JP2005114684A - Led driving circuit for vehicle instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an LED driving circuit for a vehicle instrument capable of driving an optional LED with a small power consumption. <P>SOLUTION: This circuit is equipped with a power source 1, an LED row 10 whose one end is connected to the power source 1, formed by connecting in series a plurality of LED's 11-16 used for the vehicle instrument; a plurality of switch means 21-26 connected in parallel to the LED row 10, for controlling individually operation of each LED 11-16; and a constant-current source 30 connected to the other end of the LED row 10, for determining a current value flowing in the plurality of LED's 11-16. Hereby, since a voltage is lowered at every time when the number of lit LED's is increased, the power consumption can be reduced, and since each switch is connected in parallel to the LED, an optional LED can be switched on or switched off among the plurality of LED's 11-16 connected in series by performing ON/OFF driving of the switch. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a vehicle instrument LED drive circuit for turning on and off a plurality of LEDs (Light-emitting diodes) used in a vehicle instrument.

  Conventionally, an LED drive circuit for a vehicle instrument is shown in FIG.

  The configuration of the conventional vehicle instrument LED drive circuit 200 shown in FIG. 6 includes the LED array 10 including the first to sixth LEDs 11 to 16 and the first to sixth LEDs 11 to 16 configuring the LED array 10. The IC 50 that individually controls the turn-off, the first to sixth LEDs 11 to 16 and the IC 50 are connected in parallel, and the resistors 91 to 96 determine the current flowing through the first to sixth LEDs 11 to 16.

  Further, the IC 50 includes a serial-parallel converter 31 and LED control switches 21 to 26. As an effect by this, since each component for individually controlling turning on and off of the first to sixth LEDs 11 to 16 is packaged in the IC 50, there are space saving, reduction in assembly man-hours, and the like.

  Further, as another configuration of the vehicle instrument LED drive circuit 200 in the related art, resistors 91 to 96 shown in FIG. 6 are further incorporated in the IC 50.

  As an effect of the above-described configuration, since the resistors 91 to 96 are already built in the IC 50, it is possible to reduce the number of steps for assembling the resistors 91 to 96 separately, and to cope with further space saving. It is.

  Moreover, as a structure which exhibits the same effect, as another structure of the vehicle instrument LED drive circuit 200 in the related art, the first to the downstream of the control switches 21 to 26 of the first to sixth LEDs 11 to 16 are used. A plurality of constant current sources are connected in parallel to the number corresponding to each of the first to sixth LEDs 11 to 16 to determine the current flowing through the sixth LEDs 11 to 16 individually. Some of them are incorporated in the IC 50.

  However, in the circuit configuration described above, in order to determine the currents flowing through the first to sixth LEDs 11 to 16, it is necessary to individually mount the resistors 91 to 96 separately from the IC 50. It is difficult to cope with the reduction of assembly man-hours.

  Further, when the resistors 91 to 96 or a plurality of constant current sources are built in the IC 50, the power consumed by the resistors 91 to 96 or the plurality of constant current sources becomes the power consumption of the IC 50 itself. Therefore, it becomes necessary to make the package taking into account the heat radiation of the IC 50 itself.

  For example, it is necessary to dispose a heat radiating fin separately on the exterior of the IC 50, or to dispose a heat radiating fan to cool the IC 50. On the contrary, a space is required, or the number of assembly steps may be increased. .

  In order to solve the problems described above, an object of the present invention is to provide a vehicle instrument LED drive circuit capable of individually driving a plurality of LEDs with low power consumption.

  In order to achieve the above object, the present invention employs the following technical means.

  The LED driving circuit for a vehicle instrument according to claim 1 is connected to a power source, one end of which is connected to the power source, a plurality of LEDs used in the vehicle instrument connected in series, and a plurality of LEDs in parallel. It is characterized by comprising a plurality of switch means for individually controlling the operation of each LED, and a current value determining means for determining the current flowing through the plurality of LEDs connected to the other end of the LED array.

  In the conventional circuit configuration, one current value determining means is required to determine the current flowing through one LED. However, according to the present invention, the current value determining is performed to determine the current flowing through a plurality of LEDs. Since only one means is required, it is possible to reduce power consumption as compared with the configuration of a conventional vehicle instrument LED drive circuit.

  Also, by providing a switch means in parallel with the LED array, for example, by turning on the first switch connected in parallel with the first LED, the current flowing from the power source flows through the first LED. If the first switch is turned on, it flows so as to detour toward the opened current path, and the first LED can be turned off. Thus, according to the present invention, it is possible to turn on / off any LED among a plurality of LEDs connected in series.

  The LED drive circuit for a vehicle instrument according to claim 2 is characterized in that the switch train and the current value determining means are built in one IC.

  According to the present invention, by incorporating a plurality of switch means and current value determining means in one IC, it is possible to reduce the number of assembling steps and to reduce the cost.

  The current value determining means in the LED drive circuit for a vehicle instrument according to claim 3 is a constant current source.

  According to the present invention, since the current value flowing through the LED array surely flows regardless of the number of LEDs to be lit, the luminance of each LED can be stabilized.

  The LED driving circuit for a vehicle instrument according to claim 4 is characterized in that the current value determining means is a current adjusting resistor.

  According to the present invention, the number of parts constituting the current value determining means can be reduced, and the cost can be reduced.

  The IC in the vehicle instrument LED drive circuit according to claim 5 is internally connected to a serial control signal line from the outside, and is connected in parallel to each of a plurality of switch means built in the IC. A serial-parallel conversion means for turning on / off an arbitrary switch means among the plurality of switch means based on the LED drive control signal transmitted through the serial control signal line is incorporated.

  According to the present invention, it is possible to reduce the number of external LED control signal lines connected to the IC, and thus it is possible to reduce the number of signals on the control side circuit such as a microcomputer.

  The LED drive circuit for a vehicle instrument according to claim 6 is characterized in that the IC incorporates a plurality of switch arrays for individually controlling the operations of the plurality of LED arrays.

  According to the present invention, it is possible to reduce the cost as compared with the case where a plurality of ICs that control turning on / off of one LED row are used and a plurality of LED rows are controlled.

  The LED driving circuit for a vehicle instrument according to claim 7 is characterized in that the IC includes current value variable means for individually changing each current value determined by the plurality of current value determining means.

  According to the present invention, it is possible to individually and arbitrarily vary the value of the current flowing through each LED array. Thereby, for example, in a vehicle meter composed of a plurality of lighting parts, it is possible to cope with the case where it is necessary to have a difference in luminance of each lighting part.

(First embodiment)
First, the structure of 1st embodiment of this invention is demonstrated using FIG.1 and FIG.2. FIG. 1 is a schematic configuration diagram showing a vehicle instrument LED drive circuit 100 according to the present invention.

  FIG. 2 shows a vehicle instrument panel 300 in which a first instrument 301, a second instrument 302, and a shift position indicator 303 are arranged on the front surface side, and a vehicle instrument LED drive circuit 100 is arranged on the rear surface side. It is a front view.

  A vehicle instrument LED drive circuit 100 shown in FIG. 1 is configured with a power source 1, one end connected to the power source 1, an LED row 10 including first to sixth LEDs 11 to 16, and the LED row 10. It comprises an IC 50 that individually controls turning on and off of the first to sixth LEDs 11 to 16.

  The power source 1 is a known DC power source and is a voltage supply source that supplies a constant voltage VDD. It is also possible to use an in-vehicle battery voltage as the power source 1.

  The LED array 10 is a light source member in which the first to sixth LEDs 11 to 16 are connected in series, one end is connected to the power source 1 and the other end is connected directly above the constant current source 30 built in the IC 50. .

  The first to sixth LEDs 11 to 16 are light sources of six shift position lighting units constituting the shift position indicator 303 shown in FIG.

The six shift position lighting units are a "P" lighting unit 303a indicating a parking mode, an "R" lighting unit 303b indicating a reverse mode, an "N" lighting unit 303c indicating a neutral mode, and a drive mode. The “D” lighting unit 303d, the “2” lighting unit 303e indicating the second mode, and the “L” lighting unit 303f indicating the low mode. (First to sixth LEDs 11 to 16 correspond to “P” lighting unit 303a to “L” lighting unit 303f in order)
The IC 50 is connected in parallel to the LED string 10 and is connected to each other in series. The switch string 20 includes first to sixth switches 21 to 26, and the other end of the switch string 20 on the ground terminal 40 side in the IC 50. And a constant current source 30 connected in series.

  Each of the first to sixth switches 21 to 26 is individually connected in parallel to the first to sixth LEDs 11 to 16 described above, and the first to sixth switches 21. To 26 themselves are connected in series to form the switch train 20.

  Although the first to sixth switches 21 to 26 are shown as open / close switches in FIG. 1, they may be constituted by transistors.

  One constant current source 30 is connected to the end of the switch train 20 on the ground terminal 40 side.

  The constant current source 30 is a power supply circuit that controls to flow a constant current regardless of the magnitude of voltage or load resistance, and is an ideally infinite power source.

  Accordingly, the first to sixth switches 21 to 26 are all closed, and the first to sixth switches 21 to 26 are opened from the state where the current from the power source 1 flows in without load, and the first to sixth switches are opened. Even if the circuit state transitions to a state in which a current flows in any or all of the six LEDs 11 to 16, the current flowing in the circuit from the power source 1 to the constant current source 30 is unchanged.

  The IC 50 is connected in parallel with first to sixth LED control signal lines 21a to 26a in order to control turning on and off of the first to sixth LEDs 11 to 16 from the outside.

  Next, the operation of the vehicle instrument LED drive circuit 100 configured as described above will be described.

  When the first to sixth LEDs 11 to 16 are lit, a switch connected in parallel with the LED to be lit is opened so that the current from the power source 1 flows only to the LED to be lit.

  Conversely, when it is desired to turn off the LEDs 11 to 16, by closing the switch connected in parallel with the LED to be turned off, the current from the power source 1 does not flow to the LED, and the detour that occurs when the switch is closed. Allow current to flow through the road.

  Next, functions and effects of the above-described configuration and operation of the vehicle instrument LED drive circuit 100 will be described. Generally, the power consumption is obtained by the following formula 1.

(Expression 1) P = V × I
P: power consumption V: voltage applied to a constant current source I: current flowing through a constant current source In the case of the vehicle instrument LED drive circuit 100 described above, the constant current source 30 causes the first to sixth LEDs 11 to 16 to flow. Since the current I is always constant, the voltage V applied to the constant current source 30 becomes maximum when the LED is lit. Any one of the first to sixth LEDs 11 to 16 is lit. This is the case.

  In addition, when one or more LEDs are lit, the voltage VDD is applied to the corresponding LED, and the voltage V applied to the constant current source 30 is decreased accordingly, so that the power consumption P is also decreased in proportion to the voltage V. become.

  Thereby, it is possible to provide the vehicle instrument LED drive circuit 100 capable of turning on and off an arbitrary LED (first to sixth LEDs 11 to 16) with less power consumption P.

  In this specification, turning on / off the LED is referred to as “driving”.

(Second embodiment)
In the first embodiment described above, the IC 50 includes the first to sixth LED control signal lines 21a to 26a in order to receive a control signal for performing opening / closing control of the first to sixth switches 21 to 26. It is connected.

  For this reason, since the number of control side signals increases by the number of LED control signal lines, it is difficult to cope with further reduction of the number of control side signals.

  Further, since the current value determined by the constant current source 30 is one, the luminance of the first to sixth LEDs 11 to 16 is always constant. For this reason, for example, it is difficult to cope with a need for changing the brightness of the shift position lighting unit between day and night.

  In the present embodiment, it is also necessary to reduce the number of control side signals and arbitrarily change the luminance of the first to sixth LEDs 11 to 16 as compared with the vehicle instrument LED drive circuit 100 shown in the first embodiment. The configuration of the vehicle instrument LED drive circuit 101 that can be used will be described with reference to FIG.

  FIG. 3 is a schematic configuration diagram of the vehicle instrument LED drive circuit 101 in which the serial-parallel converter 31 and the current value variable device 32 are incorporated in the IC 50 shown in FIG.

  The serial-parallel converter 31 is connected to only one LED control signal line 21a drawn from the outside of the IC 50, and first to sixth switches based on the LED drive control signal transmitted from the LED control signal line 21a. It is a circuit which performs the opening / closing control of 21-26.

  The current value variable unit 32 receives the LED brightness control signal transmitted from the LED control signal line 21a described above via the serial-parallel converter 31 described above, and varies the current value determined by the constant current source 30. It is a circuit to do.

  Since the vehicle instrument LED drive circuit 101 having the above-described configuration enables a single LED control signal line to be connected to the IC 50, it is possible to reduce the number of assembling steps, and the first to sixth It is possible to cope with a need for arbitrarily changing the luminance of the LEDs 11 to 16.

(Third embodiment)
In the vehicle instrument LED drive circuit 101 described above in the second embodiment, there is only one LED row 10 to be turned on / off, and this LED row 10 corresponds to the light source of the shift position indicator 303.

  However, in addition to the shift position indicator 303, there is a display part on the actual vehicle instrument panel 300 that informs the occupant of the vehicle state by turning on and off.

  For example, there are a seat belt detachment state display section, a fuel display section, an emergency lighting display section, a high beam (traveling beam) mode display section, and the like. In each of these display units, the light source may be composed of LEDs.

  In order to control turning on / off of a plurality of LEDs serving as the light sources of each display unit described above, it is possible to collectively control turning on / off a plurality of LED rows rather than using a plurality of vehicle instrument LED driving circuits described above. It is cheaper to use one LED drive circuit for a vehicle instrument, and the number of steps for assembling the vehicle instrument panel 300 on the back side is also reduced.

  In the present embodiment, a configuration of a vehicle instrument LED drive circuit 102 capable of collectively turning on / off a plurality of LED rows will be described with reference to FIGS. 4 and 5.

  FIG. 4 shows an LED for a vehicle instrument that controls turning on and off the first LED row 10a composed of the first to fourth LEDs 11a to 14a and the second LED row 10b composed of the fifth to tenth LEDs 11b to 16b. 2 is a configuration diagram showing a schematic configuration of a drive circuit 102. FIG.

  In FIG. 5, the first instrument 301, the second instrument 302, the shift position indicator 303, and the vehicle status indicator 304 are arranged on the front side, and the vehicle instrument LED drive circuit 102 is arranged on the back side. 2 is a front view of a vehicle instrument panel 300. FIG.

  The vehicle instrument LED drive circuit 102 shown in FIG. 4 includes a power source 1, an IC 50 that controls turning on / off of the individual LEDs constituting the first LED row 10 a and the second LED row 10 b.

  Since the power source 1 has the same configuration as the power source 1 shown in the first and second embodiments described above, the description thereof is omitted.

  The 1st LED row | line | column 10a consists of 1st-4th LED11a-14a, and is a light source of the 1st-4th display part which comprises the vehicle status indicator 304 of the vehicle instrument panel 300 shown in FIG.

  Incidentally, the first display unit is a seat belt detachment state display unit, the second display unit is a fuel display unit, the third display unit is an emergency lighting display unit, and the fourth display unit is a high beam mode display unit.

  The second LED row 10b is a light source of each of the shift position indicators 303a to 303f of the shift position indicator 303 shown in FIG. 5, and the configuration thereof is the same as the configurations of the first and second embodiments described above. Omitted.

  The IC 50 includes a first switch row 20a, a second switch row 20b, a first constant current source 30a, a second constant current source 30b, a serial-parallel converter 31, and a current value variable device. 32.

  The first switch row 20a includes first to fourth switches 21a to 24a, and the first to fourth switches 21a to 24a individually constitute the first to fourth switches constituting the first LED row 10a. The LEDs 11a to 14a are turned on and off.

  Similarly, the second switch row 20b includes fifth to tenth switches 21b to 26b, and the fifth to tenth switches 21b to 26b individually include the fifth LED row 10b. Controls turning on / off of the tenth LEDs 11b to 16b.

  The first constant current source 30a and the second constant current source 30b are both connected to the other end of the first switch row 10a and the second switch row 10b on the ground end 40 side. The first constant current source 30a is also connected to a current value variable device 32, which will be described later, and based on the LED brightness control signal received from the current value variable device 32, the current value flowing through the first LED row 10a is The second constant current source 30b determines the value of the current flowing through the second LED row 10b.

  Since the serial-parallel converter 31 has the same configuration as the serial-parallel converter 31 in the second embodiment described above, the description thereof is omitted.

  The current value variable device 32 is described in the second embodiment except that there are a plurality of first constant current sources 30a and a plurality of second constant current sources 30b as constant current sources whose current values are to be varied. Since the configuration is almost the same as the configuration described above, the description thereof is omitted.

  The vehicle instrument LED drive circuit 102 having the above-described configuration allows the shift position indicator 303 and the vehicle state display unit 304 to be collectively turned on / off by a single LED drive circuit. Compared to using one LED drive circuit for one display unit using a row, the cost can be reduced and the number of assembling steps to the vehicle instrument panel 300 can also be reduced.

  In the first to third embodiments described above, the constant current sources 30, 30a, and 30b are used as the current value determining means. However, for current adjustment that can determine the current flowing through each LED. It may be a resistor.

  Furthermore, in 1st-3rd embodiment mentioned above, although one switch was provided in parallel with respect to 1 LED, this invention is not limited to this, Each lighting part or each display part One set of a plurality of LEDs connected in series or in parallel and one switch may be provided in parallel.

It is a schematic block diagram which shows the vehicle instrument LED drive circuit 100 in 1st embodiment of this invention. It is a front view of the vehicle instrument panel 300 containing the shift position indicator 303 in 1st embodiment of this invention. It is a schematic block diagram which shows the LED drive circuit 101 for vehicle instruments in 2nd embodiment of this invention. It is a schematic block diagram which shows the LED drive circuit 102 for vehicle instruments in 3rd embodiment of this invention. It is a front view of the vehicle instrument panel 300 containing the shift position indicator 303 and the vehicle state display part 304 in 3rd embodiment of this invention. It is a schematic block diagram which shows the conventional LED drive circuit 200 for vehicle instruments.

Explanation of symbols

1 power supply 10 LED row 10a first LED row 10b second LED row 20 switch row 20a first switch row 20b second switch row 30 constant current source (current value determining means)
30a First constant current source (current value determining means)
30b Second constant current source (current value determining means)
31 Serial-parallel converter (serial-parallel conversion means)
32 Current value variable device (current variable means)
40 Earth 50 IC
100 LED Drive Circuit for Vehicle Instrument in First Embodiment 101 LED Drive Circuit for Vehicle Instrument in Second Embodiment 102 LED Drive Circuit for Vehicle Instrument in Third Embodiment 200 Conventional LED Drive Circuit for Vehicle Instrument

Claims (7)

Power supply (1);
One end of the LED array (10) connected to the power source (1) and connected in series to a plurality of LEDs (11 to 16) used in a vehicle instrument;
A plurality of switch means (21 to 26) connected in parallel with the plurality of LEDs (11 to 16) and individually controlling the operation of the LEDs (11 to 16);
An LED drive circuit for a vehicle instrument, comprising: a current value determining means (30) connected to the other end of the LED row (10) and determining a current flowing through the plurality of LEDs (11 to 16). The LED drive circuit for a vehicle instrument according to claim 1, wherein the switch row (20) and the current value determining means (30) are built in one IC (50). 3. The vehicle instrument LED drive circuit according to claim 1, wherein the current value determining means (30) is a constant current source. The vehicle current LED drive circuit according to claim 1 or 2, wherein the current value determining means (30) is a current adjusting resistor. The IC (50) is connected to the serial control signal line (21a) from the outside, and each of the plurality of switch means (21 to 26) built in the IC (50) Parallel-connected, based on an LED drive control signal transmitted through the serial control signal line (21a), turns on / off any switch means among the plurality of switch means (21-26). 5. The LED drive circuit for a vehicle instrument according to any one of claims 2 to 4, wherein a parallel conversion means (31) is incorporated. The IC (50) includes a plurality of switch arrays (20a, 20b) for individually controlling the operations of the plurality of LED arrays (10a, 10b). LED drive circuit for vehicle instrument. 7. The IC (50) according to any one of claims 2 to 6, wherein the IC (50) includes a current value varying means (32) for individually varying each current value determined by the plurality of current value determining means (30a, 30b). An LED drive circuit for a vehicle instrument according to claim 1.

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