JP2003317978A - Lighting circuit for on-vehicle led lighting fixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems that a conventional lighting circuit adopts a current limit resistor or a constant current circuit in order to control a lighting current of an LED lamp, which causes increase of the power consumption and the cost. <P>SOLUTION: This lighting circuit 1 for the on-vehicle LED lighting fixture is constituted by a light source part 2 having a plurality of installation lines 2c connected in parallel wherein at least one of the LED lamp 2a and the current limit resistor 3 are connected in series while having the current limit resistor 3 on the grounding side, a PWM control circuit part 5 for varying a duty ratio by a signal supplied to the input side of the on-vehicle LED lighting fixture, and a switching circuit part 4 connected to the power source side or the grounding side of the light source part 2 for controlling the duty ratio of the power source applied to the light source part 2 based on the output from the PWM control circuit part 5. Thus, reduction of the power consumption and the cost can be achieved. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicular lamp that uses an LED lamp as a light source. More specifically, in a signal lamp such as a rear combination lamp, a plurality of LED lamps are used as a light source. The present invention relates to a configuration of a lighting circuit in an on-vehicle LED lighting device.

[0002]

2. Description of the Related Art FIGS. 6 and 7 show an example of a lighting circuit in a conventional vehicle-mounted LED lamp, and a lighting circuit 90 of the vehicle-mounted LED lamp shown in FIG. It is directly lit by a power source, for example, four LED lamps 91 in the series direction and five LED lamps 91 in the parallel direction.
a are connected in a matrix to form the light source unit 91,
The light source unit 91 is connected to the stop terminal S via the stop lighting resistor 92 and the tail lighting resistor 9 is connected.
It is connected to the tail terminal T via 3.

In addition, in preparation for an abnormal increase in vehicle power supply,
Between the light source unit 91 and the stop lighting resistor 92 and the tail lighting resistor 93, an overvoltage countermeasure resistor 9 is provided.
4 are connected in series, and this overvoltage countermeasure resistor 9
4 is short-circuited by the short circuit switch 95 in a normal state. Further, the reverse connection prevention diode 9 is provided in the lighting circuit 90.
6. A Zener diode 97 for surge prevention is also provided.

A resistance value suitable for lighting the light source unit 91 as a stop lamp is set in the stop lighting resistor 92, and a tail resistance suitable for lighting the tail lighting resistor 93 as a tail lamp. The resistance value is set. In addition, the overvoltage countermeasure resistor 94 does not damage the light source unit 91 by opening the short circuit switch 95 when a high voltage is generated in the vehicle power source due to disconnection of the battery or the like. The resistance value to be set is set.

A lighting circuit 80 shown in FIG. 7 has a DC / DC converter interposed in a vehicle power source and outputs the output from the light source section 8.
When the tail lamp and the stop lamp are applied, an appropriate current is supplied to obtain a predetermined brightness by applying the voltage to the light source 1. First, the light source unit 81 includes, for example, four LED lamps 81a connected in series. 5 lamp rows 81b are connected in parallel, and a current detector 81c is connected to each connected in series. Further, the light source unit 81 includes a high speed diode 82a, a coil 82b,
It is connected to a smoothing circuit 82 formed of a capacitor 82c.

Further, the smoothing circuit 82 includes a control circuit 8
3a and an output transistor 83b are connected to a constant current circuit 83. The constant current circuit 83 uses a pulse of the power supply voltage so that the current flowing through the light source unit 81 becomes a constant current by the signal from the current detector 81c. It is controlled by width control. Further, a signal from the stop terminal S is also input to the constant current circuit 83, and the light amount is switched to an amount suitable for each of the tail lamp and the stop lamp.

[0007]

However, in the lighting circuit 90 shown in FIG. 6, the stop lighting resistor 9 is used.
2. The power consumed by the resistors such as the tail lighting resistor 93 increases, and especially when the voltage of the vehicle power source is high,
Electric power equal to or more than the electric power consumed by the light source unit 91 is consumed by the resistor, which causes a problem of low efficiency. In addition, since the LED lamps 91a are connected in a matrix, there is no detection means for the case where some of the LED lamps 91a are disconnected, and when the specified illuminance cannot be obtained due to some of the plurality of light sources, the light is turned off. There is also the problem that it is difficult to meet the European standards that must be met.

Further, when the matrix connection is performed so that the other LED lamps 91a cannot be extinguished by one disconnection, the brightness can be maintained even if one of the LED lamps 91a is disconnected. In order to comply with the standards, it is necessary to reduce the ratio of one LED lamp 91a to the total illuminance so as to reduce the influence. Therefore, the number of LED lamps 91a used increases and the cost increases. There is also a problem.

Further, in the lighting circuit 80 shown in FIG. 7, the smoothing circuit 8 including the coil 82b (inductance).
Since the intermittent waveform is applied to 2, noise is easily generated due to the back electromotive force of the inductance,
For example, since it becomes a noise source of a car radio and the like, it takes time and cost to take measures against it, and there is a problem that the cost of the entire lighting circuit 80 increases.

[0010]

As a concrete means for solving the above-mentioned conventional problems, the present invention provides a lighting circuit of an on-vehicle LED lighting device using a plurality of LED lamps as a light source, wherein the lighting circuit is A column of lamps including at least one LED lamp and a current limiting resistor connected in series with the current limiting resistor on the ground side, or a light source unit in which a plurality of columns are connected in parallel. A PWM control circuit unit for varying the duty ratio by a signal given to the input side of this vehicle-mounted LED lamp, and the light source unit connected to the power source side or the ground side of the light source unit based on the output from the PWM control circuit unit. To provide a lighting circuit for a vehicle-mounted LED lamp, which is configured by a switching circuit unit that controls a duty ratio of a power source applied to the vehicle. It is intended to resolve.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail based on the embodiments shown in the drawings. Reference numeral 1 in FIG. 1 is a lighting circuit for an on-vehicle LED lighting device according to the present invention. The lighting circuit 1 is required to have a stop lamp function and a tail lamp function, and also has an LED lamp 2a.
The light source section 2 is provided in one or more rows of the lamp row 2b to which one or more of the above are connected, and the light quantity is increased / decreased by changing the amount of current applied to the light source section 2 to switch the above two functions. Some points are the same as those of the conventional example.

First, the light source unit 2 includes an LED lamp 2a.
4 are connected in series, and five lamp rows 2b are connected in parallel, and a current limiting resistor 3 is connected in series to each row 2b to form an assembly row 2c. The current flowing in each column can be detected with the potential generated at both ends of the current limiting resistor 3. Further, all the terminals on the ground side of the current limiting resistor 3 are connected to each other, and are grounded to GND via the switching circuit section 4 which is, for example, an NPN transistor.

The lighting circuit 1 of the present invention is provided with a PWM control circuit section 5. This PWM control circuit section 5 is a DC chopper in principle, and when there is an input only at the tail terminal T, the vehicle is The power supply for use is chopped to, for example, 1/10 duty as shown by voltage Tv in FIG. 2, and when there is an input at the stop terminal, chopping is stopped as shown by voltage Sv in FIG. The output from the PWM control circuit unit 5 is input to the switching circuit unit 4, specifically, the base of the transistor Q1.

In the present invention, the PWM control circuit section 5
In this embodiment, an input voltage detection circuit 5a is provided in the preceding stage of the PWM control circuit unit 5, and when the voltage rises in the vehicle power supply, 4, chopping is started with an appropriate duty as indicated by voltage Sh to prevent an excessive current from flowing through the LED lamp 2a and the current limiting resistor 3 during the operation of the stop lamp which consumes a large amount of current.

In this embodiment, the input voltage detection circuit 5a is connected to the stop terminal S, and the PWM control circuit section 5 adjusts the current when the power supply voltage rises only when operating as a stop lamp. The input voltage detection circuit 5a has a tail terminal T
It may be connected to the side and current adjustment may be performed in all states during tail operation and stop operation.

In addition to the above, the present invention can also comply with the European standard, and if the potential generated in the current limiting resistor 3 connected to each column of the light source section 2 is verified, the switching is performed. If the circuit portion 4 (transistor Q1) is in the conductive state and the four LED lamps 2a connected in series are not broken, L
The potential at the connection point P between the ED lamp 2a and the current limiting resistor 3 is "H", and if a disconnection occurs in any of the LED lamps 2a, the potential at the same connection point P becomes "L".

Therefore, when the switching circuit section 4 is turned on, the potential at the point P of each column is measured. If any of the potentials of "L" potential is generated, the disconnected LED lamp 2a is present in that column. Since it is predicted that it is included, in such a case, the signal from the PWM control circuit unit 5 to the switching circuit unit 4 is stopped by holding the output of the disconnection detection circuit 6 to turn on the light source unit 2. To stop.

The reference numeral 7 in the figure damages the light source unit 2, the PWM control circuit unit 5, etc. even when the vehicle power source is connected to the stop terminal S and the tail terminal T with the wrong polarity. Is a reverse connection prevention diode provided to prevent the occurrence of a surge voltage, and a reference numeral 8 is a surge prevention zener diode for preventing a surge voltage which is likely to enter from the vehicle power source side.

Next, the operation and effect of the lighting circuit 1 of the present invention having the above structure will be described. First, when the light source unit 2 is turned on by the vehicle power source in which voltage fluctuations are likely to occur, the current limiting resistor 3 and the PWM control circuit unit 5 are used. Since the PWM control circuit unit 5 supplies electric power that is approximately suitable for both the time and the stop lamp lighting, the current limiting resistor 3
In addition to reducing the load on the vehicle, the same current limiting resistor 3 can be used for both the tail lamp lighting and the stop lamp lighting. Also, in the LED lamp 2a, it is sufficient to simply connect in series without wiring in a matrix.

This means that it is not necessary to prepare two types of the current limiting resistor 3 for lighting the tail lamp and for lighting the stop lamp, the cost can be reduced by reducing the number of parts, and the current limiting resistor 3 can be used. In addition, the power consumption is reduced, and the size of the vehicle lamp is reduced, and the heat generation of the vehicle lamp as a whole is reduced. In addition, LED lamp 2
Since the disconnection of each column of a can be detected, it becomes easy to comply with European standards.

Also on the PWM control circuit 5 side,
Since the current limiting resistor 3 is provided, even if the duty control is performed, such accuracy is not required, the circuit can be simplified, and the coil or the like does not include the inductance. Therefore, the occurrence of noise due to the back electromotive force can be reduced.

FIG. 5 shows another embodiment of the lighting circuit 1 according to the present invention. In the previous embodiment, the switching circuit section 4 is constituted by an NPN transistor Q1 and the current limiting resistor 3 is further grounded. However, the present invention is not limited to this, and the PNP transistor Q2 may be provided on the power supply side as shown in the figure.

In this case, since the current limiting resistor 3 can be grounded at one end, as described above, the LED lamp is at the potential of the connection point P between the current limiting resistor 3 and the LED lamp 2a. When the disconnection of 2a is detected, the output potential becomes stable, which facilitates the determination of disconnection.

[0024]

As described above, according to the present invention, in the lighting circuit, the lamp array including at least one LED lamp and the current limiting resistor are connected in series with the current limiting resistor as the ground side. 1 column or a plurality of columns are connected in parallel, a PWM control circuit unit that varies the duty ratio by a signal given to the input side of the vehicle-mounted LED lamp, and is connected to the power source side or the ground side of the light source unit. The current limiting resistor according to the related art is used as a lighting circuit for an on-vehicle LED lamp, which includes a switching circuit unit that controls a duty ratio of a power source applied to a light source unit based on an output from the PWM control circuit unit. It prevents excessive power consumption when the lighting circuit is configured with only the lighting circuit, and prevents the entire lighting circuit from increasing in size and generating excessive heat. The matrix wiring of the LED lamp is also not necessary, but also possible to cope with European standards.
Further, when the lighting circuit is constructed by the DC / DC converter, the problem of noise generation from the DC / DC converter is eliminated, and therefore the performance of this kind of lighting circuit is improved and the cost is extremely excellent. It has a great effect.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram showing an embodiment of a lighting circuit of an on-vehicle LED lamp according to the present invention.

FIG. 2 is an explanatory diagram showing an example of a waveform at the time of tail lighting of the lighting circuit according to the present invention.

FIG. 3 is an explanatory diagram showing an example of waveforms when the stop circuit of the lighting circuit according to the present invention is also lit.

FIG. 4 is an explanatory diagram showing an example of a waveform when stop lighting of the lighting circuit according to the present invention is performed and the voltage of the vehicle power supply is increased.

FIG. 5 is a schematic circuit diagram showing another embodiment of a lighting circuit of an in-vehicle LED lamp according to the present invention.

FIG. 6 is a schematic circuit diagram showing a conventional example.

FIG. 7 is a schematic circuit diagram showing another conventional example.

[Explanation of symbols]

1 ... Lighting circuit 2 ... Light source 2a ... LED lamp 2b ... Lamp row 2c ... Assembly line 3 ... Current limiting resistance 4 ... Switching circuit section 5 ... PWM control circuit 5a ... Input voltage detection circuit 6 ... Disconnection detection circuit 7 ... Reverse connection prevention diode 8 ... Zener diode

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F21Q 1/00 NZ F term (reference) 3K073 AA43 AA52 AA83 AA93 AB01 BA02 BA09 CF04 CG02 CG10 CJ17 3K080 AA01 BA07 BE07

Claims (3)

[Claims] 1. A lighting circuit for an on-vehicle LED lighting device, comprising a plurality of LED lamps as a light source, wherein the lighting circuit comprises:
A lamp row composed of at least one LED lamp and a current limiting resistor are connected in series with the current limiting resistor as a ground side in series, or a light source section in which a plurality of rows are connected in parallel, A PWM control circuit unit that changes a duty ratio by a signal given to an input side of an on-vehicle LED lighting device, and a light source unit based on an output from the PWM control circuit unit, which is connected to a power source side or a ground side of the light source unit. A lighting circuit for an on-vehicle LED lighting device, comprising a switching circuit unit for controlling a duty ratio of an applied power source. 2. The PWM control circuit section is provided with an input voltage detection circuit for detecting a voltage of a vehicle power supply applied to the vehicle-mounted LED lamp, and the duty ratio is also determined by the output of the input voltage detection circuit. The lighting circuit for an on-vehicle LED lighting device according to claim 1, wherein the lighting circuit is variable. 3. The current limiting resistor of the light source section is provided with a disconnection detecting section for detecting a disconnection of the LED lamp in the assembly line by a potential difference between both ends of the current limiting resistance. The plurality of vehicles are connected in parallel, and when a disconnection is detected in any one of the assembly rows, the switching circuit section stops the lighting of all the assembly rows. Lighting circuit for LED lighting fixtures.