JP7009737B2 - Control circuit for lighting equipment - Google Patents

Description

The present invention relates to a control circuit capable of supporting a wide range of power supply voltages in a lighting device specialized in a system for supplying direct current, which uses a direct current voltage as a power source.

With the recent evolution of LED (light emitting diode) technology, various LED lighting devices are used. Therefore, LED lighting devices are required to be smaller, more efficient, and less expensive.

Among them, the power supply source of LED lighting devices that use DC voltage as the power source is not limited to one, and due to the growing awareness of energy saving in recent years, there are various power sources such as photovoltaic power generation, which is renewable energy, and various battery power. Over.

The difference in DC voltage output from these power supplies was dealt with by using a power conversion unit. However, the configuration using the power conversion unit has a problem that a loss due to conversion occurs and the efficiency is lowered.

In addition, most of the power supply conversion units are configured to keep the output constant by switching at a specific frequency. Such a power supply conversion unit has a great demerit that electromagnetic noise is generated by the switching operation.

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 DC voltage in a certain range, but for slight fluctuations in the DC voltage outside that range. , The current flowing through the LED changes significantly. Therefore, the quality of the light output from the LED lighting is deteriorated, and the life of the LED is shortened.

Further, when the DC voltage drops below a predetermined value, the order (direction) voltage VF required for lighting the LED becomes insufficient, and the LED is turned off. Therefore, there is a problem that it cannot correspond to a wide range of power supply voltages.

Therefore, there is a demand for a control circuit for an LED lighting device that can handle a wide range of power supply voltages without using a power supply conversion unit. Patent Documents 1 and 2 disclose a configuration in which the current flowing through an LED is kept constant while corresponding to a wide range of power supply voltages by controlling the lighting and extinguishing of the LED according to the increase and decrease of the power supply voltage.

Japanese Unexamined Patent Publication No. 2013-179279 Japanese Unexamined Patent Publication No. 2016-46228

However, in these configurations of Patent Documents 1 and 2, when the power supply voltage drops, the LEDs are turned off in order from the lower voltage to the upper voltage while maintaining a constant current, so that the surrounding people notice the fluctuation of the power supply voltage. There was a problem.

Therefore, as a solution to the above-mentioned problems, the present invention is for a lighting device capable of supporting a wide range of power supply voltage by automatically converting the series-parallel connection of LEDs according to the fluctuation of the power supply voltage. The purpose is to provide a control circuit for the above.

The invention of claim 1 is
The first current path and the second current path are connected to the positive electrode of the DC power supply, respectively.
In the first current path, LEDs that are always lit are provided in series, and the LEDs are branched into two, a third current path and a fourth current path, in the lower voltage direction.
In the third current path, a first LED converted by the series-parallel connection is provided in series, and the first LED and the first LED are connected in series-parallel toward the voltage lower direction. FETs that convert the current are connected in series and provided.
In the fourth current path, a FET for converting the series-parallel connection of the second LED converted by the series-parallel connection is provided in series, and the FET and the second LED are provided in the lower voltage direction. LEDs are connected in series and provided,
The FET related to the third current path and the second LED related to the fourth current path are connected, and the first current path branched into two returns to one.
In the first current path returned to one, a resistance element for determining the amount of current flowing through the first LED and the second LED is provided in series, and the first current path returned to one. Is provided in series with the second current path and is connected by a fifth current path to a transistor that determines the amount of current flowing through the first LED and the second LED .
The resistance element and the transistor are connected to the negative electrode of the DC power supply, and the resistance element and the transistor are connected to the negative electrode of the DC power supply.
The FET related to the third current path and the FET related to the fourth current path are connected to the transistor.
The total impedance of the first LED related to the third current path and the total impedance of the second LED related to the fourth current path are equal.
The control circuit for the lighting device has the same total impedance of the FET related to the third current path and the total impedance of the FET related to the fourth current path.
Further, the invention of claim 2 is
A sixth current path connecting the LED and the FET related to the third current path and the FET and the LED related to the fourth current path is further provided.
The control circuit for the lighting device according to claim 1, wherein the sixth current path is provided with a semiconductor rectifying element.

Further, the invention of claim 3 is
The control circuit for a lighting device according to claim 1 or 2, wherein the number of the first LED related to the third current path and the number of the second LED related to the fourth current path are one each. did.

Further, the invention of claim 4 is
The control circuit for a lighting device according to any one of claims 1 to 3, further comprising an LED that is always lit in series in the first current path that has returned to one.

According to the inventions of claims 1 to 4, a wide range of power supply voltage can be supported without using a power supply conversion unit by automatically converting the series-parallel connection of LEDs according to the fluctuation of the power supply voltage. Is.

In addition, since the configuration does not use a power conversion unit, it is possible to reduce the size, efficiency, and price of the lighting device. In addition, it does not generate electromagnetic noise and can be used in environments such as hospitals and precision machine rooms where electromagnetic noise is disliked. Furthermore, the risk of failure of the lighting device can be reduced.

Further, since the configuration is such that the series-parallel connection of the LEDs is automatically converted according to the fluctuation of the power supply voltage, the LED is hardly turned off, and it is difficult for the surrounding people to notice the fluctuation of the power supply voltage.

Further, in particular, when the number of LEDs provided as the LED series-parallel conversion unit in the third current path and the fourth current path is one, as in the invention of claim 3, the first The series-parallel connection is converted according to the fluctuation of the power supply voltage corresponding to the order (direction) voltage of each piece, and the resolution and sensitivity are high.

Further, in particular, according to the invention of claim 4, when the power supply voltage is insufficient, the LED (= the place where the flowing current is halved) related to the LED series-parallel conversion unit converted from series to parallel can be dispersed, so that the lighting It is convenient because the difference in the brightness of the device can be reduced.

It is a conceptual block diagram of this invention. It is a block diagram of Embodiment 1 of this invention. It is a block diagram of Embodiment 1 of this invention. It is a block diagram of Embodiment 1 of this invention. It is a block diagram of Embodiment 1 of this invention. It is a block diagram of the other embodiment of this invention. It is a block diagram of the other embodiment of this invention. It is a block diagram of the other embodiment of this invention. It is a block diagram of the other embodiment of this invention.

First, it will be described based on FIG. 1, which is a conceptual configuration diagram of the present invention. The control circuit for the lighting device of the present invention is provided with the LED always-on unit 51 in which the LED is always lit by applying the voltage of the DC power supply 50, and the series-parallel connection of the LEDs is made by the fluctuation of the voltage value of the DC power supply 50. An LED series-parallel conversion unit 52 to be converted is provided, and an LED series-parallel control unit 53 that automatically converts the LED series-parallel connection of the LED series-parallel conversion unit 52 according to the fluctuation of the voltage value is provided. The LED current value determining unit 54 for determining the current value to be passed through the LED constantly lit unit 51 and the LED series-parallel conversion unit 52 is provided. Further, each part is connected through a current path 55.

In the control circuit for this lighting device, the LED related to the LED constant lighting unit 51 and the LED series-parallel conversion unit 52 is lit by the DC voltage applied from the DC power supply 50, but the DC voltage is caused by the fluctuation of the DC power supply 50 or the like. When is changed, the LED series-parallel control unit 53 operates, and the series-parallel connection of the LED series-parallel conversion unit 52 is converted. Therefore, in the lighting device provided with this control circuit, all the LEDs related to the LED constant lighting unit 51 and the LED series-parallel conversion unit 52 are in the lighting state, and it is difficult for the surrounding people to notice the fluctuation of the power supply voltage.

(Example 1 of the embodiment)
Hereinafter, the configuration of the control circuit A for the lighting device according to the first embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 2, a current path 2 (an example of a first current path) and a current path 3 (an example of a second current path) are connected to the positive electrode of the DC power supply 1, respectively.

In the current path 2, semiconductor light emitting devices LEDs 1 to 3 made of LEDs are connected in series in the same polar direction, and the current path 21 (third) is provided from the cathode side of the semiconductor light emitting device LED 3 toward the lower voltage direction. It is branched into two (an example of a current path) and a current path 22 (an example of a fourth current path).

In the current path 21, semiconductor light emitting devices LEDs 4 to 6 composed of LEDs are connected in series in the same polar direction, and the cathode of the semiconductor light emitting device LED 6 and the drain of the semiconductor control element FET (field effect transistor) 2 are provided. They are connected in series. Further, in the current path 22, the source of the semiconductor control element FET1 is connected in series in the same polar direction, and among the semiconductor light emitting elements LEDs 7 to 9 made of LEDs, the source is connected in series with the anode of the semiconductor light emitting element LED7. It is connected.

Further, from the diode, the current path 21 connecting the current path 21 between the cathode of the semiconductor light emitting element LED 6 and the drain of the semiconductor control element FET 2 and the current path 22 between the source of the semiconductor control element FET 1 and the anode of the semiconductor light emitting element LED 7 is connected to the current path 4. The semiconductor rectifying element D1 is provided. Specifically, the anode of the semiconductor rectifying element D1 is connected to the current path 21 between the cathode of the semiconductor light emitting element LED6 and the drain of the semiconductor control element FET2, and the cathode of the semiconductor rectifying element D1 is connected to the source of the semiconductor control element FET1 and semiconductor light emission. It is connected to the current path 22 between the anodes of the element LED 7. Taking advantage of the characteristic that the current flows only in the forward direction, the semiconductor rectifying element D1 prevents the current from flowing from the source of the semiconductor control element FET1 to the drain of the semiconductor control element FET2 when the semiconductor control element FET1 is turned on. , Plays the role of cutting off the current. By providing the semiconductor rectifying element D1 in this way, when the semiconductor control element FET1 and the semiconductor control element FET2 are turned on, a current flows substantially equally in the current path 21 and the current path 22.

The source of the semiconductor control element FET 2 and the cathode of the semiconductor light emitting element LED 9 are connected, and the current path 2 that has branched into two, the current path 21 and the current path 22, returns to one current path 2 here, and from this. A resistance element R3 is provided in the lower voltage lower direction.

On the other hand, in the current path 3, the resistance element R4 and the collector of the semiconductor control element TR (transistor) are connected in series and provided.

Further, the resistance element R3 of the current path 2 and the emitter of the semiconductor control element TR of the current path 3 are connected to the negative electrode (≈ GND) of the DC power supply 1, respectively.

The gate of the semiconductor control element FET1 is connected to the collector of the semiconductor control element TR via the resistance element R1, and the gate of the semiconductor control element FET2 is connected to the collector of the semiconductor control element TR via the resistance element R2. There is. Further, a semiconductor constant voltage element ZD1 is provided between the source and the gate of the semiconductor control element FET1, and a semiconductor constant voltage element ZD2 is provided between the source and the gate of the semiconductor control element FET2. These semiconductor constant voltage elements ZD1 and ZD2 are composed of Zener diodes, and take advantage of the characteristics of Zener diodes that the voltage becomes constant with respect to changes in current to limit the voltage applied between the source and the gate. Therefore, it plays a role of protecting the semiconductor control elements FET1 and FET2 when a surge current or static electricity is generated.

Further, a current path 5 (an example of a fifth current path) in which the connection point between the source of the semiconductor control element FET 2 and the cathode of the semiconductor light emitting element LED 9 and the resistance element R3 and the base of the semiconductor control element TR are connected. ), The semiconductor constant voltage element ZD3 made of a Zener diode and the resistance element R5 are connected in series in the order of proximity to the resistance element R3. As described above, by providing the semiconductor constant voltage element ZD3 in which the output voltage is constant regardless of the applied voltage, the voltage applied to the resistance element R3 can be set. Further, by providing the resistance element R5 in this way, the current flowing through the base of the semiconductor control element TR can be limited to a certain value or less. Further, the resistance element R6 is provided in the current path 6 connecting between the semiconductor constant voltage element ZD3 and the resistance element R5 in the current path 5 and between the resistance element R3 and the semiconductor control element TR, and the resistance element R6 is DC. It is connected to the negative voltage (≈GND) of the power supply 1.

Next, the correspondence between the conceptual configuration of the present invention described with reference to FIG. 1 and the circuit configuration of the control circuit A for the lighting device described with reference to FIG. 2 will be described. The DC power supply 50 of FIG. 1 corresponds to the DC power supply 1 of FIG. Further, the LED constantly lit unit 51 of FIG. 1 corresponds to the semiconductor light emitting elements LEDs 1 to 3 of FIG. Further, the LED series-parallel conversion unit 52 of FIG. 1 corresponds to the semiconductor light emitting elements LEDs 4 to 6 and the semiconductor light emitting elements LEDs 7 to 9 of FIG. Further, the LED series-parallel control unit 53 of FIG. 1 corresponds to the semiconductor control element FET1 and the semiconductor control element FET2 of FIG. Further, the LED current value determining unit 54 in FIG. 1 corresponds to the semiconductor control element TR, the semiconductor constant voltage element ZD3, and the resistance element R3 in FIG. Further, the current path 55 in FIG. 1 corresponds to the current paths 2 to 6, the current path 21 and the current path 22 in FIG.

The semiconductor light emitting elements LEDs 1 to 3, which correspond to the LED constantly lit unit 51, are for operating the semiconductor control element FET1. explain in detail. If the potential of the gate of the semiconductor control element FET1 is not higher than the potential of the source, even if a voltage is applied to the gate, the semiconductor control element FET1 does not turn on, so that no current flows between the drain and the source. Therefore, by providing the LED constantly lit unit 51, the potential of the source of the semiconductor control element FET1 is lowered by the threshold voltage between the gate and the source with respect to the potential of the gate, so that the semiconductor control element FET1 operates. ..

Further, the semiconductor light emitting element LEDs 4 to 6 and the semiconductor light emitting element LEDs 7 to 9 of FIG. 2, which correspond to the LED series-parallel conversion unit 52, are divided into two blocks, but the connection is converted to the parallel circuit as the DC voltage decreases. In order to equalize the amount of current flowing in each current path when the current paths are separated, the total impedance between the blocks is configured to be equal. If the total impedance between the blocks is different, the current may not be evenly divided when the connection is converted to the parallel circuit, and the semiconductor light emitting element LED of one block may be turned off.

Further, the semiconductor control element FET1 and the semiconductor control element FET2 in FIG. 2, which correspond to the LED series-parallel control unit 53, also have the same current flowing when the connection is converted to the parallel circuit as the DC voltage decreases. The impedances of the are equal to each other.

Further, the LED current value determining unit 54 will be described in detail below. The "LED current value" determined by the LED current value determining unit 54 is a current value flowing through the LED constantly lit unit 51 and the LED series-parallel conversion unit 52. Most of the current flowing through the LED constantly lit unit 51 and the LED series-parallel conversion unit 52 flows to the resistance element R3. Therefore, the current flowing through the resistance element R3 is the current flowing through the LED constantly lit unit 51 and the LED series-parallel conversion unit 52. Since the resistance element R3 is a fixed resistor whose resistance value does not change, if the voltage applied to the resistance element R3 (hereinafter referred to as “VR3”) is constant, the current flowing through the resistance element R3 is also constant.

The VR3 is composed of a Zener voltage of the ZD3 of the current path 5, a voltage applied to the resistance element R5 (hereinafter referred to as “VR5”), and a voltage between the base and the emitter of the TR (generally 0.6V). However, since the current flowing through the resistance element R5 (= base current of TR) is small, VR5 is a negligible magnitude. Therefore, VR3 is mainly determined by the total value B of the base-emitter voltage of TR and the Zener voltage of ZD3. On the other hand, VR3 is also determined by a subtraction value C obtained by subtracting the voltage applied to the LED constantly lit unit 51 and the LED series-parallel conversion unit 52 from the voltage applied by the DC power supply 50. Whether VR3 is determined by the total value B or the subtraction value C depends on whether the semiconductor light emitting elements LEDs 4 to 6 and the semiconductor light emitting elements LEDs 7 to 9 related to the LED series-parallel conversion unit 52 are connected in series or in parallel. It depends on whether it is connected and the voltage value applied by the DC power supply 50. This will be described together with the operation of the control circuit A for the lighting device described below.

Next, the operation of the control circuit A for the lighting device will be described with reference to FIGS. 2 to 5. When a sufficient voltage is applied from the DC power supply 1 (for example, 29.3V or more), a sufficient base current flows through the semiconductor control element TR, the semiconductor control element TR is turned on, and the collector voltage of the semiconductor control element TR is turned on. Since the gate voltages of the semiconductor control element FET1 and the semiconductor control element FET2 are equal at 0V, the semiconductor control element FET1 and the semiconductor control element FET2 are not turned on. Therefore, as shown in FIG. 3, the current flowing through the semiconductor light emitting elements LEDs 1 to 3 is the semiconductor light emitting element LEDs 4 to 6 in the current path 21, the semiconductor rectifying element D1, the semiconductor light emitting elements LEDs 7 to 9 in the current path 22, and the resistance element. It flows through R3. That is, the semiconductor light emitting elements LEDs 4 to 6 and the semiconductor light emitting elements LEDs 7 to 9 are connected in series.

When the voltage applied from the DC power supply 1 becomes larger than 29.3V, the subtraction value C determines VR3, and as the voltage applied from the DC power supply 1 increases, the value of VR3 also increases, so that the LED current value also increases. ..

When the voltage applied from the DC power supply 1 is 29.3V, VR3 is determined by either the total value B or the subtraction value C, and VR3 becomes 3.56V in any of the values.

When the voltage from the DC power supply 1 decreases (for example, 27.4V), the base current of the semiconductor control element TR decreases, and the collector current of the semiconductor control element TR also decreases. Then, although the semiconductor control element TR is turned on, the voltage value at which the collector voltage of the semiconductor control element TR and the gate voltage of the semiconductor control element FET1 and the semiconductor control element FET2 become equal increases, and the source of the semiconductor control element FET2 When the voltage becomes higher than the voltage and exceeds the gate-source threshold voltage of the semiconductor control element FET2, the semiconductor control element FET2 is turned on. Therefore, as shown in FIG. 4, the current flowing through the semiconductor light emitting elements LEDs 1 to 3 flows through the semiconductor light emitting elements LEDs 4 to 6, the semiconductor control element FET2, and the resistance element R3 in the current path 21. On the other hand, the semiconductor light emitting devices LEDs 7 to 9 in the current path 22 are turned off.

The voltage applied from the DC power supply 1 becomes smaller than 29.3V, and as shown in FIG. 4, the current flowing through the semiconductor light emitting elements LEDs 1 to 3 is the semiconductor light emitting elements LEDs 4 to 6 in the current path 21 and the semiconductor control element FET 2. When the semiconductor light emitting devices LEDs 7 to 9 in the current path 22 are turned off while flowing through the resistance element R3, the total value B determines VR3, and VR3 becomes 3.56V.

When the voltage from the DC power supply 1 is insufficient (for example, 19.9 V or less), the base current of the semiconductor control element TR is further reduced, and the collector current of the semiconductor control element TR is also reduced. Then, although the semiconductor control element TR is turned on, the voltage value at which the collector voltage of the semiconductor control element TR and the gate voltage of the semiconductor control element FET1 and the semiconductor control element FET2 are equal increases further, and the source voltage of the semiconductor control element FET1 is increased. When the threshold voltage between the gate and the source of the semiconductor control element FET1 is exceeded, the semiconductor control element FET1 is turned on. Alternatively, the semiconductor control element TR is turned off and the semiconductor control element FET1 is turned on. Therefore, as shown in FIG. 5, the current flowing through the semiconductor light emitting elements LEDs 1 to 3 is the route flowing through the semiconductor light emitting elements LEDs 4 to 6 and the semiconductor control element FET 2 in the current path 21, the semiconductor control element FET 1 and the semiconductor light emitting element LED 7. Divided into routes that flow through 9 to 9. That is, the semiconductor light emitting elements LEDs 4 to 6 and the semiconductor light emitting elements LEDs 7 to 9 are connected in parallel. Since the total impedance of the semiconductor light emitting elements LEDs 4 to 6 and the semiconductor control element FET 2 of the current path 21 connected in parallel is equal to the total impedance of the semiconductor control element FET 1 and the semiconductor light emitting element LEDs 7 to 9 of the current path 22, the semiconductor The amounts of current flowing through the light emitting elements LEDs 4 to 6 and the semiconductor light emitting elements LEDs 7 to 9 are equal.

When the voltage applied from the DC power supply 1 is 19.9V, TR is OFF, so VR3 is determined by the subtraction value C, and VR3 is 3.30V. This is because the semiconductor control element FET 1 and the semiconductor control element FET 2 are completely turned on, so that the voltage between the drain and the source of the semiconductor control element FET 1 and the semiconductor control element FET 2 is about 0 V, and the subtraction value C can be applied.

When the voltage applied from the DC power supply 1 becomes smaller than 19.9V, VR3 is determined by the subtraction value C, and the voltage applied to the LED constantly lit unit 51 and the LED series-parallel conversion unit 52 does not change so much, so that the DC power supply The decrease in the voltage applied from 1 becomes the decrease in VR3 as it is, and the LED current value also decreases.

As in the control circuit A for the lighting device of FIG. 2, the number of semiconductor light emitting element LEDs (three of the semiconductor light emitting elements LEDs 1 to 3) related to the LED constantly lit unit 51 and the LED series-parallel conversion unit 52. , The ratio of the number of semiconductor light emitting element LEDs (three of semiconductor light emitting element LEDs 4 to 6 or semiconductor light emitting element LEDs 7 to 9) of each block when the connection is converted to a parallel circuit and the current path is divided is 1: 1. In the case of, when the voltage from the DC power supply 1 becomes about 2/3 (when the voltage from the DC power supply 1 decreases by about 1/3), the connection is converted from the series circuit to the parallel circuit.

Further, in the above-described embodiment, the operation of the control circuit A for the lighting device has been described as an example in which the voltage from the DC power supply 1 decreases or becomes insufficient. However, the control circuit A for the lighting device is not a configuration that can be dealt with only when the voltage from the DC power supply 1 decreases or becomes insufficient, and the semiconductor light emitting element LED related to the LED series-parallel conversion unit 52 is series-parallel. By converting the connection, it is a configuration that can correspond to a wide range of voltage applied by the DC power supply 1. Therefore, for example, the voltage from the DC power supply 1 is insufficient, and the voltage is increased from the state in which the semiconductor light emitting element LEDs related to the LED series-parallel conversion unit 52 are connected in parallel, and a sufficient voltage is applied. In the case of shifting to, the connection of the semiconductor light emitting element LED related to the LED series-parallel conversion unit 52 is converted from parallel to series.

With such a configuration, the power conversion unit can be made by automatically converting the series-parallel connection of the semiconductor light emitting element LED related to the LED series-parallel conversion unit 52 according to the fluctuation of the voltage of the DC power supply 50. It is possible to handle a wide range of power supply voltages without using it. Further, the amount of current supplied from the DC power supply 50 is increased by automatically converting the series-parallel connection of the semiconductor light emitting element LEDs related to the LED series-parallel conversion unit 52 according to the fluctuation of the voltage of the DC power supply 50. It becomes almost constant.

In addition, since the configuration does not use a power conversion unit, it is possible to reduce the size, efficiency, and price of the lighting device. In addition, it does not generate electromagnetic noise and can be used in environments such as hospitals and precision machine rooms where electromagnetic noise is disliked. Furthermore, the risk of failure of the lighting device can be reduced.

Further, since the configuration is such that the series-parallel connection of the semiconductor light emitting element LEDs related to the LED series-parallel conversion unit 52 is automatically converted according to the fluctuation of the voltage of the DC power supply 50, most of the LEDs in the control circuit are turned off. It is difficult for people around you to notice fluctuations in the power supply voltage.

(Modification example)
In the first embodiment, as the LED series-parallel conversion unit 52, a configuration in which a block related to the semiconductor light emitting element LEDs 4 to 6 and a block related to the semiconductor light emitting element LEDs 7 to 9 are stacked in two stages is shown. Not limited. If the semiconductor control element FET 1 having the highest potential among the semiconductor control element FETs in the control circuit can be turned on by providing the LED constantly lighting unit 51, the number of stages of the block related to the semiconductor light emitting element LED in the LED series-parallel conversion unit 52 is set. Can also be stacked in series. For example, as shown in FIG. 6, as the LED series-parallel conversion unit 52, the block related to the semiconductor light emitting element LED 4, the block related to the semiconductor light emitting element LED 5, the block related to the semiconductor light emitting element LED 6, and the block related to the semiconductor light emitting element LED 7 are arranged in four stages. It may be configured to be stacked. By stacking the blocks related to the semiconductor light emitting element LED in the LED series-parallel conversion unit 52 in series, the range that can respond to DC power supply voltage fluctuations is expanded, and it is possible to respond to large fluctuations in the power supply voltage. It is convenient.

Further, in the first embodiment, in each block related to the semiconductor light emitting element LED in the LED series-parallel conversion unit 52, three LEDs such as the semiconductor light emitting element LEDs 4 to 6 and the semiconductor light emitting element LEDs 7 to 9 are provided. Although the configuration is shown, the configuration is not limited to this, and the number of semiconductor light emitting element LEDs in each block in the LED series-parallel conversion unit 52 may be any number. For example, as shown in FIG. 6, the number of semiconductor light emitting element LEDs in each block in the LED series-parallel conversion unit 52 may be small (for example, one). The total of the order (direction) voltage values required for lighting the semiconductor light emitting element LEDs of each block in the LED series-parallel conversion unit 52 is the voltage value at which the series-parallel connection is converted. Therefore, when the number of semiconductor light emitting element LEDs in each block in the LED series-parallel conversion unit 52 is small, the power supply voltage corresponding to the forward (direction) voltage of a small number of semiconductor light emitting element LEDs is changed. The series-parallel connection is converted, and the resolution and sensitivity are high. On the other hand, for example, when the number of semiconductor light emitting element LEDs in each block in the LED series-parallel conversion unit 52 is large, it corresponds to the fluctuation of the power supply voltage corresponding to the order (direction) voltage of many semiconductor light emitting element LEDs. Therefore, the series-parallel connection is converted, and the series-parallel connection is converted according to a large change in the power supply voltage.

Further, the number of semiconductor light emitting element LEDs in each block in the LED series-parallel conversion unit 52 may be different. For example, as shown in FIG. 7, the number of semiconductor light emitting element LEDs in each block in the LED series-parallel conversion unit 52 is one (semiconductor light emitting element LEDs 4, 5) and three (semiconductor light emitting element LEDs 6 to 8, 9 to 11). ), Two (semiconductor light emitting elements LEDs 12 to 13, 14 to 15) may be used. However, when the connection is converted from series to parallel due to the shortage of the power supply voltage and the current path is separated, the impedances of the semiconductor light emitting element LEDs (for example, the semiconductor light emitting elements LEDs 4 and 5) that are in a corresponding relationship are the same. Must be the same number.

In the first embodiment, the semiconductor light emitting element LEDs 1 to 3 are provided as the LED constantly lit unit 51 at a higher potential than the semiconductor control element FET 1 so that the semiconductor control element FET 1 can be turned on. In addition to the LED constantly lit unit 51 at this position, one or a plurality of LED constantly lit units 51 may be separately provided. For example, as shown in FIG. 8, between the LED series-parallel conversion unit 52 composed of the semiconductor light-emitting element LEDs 4 to 9 and the LED series-parallel conversion unit 52 composed of the semiconductor light-emitting element LEDs 12 to 15, the semiconductor light emitting unit 51 is used as the LED constant lighting unit. The elements LEDs 10 and 11 may be provided. This is convenient because when the power supply voltage is insufficient, the points that are converted from series to parallel (= the points where the flowing current is halved) can be dispersed, and the difference in brightness of the lighting device can be reduced.

In the first embodiment of the present embodiment, a two-parallel configuration in which the current path is divided into two when the connection is converted from series to parallel due to a shortage of the power supply voltage is shown, but the configuration is limited to this configuration. is not it. For example, as shown in FIG. 9, a configuration of 4 parallels in which the current path is divided into 4 may be used, or a configuration of 8 parallels, 16 parallels, or 32 parallels may be used. It is convenient because the semiconductor light emitting element LED related to the LED series-parallel conversion unit 52 can be turned on even with a smaller power supply voltage.

1: DC power supply, 2 to 6: Current path,
LEDs 1 to 15: semiconductor light emitting elements, FETs 1 to 6: semiconductor control elements,
D1-3: semiconductor rectifying element, R1-10: resistance element,
TR: Semiconductor control element,
ZD1-7: Semiconductor constant voltage element,
50: DC power supply, 51: LED constantly lit part,
52: LED series-parallel conversion unit, 53: LED series-parallel control unit,
54: LED current value determination unit, 55: current path

Claims (4)

The first current path and the second current path are connected to the positive electrode of the DC power supply, respectively.
In the first current path, LEDs that are always lit are provided in series, and the LEDs are branched into two, a third current path and a fourth current path, in the lower voltage direction.
In the third current path, a first LED converted by the series-parallel connection is provided in series, and the first LED and the first LED are connected in series-parallel toward the voltage lower direction. FETs that convert the current are connected in series and provided.
In the fourth current path, a FET for converting the series-parallel connection of the second LED converted by the series-parallel connection is provided in series, and the FET and the second LED are provided in the lower voltage direction. LEDs are connected in series and provided,
The FET related to the third current path and the second LED related to the fourth current path are connected, and the first current path branched into two returns to one.
In the first current path returned to one, a resistance element for determining the amount of current flowing through the first LED and the second LED is provided in series, and the first current path returned to one. Is provided in series with the second current path and is connected by a fifth current path to a transistor that determines the amount of current flowing through the first LED and the second LED .
The resistance element and the transistor are connected to the negative electrode of the DC power supply, and the resistance element and the transistor are connected to the negative electrode of the DC power supply.
The FET related to the third current path and the FET related to the fourth current path are connected to the transistor.
The total impedance of the first LED related to the third current path and the total impedance of the second LED related to the fourth current path are equal.
A control circuit for a lighting device, characterized in that the total impedance of the FET related to the third current path and the total impedance of the FET related to the fourth current path are equal to each other. A sixth current path connecting the LED and the FET related to the third current path and the FET and the LED related to the fourth current path is further provided.
The control circuit for a lighting device according to claim 1, wherein the sixth current path is provided with a semiconductor rectifying element. The lighting device according to claim 1 or 2, wherein the number of the first LED according to the third current path and the number of the second LED according to the fourth current path is one each. Control circuit for. The control circuit for a lighting device according to any one of claims 1 to 3, further comprising an LED that is always lit in series in the first current path that has returned to one.

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