JP2010050010A - Lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device capable of restraining a difference of lighting luminance at the time of dimming even when driving circuits having the different numbers of light-emitting diodes are provided. <P>SOLUTION: The lighting device includes: a first driving circuit 1 where a first light source section 11 having a plurality of light-emitting diodes for lighting an illuminated object and a first current limiting resistance 12 are connected with each other in series; a second driving circuit 2 where a second light source section 21 connected in parallel with the first driving circuit 1 and having the number of light-emitting diodes fewer than those of the first light source section 11 for lighting the illuminated object and a second current limiting resistance 22 are connected with each other in series; a power supply circuit 3 for supplying power to the first and second driving circuits 1, 2 at the time of lighting of the illuminated object; first and second switch circuits 4, 5 for switching power supply to the first and second driving circuits 1, 2; and a control means 6 for performing PWM control of the first and second switch circuits 4, 5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an illumination device that illuminates an object to be illuminated using a plurality of light emitting diodes, and is particularly suitable for an illumination device having a dimming function capable of changing illumination luminance.

Conventionally, as an illuminating device, there exists a thing disclosed by patent document 1, for example. This lighting device has a configuration in which a plurality of drive circuits in which a plurality of light emitting diodes and current limiting resistors are connected in series are connected in parallel, and light control is performed by PWM (pulse width modulation) control.
JP-A-2004-228385

  However, when these lighting devices are used as lighting devices, particularly when the number of light emitting diodes in each drive circuit is different, the resistance value of the current limiting resistor is set so that the current balance flowing through each light emitting diode is substantially equal. Even if it is set, when the light is modulated by PWM control, a current balance shift occurs between the drive circuits, resulting in a difference in illumination luminance. Due to the difference in illumination brightness, there is a problem that display cannot be performed at a desired brightness, or display brightness spots or a sense of incongruity are given.

  Therefore, an object of the present invention is to pay attention to the above-mentioned problem, and even when a drive circuit having a different number of light emitting diodes is provided, the illumination brightness is adjusted when the light is adjusted. It is in providing the illuminating device which can suppress the difference of these.

  In the illumination device according to the first aspect of the present invention, the first light source unit having a plurality of light emitting diodes for illuminating the object to be illuminated and the first current limiting resistor are connected in series. A second light source part connected in parallel with the first drive circuit and having a smaller number of light emitting diodes than the first light source part for illuminating the object to be illuminated, and a second current limiting resistor Are connected in series, a power supply circuit for supplying power to the first and second drive circuits when the object to be illuminated is illuminated, and the first and second drive circuits A lighting device comprising: first and second switch circuits for switching power supply to the power supply; and control means for performing PWM control on the first and second switch circuits, wherein the second drive The circuit is connected in parallel to the second light source unit, and the first and second Current flowing through the respective light emitting diode drive circuit, characterized in that the resistance value so as to be substantially the same is provided with a set current adjustment resistor.

  Further, as described in claim 2, in the lighting device according to claim 1, the control means inputs a detection signal corresponding to a power supply voltage output from the power supply circuit, and a voltage of the power supply voltage. According to the value, PWM control is performed so that the value of the current flowing to the first drive circuit per unit time becomes a desired value.

  In the illumination device of the present invention, as described in claim 3, the first light source unit having a plurality of light emitting diodes for illuminating the object to be illuminated and the first current limiting resistor are connected in series. A first drive circuit, and a second light source unit connected in parallel with the first drive circuit and having a smaller number of light emitting diodes connected in series than the first light source unit for illuminating the illuminated body; A second drive circuit in which a second current limiting resistor is connected in series; a power supply circuit that supplies power to the first and second drive circuits when the object to be illuminated is illuminated; and the first , A lighting device comprising: first and second switch circuits for switching power supply to a second drive circuit; and control means for PWM controlling the first and second switch circuits. The second drive circuit is connected in parallel with the second light source unit. In consideration of the difference in the number of the light emitting diodes of the first and second drive circuits, a current adjusting resistor having a resistance value set so that the currents flowing through the light emitting diodes are substantially the same is provided. It is characterized by.

  The present invention relates to an illuminating device that illuminates an object to be illuminated using a plurality of light emitting diodes, even when a drive circuit provided with a different number of light emitting diodes is provided. Can be suppressed.

  Embodiments to which the present invention is applied will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an electrical configuration relating to an illumination structure, which is an embodiment in which the present invention is applied to a dimmable vehicle instrument. The lighting device includes a first drive circuit 1, a second drive circuit 2, a power supply circuit 3, a first switch circuit 4, a second switch circuit 5, and a control means 6. Yes.

  The first drive circuit 1 is a first light source unit in which n (plural) light emitting diodes for illuminating a meter which is an object to be illuminated, such as a pointer, dial, and liquid crystal panel (not shown) are connected in series. 11 and a first current limiting resistor 12 connected in series with the first light source unit 11.

  The second drive circuit 2 is connected in parallel to the first drive circuit 1, and includes a second light source unit 21 made up of light emitting diodes (in this case, one) that is smaller in number than the first light source unit 11, Two current limiting resistors 22 are connected in series. In this case, the light emitting diodes constituting the first and second drive circuits 1 and 2 are selected to have substantially the same light emission characteristics in order to realize uniform illumination. The second current limiting resistor 22 is selected to have the same resistance value as that of the first current limiting resistor 12.

  The second drive circuit 2 is connected in parallel to the second light source unit 21 so that the currents flowing through the light emitting diodes in the first and second drive circuits 1 and 2 are substantially the same. A current adjusting resistor 23 having a set resistance value is provided. In this case, the resistance value of the current adjusting resistor 23 is the resistance value R of the current limiting resistors 12 and 22 in the first and second drive circuits 1 and 2, and the number of light emitting diodes (n And a value close to “R / (n−1)” divided by n−1, which is the difference between the number of light emitting diodes of the second light source unit 21 and the number of light emitting diodes (one).

  As another example of the power adjustment resistor 23 (similar parts are given the same reference numerals and detailed description is omitted), as shown in FIG. 2, the current adjustment resistor 24 includes first and second current limiting resistors. The resistors having the same resistance value R as the resistors 12 and 22 are selected, and (n−1) pieces which are the difference between the number of light emitting diodes of the first light source unit 11 and the number of light emitting diodes of the second light source unit 21 are selected. It may be configured to be connected in parallel to each other.

  The power supply circuit 3 is a circuit that is connected to a battery or a generator mounted on the vehicle and supplies power to the first and second drive circuits 1 and 2 when the instrument is illuminated. In this case, a power supply voltage that changes within an allowable range of 8 to 16 V is supplied to the first and second drive circuits 1 and 2. Further, a voltage value corresponding to the power supply voltage from the power supply circuit 3 is output to the control means 6 as a detection signal.

  The first switch circuit 4 is connected in series with the first drive circuit 1 and has a transistor for switching on / off the power supply to the first drive circuit 1 based on a control signal from the control means 6. Applicable.

  The second switch circuit 5 is connected in series with the second drive circuit 2, and a transistor for switching on / off the power supply to the second drive circuit 2 can be applied based on the control signal.

  The control means 6 is, for example, a microcomputer and is a circuit that performs PWM control on the first and second switch circuits 4 and 5. In this case, the control means 6 generates a duty ratio control signal that prompts the vehicle user to obtain the desired illumination brightness based on information from the input means including a dimming switch provided in the steering of the vehicle, The light-emitting diode is dimmed by PWM control via the first and second switch circuits 4 and 5.

  Further, the control means 6 receives a detection signal corresponding to the power supply voltage output from the power supply circuit 3, and the value of the current flowing to the first drive circuit 1 per unit time is determined according to the voltage value of the power supply voltage. A control signal having a desired value is generated, and the light emitting diodes of the first and second drive circuits 2 are PWM-controlled through the first and second switch circuits 4 and 5. Therefore, even if the power supply voltage supplied from the battery or the generator varies, the duty ratio of the control signal can be adjusted according to the detection signal, and a constant luminance can be output.

  Note that the input means may be provided on an instrument panel or a meter instead of the adjustment switch provided on the steering described above. Further, a manual switch of a vehicle headlamp, an illuminance sensor, or the like can be applied as the input means, or a desired illumination brightness may be determined by combining these.

  Such an illuminating device includes a first drive circuit 1 in which a first light source unit 11 having a plurality of light emitting diodes for illuminating an object to be illuminated, and a first current limiting resistor 12 are connected in series. A second light source unit 21 connected in parallel with one drive circuit 2 and having a smaller number of light emitting diodes than the first light source unit 11 for illuminating the object to be illuminated, and a second current limiting resistor 22 are connected in series. A second drive circuit 2 connected to the power source, a power supply circuit 3 for supplying power to the first and second drive circuits 1 and 2 when the object to be illuminated is illuminated, and a first and second drive circuit Illumination comprising first and second switch circuits 4 and 5 for switching power supply to 1 and 2 and control means 6 for PWM controlling the first and second switch circuits 4 and 5 The second drive circuit 2 is connected in parallel with the second light source unit 21. First, formed by a second of said current regulation resistor 23 the current flowing to each light emitting diode is set resistance value so as to be substantially identical drive circuits 1 and 2 is provided.

With these configurations, the current values (current balance) supplied to the first and second drive circuits 1 and 2 are substantially the same.
"Formula 1"
“Value of current flowing in first driving circuit 1” = “duty ratio of control signal” × (“power supply voltage value” − (“number of light emitting diodes” × “voltage drop of light emitting diode”)) / “first Resistance value of current limiting resistor 12 "

  As shown in the above “Equation 1”, the value of the current flowing through the first drive circuit 1 is calculated. In the second drive circuit 2, a light emitting diode that performs the same voltage drop as the first drive circuit 1 and When the current limiting resistor 22 and the current adjusting resistor 23 value similar to the current limiting resistor 12 are used, the value of the current flowing through the second drive circuit 2 is calculated by the same calculation formula. Even if the duty ratio or the power supply voltage value changes, the current balance is not lost, so that the instrument illumination can be performed without causing a difference in illumination brightness emitted by each light emitting diode.

  Therefore, even when the drive circuits 1 and 2 having different numbers of light emitting diodes are provided, the illumination device can suppress the difference in illumination luminance when the light is adjusted. Moreover, it can display by desired brightness | luminance and can suppress the brightness spot and discomfort of a display.

  Further, the control means 6 receives a detection signal corresponding to the power supply voltage output from the power supply circuit 3, and the value of the current flowing to the first drive circuit 1 per unit time is determined according to the voltage value of the power supply voltage. Even if fluctuations occur in the power supply voltage supplied from the battery or the generator, the duty ratio of the control signal is adjusted in accordance with this to achieve a constant luminance. Output is possible, and stable illumination can be performed without a sense of incongruity.

  In addition, although the illuminating device of this invention was mentioned as an example in the structure of embodiment mentioned above, this invention is not limited to this, It does not deviate from the summary of this invention in another structure. It goes without saying that various improvements and design changes can be made in the range.

  For example, when the control means generates a control signal, an optimal current value is set in consideration of the light emitting diode characteristics due to temperature fluctuations in addition to the power supply voltage, and light control is performed based on this to adjust the desired current. Brightness can be realized more reliably. In addition, since the above-described configuration can be realized by PWM control for switching the illumination luminance during the day and night, it is possible to perform dimming in a state where the luminance difference between the respective light emitting diodes is suppressed while being a simple configuration.

  Further, the second drive circuit 20 may be configured by connecting a smaller number of light emitting diodes than the first drive circuit 1 in series. For example, as shown in FIG. The second drive circuit 20 is connected in parallel to the second light source unit 210, and each of the first and second drive circuits 1 and 20 is connected to each other. A current adjusting resistor 230 having a resistance value set so that the currents flowing through the light emitting diodes are substantially the same is provided. In this case, the resistance value of the current adjusting resistor 230 includes the resistance value R of the current limiting resistors 12 and 220 in the first and second drive circuits 1 and 20 and the number of light emitting diodes in the first light source unit 11 (m ), And this value is divided by nm which is the difference between the number of light emitting diodes of the first light source unit 11 (n) and the number of light emitting diodes of the second light source unit 21 (m). A value close to the obtained value “mR / (n−m)” is selected. Therefore, even when the drive circuits 1 and 2 having different numbers of light emitting diodes are provided, the illumination device can suppress the difference in illumination luminance when the light is adjusted. In addition, this allows each light emitting diode to emit light with a desired luminance, thereby suppressing display luminance unevenness and discomfort.

The block diagram which shows the structure of embodiment of this invention. The block diagram which shows another example of the above-mentioned embodiment. The block diagram which shows another example of the above-mentioned embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st drive circuit 11 1st light source part 12 1st current limiting resistor 2 2nd drive circuit 21 2nd light source part 22 2nd current limiting resistor 23 Current adjustment resistor 3 Power supply circuit 4 1st Switch circuit 5 Second switch circuit 6 Control means

Claims (3)

A first light source unit having a plurality of light emitting diodes for illuminating an object to be illuminated, and a first drive circuit in which a first current limiting resistor is connected in series;
A second light source unit connected in parallel with the first drive circuit and having a smaller number of light emitting diodes than the first light source unit for illuminating the object to be illuminated, and a second current limiting resistor are connected in series. A second drive circuit,
A power supply circuit for supplying power to the first and second drive circuits during illumination of the object to be illuminated;
First and second switch circuits for switching power supply to the first and second drive circuits;
Control means for PWM controlling the first and second switch circuits;
A lighting device comprising:
The second drive circuit is connected in parallel with the second light source unit, and a resistance value is set so that currents flowing through the light emitting diodes of the first and second drive circuits are substantially the same. An illumination device comprising a current adjusting resistor.   The control means inputs a detection signal corresponding to the power supply voltage output from the power supply circuit, and a current value flowing to the first drive circuit per unit time is desired according to the voltage value of the power supply voltage. The lighting device according to claim 1, wherein PWM control is performed so as to obtain a value. A first light source unit having a plurality of light emitting diodes for illuminating an object to be illuminated, and a first drive circuit in which a first current limiting resistor is connected in series;
A second light source part connected in parallel with the first drive circuit and having a smaller number of light emitting diodes connected in series than the first light source part for illuminating the object to be illuminated; a second current limiting resistor; A second drive circuit connected in series;
A power supply circuit for supplying power to the first and second drive circuits during illumination of the object to be illuminated;
First and second switch circuits for switching power supply to the first and second drive circuits;
Control means for PWM controlling the first and second switch circuits;
A lighting device comprising:
The second driving circuit is connected in parallel with the second light source unit, and the current flowing through each light emitting diode is substantially reduced in consideration of the difference in the number of the light emitting diodes in the first and second driving circuits. A lighting device comprising a current adjusting resistor having a resistance value set to be the same.

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