and the current flowing through the inductor 52 increases. On the other hand, when the switching element 54 has the off time Toff, the energy stored in the inductor 52 is released through the diode 51, so that a current flows through the inductor 52, the diode 51, and the light emitting element 3. Then, the current flowing through the inductor 52 gradually decreases. In this way, a triangular wave current having a constant period flows through the inductor 52 by switching of the switching element 54.

  As shown in FIGS. 1 and 3C, the current flowing through the diode 51 is due to the release of energy stored in the inductor 52 when the switching element 54 is off. A current flows through the inductor 52, the diode 51, and the light emitting element 3. On the other hand, when the switching element 54 is on-time Ton, a current flows through the light emitting element 3, the inductor 52, the switching element 54 and the resistor 11, and no current flows through the diode 51. In this way, the light emitting element 3 continues to emit light even when the off time Toff is applied, by supplying a constant output current to the light emitting element 3 by smoothing the capacitor 53. By such an operation, a voltage having a waveform as shown in FIG.

  FIG. 4A is a timing chart showing the relationship between the voltage of the switching element of the lighting device and the dimming level in the first embodiment. FIG. 4B is a timing chart showing the relationship between the current of the switching element of the lighting device and the dimming level in the first embodiment.

  FIG. 4A is a graph showing the voltage applied to the gate electrode of the switching element 54 and the dimming level. FIG. 4B is a graph showing the current applied to the gate electrode of the switching element 54 and the dimming level. In FIG. 4, the switching operation is performed when the on-time Ton is equal to or longer than the predetermined time, and the linear operation is performed when the on-time Ton is less than the predetermined time. Further, in FIG. 4, (A) in FIG. 4 corresponds to (B) in FIG. For example, the voltage per cycle in FIG. 4A corresponds to the current in FIG. 4B, and the dimming level is 5% and the on-time Ton is a predetermined time. doing.

  As shown in FIGS. 1 and 4, the switching unit 81 determines whether the on time Ton is equal to or longer than a predetermined time. The predetermined time means a time during which the switching element 54 becomes difficult to operate stably. This predetermined time depends on the performance of the switching element 54. The switching circuit 8 operates the first control circuit 60 when the on-time Ton is equal to or longer than the predetermined time.

  As shown in FIGS. 4A and 4B, the pulse power supply 61 of the first control circuit 60 changes the ON time Ton in the ON / OFF repetition of the switching element 54 according to the dimming level. Thus, the switching element 54 is controlled. In other words, the pulse power supply 61 of the first control circuit 60 sets the same period for turning on and off the switching element 54. Then, the dimming level (brightness) of the light emitting element 3 is adjusted by changing the duty ratio of the switching element 54 by changing the ratio of the ON time Ton of the switching element 54 per cycle.

  Specifically, the first control circuit 60 shortens the on-time Ton of the switching element 54 when the dimming level is lowered in the state where the switching elements 54 are turned on and off at the same period. The off time Toff of 54 is lengthened. In this case, the duty ratio decreases. In the light emitting element 3, the ratio of the on time Ton is shortened and the ratio of the off time Toff is increased per cycle, and the light control level is low. Further, when increasing the dimming level of the light emitting element 3, the first control circuit 60 increases the ratio of the on time Ton of the switching element 54 and shortens the ratio of the off time Toff of the switching element 54 per cycle. To increase the duty ratio.

  Here, when the ratio of the on-time Ton of the switching element 54 per cycle is extremely short (the width of the on-time Ton is extremely narrow), the off-time Toff of the switching element 54 per cycle is extremely long (off The width of the time Toff becomes extremely wide). In this case, since the on time Ton is extremely short, the switching element 54 is not stably turned on, the circuit operation becomes unstable, and the light emitting element 3 does not light up. Therefore, in this case, the second control circuit 70 performs a linear operation.

  Next, the operation of the lighting device 2 when the second control circuit 70 of the control circuit 6 performs a linear operation will be described.

  As shown in FIG. 4B, the switching unit 81 switches the switch 82 from the first control circuit 60 to the second control circuit 70 (switches from the switching operation to the linear operation) when the on-time Ton is less than the predetermined time. ). At this time, the output current of the first control circuit 60 and the output current of the second control circuit 70 are made to coincide with each other. That is, the same output current when switching from the first control circuit 60 to the second control circuit 70 is input to the gate electrode of the switching element 54. Even when switching from the second control circuit 70 to the first control circuit 60, the output current of the first control circuit 60 and the output current of the second control circuit 70 are made to coincide with each other.

  When the dimming signal from the dimming circuit 9 smoothed by the switching circuit 8 is input, the second control circuit 70 outputs a voltage to the switching element 54 so as to obtain a gate voltage corresponding to the dimming signal. To do. That is, the second control circuit 70 performs control so that the output current of the step-down converter 5 is constant by linear control. In the lighting device 2, dimming of the light emitting element 3 is stabilized by switching the switching element 54 to the second control circuit 70 when the on time Ton is less than the predetermined time.

[Action / Effect]
Next, the function and effect of the lighting device 2 according to the first embodiment will be described.

  As described above, the lighting device 2 according to Embodiment 1 is the lighting device 2 that causes a current to flow through the light emitting element 3 in accordance with a dimming level instructed from the outside. The lighting device 2 includes a step-down converter 5, a first control circuit 60, a second control circuit 70, and a switching circuit 8. The step-down converter 5 includes a switching element 54, and converts the input DC voltage into a DC voltage applied to the light emitting element 3 using the switching element 54. The first control circuit 60 controls the switching element 54 so that the switching element 54 performs a switching operation according to the dimming level. Further, the second control circuit 70 controls the switching element 54 so that the switching element 54 performs a linear operation according to the dimming level. The switching circuit 8 operates only the first control circuit 60 among the first control circuit 60 and the second control circuit 70 when the dimming level is equal to or higher than a predetermined value, and when the dimming level is lower than the predetermined value. Of the first control circuit 60 and the second control circuit 70, only the second control circuit 70 is operated.

  According to this configuration, the switching circuit 8 switches to the first control circuit 60 of the control circuit 6 that performs the switching operation when the dimming level is equal to or higher than the predetermined value, and performs the linear operation when the dimming level is lower than the predetermined value. The control circuit 6 is switched to the second control circuit 70 to be performed. For this reason, in this lighting device, the first control circuit 60 and the second control circuit 70 are 1 in comparison with the case where the switching element that performs the switching operation and the switching element that performs the linear operation use different members. Since one switching element 54 is controlled, the number of parts is reduced. Moreover, since the control circuit 6 can be reduced in size compared with the case where the different switching elements 54 are provided, the lighting device 2 can be reduced in size.

  In the lighting device 2, if the dimming level is equal to or higher than a predetermined value, the first control circuit 60 performs a switching operation, and the power consumption of the light emitting element 3 can be suppressed. In the lighting device 2, if the dimming level is less than a predetermined value, the second control circuit 70 performs a linear operation, and a stable lighting operation can be performed even at a low dimming level. In other words, the lighting device 2 can be driven by a switching operation with low power consumption in the high luminance region and can be driven by a linear operation in which the voltage is stable in the low luminance region.

  Further, in the lighting device 2, when switching to one of the first control circuit 60 and the second control circuit 70, an equal output current is output from the first control circuit 60 and the second control circuit 70 to the switching element 54. Input to the gate electrode. For this reason, even when the switching operation and the linear operation are switched, the light control of the light emitting element 3 is stabilized.

  Therefore, the lighting device 1 including the lighting device 2 and the lighting device 2 can be downsized and manufactured while performing stable light control from a high light control level to a low light control level by switching between a switching operation and a linear operation. Cost reduction can be realized.

  Furthermore, in the lighting device 2 according to the first embodiment, the first control circuit 60 controls the switching element 54 by changing the on-time Ton when the switching element 54 is repeatedly turned on and off according to the dimming level. . Then, the switching circuit 8 operates only one of the first control circuit 60 and the second control circuit 70 by determining whether the ON time Ton corresponding to the dimming level is equal to or longer than a predetermined time.

  According to this configuration, the first control circuit 60 changes the duty ratio by changing the on-time Ton of the switching element 54 in the state where the periods in which the switching element 54 is turned on and off are the same. For this reason, in this lighting device 2, if the on-time Ton is equal to or longer than a predetermined time, the switching operation is performed by the first control circuit 60, and the power consumption of the light emitting element 3 can be suppressed. In the lighting device 2, if the on-time Ton is less than the predetermined time, the linear operation is performed by the second control circuit 70, and a stable lighting operation can be performed even at a low dimming level. In other words, the lighting device 2 can be driven by a switching operation with low power consumption in the high luminance region and can be driven by a linear operation in which the voltage is stable in the low luminance region.

(Modification 1 of Embodiment 1)
[Constitution]
Next, the structure of the lighting device 2 in the first modification of the first embodiment will be described with reference to FIG.

  The configuration and operational effects of the first modification of the first embodiment are the same as those of the first embodiment. For this reason, about the same structure and effect as Embodiment 1 and the modification 1 of Embodiment 1, the same code | symbol is attached | subjected and the detailed description regarding a structure and an effect is abbreviate | omitted.

  FIG. 5A is a timing chart showing the relationship between the voltage of the switching element of the lighting device and the dimming level in Modification 1 of Embodiment 1. FIG. FIG. 5B is a timing chart showing the relationship between the current of the light emitting element of the lighting device and the dimming level in the first modification of the first embodiment.

  FIG. 5A is a graph showing the voltage applied to the gate electrode of the switching element 54 and the dimming level. FIG. 5B is a graph showing the current applied to the gate electrode of the switching element 54 and the dimming level. In FIG. 5, the switching operation is performed when the ON / OFF repetition frequency of the switching element 54 is equal to or higher than the predetermined frequency, and the linear operation is performed when the ON / OFF repetition frequency of the switching element 54 is less than the predetermined frequency. In FIG. 5, (A) in FIG. 5 corresponds to (B) in FIG. For example, the voltage per cycle in FIG. 5A corresponds to the current in FIG. 5B, and the dimming level corresponds to 5% and the predetermined frequency.

  As shown in FIGS. 1 and 5, the switching circuit 8 determines whether the repetition frequency corresponding to the dimming level is equal to or higher than a predetermined frequency. The switching circuit 8 operates the first control circuit 60 when the repetition frequency is equal to or higher than a predetermined frequency. The first control circuit 60 controls the switching element 54 by changing the ON / OFF repetition frequency of the switching element 54 according to the dimming level. In other words, the pulse power source 61 of the first control circuit 60 changes the period for turning on and off the switching element 54 by changing the off time Toff while keeping the on time Ton of the switching element 54 constant. A signal is output to the switching element 54. The pulse power supply 61 adjusts the dimming level of the light emitting element 3 by changing the duty ratio.

  Specifically, when lowering the dimming level of the light emitting element 3, the first control circuit 60 keeps the on time Ton of the switching element 54 constant, and sets the ratio of the off time Toff per cycle of the switching element 54. increase. In this case, the duty ratio per cycle in which the switching element 54 is turned on / off decreases. Even if the on-time Ton is constant, if the ratio of the off-time Toff per cycle increases, the repetition frequency becomes low. That is, the repetition frequency decreases in inverse proportion to the increase in the off time Toff.

  Further, when the dimming level of the light emitting element 3 is increased, when the on time Ton of the switching element 54 is constant, the ratio of the off time Toff per cycle in which the switching element 54 is turned on / off is decreased. On the other hand, when the dimming level of the light emitting element 3 is lowered, the ratio of the on time Ton per cycle in which the switching element 54 is turned on / off is decreased when the off time Toff of the switching element 54 is constant.

  In the case where the dimming level of the light emitting element 3 changes, even when the off time Toff of the switching element 54 is constant, the ratio of the on time Ton per cycle in which the switching element 54 turns on and off is changed. Good.

  In the lighting device 2, even when the off time Toff of the switching element 54 operating in the first control circuit 60 is extremely shortened, the switching element 54 cannot be stably turned off, and the light emitting element 3 The lit state continues and energy saving cannot be achieved.

  When the repetition frequency becomes less than the predetermined frequency, the switching circuit 8 switches from the first control circuit 60 to the second control circuit 70 (switches from the switching operation to the linear operation). At this time, the output current of the first control circuit 60 and the output current of the second control circuit 70 are made to coincide with each other. That is, the same output current when switching from the first control circuit 60 to the second control circuit 70 is input to the gate electrode of the switching element 54. Even when switching from the second control circuit 70 to the first control circuit 60, the output current of the first control circuit 60 and the output current of the second control circuit 70 are made to coincide with each other.

  The switching circuit 8 operates the second control circuit 70 when the repetition frequency is less than the predetermined frequency. The second control circuit 70 performs a linear operation according to the dimming level.

[Action / Effect]
Next, the effect of the lighting device 2 in Modification 1 of Embodiment 1 will be described.

  As described above, in the lighting device 2 according to the first modification of the first embodiment, the first control circuit 60 changes the ON / OFF repetition frequency of the switching element 54 in accordance with the dimming level, thereby switching the switching element 54. 54 is controlled. The switching circuit 8 operates only one of the first control circuit 60 and the second control circuit 70 by determining whether the repetition frequency corresponding to the dimming level is equal to or higher than a predetermined frequency. The switching circuit 8 operates the second control circuit 70 when the repetition frequency corresponding to the dimming level is lower than a predetermined frequency higher than the human audible range (20 Hz to 20 kHz).

  According to this configuration, the switching circuit 8 can perform a switching operation and a linear operation according to the repetition frequency. The switching circuit 8 operates the second control circuit 70 to perform a linear operation before the repetition frequency becomes lower than a predetermined frequency higher than the human audible range. For this reason, in this lighting device 2, even if the on / off repetition frequency of the switching element 54 decreases, the repetition frequency does not reach the human audible range. As a result, the lighting device 2 can perform dimming without causing discomfort to the person. In this embodiment, it is preferable to set the repetition frequency to 30 kHz. However, if the repetition frequency is higher than the human audible range, the repetition frequency may be higher than 30 kHz, and the repetition frequency is lower than 30 kHz. It is good also as a frequency.

  In the lighting device 2, the step-down converter 5 may be driven in a current discontinuous mode (Discontinuous Current Mode), the off time Toff (also referred to as Toff width) may be constant, and the Ton width may be varied.

(Modification 2 of Embodiment 1)
[Constitution]
Next, the lighting device 2 according to the second modification of the first embodiment will be described with reference to FIG.

  The configuration and operational effects of the second modification of the first embodiment are the same as those of the first embodiment. For this reason, about the same structure and effect as Embodiment 1 and the modification 2 of Embodiment 1, the same code | symbol is attached | subjected and the detailed description regarding a structure and an effect is abbreviate | omitted.

  FIG. 6A is a timing chart showing the relationship between the voltage of the switching element of the lighting device and the dimming level in Modification 2 of Embodiment 1. FIG. FIG. 6B is a timing chart showing the relationship between the current of the switching element of the lighting device and the dimming level in the second modification of the first embodiment.

  6A is a graph showing the voltage applied to the gate electrode of the switching element 54 and the dimming level. FIG. 6B is a graph showing the current applied to the gate electrode of the switching element 54 and the dimming level. In FIG. 6, the switching operation is performed when the duty ratio indicating the dimming signal is equal to or greater than a predetermined value, and the linear operation is performed when the duty ratio indicating the dimming signal is less than the predetermined value. In FIG. 6, (A) in FIG. 6 corresponds to (B) in FIG. For example, the voltage per cycle in FIG. 6A corresponds to the current in FIG. 6B. For example, the dimming level is 5% and the duty ratio is a predetermined value. Corresponds.

  As shown in FIGS. 1 and 6, the switching circuit 8 determines whether the duty ratio indicating the dimming signal is greater than or less than a predetermined value. The switching circuit 8 operates the first control circuit 60 when the duty ratio indicating the dimming signal is equal to or greater than a predetermined value. The first control circuit 60 controls the switching element 54 by changing the on time Ton and the off time Toff of the switching element 54 in a state where the duty ratio indicated by the dimming signal is constant. That is, the pulse power supply 61 of the first control circuit 60 outputs a dimming signal in which the on time Ton and the off time Toff are changed according to the dimming signal input from the dimming circuit 9 to the switching element 54. The pulse power supply 61 adjusts the dimming level of the light emitting element 3 by changing the duty ratio indicating the dimming signal.

  Specifically, the first control circuit 60 decreases the on time Ton and the off time Toff of the switching element 54 when the light control level of the light emitting element 3 is lowered. For example, the rate at which the on-time Ton and the off-time Toff are decreased is smaller than the rate at which the on-time Ton decreases per cycle than the rate at which the on-time Ton decreases per cycle. In this case, the off time Toff becomes longer than the on time Ton as the dimming level decreases. That is, the duty ratio per cycle decreases. In other words, the first control circuit 60 decreases the length of the dimming signal cycle (hereinafter, the dimming signal cycle is referred to as a “PWM cycle”) (the dimming signal frequency increases) and the duty cycle. The ratio decreases. On the other hand, when increasing the dimming level of the light emitting element 3, the first control circuit 60 increases the rate of increasing the on time Ton and the off time Toff at a rate where the on time Ton and the off time Toff are different. . Specifically, when the first control circuit 60 increases the dimming level of the light emitting element 3, the off time Toff per cycle is greater than the rate at which the on time Ton increases per cycle. The rate of increase is reduced.

  When the duty ratio becomes less than a predetermined value, the switching circuit 8 switches from the first control circuit 60 to the second control circuit 70 (switches from the switching operation to the linear operation). At this time, the output current of the first control circuit 60 and the output current of the second control circuit 70 are made to coincide with each other. That is, the same output current when switching from the first control circuit 60 to the second control circuit 70 is input to the gate electrode of the switching element 54. Even when switching from the second control circuit 70 to the first control circuit 60, the output current of the first control circuit 60 and the output current of the second control circuit 70 are made to coincide with each other.

  The switching circuit 8 operates the second control circuit 70 when the duty ratio indicated by the dimming signal is less than a predetermined value. The second control circuit 70 performs a linear operation according to the dimming level.

[Action / Effect]
Next, the effect of the lighting device 2 in the second modification of the first embodiment will be described.

  In the lighting device 2 according to the second modification of the first embodiment, the dimming level instructed from the outside is specified by the dimming signal indicating the duty ratio at which the switching element 54 is turned on at regular intervals. Then, the switching circuit 8 operates only one of the first control circuit 60 and the second control circuit 70 by determining whether the duty ratio indicating the dimming signal is greater than or less than a predetermined value.

  According to this configuration, in the lighting device 2, if the duty ratio is equal to or greater than the predetermined value, the first control circuit 60 performs the switching operation, and the power consumption of the light emitting element 3 can be suppressed. In the lighting device 2, if the duty ratio indicating the dimming signal is less than a predetermined value, the linear operation is performed by the second control circuit 70, and a stable lighting operation can be performed even at a low dimming level. In other words, the lighting device 2 can be driven by a switching operation with low power consumption in the high luminance region and can be driven by a linear operation in which the voltage is stable in the low luminance region.

(Embodiment 2)
Next, the lighting device 2 according to the second embodiment will be described.

  The second embodiment is different from the first embodiment in that a comparator 83 (an example of the switching circuit 8) is used as the switching unit 81 of the first embodiment. The second embodiment is the same as the first embodiment in other respects. For this reason, about the same structure as Embodiment 1 and Embodiment 2, the same code | symbol is attached | subjected and the detailed description regarding a structure is abbreviate | omitted.

  FIG. 7 is a circuit diagram illustrating a partial configuration of the lighting device according to the second embodiment.

  As shown in FIG. 7, the dimming circuit 9 is connected to the non-inverting input terminal of the comparator 83. The inverting input terminal of the comparator 83 is connected between the switching element 54 and the current detection resistor 11.

  The switching circuit 8 includes a comparator 83 and a switch 82. The detection current flowing from the step-down converter 5 is input to the non-inverting input terminal of the comparator 83 when the switching element 54 is on. A predetermined current value is input to the inverting input terminal of the comparator 83. The switch 82 is configured to switch on and off by the output current from the comparator 83. For example, when the predetermined current value is lower than the current flowing through the light emitting element 3 (when the inverting input terminal is higher than the non-inverting input terminal), the output of the comparator 83 is in the HIGH state, and the switch 82 is in the first state. The control circuit 60 is switched. On the other hand, when the predetermined current value is higher than the current flowing through the light emitting element 3 (when the inverting input terminal is lower than the non-inverting input terminal), the output of the comparator 83 is in the LOW state, and the switch 82 is in the second state. The control circuit 70 is switched.

  When the comparator 83 operates the first control circuit 60, the current detection resistor 11 detects the value of the current flowing through the light emitting element 3 and feeds back the current (detected current) to the comparator 83. The comparator 83 compares the detected current value with a predetermined current value that is a current value when dimming. Further, the comparator 83 determines whether the current flowing through the light emitting element 3 corresponding to the dimming level is greater than or less than a predetermined current value. If the detected current value is equal to or greater than the predetermined current value, the comparator 83 switches to the first control circuit 60 and causes the light emitting element 3 to emit light by the switching operation. On the other hand, if it is less than the detected current value, the comparator 83 switches to the second control circuit 70 and causes the light emitting element 3 to emit light by a linear operation.

  FIG. 8 is a timing chart showing the operation of the lighting device in the second embodiment.

  The graph of FIG. 8 is a graph showing the detected current and the dimming level. In FIG. 8, a switching operation is performed when the current flowing through the light emitting element 3 is equal to or greater than a predetermined current value, and a linear operation is performed when the current flowing through the light emitting element 3 is less than the predetermined current value. FIG. 8 shows a predetermined current value when the dimming level is 5%, for example.

  The switching circuit 8 switches from the first control circuit 60 to the second control circuit 70 when the current becomes less than the predetermined current value (switching from the switching operation to the linear operation). At this time, the output current of the first control circuit 60 and the output current of the second control circuit 70 are made to coincide with each other. That is, the same output current when switching from the first control circuit 60 to the second control circuit 70 is input to the gate electrode of the switching element 54. Even when switching from the second control circuit 70 to the first control circuit 60, the output current of the first control circuit 60 and the output current of the second control circuit 70 are made to coincide with each other.

  The comparator 83 operates the second control circuit 70 when the current flowing through the light emitting element 3 corresponding to the dimming level is less than a predetermined current value. The second control circuit 70 performs a linear operation according to the dimming level.

[Action / Effect]
Next, the effect of the lighting device 2 in this Embodiment 2 is demonstrated.

  In the lighting device 2 according to the second embodiment, the comparator 83 determines whether the current flowing through the light emitting element 3 is equal to or greater than a predetermined current value corresponding to the dimming level. Only one of the control circuits 70 is operated.

  According to this configuration, the current detection resistor 11 detects (detected current) this current value flowing through the light emitting element 3 and feeds back the detected current to the comparator 83. The comparator 83 compares this detected current with a predetermined current value. Then, the comparator 83 determines whether the current flowing through the light emitting element 3 corresponding to the dimming level is greater than or less than a predetermined current value. If the detected current value is equal to or greater than the predetermined current value, the comparator 83 switches to the first control circuit 60 and performs a switching operation. On the other hand, if the detected current value is less than the predetermined current value, the comparator 83 switches to the second control circuit 70 and performs a linear operation. As a result, the lighting device 2 can be driven by a switching operation with low power consumption in the high luminance region, and can be driven by a linear operation in which the voltage is stable in the low luminance region.

  The operational effects of the second embodiment are the same operational effects as the first embodiment. For this reason, about the same effect as Embodiment 1 and Embodiment 2, the same code | symbol is attached | subjected and the detailed description regarding an effect is abbreviate | omitted.

(Embodiment 3)
[Constitution]
Next, the lighting device 2 according to the third embodiment will be described.

  The third embodiment is different from the first embodiment in that a transformer Tr is used instead of the inductor 52 of the first embodiment. The third embodiment is the same as the first embodiment in other respects. For this reason, about the same structure as Embodiment 1 and Embodiment 3, the same code | symbol is attached | subjected and the detailed description regarding a structure is abbreviate | omitted.

  FIG. 9 is a circuit diagram illustrating a partial configuration of the lighting device according to the third embodiment.

  As shown in FIG. 9, it is a circuit diagram showing the configuration of the control circuit 6 and the step-down converter 5 of the lighting device 2 in the third embodiment.

  A primary winding T1 of a transformer Tr and a switching element 54 are connected in series between output terminals of a rectifying / smoothing circuit including a diode bridge 42 and a capacitor 43. A capacitor 53 is connected between both ends of the secondary winding T2 of the transformer Tr, and a diode 51 is connected between one end of the secondary winding T2 and the capacitor 53. The polarity of the secondary winding T2 is opposite to the polarity of the primary winding T1. That is, the lighting device 2 uses a flyback method.

  By repeatedly turning on and off the switching element 54, the voltage Vin supplied to the primary winding T1 is converted into a high-frequency voltage. The converted high frequency voltage is transferred to the secondary winding T2. That is, by repeatedly turning on and off the switching element 54, an AC voltage corresponding to the turn ratio between the primary winding T1 and the secondary winding T2 is generated in the secondary winding T2 of the transformer Tr. The AC voltage generated in the secondary winding T2 is rectified by the diode 51, and the capacitor 53 is smoothed to generate the DC voltage output voltage Vo. The output voltage Vo flows to the light emitting element 3.

[Action / Effect]
Next, the effect of the lighting device 2 in this Embodiment 3 is demonstrated.

  In addition, the lighting device 2 according to Embodiment 1 includes a DC power supply circuit 4 that generates a DC voltage input to the step-down converter 5. When operating the second control circuit 70, the switching circuit 8 controls the DC power supply circuit 4 to reduce the DC voltage input to the step-down converter 5.

  According to this configuration, the DC power supply circuit 4 on the input side of the step-down converter 5 makes the input voltage and the output voltage of the step-down converter 5 close to each other when the switching circuit 8 is linearly operated by the second control circuit 70. Control. For this reason, in this lighting device 2, by making the input voltage and the output voltage of the step-down converter 5 close to each other, the power loss W between the input voltage and the output voltage can be reduced, and high efficiency is realized. can do.

  For example, in the step-down converter 5, when the input voltage Vin is 100 (V) and the output voltage Vout is 60 (V), even if the input voltage Vin is 65 (V), the output voltage Vout is 60 (V). Remains. In this case, a calculation formula for obtaining the power loss W can be expressed by the following formula using the input voltage Vin, the output voltage Vout, and the current of the step-down converter 5.

  W = (Vin−Vout) I

  For this reason, if it calculates using the calculation formula of this power loss W, the power loss W will be 40 (W) to 5 (W). That is, in this lighting device 2, the power loss W can be reduced to 1/8. As a result, in the lighting device 2, energy saving can be realized in the second control circuit 70 that performs the linear operation.

(Embodiment 4)
[Constitution]
Next, the lighting fixture in this Embodiment 4 is demonstrated.

  In the fourth embodiment, a lighting fixture 1 including the lighting device 2 according to the first to third embodiments and the first and second modifications of the first embodiment will be described with reference to FIGS.

  10-12 is an external view of the lighting fixture in Embodiment 4. FIG.

  The luminaire 1 shown in FIG. 10 is a downlight, and the luminaire 1 shown in FIGS. 11 and 12 is a spotlight. The luminaire 1 includes a circuit box 101, a lamp body 102, and a wiring 103. The circuit box 101 houses the lighting device 2. The lamp body 102 houses the light emitting element 3. The wiring 103 is electrically connected to the circuit box 101 and the lamp body 102.

  The operational effects of the fourth embodiment are the same as those of the first embodiment. For this reason, in Embodiment 4, the detailed description regarding an effect is abbreviate | omitted.

(Other variations)
As mentioned above, although the lighting device 2 and the lighting fixture 1 which concern on this invention were demonstrated based on Embodiment 1-4 and the modifications 1 and 2 of Embodiment 1, this invention is these Embodiment 1 ~. 4 and modifications 1 and 2 of the first embodiment are not limited.

  For example, in this lighting device 2, a plurality of light-emitting elements 3 may be connected in series and in parallel, or a plurality of light-emitting elements 3 connected to be modularized (apparatus or systemized), or modularized. May be combined.

  In the lighting device 2, a step-up / step-down converter, a PFC (Power Factor Correction) type flyback converter, or the like may be combined on the input side of the step-down converter 5.

  In addition, Embodiments 1 to 4 and Modifications 1 and 2 of Embodiment 1 can be obtained by making various modifications conceived by those skilled in the art, and Embodiments 1 to 3 are within the scope of the present invention. 4 and an embodiment realized by arbitrarily combining the components and functions in Modifications 1 and 2 of Embodiment 1 are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 Lighting fixture 2 Lighting device 3 Light emitting element 4 DC power supply circuit 5 DC / DC converter 8 Switching circuit 54 Switching element 60 1st control circuit 70 2nd control circuit Ton ON time

Claims (8)

A lighting device that allows a current to flow through a light emitting element according to a dimming level instructed from the outside,
A DC / DC converter having a switching element and converting the input DC voltage to a DC voltage to be applied to the light emitting element using the switching element;
A first control circuit for controlling the switching element so that the switching element performs a switching operation according to the dimming level;
A second control circuit for controlling the switching element so that the switching element performs a linear operation according to the dimming level;
When the dimming level is equal to or higher than a predetermined value, only the first control circuit is operated among the first control circuit and the second control circuit, and when the dimming level is lower than the predetermined value, the first control circuit And a switching circuit that operates only the second control circuit of the second control circuit. The first control circuit controls the switching element by changing an ON time in repeated ON / OFF of the switching element according to the dimming level,
The switching circuit operates only one of the first control circuit and the second control circuit by determining whether the ON time corresponding to the dimming level is equal to or longer than a predetermined time. Lighting device. The first control circuit controls the switching element by changing a repetition frequency of on / off of the switching element according to the dimming level,
The switching circuit operates only one of the first control circuit and the second control circuit by determining whether the repetition frequency corresponding to the dimming level is equal to or higher than a predetermined frequency. Lighting device. The lighting device according to claim 3, wherein the switching circuit operates the second control circuit when the repetition frequency corresponding to the dimming level is lower than a predetermined frequency higher than a human audible range. The switching circuit operates only one of the first control circuit and the second control circuit by determining whether the current flowing through the light emitting element is greater than or less than a predetermined current value corresponding to the dimming level. The lighting device according to claim 1. The dimming level instructed from the outside is specified by a dimming signal indicating a duty ratio at which the switching element is turned on at regular intervals,
2. The lighting according to claim 1, wherein the switching circuit operates only one of the first control circuit and the second control circuit by determining whether the duty ratio indicating the dimming signal is greater than or less than a predetermined value. apparatus. Furthermore, a DC power supply circuit that generates the DC voltage input to the DC / DC converter is provided,
The said switching circuit reduces the said DC voltage input into the said DC / DC converter by controlling the said DC power supply circuit, when operating the said 2nd control circuit. The lighting device described in 1. A light emitting element;
A lighting fixture comprising: the lighting device according to claim 1, wherein a current is applied to the light emitting element.

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