JP5699275B2 - LED lighting device and lighting apparatus using the same - Google Patents

Description

  The present invention relates to an LED lighting device and a lighting fixture using the same.

  In recent years, with the increase in luminous efficiency of LEDs (light emitting diodes), it has become possible to use light emitting diodes with low power consumption and long life as light sources of lighting devices. It is disclosed in Patent Document 1. An illumination device described in Patent Document 1 includes an LED board on which a plurality of light emitting diodes are mounted on one surface, a circuit board on which a power supply circuit component including a constant current portion that makes the forward current of each light emitting diode constant is mounted, Is held inside the outer tube body.

JP 2009-43447 A

  By the way, the above-mentioned conventional example has a plurality of light emitting diodes mounted on an LED substrate. Conventionally, such LED substrates are connected in series or in parallel as a single LED module. On the other hand, there has never been any LED lamp that holds such an LED module held in a tube in parallel connection.

  Here, for example, when two LED lamps are connected in parallel to be lit, if the forward voltage of the light emitting diode of each LED lamp varies, the tube voltage of each LED lamp also varies. As a result, a difference also occurs in the lamp current flowing through each LED lamp, and there is a problem that a difference occurs in the light output of each LED lamp.

  In addition to the variation in forward voltage of the light emitting diodes, there is a problem that the lamp current flowing through each LED lamp varies due to variations in the performance of the components constituting the lighting device, resulting in a difference in the light output of each LED lamp. It was. As a means for solving the above problem, there can be considered means for providing a lighting circuit for each LED lamp for controlling the lamp current to be constant. However, this means has a problem that the lighting device becomes expensive.

  The present invention has been made in view of the above points, and provides an LED lighting device that can reduce the difference in light output between LED lamps connected in parallel with each other and a lighting fixture using the LED lighting device. The purpose is to provide.

The LED lighting device according to the present invention includes at least one switching element, a first inductor and a second inductor, a first capacitor and a second capacitor, and the first inductor and the first inductor. A series circuit of a capacitor and a series circuit of the second inductor and the second capacitor are connected in parallel to one end of the switching element, and an input voltage is changed by switching on / off of the switching element. A voltage conversion unit that converts the converted output voltage to a first LED lamp and a second LED lamp each including one to a plurality of light-emitting diodes, and converts the converted output voltage to a direct current voltage, If by the first capacitor charged by the path through the inductor supplying lighting power to the first LED Lumped In the first the second the second capacitor charged inductor path through the supplying lighting power to the second LED lamp, the first inductor and the second inductor, the respective The first diode and the second diode are connected in series, and the first diode has an anode connected to one end of the switching element, a cathode connected to the first inductor, and the second diode has an anode A cathode is connected to the second inductor at one end of the switching element, and both the first inductor and the second inductor have secondary windings and are induced in the secondary windings. A zero-cross detector that detects a zero-cross of a main winding current flowing through each inductor from a secondary winding voltage; and the voltage converter detects the zero-cross The switching element is driven based on an output signal from parts, the zero-crossing detection unit transmits the output signal to the voltage converter at said detected zero crossing of the main winding current among destinations of the inductor timing It is characterized by that.

Lighting apparatus of the present invention is characterized by comprising a LED lighting device of the above SL, and a fixture main body for holding the LED lighting device and the respective LED lamps.

  The present invention has an effect that it is possible to reduce the difference in the light output of each LED lamp connected in parallel with an inexpensive structure.

It is the circuit schematic which shows Embodiment 1 of the LED lighting device which concerns on this invention. It is explanatory drawing of the light emitting diode in an LED lighting device same as the above, (a) is a figure which shows the current-voltage characteristic of the forward direction of one light emitting diode, (b) is an example of the LED lamp which connected the several light emitting diode. (C) is a figure which shows the current-voltage characteristic of the forward direction of the LED lamp shown to (b). It is a figure which shows the current-voltage characteristic of a forward direction when there exists dispersion | variation in the LED lamp which consists of a several light emitting diode. It is the circuit schematic which shows the case where a 1st diode and a 2nd diode are not provided in the LED lighting device same as the above. (A) is a figure which shows the current-voltage characteristic of a forward direction when there exists dispersion | variation in the forward voltage of each LED lamp in the LED lighting device same as the above, (b) is the order of each LED lamp in the circuit structure of FIG. It is a figure which shows the current-voltage characteristic of the forward direction when there exists dispersion | variation in direction voltage. It is the circuit schematic which shows Embodiment 2 of the LED lighting device which concerns on this invention. It is the circuit schematic which shows the case where a 1st diode and a 2nd diode are not provided in the LED lighting device same as the above. It is the circuit schematic which shows Embodiment 3 of the LED lighting device which concerns on this invention. It is operation | movement explanatory drawing when there is no dispersion | variation in the inductance of a 1st inductor and a 2nd inductor in the LED lighting device same as the above. It is operation | movement explanatory drawing at the time of based on the inductor which detected the zero cross previously in the LED lighting device same as the above. It is operation | movement explanatory drawing at the time of based on the inductor which detected zero crossing later in the LED lighting device same as the above. It is the schematic which shows embodiment of the lighting fixture which concerns on this invention.

(Embodiment 1)
Hereinafter, Embodiment 1 of the LED lighting device according to the present invention will be described with reference to the drawings. As shown in FIG. 1, the present embodiment includes a rectifying unit 1, a boosting unit 2, a bucking unit 3, and a driver 4 that supplies a driving signal to each of switching elements Q <b> 1, Q <b> 2, and Q <b> 20 described later. An external AC power supply AC1 and a switch SW1 for switching on / off the power supply path from the AC power supply AC1 to the present embodiment are connected to the input end of the present embodiment. In addition, a first LED lamp 5 and a second LED lamp 6 each formed by connecting a plurality of light emitting diodes 50 and 60 in series are connected in parallel to the output end of the present embodiment.

  As shown in FIG. 1, the rectifying unit 1 is composed of, for example, a diode bridge, and full-wave rectifies the AC voltage input from the AC power supply AC <b> 1 and outputs a pulsating voltage to the subsequent boosting unit 2.

  As shown in FIG. 1, the booster unit 2 includes a series circuit of an inductor L20 and a switching element Q20, and a series circuit of a diode D20 and a capacitor C20 connected in parallel to the switching element Q20. The switching element Q20 is composed of an N-type channel MOSFET and is controlled to be turned on / off by receiving a drive signal from the driver 4. Therefore, the booster 2 boosts the pulsating voltage from the rectifier 1 by appropriately controlling on / off of the switching element Q20, converts it to a DC voltage of a predetermined voltage, and outputs it to the subsequent buck 3 To improve the power factor.

  As shown in FIG. 1, the step-down unit 3 includes a series circuit of a first switching element Q1 and a second switching element Q2. The connection point of each switching element Q1, Q2 includes a series circuit of a first diode D1, a first inductor L1, a first capacitor C1, a second diode D2, a second inductor L2, and a second capacitor. The C2 series circuit is connected in parallel. A diode D3 for flowing a regenerative current is connected in parallel to the series circuit of the first inductor L1 and the first capacitor C1. Similarly, a diode D4 for flowing a regenerative current is connected in parallel to the series circuit of the second inductor L2 and the second capacitor C2. The first LED lamp 5 is connected in parallel to the first capacitor C1, and the second LED lamp 6 is connected in parallel to the second capacitor C2.

  The first switching element Q1 is composed of an N-type channel MOSFET and is controlled to be turned on / off by receiving a drive signal from the driver 4. Accordingly, when the first switching element Q1 is turned on, the first capacitor C1 and the second capacitor C2 are passed through the first diode D1 and the second diode D2, and the first inductor L1 and the second inductor L2. To charge. When the first switching element Q1 is off, a regenerative current is passed through the diodes D3 and D4, and the first capacitor C1 and the second capacitor C2 are discharged. Is reduced and applied to the LED lamps 5 and 6 in the subsequent stage. In other words, in the present embodiment, a voltage conversion unit is configured in which the step-down unit 3 and the driver 4 convert the input voltage into a predetermined DC voltage and supply it to the LED lamps 5 and 6.

  In order to start the switching operation of the first switching element Q1, the driver 4 switches on the second switching element Q2 before starting the operation, so that the first switching element Q1 and the second switching element Q2 are switched on. The midpoint potential with the element Q2 is set to about 0V. After the start of the switching operation, the driver 4 switches off the second switching element Q2. Here, instead of providing the second switching element Q2, a resistance of about several hundred kΩ may be inserted between the source terminal of the first switching element Q1 and the ground. In this case, since the source voltage of the first switching element Q1 at the start of the switching operation can be set to about 0 V, the same function as when the second switching element Q2 is provided can be achieved.

  Hereinafter, the case where there is variation in the forward voltage of each LED lamp will be described. FIG. 2A shows current-voltage characteristics in the forward direction of the light-emitting diodes 50 and 60 forming the LED lamps 5 and 6. As shown in the figure, the current change with respect to the voltage change of the light emitting diodes 50 and 60 is steep. For example, the forward current is different by 40 mA when the forward voltage is 2.0 V and 2.1 V. Here, as in the present embodiment, each of the LED lamps 5 and 6 includes a plurality of light emitting diodes 50 and 60, respectively. For example, as shown in FIG. 2 (b), if an LED lamp is a series circuit in which 20 light-emitting diodes are connected in series and connected in parallel in 5 rows, the current-voltage characteristics in the forward direction of the LED lamp. Is as shown in FIG. The variation in forward voltage in such an LED lamp means that the forward current with respect to the forward voltage is different as shown in FIG.

  Here, as shown in FIG. 4, consider a case where each of the LED lamps 5 and 6 is lit with a configuration in which the first diode D1 and the second diode D2 are excluded from the present embodiment. The applied voltage of the LED lamps 5 and 6 becomes a voltage corresponding to the forward voltage of the LED lamps 5 and 6 depending on the current supplied according to the switching frequency and on-time of the first switching element Q1. And as shown to Fig.5 (a), when there exists dispersion | variation in the forward voltage of each LED lamp 5 and 6, the 2nd LED lamp with a small forward voltage is changed from the 1st LED lamp 5 with a large forward voltage. A current flows into 6 (see FIG. 4). As a result, the applied voltages of the LED lamps 5 and 6 become equal, and a larger lamp current flows in the second LED lamp 6 than in the first LED lamp 5. As a result, in the example shown in FIG. 5B, a difference in lamp current of 100 mA occurs between the first LED lamp 5 and the second LED lamp 6. For this reason, there is a difference in light output between the first LED lamp 5 and the second LED lamp 6, so that the brightness of the LED lamps 5 and 6 is different.

  On the other hand, in the present embodiment, since the first diode D1 and the second diode D2 are provided, even if the forward voltage of the LED lamps 5 and 6 varies, the LED lamp from one LED lamp to the other LED Current can be prevented from flowing into the lamp. Accordingly, the voltage applied to each of the LED lamps 5 and 6 has a voltage value corresponding to the supply current and the forward voltage via the first switching element Q1, respectively. The difference is reduced.

  As described above, the present embodiment reduces the difference in the lamp current flowing through the LED lamps 5 and 6 in parallel even if the forward voltage of the LED lamps 5 and 6 varies. A difference in light output between the connected LED lamps 5 and 6 can be reduced. In addition, the present embodiment can achieve the above effect by an inexpensive configuration in which the first diode D1 and the second diode D2 are provided in the step-down unit 3 that is a voltage conversion unit.

(Embodiment 2)
Hereinafter, Embodiment 2 of the LED lighting device according to the present invention will be described with reference to the drawings. However, since the basic configuration of the present embodiment is common to that of the first embodiment, common portions are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, as shown in FIG. 6, a detection resistor R1 connected to the low potential side of each LED lamp 5, 6 to detect the sum of the lamp currents flowing through each LED lamp 5, 6 and the lamp current And a control unit 7 that transmits a control signal to the driver 4 so that the sum becomes a predetermined value.

  The driver 4 includes an operational amplifier (not shown), for example, and performs feedback control so that the command value included in the control signal from the control unit 7 matches the current value detected by the detection resistor R1. That is, the driver 4 controls the switching frequency and on-time of the first switching element Q1 so that the sum of the lamp currents flowing through the LED lamps 5 and 6 becomes a predetermined current value.

  Here, as shown in FIG. 7, the case where each LED lamp 5 and 6 is made to light by the structure except the 1st diode D1 and the 2nd diode D2 from this embodiment is considered. In this case, as described in the first embodiment, a current flows from the first LED lamp 5 having a large forward voltage to the second LED lamp 6 having a small forward voltage. Then, the driver 4 performs control so that the sum of the lamp currents flowing through the LED lamps 5 and 6 becomes a predetermined current value by the feedback control described above, and therefore, the first current by the amount of current flowing into the second LED lamp 6 is set. The lamp current flowing through the LED lamp 5 becomes smaller.

  On the other hand, in the present embodiment, even if there is a variation in the forward voltage of the LED lamps 5 and 6 with an inexpensive configuration in which the first diode D1 and the second diode D2 are provided as in the first embodiment, A difference in lamp current flowing through the LED lamps 5 and 6 can be reduced. For this reason, in this embodiment, while the difference of the light output of each LED lamp 5 and 6 connected in parallel with 2 lamps can be reduced, the sum of the lamp current which flows through each LED lamp 5 and 6 can be kept constant.

(Embodiment 3)
Hereinafter, Embodiment 3 of the LED lighting device according to the present invention will be described with reference to the drawings. However, since the basic configuration of the present embodiment is common to that of the second embodiment, common portions are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 8, the present embodiment is based on the secondary windings provided in the first inductor L1 and the second inductor L2, respectively, and the secondary winding voltage induced in these secondary windings. A zero cross detector 8 for detecting zero cross is provided. In the present embodiment, a resistor (not shown) is inserted between the source terminal of the first switching element Q1 and the ground instead of providing the second switching element Q2.

  The zero-cross detector 8 is composed of, for example, a rectifier element such as a diode or a resistor, and the main winding current flowing through each inductor L1, L2 from the secondary winding voltage induced in the secondary winding of each inductor L1, L2. Detect zero cross. That is, a voltage corresponding to the voltage of the main winding of each of the inductors L1 and L2 is generated in the secondary winding of each of the inductors L1 and L2, and the zero crossing timing at which the main winding current of the main winding is completely discharged is generated. The polarity is reversed. For this reason, the zero cross detector 8 detects the timing at which the polarity of the secondary winding voltage induced in the secondary winding of each of the inductors L1 and L2 is inverted as the zero cross of the main winding current.

  And the zero cross detection part 8 transmits an ON signal (output signal) to the driver 4 at the timing which detected the zero cross of the main winding current previously among the inductors L1 and L2. When the driver 4 receives the ON signal from the zero-cross detection unit 8, the driver 4 switches on the first switching element Q1, and the current value detected by the detection resistor R1 matches the command value included in the control signal from the control unit 7. Then, the first switching element Q1 is switched off. That is, the driver 4 performs critical control based on the ON signal from the zero-cross detection unit 8 and the current value detected by the detection resistor R1.

  Hereinafter, critical control when there is no variation in the inductances of the inductors L1 and L2 will be described with reference to FIG. FIG. 9 shows the waveforms of the main winding currents IL1 and IL2 flowing through the inductors L1 and L2, the waveform of the gate voltage of the first switching element Q1, and the secondary induced in the secondary windings of the inductors L1 and L2. The waveform of winding voltage VL0 is shown. As shown in the figure, when there is no variation in the inductances of the inductors L1 and L2, the main winding currents IL1 and IL2 zero-cross at almost the same timing, so that the main winding currents IL1 and IL2 are smoothed. The lamp currents I1 and I2 are substantially equal.

  Next, the case where the inductances of the inductors L1 and L2 vary and the ON signal is transmitted to the driver 4 at the timing when the zero crossing of the main winding current is detected later among the inductors L1 and L2 will be described with reference to FIG. explain. FIG. 11 shows the waveforms of the main winding currents IL1 and IL2 when the inductance of the first inductor L1 is larger than the inductance of the second inductor L2, and the waveform of the gate voltage of the first switching element Q1. Show. As shown in the figure, the main winding current IL1 flows through the first inductor L1 where the main winding current IL1 previously crossed zero until the main winding current IL2 of the second inductor L2 crosses zero. Absent. For this reason, the on-time T1 and the off-time T2 of the first switching element Q1 are compared, and when T1 <T2, the period during which no current flows through the first inductor L1 becomes long. As a result, the difference between the lamp currents I1 and I2 increases, and the difference between the light outputs of the LED lamps 5 and 6 increases.

  Here, the case where an ON signal is transmitted to the driver 4 at the timing when the zero cross of the main winding current is detected first among the inductors L1 and L2 as in the present embodiment will be described with reference to FIG. In FIG. 10, similarly to FIG. 11, the waveforms of the main winding currents IL1 and IL2 when the inductance of the first inductor L1 is larger than the inductance of the second inductor L2, and the first switching element Q1 The waveform of the gate voltage is shown. As shown in the figure, the difference between the lamp currents I1 and I2 is small compared to the case where the ON signal is transmitted to the driver 4 at the timing when the zero cross of the main winding current is detected later among the inductors L1 and L2. Thus, the difference in light output between the LED lamps 5 and 6 can be kept small.

  As described above, in the present embodiment, even when the inductances of the inductors L1 and L2 that contribute most to the lamp currents I1 and I2 flowing through the LED lamps 5 and 6 vary, the light output of the LED lamps 5 and 6 is as follows. Can be kept small.

  Hereinafter, embodiments of a lighting apparatus according to the present invention will be described with reference to the drawings. As shown in FIG. 12, the present embodiment includes an instrument main body 100 made of a long box housing the LED lighting device (not shown) of any of the first to third embodiments. Two pairs of sockets 101 and 102 are mechanically held at both longitudinal ends of the instrument body 100, and straight tube type LED lamps 5 and 6 are detachably attached to the sockets 101 and 102, respectively. Is done.

  This embodiment can produce the same effect as any of the first and second embodiments by using any of the LED lighting devices of the first and second embodiments. Of course, the configuration of the lighting fixture is not limited to the configuration of the present embodiment, and any other configuration is possible as long as the configuration includes an LED lighting device and a fixture main body that holds the LED lighting device and the LED lamp. May be.

3 Step-down unit (voltage converter)
4 Drivers (voltage converter)
5 1st LED lamp 50 Light emitting diode 6 2nd LED lamp 60 Light emitting diode C1 1st capacitor C2 2nd capacitor D1 1st diode D2 2nd diode L1 1st inductor L2 2nd inductor Q1 1st 1 switching element

Claims (2)

At least one switching element; a first inductor; a second inductor; a first capacitor; a second capacitor; a series circuit of the first inductor and the first capacitor; A series circuit of the inductor 2 and the second capacitor is connected in parallel to one end of the switching element, and converts the input voltage to a desired DC voltage by switching on / off of the switching element. A voltage converter for supplying the output voltage to the first LED lamp and the second LED lamp each having one or more light emitting diodes,
The voltage converter supplies lighting power to the first LED lamp by the first capacitor that is charged through a path through the first inductor, and is charged through a path through the second inductor. lighting power to the second LED lamp by said second capacitor supplies,
Wherein the first inductor and the second inductor, a first diode and a second diode connected in series,
The first diode has an anode connected to one end of the switching element and a cathode connected to the first inductor,
The second diode has an anode connected to one end of the switching element and a cathode connected to the second inductor,
Each of the first inductor and the second inductor has a secondary winding, and a zero cross of a main winding current flowing through each inductor is determined by a secondary winding voltage induced in each secondary winding. Equipped with a zero-cross detector to detect,
The voltage conversion unit drives the switching element based on an output signal from the zero-cross detection unit, and the zero-cross detection unit detects the zero-cross of the main winding current first in each inductor. An LED lighting device , wherein the output signal is transmitted to a conversion unit . A lighting fixture comprising: the LED lighting device according to claim 1; and a fixture main body that holds the LED lighting device and the LED lamp .

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