Control circuit for lighting device

Abstract

To provide a control circuit for a lighting device which is applicable to a wide range of power supply voltages and reduces a voltage loss.SOLUTION: One end of a second current path 2 to which LEDs 21-25, a Tr 27 and an R 28 are connected and one end of a third current path 3 in which a Tr 33 is provided are connected to a positive electrode terminal 11. The LEDs 21-25 are divided into continuously lighted elements LEDs 21-23 which are continuously lighted and appropriately lighted elements LEDs 24 and 25 which are appropriately lighted. FETs 51 and 52 are connected in parallel to the appropriately lighted elements LEDs 24 and 25, and gates of the FETs 51 and 52 are connected with the third current path 3. A base of the Tr 33 is connected with the second current path 2, and one end of a seventh current path 7 is connected with the third current path 3. On the seventh current path 7, an R71, a Tr 72 and an R73 are connected in series and bases of the Tr 72 and the Tr 27 are connected. There are provided a current path to which the bases of the Tr 72 and the Tr 27 are connected and an eighth current path to which the seventh current path 7 is connected.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control circuit that is capable of handling a wide range of power supply voltages in a lighting device that uses a DC voltage as a power supply and is specialized for a system that supplies DC. [Background technology]

[0002] With the recent advances in LED (light-emitting diode) technology, a variety of LED lighting devices are being used, which has led to demands for LED lighting devices to be smaller, more efficient, and more affordable.

[0003] Among these, the power source for LED lighting devices that use DC voltage is not limited to one source, but rather, due to the growing awareness of energy conservation in recent years, the power source is diverse, including renewable energy such as solar power generation and various types of battery power.

[0004] The difference in DC voltage output from these power supplies was addressed by using a power conversion unit, but configurations using a power conversion unit had the problem of loss due to conversion, reducing efficiency.

[0005] Furthermore, most power conversion units are designed to maintain a constant output by switching at a specific frequency, which has the major disadvantage of generating electromagnetic noise due to the switching operation.

[0006] On the other hand, in a configuration that does not use a power conversion unit, it is possible to keep the current flowing through the LED constant for a certain range of DC voltage, but even a slight fluctuation in DC voltage outside that range will cause the current flowing through the LED to change significantly, which will result in a decrease in the quality of the light output from the LED lighting and a shortened lifespan of the LED.

[0007] Furthermore, if the DC voltage drops below a certain value, the forward (direction) voltage VF required to light the LED will be insufficient, causing the LED to go out. This has led to the problem of not being able to accommodate a wide range of power supply voltages.

[0008] Therefore, there is a need for a control circuit for an LED lighting device that can accommodate a wide range of power supply voltages without using a power conversion unit.Patent documents 1 and 2 disclose a configuration that keeps the current flowing through the LED constant while accommodating a wide range of power supply voltages by controlling the on / off of the LED in accordance with increases and decreases in the power supply voltage. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-179279 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-46228 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0010] However, in the configurations of Patent Documents 1 and 2, since the LEDs are connected in series, there is a risk that a large current will flow if a voltage even slightly larger than the forward voltage of the LED is applied, and to prevent this risk, it is necessary to provide a limiting resistor in series with the LED, because LEDs have the property of passing a large current when a voltage is applied to them.

[0011] This limiting resistor will be explained in detail below. According to standard Ohm's law, if V = 300V, I = 500mA, there are 90 LEDs, and each LED's VF (= voltage drop) = 3V, a 60Ω resistor is required as the LED limiting resistor. This 60Ω resistor is then placed in series with the circuit in which the LEDs are connected in series. In this case, the voltage generated across the 60Ω resistor is 500mA x 60Ω = 30V, and this 30V becomes a voltage loss (which can be converted into power loss: 500mA x 30V = 15W).

[0012] Therefore, in order to solve the above-mentioned problems, the present invention aims to provide a control circuit for a lighting device that can accommodate a wide range of power supply voltages without using a power conversion unit and has little voltage loss. [Means for solving the problem]

[0013] The invention of claim 1 is as follows: 1. A control circuit for a lighting device, comprising: A positive terminal to which the positive electrode of a DC power supply is connected is connected to one end of a second current path in which a plurality of semiconductor light-emitting elements LED, a first semiconductor control element Tr, and a first resistor R arranged in the same polarity direction are connected in series, and one end of a third current path in which a second semiconductor control element Tr is provided, The plurality of semiconductor light-emitting elements LED are divided into constant lighting elements that are constantly lit and appropriate lighting elements that are appropriately lit according to the voltage of the DC power supply, A first semiconductor control element FET is connected in parallel to each of the lighting elements; a gate of the first semiconductor control element FET connected to the third current path at a position where the potential is higher than that of the second semiconductor control element Tr; The base of the second semiconductor control element Tr is connected to the second current path 2 by a sixth current path, one end of a seventh current path is connected to the third current path at a position where the potential is higher than that of the connection point of the gate of the first semiconductor control element FET; A second resistor R, a third semiconductor control element Tr, and a third resistor R are connected in series on the seventh current path 7 in descending order of potential, an eighth current path having an 81st current path connecting a base of the third semiconductor control element Tr and a base of the first semiconductor control element Tr; and an 82nd current path connecting a position on the seventh current path between the second resistor R and the third semiconductor control element Tr and the 81st current path; The other ends of the second current path, the third current path, and the seventh current path are connected to a negative terminal to which a negative electrode of a DC power supply is connected, forming a control circuit for a lighting device.

[0014] The invention of claim 2 is as follows: a second semiconductor control element FET is further provided at a position on the second current path between the plurality of semiconductor light emitting elements LED and the first semiconductor control element Tr; In the control circuit for a lighting device according to claim 1, the gate of the second semiconductor control element FET is connected to the third current path at a position where the potential is higher than that of the second semiconductor control element Tr.

[0015] The invention of claim 3 is as follows: A fourth resistor R is further provided on the sixth current path, a ninth current path having one end connected to the second current path at a position between the constantly lighting element and the occasional lighting element, and the other end connected to the sixth current path at a position between the base of the second semiconductor control element Tr and the fourth resistor R; In the control circuit for a lighting device according to claim 1, a fifth resistor R is provided on the ninth current path.

[0016] The invention of claim 4 is as follows: a fourth semiconductor control element Tr is further provided on the third current path at a position where the potential is higher than that of the second semiconductor control element Tr; a fourth current path provided with a sixth resistor R and a semiconductor control element ZD in order of increasing potential; The control circuit for a lighting device according to claim 1, wherein the base of the fourth semiconductor control element is connected to the fourth current path at a position between the sixth resistor R and the semiconductor control element ZD. [Effects of the Invention]

[0017] By applying and using the control circuit according to the present invention to a lighting device, voltage loss can be reduced and energy saving effects can be enhanced.

[0018] Furthermore, the circuit can be constructed using only inexpensive components such as resistors, transistors, and diodes, without using expensive components such as a microcomputer with a control IC, thereby reducing costs.

[0019] Furthermore, by applying and using the control circuit according to claim 2 to a lighting device, even if an overvoltage is applied to the circuit, the excessive voltage can be absorbed, and since the excessive voltage can be absorbed, the circuit can be maintained in a constant power state.

[0020] Furthermore, by applying and using the control circuit according to claim 3 to a lighting device, when the DC power distribution voltage applied to the circuit increases, the current flowing through the semiconductor light-emitting element LED in the circuit can be reduced.

[0021] Furthermore, by applying and using the control circuit according to claim 4 to a lighting device, it is possible to drive a larger number of loads and to supply a more stable voltage to the so-called current mirror circuit within the circuit than to a circuit that supplies or generates voltage by connecting a resistor and a Zener diode in series, which is commonly used. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a configuration diagram of a control circuit for a lighting device according to a first embodiment of the present invention. [Figure 2] 4 is an explanatory diagram illustrating the operation of a part of a control circuit for the lighting device according to the first embodiment of the present invention. FIG. [Figure 3] 4 is an explanatory diagram illustrating the operation of a part of a control circuit for the lighting device according to the first embodiment of the present invention. FIG. [Figure 4]FIG. 10 is a configuration diagram of a control circuit for a lighting device according to another embodiment of the present invention. [Figure 5] FIG. 10 is a configuration diagram of a control circuit for a lighting device according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0023] (Embodiment Example 1) First, the configuration of a control circuit A for a lighting device according to the first embodiment of the present invention will be described with reference to FIG.

[0024] <Configuration of control circuit A for lighting device> As shown in Fig. 1, a positive terminal 11 to which the positive electrode of a DC power supply is connected is connected to one end of a second current path 2 in which semiconductor light-emitting elements LED21-LED25 arranged in the same polarity direction, a semiconductor control element FET26 (an example of a second semiconductor control element FET), a semiconductor control element Tr27 (an example of a first semiconductor control element Tr), and a resistor R28 (an example of a first resistor R) are connected in series; one end of a third current path 3 in which, in descending order of potential, a semiconductor control element Tr31 (an example of a fourth semiconductor control element Tr), a resistor R32, and a semiconductor control element Tr33 (an example of a second semiconductor control element Tr) are connected in series; and one end of a fourth current path 4 in which, in descending order of potential, a resistor R41 (an example of a sixth resistor R) and a Zener diode semiconductor control element ZD42 (an example of a semiconductor control element ZD) are connected in series. Note that the semiconductor control element Tr31 in the first embodiment is an NPN-type transistor. Furthermore, among the semiconductor light emitting elements LED21 to LED25, the semiconductor light emitting elements LED21 to LED23 are "constantly lit elements" that are constantly lit, and the semiconductor light emitting elements LED24 and LED25 are "appropriately lit elements" that are appropriately lit according to the voltage of the DC power supply. Furthermore, although three elements, LED21 to LED23, are shown as constantly lit elements in FIG. 1 for the sake of convenience in the drawing, the number of constantly lit elements in the first embodiment is 54. Furthermore, although two elements, LED24 and LED25, are shown as appropriate lit elements in FIG. 1 for the sake of convenience in the drawing, the number of appropriate lit elements in the first embodiment is 36.

[0025] Between the anodes and cathodes of the semiconductor light emitting elements LED24 and 25, semiconductor control element FETs 51 (an example of a first semiconductor control element FET) and 52 (an example of a first semiconductor control element FET) are connected in parallel, respectively. The gates (G) of the semiconductor control element FETs 51 and 52 are connected to the third current path 3 via a rectifier element D53 at a position between the resistor R32 and the semiconductor control element Tr33. A resistor element R54 is provided between the source (S) terminal and gate (G) terminal of each of the semiconductor control element FETs 51 and 52. The semiconductor control element FETs 51 and 52 according to the first embodiment are N-channel FETs. The semiconductor control element Tr33 is an NPN-type transistor.

[0026] The gate (G) of the semiconductor control element FET26 is connected to the third current path 3 via a rectifier element D53 at a position between the resistor R32 and the semiconductor control element Tr33. A resistor element R54 is provided between the source (S) terminal and the gate (G) terminal of the semiconductor control element FET26.

[0027] The base (B) of the semiconductor control element Tr33 is connected to the second current path 2 by a sixth current path 6. A resistor R61 (an example of the fourth resistor R) is provided on the sixth current path. In the first embodiment, the resistance value of the resistor R61 is set to 100 kΩ.

[0028] The base (B) of the semiconductor control element Tr31 is connected to the fourth current path 4 at a position between the resistor R41 and the semiconductor control element ZD42.

[0029] One end of the seventh current path 7 is connected to the third current path 3 at a position between the semiconductor control element Tr31 and the resistor R32. On the seventh current path 7, a resistor R71 (an example of the second resistor R), a semiconductor control element Tr72 (an example of the third semiconductor control element Tr), and a resistor R73 (an example of the third resistor R) are connected in series in order of increasing potential.

[0030] The eighth current path 8 serves to connect the collector (C) of the semiconductor control element Tr72 with the base (B) of the semiconductor control element Tr72 and the base (B) of the semiconductor control element Tr27. Therefore, the eighth current path 8 is composed of an 81st current path 81 that connects the base (B) of the semiconductor control element Tr72 with the base (B) of the semiconductor control element Tr27, and an 82nd current path 82 that has one end connected to the seventh current path at a position between the resistor R71 and the semiconductor control element Tr72 and the other end connected to the 81st current path 81 at approximately the midpoint of the 81st current path 81.

[0031] One end of the ninth current path 9 is connected to the second current path 2 at a position between the semiconductor light emitting element LED23 and the semiconductor light emitting element LED24. A resistor R91 (an example of the fifth resistor R) is provided on the ninth current path 9. The other end of the ninth current path 9 is connected to the sixth current path 6 at a position between the base (B) of the semiconductor control element Tr33 and the resistor R61.

[0032] The other ends of the second current path 2, the third current path 3, the fourth current path 4 and the seventh current path are connected to a negative terminal 12 to which the negative electrode of a DC power supply is connected.

[0033] <Current mirror circuit> 2, in the lighting device control circuit A, a so-called current mirror circuit is provided by the semiconductor control element Tr27 and resistor R28 on the second current path 2, the resistor R71, the semiconductor control element Tr72 and resistor R73 on the seventh current path 7, and the eighth current paths 81 and 82. Therefore, the current flowing through the seventh current path 7 is copied and flows through the second current path 2. That is, when a current flows from the collector (C) to the emitter (E) of the semiconductor control element Tr72 on the seventh current path 7, a current also flows from the collector (C) to the emitter (E) of the semiconductor control element Tr27 on the second current path 2. Furthermore, depending on the ratio between the resistance value of the resistor R73 on the seventh current path 7 and the resistance value of the resistor 28 on the second current path 2, a current corresponding to that ratio flows through each current path.

[0034] This will be explained in more detail below. For example, let's say the current consumed by the semiconductor light-emitting elements LED21-25 is 500 mA, and the resistance of resistor R28 is 1 Ω. In this case, the voltage across resistor R28 is 500 mA x 1 Ω = 0.5 V. If the ratio of the resistance of resistor R28 to the resistance of resistor R73 is "R28:R73 = 1:100," the resistance of resistor R73 will be 100 Ω. Because the base-emitter (B-E) voltage difference of semiconductor control element Tr72 and semiconductor control element Tr27 is typically about 0.6 V (= the base is about 0.6 V higher) due to the PN junction, the base (B) voltage common to semiconductor control element Tr72 and semiconductor control element Tr27 is "0.5 + 0.6 = 1.1 V."

[0035] Furthermore, the voltage across resistor R73 on the seventh current path 7 is the same as the voltage across resistor R28 on the second current path 2, 0.5V, so the current that flows is "0.5V / 100Ω=5mA".

[0036] For example, if the reference voltage generated by the emitter follower circuit described below is 20V, the voltage across resistor R71 on the seventh current path 7 will be 20V-1.1V=18.9V. Therefore, the resistor R71 must have a resistance value of 18.9V / 5mA=3780Ω=3.8kΩ.

[0037] Incidentally, if a configuration that does not include a current mirror circuit as described above is adopted, and the (DC power distribution) voltage applied to the second current path 2 is 300 V, the current flowing is 500 mA, there are 90 LEDs (LEDs 21 to 25), and the VF (voltage drop) of each LED is 3 V, then resistor R28, which serves as the limiting resistor for semiconductor light-emitting elements LED21 to 25, needs to have a resistance value of (300 V - 3 V × 90) ÷ 500 mA = 60 Ω. The voltage across resistor R28 at this time, 500 mA × 60 Ω = 30 V, becomes the voltage loss.

[0038] On the other hand, by providing a current mirror circuit, the current of the seventh current path 7 can be copied, and there is no need to use a high resistance resistor R28 as the limiting resistor for the semiconductor light-emitting elements LED21-25, which is convenient because it reduces voltage loss. For example, if the current consumed by the semiconductor light-emitting elements LED21-25 is 500 mA and the resistance of resistor R28 is 1 Ω, the voltage across resistor R28 at that time, "500 mA x 1 Ω = 0.5 V," is the voltage loss. This voltage loss can be kept lower than the 30 V that would be obtained without the current mirror circuit.

[0039] <Emitter follower> In the control circuit A for the lighting device, as shown in FIG. 3, an emitter follower (common collector) circuit is provided by a resistor R41 and a semiconductor control element ZD42 on the fourth current path 4, and a semiconductor control element Tr31 whose base (B) is connected to the fourth current path 4 at a position between the resistor R41 and the semiconductor control element ZD42.

[0040] For example, if the resistance of resistor R41 is 1 MΩ and the Zener voltage of semiconductor control element ZD42 is 20 V, when a DC voltage of 300 V is applied to control circuit A for a lighting device, the voltage is distributed between resistor R41 and semiconductor control element ZD42. That is, current flows through resistor R41, which has a large resistance of 1 MΩ, causing semiconductor control element ZD42 to output a Zener voltage. Because the output Zener voltage is 20 V, a voltage of 300 V - 20 V = 280 V is applied across resistor R41.

[0041] When a Zener voltage of 20V is applied to the base (B) of the semiconductor control element Tr31, the output from the emitter (E) of the semiconductor control element Tr31 becomes 20V.

[0042] In this way, the lighting device control circuit A is provided with an emitter follower circuit and configured to output voltage from the emitter (E) of semiconductor control element Tr31, so it has a lower output impedance than the commonly used circuits that supply or create voltage by connecting a resistor and a Zener diode in series, which allows it to drive more loads and serves as a stable voltage source for semiconductor control elements FET26, semiconductor control elements FET51, and semiconductor control elements FET52 and the above-mentioned current mirror circuits.

[0043] <Power supply voltage monitoring resistor> In the control circuit A for the lighting device, a resistor R91 is provided on the ninth current path 9. This resistor R91 serves as a power supply voltage monitoring resistor that changes the current flowing to the base (B) of the semiconductor control element Tr33 in accordance with fluctuations in the DC distribution voltage, thereby changing the conduction state (ON / OFF) of the semiconductor control element Tr33.

[0044] For example, if resistor R91 is 1 MΩ and the DC distribution voltage fluctuates significantly, the current flowing through resistor R91 increases. As a result, the current flowing to the base (B) of semiconductor control element Tr33 via ninth current path 9 increases, causing conduction (ON) between the collector (C) and emitter (E) of semiconductor control element Tr33. Depending on the conduction (ON) of semiconductor control element Tr33, the potential of the collector (C) of semiconductor control element Tr33 approaches the GND potential.

[0045] When the potential of the collector (C) of the semiconductor control element Tr33 approaches the GND potential, the current flowing to the gate (G) of the semiconductor control element FET52 decreases, the drain (D)-source (S) of the semiconductor control element FET52 becomes non-conductive (OFF), and the semiconductor light-emitting element LED25, which is provided in parallel with the semiconductor control element FET52, lights up.

[0046] As the number of lit semiconductor light-emitting elements LED increases (number of lit LEDs: 3 (LEDs 21 to 23) → 4 (LEDs 21 to 23 and 25)), the current flowing through each of the semiconductor light-emitting elements LED21 to 23 and 25 decreases compared to before the DC distribution voltage fluctuated high.

[0047] Next, if the DC distribution voltage fluctuates further, the current flowing through resistor R91 further increases, which results in a further increase in the current flowing through the ninth current path 9 to the base (B) of semiconductor control element Tr33, making semiconductor control element Tr33 more conductive (ON), and bringing the potential of the collector (C) of semiconductor control element Tr33 even closer to the GND potential.

[0048] When the potential of the collector (C) of the semiconductor control element Tr33 approaches the GND potential further, the current flowing to the gate (G) of the semiconductor control element FET51 decreases, the drain (D)-source (S) of the semiconductor control element FET51 becomes non-conductive (OFF), and the semiconductor light-emitting element LED24, which is provided in parallel with the semiconductor control element FET51, lights up.

[0049] As the number of lit semiconductor light-emitting elements LED increases (number of lit LEDs: 4 (LEDs 21 to 23 and 25) → 5 (LEDs 21 to 25)), the current flowing through each of the semiconductor light-emitting elements LED21 to 25 decreases compared to before the DC distribution voltage fluctuated further higher.

[0050] In other words, when the DC distribution voltage increases, the current flowing through resistor R91, which is a power supply voltage monitoring resistor, increases, and the potential of the collector (C) of semiconductor control element Tr33 approaches the GND potential. As a result, the drain (D)-source (S) of semiconductor control element FET52 and other elements become non-conductive (OFF), semiconductor light-emitting element LED25 and other elements provided in parallel emit light, and the current flowing through semiconductor light-emitting elements LED21-23 and 25 and other elements decreases.

[0051] On the other hand, when the DC distribution voltage decreases, the lighting device control circuit A operates in the opposite manner to the above. That is, when the DC distribution voltage decreases, the current flowing through resistor R91, which is a power supply voltage monitoring resistor, decreases, and the potential of the collector (C) of semiconductor control element Tr33 becomes higher than the GND potential. As a result, the drain (D)-source (S) of semiconductor control element FET52 and other elements become conductive (ON), semiconductor light-emitting element LED25 and other elements connected in parallel are turned off, and the current flowing through semiconductor light-emitting elements LED21-23 and other elements increases.

[0052] <Overvoltage absorption element> In the control circuit A for the lighting device, as shown in FIG. 1, a semiconductor control element FET 26 is provided on the second current path 2, and this semiconductor control element FET 26 plays a role of absorbing overvoltage and also of maintaining the inside of the control circuit A for the lighting device in a constant power state.

[0053] This will be explained in detail below. If the DC power distribution voltage becomes extremely high and excessive voltage is applied to the semiconductor light emitting elements LED21-25, without the semiconductor control element FET26, the current flowing through the LEDs 21-25 would increase rapidly due to the voltage-current characteristics of the LEDs. However, by providing the semiconductor control element FET26 in series on the second current path 2, the excessive voltage is absorbed (i.e., handled) between the drain (D) and source (S) of the semiconductor control element FET26, and the amount of current flowing in the lighting device control circuit A is maintained at a predetermined level. As a result, the circuit is protected and will not be damaged.

[0054] Furthermore, when an overvoltage is applied in a state in which all of the semiconductor light-emitting elements LED21-25 of the lighting device control circuit A are lit (conduction (ON) between the collector (C) and emitter (E) of the semiconductor control element Tr33 causes the potential of the collector (C) of the semiconductor control element Tr33 to approach the GND potential, reducing the current flowing to the gates (G) of the semiconductor control elements FET51 and 52 and causing the drains (D) and sources (S) of the semiconductor control elements FET51 and 52 to be in a non-conduction (OFF) state), the current flowing to the gate (G) of the semiconductor control element FET26 decreases, as with the semiconductor control elements FET51 and 52, and the degree of non-conduction (OFF) between the drain (D) and source (S) of the FET26 increases. Normally, when the degree of non-conduction (OFF) between the drain (D) and source (S) of a semiconductor control element FET increases, the resistance component between the drain (D) and source (S) increases, making it difficult for current to flow. Due to the characteristics of this semiconductor control element FET, when an overvoltage is applied, it becomes difficult for current to flow between the drain (D) and source (S) of FET 26, which creates room for the current flowing through the semiconductor light-emitting elements LED21 to 25 to decrease, and as a result, the control circuit A for the lighting device can be maintained in a constant power state.

[0055] <Variation 1> In the above-described first embodiment, one end of the ninth current path 9 is connected to the second current path 2 at a position between the semiconductor light emitting element LED23 and the semiconductor light emitting element LED24, and the resistor R91 is provided on the ninth current path 9, so that the resistor R91 serves as a power supply voltage monitoring resistor. However, the configuration in which the resistor R91 serves as a power supply voltage monitoring resistor is not limited to this configuration.

[0056] For example, as shown in FIG. 4, one end of the ninth current path 9 may be connected to a positive terminal 11 to which the positive electrode of a DC power supply is connected, and a semiconductor control element ZD92, which is a Zener diode, may be provided on the ninth current path 9 at a position where the potential is higher than that of the resistor R91.

[0057] The VF (=voltage drop) of the semiconductor light emitting elements LED21 to 23 is compensated for by the output voltage from the Zener diode.

[0058] <Variation 2> For example, as shown in Fig. 5, one end of the ninth current path 9 may be connected to a positive terminal 11 to which the positive electrode of a DC power supply is connected, and a resistor R93 may be provided on the ninth current path 9 at a position where the potential is higher than that of the resistor R91. The resistance value of the resistor R93 may be, for example, 1 MΩ. The resistor R93 compensates for the VF (voltage drop) of the semiconductor light-emitting elements LED21-23. Note that instead of using two resistors, resistors R91 and R93, as in the second modification, a single resistor (here, 2 MΩ) having a resistance value equivalent to two may be used.

[0059] However, in the case of a configuration using resistor R93 as in this modification 2, the resolution is coarser than the configurations shown in the above embodiment 1 and modification 1, making it difficult to respond to small fluctuations in the DC distribution voltage.

[0060] This will be explained in detail below. For example, in the case of the first embodiment, if the resistance value of resistor R91 is 1 MΩ and the resistance value of resistor R61 is 100 kΩ, the voltage applied to the base (B) of semiconductor control element Tr33 through the ninth current path 9 is divided by resistors R91 and R61. Since the resistance value of resistor R91 is 1 MΩ and the resistance value of resistor R61 is 100 kΩ, the relationship is "resistor R61:resistor R91=1:10". This results in finer resolution and makes it possible to respond to small fluctuations in the DC distribution voltage.

[0061] On the other hand, in the case of the present modification 2, if the resistance values ​​of resistors R91 and R93 are each 1 MΩ and the resistance value of resistor R61 is 100 kΩ, the voltage applied to the base (B) of semiconductor control element Tr33 through the ninth current path 9 is divided by resistors R91, R93, and resistor R61. The combined resistance value of resistors R91 and R93 is 2 MΩ, and the resistance value of resistor R61 is 100 kΩ, so the relationship is "resistor R61:resistor R91+resistor R93=1:20." Compared to the configurations shown in the above-described first embodiment and modification 1, the configuration of the present modification 2 has coarser resolution, making it difficult to respond to small fluctuations in the DC distribution voltage.

[0062] In addition, in the first embodiment, a configuration using transistors such as semiconductor control element Tr27, semiconductor control element Tr31, and semiconductor control element Tr72 has been shown, but the present invention is not limited to this configuration. For example, any or all of these elements may be configured to use N-channel FETs.

[0063] Although the preferred embodiments of the present invention have been described above, it goes without saying that the control circuit for a lighting device according to the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. [Explanation of symbols]

[0064] A: A control circuit for a lighting device; 11: positive terminal, 12: negative terminal, 2: second current path, 21: semiconductor light emitting element LED, 22: semiconductor light emitting element LED, 23: semiconductor light emitting element LED, 24: semiconductor light emitting element LED, 25: semiconductor light emitting element LED, 26: semiconductor control element FET, 27: semiconductor control element Tr, 28: resistor R, 3: third current path, 31: semiconductor control element Tr, 32: resistor R, 33: semiconductor control element Tr, 4: fourth current path, 41: resistor R, 42: semiconductor control element ZD, 51: semiconductor control element FET, 52: semiconductor control element FET, 53: rectifier element D, 54: resistor R, 6: 6th current path, 61: Resistor, 7: seventh current path, 71: resistor, 72: semiconductor control element Tr, 73: resistor R, 81: 8th current path, 82: 8th current path, 9: ninth current path, 91: resistor, 92: semiconductor control element ZD, 93: resistor R

Claims

1. 1. A control circuit for a lighting device, comprising: a positive terminal to which the positive electrode of a DC power supply is connected is connected to one end of a second current path in which a plurality of semiconductor light-emitting elements LED, a first semiconductor control element Tr, and a first resistor R arranged in the same polarity direction are connected in series, and one end of a third current path in which a second semiconductor control element Tr is provided; The plurality of semiconductor light-emitting elements LED are divided into constant lighting elements that are constantly lit and appropriate lighting elements that are appropriately lit according to the voltage of the DC power supply, A first semiconductor control element FET is connected in parallel to each of the appropriate lighting elements, a gate of the first semiconductor control element FET connected to the third current path at a position where the potential is higher than that of the second semiconductor control element Tr; the base of the second semiconductor control element Tr is connected to the second current path 2 by a sixth current path; one end of a seventh current path is connected to the third current path at a position where the potential is higher than that of the connection point of the gate of the first semiconductor control element FET; A second resistor R, a third semiconductor control element Tr, and a third resistor R are connected in series on the seventh current path 7 in descending order of potential, an eighth current path including an 81st current path connecting a base of the third semiconductor control element Tr and a base of the first semiconductor control element Tr; and an 82nd current path connecting a position on the seventh current path between the second resistor R and the third semiconductor control element Tr and the 81st current path; the other ends of the second current path, the third current path, and the seventh current path are connected to a negative terminal to which a negative terminal of a DC power supply is connected.

2. a second semiconductor control element FET is further provided on the second current path between the plurality of semiconductor light emitting elements LED and the first semiconductor control element Tr; 2. The control circuit for a lighting device according to claim 1, wherein the gate of the second semiconductor control element FET is connected to the third current path at a position where the potential is higher than that of the second semiconductor control element Tr.

3. a fourth resistor R is further provided on the sixth current path, a ninth current path, one end of which is connected to the second current path at a position between the constantly lighting element and the occasional lighting element, and the other end of which is connected to the sixth current path at a position between the base of the second semiconductor control element Tr and the fourth resistor R; 2. The control circuit for a lighting device according to claim 1, further comprising a fifth resistor R provided on said ninth current path.

4. a fourth semiconductor control element Tr is further provided on the third current path at a position where the potential is higher than that of the second semiconductor control element Tr; a fourth current path provided with a sixth resistor R and a semiconductor control element ZD in order of increasing potential; 2. The control circuit for a lighting device according to claim 1, wherein the base of the fourth semiconductor control element is connected to the fourth current path at a position between the sixth resistor R and the semiconductor control element ZD.

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