JP2013037837A - Led lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make flicker less noticeable when driving an LED element directly with a pulsating voltage obtained by rectifying a commercial power supply.SOLUTION: The number of driven LED elements is switched depending on a pulsating voltage VM, by driving LED strings STR1-STR4 with the pulsating voltage VM obtained by full-wave rectifying a commercial power supply VAC, and starting the operation of a plurality of current control circuits 3A-3D selectively. A driving current I1 of the current control circuit 3A pertaining to driving of the smallest number of LED elements is set to a larger current value when compared with a driving current I2 of the current control circuit 3B pertaining to driving of a next to the smallest number of LED elements.

Description

  The present invention relates to an LED lighting device that uses an LED (Light Emitting Diode) as a light source.

  In recent years, LED lighting devices that use LEDs as light sources have become widespread. With regard to this type of LED lighting device, for example, in Patent Document 1, a series circuit of LED elements is directly driven by a pulsating voltage obtained by rectifying a commercial power supply in order to easily and efficiently emit a plurality of LEDs. Thus, a configuration is disclosed in which the number of LED elements used for driving is switched according to the pulsating voltage value.

JP 2006-147933 A

  By the way, in this type of LED element, when the LED element is directly driven by a pulsating voltage obtained by rectifying a commercial power supply, the product life of the smoothing capacitor is limited by not using a large-capacity smoothing capacitor. It can be avoided and can be used for a long time.

  However, when the LED element is directly driven by the pulsating voltage obtained by rectifying the commercial power supply, there is a problem that the flicker is conspicuous.

  The present invention has been made in view of the above circumstances, and provides an LED lighting device that can make flicker less noticeable when an LED element is directly driven by a pulsating voltage obtained by rectifying a commercial power supply. Objective.

  In order to solve the above problems, the invention according to claim 1 is based on a rectifier circuit that outputs a pulsating voltage by full-wave rectifying a commercial power supply, and a plurality of LED strings including one or a plurality of LED elements. A series circuit of LED strings, one end of which is connected to the positive output end or the negative seed end of the rectifier circuit, and one end of the corresponding LED string in the series circuit of the LED strings. A plurality of current control circuits for causing a drive current to flow to the negative output terminal of the rectifier circuit or a drive current to flow from the positive output terminal of the rectifier circuit; and the plurality of current controls by monitoring the pulsating voltage A control circuit for controlling the operation of the circuit, wherein the control circuit selectively activates the operations of the plurality of current control circuits according to the pulsating voltage, The number of LED elements to be driven is switched according to the current voltage, and the plurality of current control circuits are configured such that the drive current of the current control circuit for driving the LED element having the smallest number of elements is subsequently It is characterized in that the current value is set to be larger than the driving current of the current control circuit for driving.

  According to a second aspect of the present invention, in the first aspect of the invention, the control circuit includes a plurality of comparison circuits that respectively output a comparison result between the pulsating voltage and a reference voltage, and the plurality of comparison circuits. And a plurality of logic operation circuits that sequentially output control signals for selectively starting up the operations of the plurality of current control circuits according to the pulsating voltage by the logic operation processing of the comparison result.

  According to the first aspect of the present invention, the LED strings can be directly driven by the pulsating voltage, and the LED elements can be efficiently driven by switching the number of LED elements to be driven according to the pulsating voltage. . At this time, the drive current of the current control circuit for driving the LED element with the smallest number of elements is set to a large current value compared to the drive current of the current control circuit for driving the LED element with the smallest number of elements. Therefore, when the number of LED elements used for light emission is reduced before and after the period during which light emission stops, it is possible to prevent a decrease in the total amount of emitted light. Thereby, flicker can be made inconspicuous.

  According to the second aspect of the invention, a more specific configuration that can achieve the effects of the first aspect of the invention can be provided by the discrete circuit.

It is a figure of the LED lighting apparatus which concerns on 1st Embodiment of this invention. It is a figure where it uses for description of operation | movement of the LED lighting apparatus of FIG. It is a figure of the LED lighting apparatus which concerns on 2nd Embodiment of this invention. It is a figure of the LED lighting apparatus which concerns on 3rd Embodiment of this invention.

[First Embodiment]
A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a connection diagram illustrating an LED lighting device according to a first embodiment of the present invention. In the LED lighting device 1, each of the LED strings STR1, STR2, STR3, and STR4 is an array of LED elements in which a plurality of LED elements are connected in series. The LED strings STR <b> 1 to STR <b> 4 are arranged such that the LED elements are continuous in a straight line, and the LED lighting device 1 forms a rod-shaped light source using the LED elements of the LED strings STR <b> 1 to STR <b> 4 as light sources. In the LED lighting device 1, these LED strings STR1 to STR4 are further connected in series to form a series circuit of LED strings. In the following, the forward voltages of the LED strings STR1, STR2, STR3, and STR4 (the total voltages of the forward voltages of the series-connected LED elements that form the LED strings) are respectively denoted by symbols Vf1, Vf2, Vf3, Indicated by Vf4. In the LED lighting device 1, capacitors C1A, C1B, C1C, and C1D are arranged in parallel to the LED strings STR1, STR2, STR3, and STR4, respectively, thereby alleviating high-pressure stress on the LED elements and further flickering. To reduce.

  In the LED lighting device 1, the rectifier circuit 2 is a diode bridge circuit composed of diodes D1, D2, D3, and D4, and outputs a pulsating voltage VM by full-wave rectifying the commercial power supply VAC. The LED illumination device 1 directly drives the LED strings STR1 to STR4 to emit light with the pulsating voltage VM output from the rectifier circuit 2. Thereby, the LED lighting device 1 omits the use of a large-capacity smoothing capacitor and drives the LED element, and prevents a decrease in product life when the large-capacity smoothing capacitor is used. That is, as the smoothing capacitor, an electrolytic capacitor using an electrolytic solution is applied because a large capacity is required. However, when an electrolytic capacitor is used, the electrolytic solution may be deteriorated due to a temperature rise in the lighting device. In this case, the capacity may be significantly reduced, the light may flicker or the light may not be lit. However, in this embodiment, by not using a smoothing capacitor in the first place, it is possible to prevent such deterioration of the function and prevent a reduction in product life.

  That is, in the LED lighting device 1, the first LED strings STR1 side end of the series circuit of the LED strings STR <b> 1 to STR <b> 4 is connected to the positive side output end of the full-wave rectifier circuit 2. In the LED lighting device 1, the other ends of the corresponding LED strings STR1 to STR4 in this series circuit are connected to the first to fourth current control circuits 3A to 3D, respectively, and the first to fourth current control circuits 3A. It is connected to the negative side output terminal of the full-wave rectifier circuit 2 through 3D. More specifically, in the LED lighting device 1, the connection middle points of the LED strings STR1 to STR4 in the series circuit of the LED strings STR1 to STR4 are the first, second, and third current control circuits 3A, 3B, and 3C, respectively. To the negative output end of the full-wave rectifier circuit 2. Furthermore, the fourth LED strings STR4 side end of the series circuit of LED strings STR1 to STR4 is connected to the negative side output end of the full-wave rectifier circuit 2 via the fourth current control circuit 3D.

  The LED lighting device 1 controls the operations of the first to fourth current control circuits 3A to 3D by the control circuit 6 including the voltage monitoring circuit 4 and the switching circuit 5, and thereby, according to the pulsating voltage VM. The LED strings STR1 to STR4 are driven by switching the number of LED elements to be driven.

  For this reason, the voltage monitoring circuit 4 monitors the pulsating voltage VM output from the rectifying circuit 2 and outputs a monitoring result. That is, the voltage monitoring circuit 4 divides the pulsating voltage VM by the voltage dividing resistors R1 and R2, and generates a divided voltage for monitoring. Here, a semi-fixed resistor is applied to the voltage dividing resistor R2, so that the voltage monitoring circuit 4 is set so that the voltage dividing ratio can be adjusted.

  The voltage monitoring circuit 4 inputs the divided voltage for monitoring to the inverting input terminals of the first to fourth comparison circuits 7A, 7B, 7C, and 7D via the input resistors R3A, R3B, R3C, and R3D, respectively. Here, the reference voltages V1, V2, V3, and V4 are supplied to the non-inverting input terminals of the comparison circuits 7A, 7B, 7C, and 7D, respectively. As a result, the first to fourth comparison circuits 7A, 7B, 7C, and 7D monitor the pulsating current voltage VM through the divided voltage for monitoring using the reference voltages V1, V2, V3, and V4, respectively, and the reference voltage V1. When the pulsating voltage VM is higher than the voltage determined by V2, V3, and V4, the output terminal voltage is lowered.

  Specifically, the first comparison circuit 7A lowers the comparison output when the pulsating voltage VM is higher than the forward voltage Vf1 necessary for lighting the first LED strings STR1. Further, the second comparison circuit 7B causes the comparison output to fall when it is higher than the forward voltage Vf1 + Vf2 required for lighting the series circuit of the first and second LED strings STR1 and STR2. The third comparison circuit 7C displays the comparison result when the pulsating voltage VM is higher than the forward voltage Vf1 + Vf2 + Vf3 required for lighting the series circuit of the first, second, and third LED strings STR1, STR2, and STR3. Fall down. Further, the fourth comparison circuit 7D has a pulsating voltage VM higher than the forward voltage Vf1 + Vf2 + Vf3 + Vf4 required for lighting the series circuit of the first, second, third and fourth LED strings STR1, STR2, STR3 and STR4. Then, the comparison result is lowered.

  The switching circuit 5 sequentially activates the operations of the current control circuits 3A to 3D based on the comparison results of the comparison circuits 7A to 7D. That is, in the switching circuit 5, the first to fourth logic operation circuits 8A to 8C are respectively logic operation circuits. The first logic operation circuit 8A is a case where the control data DC and the comparison outputs of the second to fourth comparison circuits 7B to 7D rise, and the comparison output of the first comparison circuit 7A falls. (That is, when the pulsating voltage VM is higher than the voltage required for lighting the first LED strings STR1 and lower than the voltage required for lighting the series circuit of the first and second LED strings STR1 and STR2) When the control data DC is at the H level), the output terminal is lowered. In this embodiment, the control data DC is a control signal for controlling the lighting of the LED lighting device 1. When the LED lighting device 1 is turned on, the control data DC is set to the H level by a switch or the like, for example.

  The second logical operation circuit 8B is a case where the control data DC and the comparison outputs of the third and fourth comparison circuits 7C and 7D rise, and the first and second comparison circuits 7A and 7B. When the comparison output is falling (that is, the pulsating voltage VM is higher than the voltage required for lighting the series circuit of the first and second LED strings STR1 and STR2, the first, second and third LED strings When the voltage is lower than the voltage necessary for lighting the series circuit of STR1, STR2, and STR3 and the control data DC is at the H level), the output terminal is lowered.

  In the third logic operation circuit 8C, the control data DC and the comparison output of the fourth comparison circuit 7D rise, and the comparison outputs of the first to third comparison circuits 7A to 7C fall. (Ie, the pulsating voltage VM is higher than the voltage required for lighting the series circuit of the first, second and third LED strings STR1, STR2 and STR3, and the first, second, third and fourth When the voltage is lower than the voltage required for lighting the series circuit of the LED strings STR1, STR2, STR3, and STR4 and when the control data DC is at the H level), the output terminal is lowered.

  The fourth logical operation circuit 8D is when the control data DC is rising and when the comparison outputs of the first to fourth comparison circuits 7A to 7D are falling (that is, the pulsating voltage VM is When the voltage is higher than the voltage required for lighting the series circuit of the first, second, third and fourth LED strings STR1, STR2, STR3 and STR4 and the control data DC is at the H level), the output terminal Fall down.

  As a result, the switching circuit 5 selectively lowers the outputs of the logic operation circuits 8A to 8D sequentially as the pulsating voltage VM increases. In the LED lighting device 1, the outputs of the first to fourth logic operation circuits 8A to 8D are input to the first to fourth current control circuits 3A to 3D, respectively.

  Here, the first current control circuit 3A determines the connection middle point of the first and second LED strings STR1 and STR2 through the series circuit of the FET Q1A and the current-voltage conversion resistor RSA, and outputs the negative side output of the full-wave rectifier circuit 2. Connect to the end. The first current control circuit 3A inputs the FETQ1-side voltage of the current-voltage conversion resistor RSA to the non-inverting input terminal of the operational amplifier circuit 9A via the input resistor R6A. The operational amplifier circuit 9A is provided with a feedback circuit including a resistor R7A and a capacitor CA, and drives the FET Q1A by an operational output. Thereby, the first current control circuit 3A controls the current of the FET Q1A by controlling the gate voltage of the FET Q1A so that the terminal voltage of the current-voltage conversion resistor RSA becomes equal to the voltage of the non-inverting input terminal of the operational amplifier circuit 9A. To do.

  Here, in the operational amplifier circuit 9A, a predetermined reference voltage Vref is input to the non-inverting input terminal via the resistor R8A, and this non-inverting input terminal is grounded via the grounding resistor R9A. The ground resistor R9A is connected at both ends to the source and drain of the FET Q2A, and the FET Q2 is on / off controlled by the output of the first logic operation circuit 8A. As a result, the first current control circuit 3A assumes that the control data DC is held at the H level, the pulsating current voltage VM is higher than the voltage necessary for lighting the first LED strings STR1, and the first current control circuit 3A Only when the voltage is lower than the voltage required for lighting the series circuit of the second LED strings STR1 and STR2, the FET Q2A is set to the OFF state, and the reference voltage Vref, the resistor R8A, A predetermined voltage determined by R9A is applied. The current control circuit 3A starts operation by applying the predetermined voltage, and causes the current I1 corresponding to the applied voltage to flow out from the connection midpoint of the first and second LED strings STR1 and STR2. Further, when the pulsating voltage VM is a voltage other than this, the FET Q2A is set to the on state, the voltage at the non-inverting input terminal of the operational amplifier circuit 9A is set to 0V, and the operation is stopped thereby, the first and first The current outflow from the connection midpoint of the two LED strings STR1 and STR2 is stopped.

  The second to fourth current control circuits 3B to 3D are configured in the same manner as the first current control circuit 3A. As a result, the second current control circuit 3B requires the pulsating voltage VM to light the series circuit of the first and second LED strings STR1 and STR2 on the assumption that the control data DC is held at the H level. The FET Q2B is set to the OFF state only when the voltage is higher than the required voltage and lower than the voltage required for lighting the series circuit of the first to third LED strings STR1 to STR2, and the non-inverting input terminal of the operational amplifier circuit 9B A predetermined voltage determined by the reference voltage Vref and the resistors R8B and R9B is applied. As a result, the current control circuit 3B starts up the operation and causes the current I2 corresponding to the applied voltage to flow out from the connection midpoint of the second and third LED strings STR2 and STR3. When the pulsating voltage VM is a voltage other than the above, the FET Q2B is set to the on state, the voltage at the non-inverting input terminal of the operational amplifier circuit 9B is set to 0 V, and the operation is stopped thereby to stop the second and second The current outflow from the midpoint of connection of the three LED strings STR2 and STR3 is stopped.

  Further, the third current control circuit 3C is required for lighting the series circuit of the first to third LED strings STR1 to STR3 on the assumption that the control data DC is held at the H level. Only when the voltage is higher than the voltage and lower than the voltage necessary for lighting the series circuit of the first to fourth LED strings STR1 to STR4, the FET Q2C is set to the off state, and the non-inverting input terminal of the operational amplifier circuit 9C is set as a reference. A predetermined voltage determined by voltage Vref and resistors R8C and R9C is applied. As a result, the current control circuit 3C starts up the operation and causes the current I3 corresponding to the applied voltage to flow out from the connection midpoint of the third and fourth LED strings STR3 and STR4. When the pulsating voltage VM is a voltage other than this, the FET Q2C is set to the on state, the voltage at the non-inverting input terminal of the operational amplifier circuit 9C is set to 0 V, the operation is stopped, and the third and fourth Current outflow from the connection midpoint of the LED strings STR3 and STR4 is stopped.

  Further, the fourth current control circuit 3D requires the pulsating current voltage VM to turn on the series circuit of the first to fourth LED strings STR1 to STR4 on the assumption that the control data DC is held at the H level. Only when the voltage is higher than the voltage, the FET Q2D is set to the OFF state, and a predetermined voltage determined by the reference voltage Vref and the resistors R8D and R9D is applied to the non-inverting input terminal of the operational amplifier circuit 9D. As a result, the current control circuit 3D starts up the operation and causes the current I4 corresponding to the applied voltage to flow out of the fourth LED string STR4. When the pulsating voltage VM is a voltage other than this, the FET Q2D is set to the on state, the voltage at the non-inverting input terminal of the operational amplifier circuit 9D is set to 0 V, the operation is stopped, and the fourth LED string STR4 Stop the current flow from the.

  Accordingly, as shown in FIG. 2, the LED lighting device 1 stops driving all the LED strings STR1 to STR4 and the pulsating voltage VM is Vf1 to Vf1 when the pulsating voltage VM is in the range of 0 [V] to Vf1. In the range of VF1 + Vf2, only the first LED string STR1 is caused to emit light. When the pulsating voltage VM is in the range of Vf1 + Vf2 to VF1 + Vf2 + Vf3, the series circuit of the first and second LED strings STR1 and STR2 is driven by the current control circuit 3B to emit light, and the pulsating voltage VM is in the range of Vf1 + Vf2 + Vf3 to VF1 + Vf2 + Vf3 + Vf4. The series circuit of the first to third LED strings STR1 to STR3 is driven by the current control circuit 3C to emit light. In the range where the pulsating voltage VM is Vf1 + Vf2 + Vf3 + VF4 or more, the series circuit of the first to fourth LED strings STR1 to STR4 is driven by the current control circuit 3D to emit light. In these FIG. 2, the drive currents by these current control circuits 3A to 3D are indicated by reference numerals I1 to I4.

  Thus, the LED lighting device 1 connects the LED strings STR1 to STR4 in series, and controls the drive of the current control circuits 3A to 3D connected to one end of the LED strings STR1 to STR4 in this series circuit, thereby causing the pulsating voltage VM Accordingly, the number of LED elements used for driving is switched to cause the LED strings STR1 to STR4 to emit light.

  By the way, when the LED element is driven in this way, all LED strings STR1 to STR4 stop emitting light when the pulsating voltage VM is in the range of 0 [V] to Vf1. Therefore, a pause period T1 in which all the LED elements stop emitting light periodically occurs. Further, before and after the rest period T1, only the first LED string STR1 emits light, so that the number of elements used for light emission is reduced and the amount of emitted light is small. Thereby, when the LED element is directly driven by the pulsating voltage, flicker becomes conspicuous.

  Therefore, in the LED lighting device 1, as shown in FIG. 2B, the driving current I1 of only the first LED strings STR1 before and after the pause period T1 is the first and second LEDs adjacent thereto. The current value is set to be larger than the drive current I2 related to the series circuit of the strings STR1 and STR2. This setting can be set by the current-voltage conversion resistor RSA and / or the voltage dividing resistors R8A and R9A. On the other hand, the drive currents I3 and I4 of the current control circuits 3C and 3D, which are other drive currents, are set to a current value equal to the drive current I2 of the second current control circuit 3B.

  As a result, the LED lighting device 1 makes the flicker inconspicuous by making the light emission stop in the pause period T1 and the decrease in light quantity before and after the pause period T1 inconspicuous.

  In the LED lighting device 1 of this embodiment, the number of LED elements to be driven is switched by switching the current control circuits 3A to 3D according to the pulsating voltage VM to be driven, and the LED element having the smallest number of elements is driven. By setting the drive current I1 of the current control circuit 3A related to the current control circuit 3A to a current value larger than the drive current I2 of the current control circuit 3B related to the drive of the LED element having a smaller number of elements, the commercial power supply is rectified. In the case where the LED element is directly driven by the pulsating voltage obtained as described above, flicker can be made inconspicuous.

  In addition, the control circuit 6 relating to the switching of the current control circuits 3A to 3D includes a plurality of comparison circuits 7A to 7D that respectively output comparison results between the pulsating voltage VM and the reference voltages V1 to V4, and the plurality of comparison circuits 7A. It is configured by a plurality of logic operation circuits 8A to 8D that output a control signal for selectively starting the operation of the current control circuits 3A to 3D sequentially according to the pulsating voltage VM by the logic operation processing of the comparison results of ˜7D. Thus, flicker can be made inconspicuous when the LED element is directly driven by a pulsating voltage obtained by composing a control circuit with a discrete circuit and rectifying the commercial power supply.

[Second Embodiment]
FIG. 3 is a diagram showing an LED lighting device according to a second embodiment of the present invention. In this LED illumination device 11, the same configuration as that of the LED illumination device 1 described above with reference to FIG.

  The LED lighting device 11 controls the operation of the first to fourth current control circuits 3A to 3D by the control circuit 16 including the voltage monitoring circuit 14 and the switching circuit 15, and is driven according to the pulsating voltage VM. The LED strings STR1 to STR4 are driven by switching the number of LED elements to be provided.

  The voltage monitoring circuit 14 is different from the voltage monitoring circuit 4 according to the first embodiment except that the fourth comparison circuit 7D is omitted and the reference voltage setting for the remaining comparison circuits 7A to 7C is different. Configured identically. That is, the first comparison circuit 7A causes the comparison result to fall when the pulsating voltage VM is higher than a voltage necessary for lighting the first LED strings STR1 by a certain voltage or more. In addition, the second comparison circuit 7B falls the comparison result when the pulsating voltage VM is higher than a voltage required for lighting the series circuit of the first and second LED strings STR1 and STR2 by a certain voltage or more. Further, the third comparison circuit 7C lowers the comparison result when the pulsating voltage VM is higher than a voltage required for lighting the series circuit of the first to third LED strings STR1 to STR3 by a certain voltage or more.

  The switching circuit 15 sequentially starts up the operations of the current control circuits 3A to 3D based on the comparison results of the comparison circuits 7A to 7C provided in the voltage monitoring circuit 14. That is, in the switching circuit 15, the first to fourth logic operation circuits 18A to 18C are respectively logic operation circuits. The first logic operation circuit 18A lowers the output terminal when the control data DC and the comparison outputs of the first to third comparison circuits 7A to 7C rise.

  The second logic operation circuit 18B is a case where the control data DC and the comparison outputs of the second and third comparison circuits 7B and 7C rise, and the comparison output of the first comparison circuit 7A falls. If so, turn off the output. The third logic operation circuit 18C is a case where the control data DC and the comparison output of the third comparison circuit 7C rise, and the comparison outputs of the first and second comparison circuits 7A and 7B fall. If so, turn off the output. The fourth logic operation circuit 18D lowers the output terminal when the control data DC is rising and the comparison outputs of the first to third comparison circuits 7A to 7C are falling.

  Accordingly, the switching circuit 15 selectively lowers the outputs of the logic operation circuits 18A to 18D sequentially as the pulsating voltage VM increases. In the LED lighting device 11, the outputs of the first to fourth logic operation circuits 18A to 18D are input to the first to fourth current control circuits 3A to 3D, respectively.

  Thereby, the LED lighting apparatus 11 of this 2nd Embodiment can acquire the effect similar to the LED lighting apparatus of 1st Embodiment by simple structure compared with the LED lighting apparatus 1 of 1st Embodiment.

[Third Embodiment]
FIG. 4 is a diagram showing an LED lighting device according to a third embodiment of the present invention. In this LED illumination device 21, the same configurations as those of the LED illumination devices 1 and 11 described above with reference to FIGS. 1 and 3 are denoted by the corresponding reference numerals, and redundant description is omitted. The LED illumination device 21 is provided with three LED strings STR1 to STR3. The LED lighting device 21 sequentially drives the LED strings STR1 to STR3 according to the pulsating voltage VM, thereby driving the LED strings STR1 to STR3 while switching the number of elements according to the pulsating voltage VM. The LED lighting device 21 drives the LED strings STR1 to STR3 by a control circuit 26 that is a digital signal processing circuit.

  That is, in the LED lighting device 21, each of the LED strings STR1 to STR3 has a negative output terminal side in the series circuit of the FET Q1A and the current-voltage conversion resistor RSA, the series circuit of the FET Q1B and the current-voltage conversion resistor RSB, the FET Q1C, and the current-voltage conversion resistor RSC. It is grounded through a series circuit. As a result, the LED strings STR1 to STR3 can detect the drive current via the terminal voltages of the current-voltage conversion resistors RSA, RSB, and RSC, respectively, and can further control the drive current by controlling the FETs Q1A, Q1B, and Q1C. Composed. The gates of the FETs Q1A, Q1B, and Q1C are grounded through gate resistors R10A, R10B, and R10C for extracting gate charges, respectively.

  The control circuit 26 divides the pulsating voltage VM by the voltage dividing resistors R1 and R2, and generates a divided voltage for monitoring. The control circuit 26 inputs the divided voltage for monitoring to the analog-digital conversion circuit (AD) 27 through the input resistor R11, performs analog-digital conversion processing here, and outputs it to the controller 28. Further, the control circuit 26 selects the terminal voltages of the current-voltage conversion resistors RSA, RSB, and RSC by the multiplexer 29 and inputs them to the analog-digital (AD) 30, where the analog-digital conversion processing is performed and input to the controller 28. The control circuit 26 inputs the control data output from the controller 28 to a digital analog (DA) 31 and converts it into a control signal based on an analog signal. The multiplexer 32 selectively selects the control signal for the FETs Q1A, Q1B, or Q1C. Output to.

  In the control circuit 26, the timing control circuit 33 controls the operations of the multiplexers 29 and 32 under the control of the controller 28. The controller 28 is a digital signal processing circuit that executes a predetermined processing procedure. The controller 28 monitors the divided voltage for monitoring via the analog-digital conversion circuit 27 by executing this processing procedure. Further, by this monitoring, the pulsating voltage VM is equal to or higher than the voltage Vf1 required for lighting the first LED string STR1, and the voltage Vf1 + Vf2 required for lighting the series circuit of the first and second LED strings STR1 and STR2. If smaller, the operation of the multiplexer 32 is controlled via the timing control circuit 33 so that the control signal output from the digital-analog conversion circuit 31 is output to the first FET Q1A.

  Further, the controller 28 is configured such that the pulsating voltage VM is equal to or higher than the voltage Vf1 + Vf2 required for lighting the series circuit of the first and second LED strings STR1 and STR2, and the first to third LED strings STR1 to STR3. When the voltage is lower than the voltage Vf1 + Vf2 + Vf3 required for lighting the series circuit, the operation of the multiplexer 32 is controlled via the timing control circuit 33 so that the control signal output from the digital-analog conversion circuit 31 is output to the second FET Q2B.

  In addition, when the pulsating voltage VM is equal to or higher than the voltage Vf1 + Vf2 required for lighting the series circuit of the first to third LED strings STR1 to STR3, the controller 28 outputs a control signal output from the digital / analog conversion circuit 31 to the third signal. The operation of the multiplexer 32 is controlled via the timing control circuit 33 so as to output to the FET Q2C.

  On the other hand, when the pulsating voltage VM is smaller than the voltage Vf1 required for lighting the first LED string STR1, the control signal is not output to any FET Q1A, Q1B, Q1C via the timing control circuit 33. Thus, the operation of the multiplexer 32 is controlled.

  Thus, the FETs Q1A, Q1B, and Q1C have their gates grounded by the gate resistors R10A, R10B, and R10C, respectively, so that when no control signal is input, the drive current flows out from the corresponding LED strings STR1, STR2, and STR3. Is controlled to stop. On the other hand, when a control signal is input via the multiplexer 32, a drive current corresponding to the setting of the gate voltage by this control signal is caused to flow out from the first to third LED strings STR1 to STR3. .

  In this way, the controller 28 switches the number of elements in accordance with the pulsating current voltage VM to drive the LED strings STR1 to STR3, sets the multiplexer 29 to correspond to the setting of the multiplexer 32, and controls it accordingly. The drive current due to the signal supply is detected by the terminal voltages of the corresponding current-voltage conversion resistors RSA, RSB, RSC.

  The controller 28 varies the control data output to the digital-analog conversion circuit 31 so that the drive current becomes the target current by monitoring the drive current based on the terminal voltage. Specifically, if the target currents are I1, I2, and I3, the terminal voltages of the current-voltage conversion resistors RSA, RSB, and RSC are VS1, VS2, and VS3, and the gain coefficients are k1, k2, and k3, VG1 (n) = VG1 (N-1) + k1 (I1-VS1 / RSA), VG2 (n) = VG2 (N-1) + k2 (I2-VS2 / RSB), VG3 (n) = VG3 (N-1) + k3 (I3-VS3 / RSC), the control data VG1, VG2, and VG3 are sequentially updated, and the control data VG1 and VG2 output to the digital / analog conversion circuit 31 so that the drive current becomes the target currents I1, I2, and I3. , VG3 is adjusted. In addition, by this, in this LED lighting device 21, the current control circuit related to the control of the drive current includes the control circuit 26, FETs Q1A, Q1B, Q1C, gate resistors R10A, R10B, R10C, current-voltage conversion resistors RSA, RSB, RSC. It is comprised by.

  In this embodiment, the drive currents I1, I2, and I3 are set in this way. In this embodiment, the drive current I1 related to driving the LED element with the smallest number of elements is subsequently driven to the LED element with the few elements. The current value is set larger than the driving current I2. The drive current I3 is set to be the same as the drive current I2. Thereby, even in this embodiment, the flicker becomes inconspicuous.

  In the third embodiment, even if the control circuit or the like is configured by a digital signal processing circuit, the same effects as those of the first embodiment and the second embodiment can be obtained.

[Fourth Embodiment]
The LED lighting device according to this embodiment is applied to optical communication, and transmission data provided for the optical communication is input to the control circuit instead of the control data described above. Thereby, the LED lighting apparatus of this embodiment modulates the light from the LED element used for illumination with the data for transmission, and sends this data for transmission by optical communication. The LED lighting device of this embodiment is configured in the same manner as the above-described LED lighting devices 1, 11, and 21 except that data input to the control circuit is different.

  In this embodiment, flicker can be made inconspicuous, so that desired data can be transmitted more stably than in the prior art when applied to optical communication.

[Other Embodiments]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

  That is, in the above-described embodiment, the drive current I1 when the number of elements used for driving is the smallest is increased more than the drive current I2 when the number of elements used for drive is small, so that the other drive currents I3 and I4 are increased. Is set to a current equal to the drive current I2. However, the present invention is not limited to this, and the other drive currents I3 and I4 can be set variously. That is, when the illuminance is insufficient, both or one of the other drive currents I3 and I4 may be increased from the drive current I2 to increase the illuminance. In addition, when data transmission is more stably applied to optical communication, it may be set such that I4> I3> I2 to reduce fluctuations in the amount of light.

  In the above-described embodiment, the case where the current control circuit is arranged on the negative output end side of the full-wave rectifier circuit to control the drive current flowing out from the LED strings has been described, but the present invention is not limited thereto, A current control circuit may be disposed on the positive output end side of the full-wave rectifier circuit to control the drive current flowing into the LED strings, or may be combined to control the drive current.

  In the above-described embodiment, the case where the LED lighting device is configured by three or four LED strings has been described. However, the present invention is not limited to this, and when the LED lighting device is configured by two LED strings, five LED lighting devices are used. The present invention can be widely applied to the case where an LED lighting device is constituted by the above LED strings.

DESCRIPTION OF SYMBOLS 1, 11, 21 LED lighting apparatus 2 Full wave rectifier circuit 3A-3D Current control circuit 4,14 Voltage monitoring circuit 5,15 Switching circuit 6,16,26 Control circuit 7A-7D Comparison circuit 8A-8D, 18A-18D Logic Arithmetic circuit 9A to 9D Operational amplifier circuit 27, 30 Analog-digital conversion circuit 28 Controller 29, 32 Multiplexer 31 Digital-analog conversion circuit 33 Timing control circuit STR1-STR4 LED strings

Claims (2)

A rectifier circuit for full-wave rectification of the commercial power supply and outputting pulsating voltage;
A series circuit of a plurality of LED strings including one or a plurality of LED elements, the LED string series circuit having one end connected to one end of the output end of the rectifier circuit;
Connected to one end of the corresponding LED string in the series circuit of the LED strings, the drive current flows out to the negative side output terminal of the rectifier circuit, or the drive current flows from the positive side output terminal of the rectifier circuit A plurality of current control circuits;
A control circuit for controlling operations of the plurality of current control circuits by monitoring the pulsating voltage,
The control circuit includes:
In accordance with the pulsating voltage, by selectively starting up the operations of the plurality of current control circuits, the number of LED elements to be driven is switched according to the pulsating voltage,
The plurality of current control circuits are:
The drive current of the current control circuit for driving the LED element with the smallest number of elements is set to a larger current value than the drive current of the current control circuit for driving the LED element with the smallest number of elements. LED lighting device characterized by this. The control circuit includes:
A plurality of comparison circuits each outputting a comparison result between the pulsating voltage and the reference voltage;
A plurality of logic operation circuits for outputting a control signal for selectively starting up the operations of the plurality of current control circuits in accordance with the pulsating voltage by logical operation processing of the comparison results of the plurality of comparison circuits; The LED lighting device according to claim 1.

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