JP4262565B2 - Lighting device - Google Patents

Description

  The present invention relates to an illuminating device in which a plurality of light emitting elements such as LEDs are assembled to form a single light source, and the light source can be controlled to have an arbitrary brightness as an illumination lamp.

In recent years, LEDs (light-emitting diodes) have been rapidly improved in performance, and white LEDs indispensable for illumination have been developed. In addition, even in brightness, it has become possible to emit light with a luminance that can be sufficiently used as illumination. Along with this, an illuminating lamp is constructed by assembling a plurality of LEDs instead of a light bulb using tungsten as a heating wire or a discharge lamp enclosing gas such as neon, argon or mercury. Has emerged (see, for example, Patent Documents 1 and 2).
This type of illuminating lamp is advantageous in that it can be reduced in weight and size as compared with a tungsten light bulb or a discharge lamp, and can save power and extend its life.
Japanese Patent Laid-Open No. 11-298044 JP 2003-59335 A

However, the individual LEDs of the illuminating lamp made up of the LED aggregates vary in forward voltage, so that their drive currents vary, and as a result, their brightness also varies. Further, when the brightness of the LED varies, there is a problem that a partial luminance unevenness occurs on the light emitting surface of the illuminating lamp and the quality as the illuminating lamp is deteriorated.
Therefore, in the prior art, a constant current circuit is provided for each LED or for each series circuit formed by connecting a plurality of LEDs (about six) in series, and each LED corresponding to the constant current circuit is provided. The LED current is controlled to be constant so as to eliminate variations in the brightness of the LEDs.
However, such a conventional circuit system has a problem that a large number of constant current circuits are required, and a control circuit including these constant current circuits becomes complicated, resulting in high costs.

  The present invention has been made to solve the above-described conventional problems. Even if the forward voltage of the LED varies, the relative luminous intensity of each LED is averaged without attenuating the light emission efficiency of the LED. An object of the present invention is to provide an illuminating device that can secure a substantially constant illuminance and can share a constant current circuit for each LED.

To achieve the above object, according to the present invention, a plurality of LED series circuits in which a plurality of LEDs are connected in series are connected in parallel to form one illuminating lamp, and lighting control of the illuminating lamp is controlled to an arbitrary brightness. And a driving circuit that lights each LED of each LED series circuit simultaneously, and a current that flows through each LED series circuit through the driving circuit is controlled to a predetermined current according to a dimming setting voltage. A constant current circuit, a dimming voltage setting means for setting the dimming setting voltage to the constant current circuit according to the brightness required for the illuminating lamp, the drive circuit, the constant current circuit, and the and a operating power supply of the dimming voltage setting means, the light control voltage setting means, adjustment of the LED by compensating the rising of the the supplied dimming setting voltage to the constant current circuit from the set voltage generation unit Slow motion to light Was provided with a rising voltage compensation device to launch operation to the dimming of the LED the operating power supply unit from becoming fully operable, in proportion to the forward current flowing through the LED series circuits in each of the LED series circuits Each of the detection elements for detecting the detected voltage is provided, and a voltage value obtained by averaging the voltages detected by the respective detection elements is fed back to the constant current circuit as a control signal.

In the lighting device according to the present invention, the voltages detected by the detection elements of the LED series circuits are averaged, and the constant current circuit is driven and controlled based on the voltage value obtained by the averaging and the dimming setting voltage. As a result, the forward current of the LEDs flowing through each LED series circuit is averaged, so that even if the forward voltage of the LEDs varies, the light emission efficiency of each LED is not attenuated. Relative luminous intensity is averaged, almost constant illuminance can be secured, and one constant current circuit can be shared for each LED series circuit, and the lighting control circuit including the constant current circuit can be simplified and reduced in cost. become.
Furthermore, according to the present invention, the rising of the dimming setting voltage Vf supplied from the setting voltage generator to the constant current circuit is compensated by the rising voltage compensation element, so that the operation of the LED for dimming is delayed. After the operation power supply unit becomes sufficiently operable, the operation for dimming the LED can be started up, and variations in the start-up of the LED can be eliminated.

  In the best mode of this embodiment, each LED series circuit constituting the illuminating lamp is connected to a resistor for detecting a voltage proportional to the forward current flowing in the LED series circuit, and the voltage detected by each of the detection resistors. The constant current circuit is driven and controlled on the basis of the voltage value obtained by averaging and the dimming setting voltage. As a result, even if there is variation in the forward voltage of the LEDs, the relative luminous intensity of each LED is averaged without attenuating the luminous efficiency of each LED, ensuring a substantially constant illuminance and one constant current. The circuit can be shared for each LED series circuit. Further, the rise of the dimming set voltage Vf supplied from the set voltage generator to the constant current circuit is compensated by the rise voltage compensation element.

Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing the entire illumination device according to the present invention.
In FIG. 1, reference numeral 10 denotes an illuminating lamp formed by assembling a large number of LEDs. The illuminating lamp 10 includes, for example, a plurality of (for example, 16) LED series circuits 11 in which six LEDs are connected in series. Composed of things.
In FIG. 1, reference numeral 12 denotes a drive circuit for simultaneously lighting the LEDs of each LED series circuit 11. Reference numeral 13 denotes a constant current flowing through the LED series circuit 11 through the drive circuit 12 according to the dimming setting voltage. Reference numeral 14 denotes a constant current circuit to be controlled, and reference numeral 14 denotes a dimming voltage setting means for setting a dimming setting voltage to the constant current circuit 13 according to the brightness required for the illumination lamp 10.

  The drive circuit 12 comprises a power MOSFET 12a, and one end of each LED series circuit 11, that is, the anode side of the LED is connected to the drain D of the power MOSFET 12a. Further, one end of a current limiting resistor (about 100Ω) 15 for limiting the current flowing in each LED series circuit 11 is connected in series to each LED series circuit 11 at the other end of each LED series circuit 11. The other end of the current limiting resistor 15 is connected to the ground terminal A. The source S of the power MOSFET 12a is connected to the power supply + V (+ 24V).

  The constant current circuit 13 has an operational amplifier 13a, and a non-inverting input terminal (+) of the operational amplifier 13a is connected to a power source + V (+ 24V) through a resistor R1. Further, a dimming setting voltage Vf, which will be described later, is supplied to the inverting input terminal (−) of the operational amplifier 13a. The output terminal of the operational amplifier 13a is connected to the gate of the power MOSFET 12a via the resistor R3.

  Each LED series circuit 11 is connected to one end of a detection resistor (detection element, about 1 KΩ) 16 for detecting a voltage proportional to the forward current flowing in each LED series circuit 11. The other end is connected in parallel and connected to the non-inverting input terminal (+) of the operational amplifier 13a via a resistor R2. Thus, the non-inverting input terminal (+) of the operational amplifier 13a is configured such that a voltage having a value obtained by averaging the voltages detected by the detection resistors 16 is fed back as a control signal.

  The dimming voltage setting means 14 generates an AC output v1 synchronized with the power cycle every half cycle of the AC power supply by phase-controlling a control rectifier element such as a thyristor or triac with a gate signal synchronized with the AC power supply. An AC output generation unit 141 that outputs, a waveform shaping circuit (for example, composed of an AC photocoupler) 142 that shapes the AC output v1 output from the AC output generation unit 141 into a rectangular wave shape, and the waveform shaping circuit 142 A set voltage generation unit (for example, composed of a low-pass filter: LPF) 143 that averages the rectangular wave voltage V1 output from the output to generate a dimming set voltage Vf, and a constant current circuit from the set voltage generation unit 143 13 is a rising voltage compensation element that compensates the rising of the dimming setting voltage Vf supplied to the light source 13 (for example, a plurality of diodes are connected in series). 144), a 5 V reference power supply unit 145 for supplying power for operation to the waveform shaping circuit (AC photocoupler) 142, and a waveform shaping circuit from the reference power supply unit 145 in response to an increase in ambient temperature. (AC photocoupler) It is comprised from the temperature correction element (for example, comprised from a diode) 146 which changes the electric current amount to 142 in the increase direction.

  In FIG. 1, reference numeral 17 denotes an operation power supply unit such as a drive circuit 12, a constant current circuit 13, a set voltage generation unit 14, and each LED series circuit 11. The operation power supply unit 17 generates the AC output generation. A smoothing circuit comprising a diode-bridged full-wave rectifier circuit 171 that rectifies the AC output v1 output from the unit 141, and an RC filter that smoothes and converts the output voltage rectified by the full-wave rectifier circuit 171 into a direct current 172 and a switching regulator 173 that converts a direct current output from the smoothing circuit 172 into a direct current of a predetermined voltage and outputs it.

Next, the operation of the lighting device configured as described above will be described.
When the dimming setting voltage Vf set by the dimming voltage setting means 14 is input to the inverting input terminal (−) of the operational amplifier 13a, the constant current circuit 13 receives the current i corresponding to the dimming setting voltage Vf. It flows to each LED series circuit 11 through the drive circuit 12. In this embodiment, the forward current value flowing through each LED series circuit 11 is about 20 mA, and the current value flowing through the drive circuit 12 is the number of circuits of the LED series circuit 11 × 20 mA.
Thus, when the above-mentioned current flows through each LED series circuit 11, each LED is lit to a brightness corresponding to the current value.

On the other hand, when a forward current flows through each LED series circuit 11, each forward current is shunted to the detection resistors 16 provided in the respective LED series circuits 11. A voltage proportional to the current is generated. Here, since the detection resistors 16 are arranged in parallel, these voltages are averaged voltages, and this voltage is fed back as a control signal to the non-inverting input terminal (+) of the operational amplifier 13a. As a result, the constant current circuit 13 is driven to average the forward currents of the LEDs flowing through the LED series circuits 11 connected in parallel. For this reason, the average current flows through each LED series circuit 11, so that even if the forward voltage of the LED varies, the relative luminous intensity of each LED is averaged without attenuating the luminous efficiency of each LED. It is possible to secure almost constant illuminance.
In addition, since one constant current circuit 13 can be shared with each LED series circuit 11, the lighting control circuit including the constant current circuit 13 can be simplified and the cost can be reduced.

  In the lighting device shown in this embodiment, the ambient temperature rises in the dimming voltage setting means 14 that sets the dimming setting voltage Vf to the constant current circuit 13 according to the brightness required for the illuminating lamp 10. Accordingly, the amount of current from the reference power supply unit 145 to the waveform shaping circuit (AC photocoupler) 142 is changed in the increasing direction by the temperature correction element 146, so that the ambient temperature of the lighting device rises and the relative luminous intensity of the LED is increased. Even in a state in which the LED decreases, it is possible to increase the forward current of the LED using the temperature correction element 146, thereby correcting the decrease in the relative luminous intensity of the LED.

  Further, in the lighting device shown in this embodiment, the dimming voltage setting unit 14 compensates the rising of the dimming setting voltage Vf supplied from the setting voltage generator 143 to the constant current circuit 13 by the rising voltage compensation element 144. As a result, the operation for LED dimming can be delayed, and the operation for LED dimming can be started up after the operation power supply unit 17 becomes fully operable, thereby eliminating variations in LED startup. be able to.

  Further, in the lighting device shown in this embodiment, the AC power source phase-controlled by the AC output generation unit 141 is rectified by the full-wave rectifier circuit 171 and smoothed by the smoothing circuit 172 to be converted to DC, and this DC output is converted. By using the operation power supply unit 17 that is converted into a direct current of a predetermined voltage by the switching regulator 173, the noise from the noise filter choke as in the conventional switching direct current power supply device is eliminated, and it is suitable for illumination of a quiet museum or the like. In addition, there is an advantageous effect when the illumination light is lowered to illuminate.

  In addition, the configuration of each LED series circuit 11, drive circuit 12, constant current circuit 13, set voltage generation unit 14, and operation power supply unit 17 in the lighting device of the present invention is not limited to the configuration shown in the above embodiment, Various changes and modifications can be made without departing from the technical configuration described in the claims.

It is a block diagram which shows the whole illuminating device concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Illuminating lamp 11 LED series circuit 12 Drive circuit 13 Constant current circuit 14 Dimming voltage setting means 141 AC output generation part 142 Waveform shaping circuit 143 Setting voltage generation part 144 Rising voltage compensation element 145 Reference power supply part 146 Temperature correction element 15 Current limitation Resistor 16 Detection resistor 17 Operating power supply unit 171 Full wave rectifier circuit 172 Smoothing circuit 173 Switching regulator

Claims (4)

A lighting device in which a plurality of LED series circuits in which a plurality of LEDs are connected in series is connected in parallel to constitute one illuminating lamp, and this illuminating lamp is controlled to be controlled to an arbitrary brightness.
A drive circuit that lights each LED of each LED series circuit simultaneously; a constant current circuit that controls a current flowing through each LED series circuit through the drive circuit to a predetermined current according to a dimming setting voltage; A dimming voltage setting means for setting the dimming setting voltage to the current circuit according to the brightness required for the illuminating lamp, and an operating power source for the drive circuit, the constant current circuit, and the dimming voltage setting means And
The dimming voltage setting means delays the operation of the LED to dimming by compensating for the rise of the dimming setting voltage supplied from the set voltage generation unit to the constant current circuit, and the operation power supply unit A rising voltage compensation element for starting up the operation to dimming the LED after becoming fully operable ,
Each LED series circuit is provided with a detection element for detecting a voltage proportional to the forward current flowing in the LED series circuit,
An illumination device, wherein a voltage value obtained by averaging the voltages detected by the respective detection elements is fed back to the constant current circuit as a control signal.   The dimming voltage setting means generates an AC output synchronized with the power cycle by outputting a phase control with a signal synchronized with the AC power source, and outputs the AC output every half cycle of the AC power source, and A waveform shaping circuit that shapes the AC output output from the AC output generation unit into a rectangular wave, and a set voltage generation unit that averages the rectangular wave voltage output from the waveform shaping circuit to generate the dimming setting voltage The lighting device according to claim 1, further comprising:   The dimming voltage setting means includes a reference power supply unit that supplies power to the waveform shaping circuit, and a temperature correction that changes the amount of current from the reference power supply unit to the waveform shaping circuit in an increasing direction in accordance with an increase in ambient temperature. The lighting device according to claim 1, further comprising an element. The operating power supply unit generates an AC output synchronized with a power supply cycle every half cycle of the AC power supply by phase-controlling the control rectifier element with a signal synchronized with the AC power supply, and outputs the AC output. A full-wave rectifier circuit that rectifies the AC output output from the output generator, a smoothing circuit that smoothes and converts the output voltage rectified by the full-wave rectifier circuit into direct current, and a direct current output from the smoothing circuit The lighting device according to claim 1, further comprising: a switching regulator that converts the voltage into a direct current and outputs the constant current circuit, the set voltage generation unit, and an operation power source of the LED.