JP2003187614A - Rear combination lamp device for vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to minimize heat generation of a circuit, reduce the number of wirings, uniformize brightness of light-emitting diodes, and prevent deviation of brightness. <P>SOLUTION: An LED unit 10 has eight LED's 9 all connected in series and the 12 V voltage of a power source 3 by way of a battery of a vehicle is not enough, so that a booster circuit 4 is provided in a control unit 2, by which a boosted voltage of about 16 V is impressed on the eight LED's. The tip of the LED unit 10 is connected to a constant-current circuit 8, in the vicinity of which is a voltage detecting circuit 7 connected to the constant-current circuit 8 for detecting voltage impressed on the constant-current circuit 8, which, compared with a standard voltage 5 taken in from the power source 3, and amplified by an amplifier 6, is inputted to the booster circuit 4 as a booster control signal. The booster control signal is outputted to control the booster current so that voltage detected by the voltage detecting circuit 7 be as low as possible. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle rear combination lamp device for controlling a vehicle rear combination lamp using a light emitting diode as a light source.

In the present specification, the LED chip itself or the entire package including an optical device such as a package resin or a lens system on which the LED chip is mounted is referred to as a "light emitting diode" or "LED".

[0003]

2. Description of the Related Art With the increase in brightness of light-emitting elements, vehicle rear combination lamps using LEDs as light sources have been increasingly used for stop lamps of automobiles. LEDs have a sharp spectrum and good visibility.
Further, since the response speed is fast, the signal transmission speed to the following vehicle is fast, and it is recognized that the stationary distance is shortened during high speed running. Further, since the LED itself is a monochromatic light source, it is not necessary to filter out light other than the necessary colors as in an incandescent light bulb, and it is highly efficient as a monochromatic light source, leading to energy saving.

An example of such a vehicle rear combination lamp device is shown in FIG. FIG. 3 is a circuit diagram showing an example of a conventional vehicle rear combination lamp device.
As shown in FIG. 3, the vehicle rear combination lamp device 50 includes a control unit 51 and a light emitting diode unit 52, and eight light emitting diodes 54 of the light emitting diode unit 52 are connected in parallel with each other. There is.

[0005]

Therefore, a current limiting circuit (resistor or transistor) 55 is required for each light emitting diode 54, and as the number of light emitting diodes 54 increases, the number of current limiting circuits 55 also increases. The calorific value of itself cannot be ignored. In addition, since the number of wirings connecting the control unit 51 and the light emitting diode unit 52 is large, that is, the number of power source lines + the number of parallel wirings, the wiring is troublesome and the cost is high. Further, if there is variation in the forward voltage of each light emitting diode 54, the flowing current will vary, and thus the brightness of the light emitting diode 54 will vary.
Further, when the current limiting circuit 55 is a resistor, there is a problem that when the power supply voltage changes, the current flowing through the light emitting diode 54 also changes and the brightness changes.

Therefore, the present invention provides a rear combination lamp device for a vehicle which can minimize the heat generation of the circuit, reduce the number of wirings, make the brightness of the light emitting diode uniform, and prevent the brightness from varying. This is an issue.

[0007]

According to a first aspect of the present invention, there is provided a rear combination lamp device for a vehicle, wherein a light emitting diode is used as a light source, a plurality of the light emitting diodes are connected in series, and a voltage boosted from a power supply voltage is applied. It is applied and turned on.

Normally, the voltage of an automobile battery is about 12V.
The forward voltage of the light emitting diode is about 2V. Therefore, when the LEDs are arranged in series and turned on, the limit is six. Therefore, the LEDs are rearranged from the conventional parallel to the serial, and a booster circuit is provided between the LEDs arranged in series with the battery to increase the voltage.
It is now possible to cope with the increase in the number of. by this,
Since there are two wires between the power source and the LED unit, workability can be improved and cost can be reduced. In addition, since the LEDs of the same size are arranged in series, the same amount of current flows through all the LEDs, so variations in brightness among the LEDs are suppressed, and even if the power supply voltage fluctuates, the voltage applied to the LEDs is also controlled by the booster circuit. Therefore, the brightness does not fluctuate.

In this way, the vehicle rear combination lamp device can be provided in which the number of wirings is reduced, the brightness of the light emitting diode is made uniform, and the fluctuation of the brightness can be prevented.

According to a second aspect of the present invention, in the vehicle rear combination lamp device according to the first aspect, the light emitting diodes connected in series are driven with a constant current and a variable voltage is applied.

In this vehicle rear combination lamp device, in addition to arranging the LEDs in series to boost and apply the power supply voltage, a constant current circuit is added to drive the constant current. Then, a variable voltage is applied so that this constant current matches the forward current of the LED. by this,
Since the voltage applied to the constant current circuit and the like decreases, the amount of heat generated in this portion decreases, and heat is generated almost exclusively in this portion. Therefore, the amount of heat generated in the entire device also decreases and efficiency improves. .

In this way, the vehicle rear combination lamp device can minimize the heat generation of the circuit, reduce the number of wirings, make the brightness of the light emitting diode uniform, and prevent the brightness from varying.

In the vehicle rear combination lamp device according to a third aspect of the present invention, in the configuration of the second aspect, the circuit for the voltage boosted from the power supply voltage has a constant current circuit and a voltage detection circuit for the constant current circuit. The variable voltage is applied to the plurality of light emitting diodes as a voltage boosted from the power supply voltage as low as possible so that the voltage detected by the voltage detection circuit can cause the plurality of light emitting diodes to emit light. To do.

This vehicle rear combination lamp device has a constant current circuit for driving the LED with a constant current and a voltage detection circuit for detecting the voltage applied to the constant current circuit. Then, the magnitude of the variable voltage is changed so that the voltage detected by the voltage detection circuit becomes as low as possible enough to cause the plurality of light emitting diodes to emit light, and the voltage is applied. As a result, the amount of heat generated in the constant current circuit decreases, and heat is generated only in this portion, so that the amount of heat generated in the entire device also decreases and efficiency improves.

In this way, a vehicle rear combination lamp device which can more reliably minimize the heat generation of the circuit, reduce the number of wirings, make the brightness of the light emitting diodes uniform, and prevent the brightness from varying. Become.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram showing an outline of a circuit of a vehicle rear combination lamp device according to an embodiment of the present invention. FIG. 2 is a circuit diagram showing a more detailed circuit of the vehicle rear combination lamp device according to the embodiment of the present invention.

As shown in FIG. 1, the vehicle rear combination lamp device 1 of the present embodiment comprises a control unit 2 and a light emitting diode unit 10. In this LED unit 10, 8 LEDs 9
Are all connected in series to form a rear combination lamp. Since the voltage of the power supply 3, that is, the battery of the vehicle is about 12V, LE which requires about 2V × 8 = about 16V
The voltage of the D unit 10 is insufficient. Therefore, the booster circuit 4 is provided in the control unit 2 and the voltage boosted to about 16 V is applied to the eight LEDs 9. LED unit 1
The tip of 0 is connected to the constant current circuit 8 and grounded. A voltage detection circuit 7 for detecting the voltage applied to the constant current circuit 8 is connected in the vicinity of the constant current circuit 8, and is compared with the reference voltage 5 taken from the power source 3 and amplified by the amplifier 6. It is input to the booster circuit 4 as a boosting control signal. The boost control signal is output so as to control the boost voltage so that the voltage detected by the voltage detection circuit 7 is as low as possible.

As a result, the amount of heat generated by the constant current circuit 8 itself can be suppressed as low as possible, and the efficiency of the circuit can be increased. Further, since all eight LEDs 9 are connected in series, the same current flows through all the LEDs, so that variations in brightness can be suppressed. Also LED
Since the voltage (boosted voltage) applied to LED 9 is also controlled, the brightness of LED 9 does not change even if the power supply voltage changes. Further, only two wires are required between the control unit 2 and the LED unit 10, workability is improved, and cost can be reduced.

Next, a more detailed operation of the circuit will be described with reference to FIG. The booster circuit 4 for boosting to generate the boosted voltage V2 to be applied to the LED 9 is of a chopper type using the coil L and the transistor Tr in the present embodiment. Further, a rectifying diode D and a smoothing capacitor C are also used. Here, the transistor Tr repeats ON / OFF at high speed, and the boosted voltage V2 can be changed by controlling the ON / OFF ratio duty ratio of the transistor Tr.
Duty ratio = ON time of transistor Tr / (ON
Time + OFF time), and the boosted voltage V2 rises when the duty ratio is increased and falls when the duty ratio is decreased. 8
The current I flowing through the individual LEDs 9 flows to the resistor R1.
The resistor R1 corresponds to the constant current circuit 8 in FIG.

The voltage V1 of the resistor R1 is detected by the operational amplifier Q1, amplified to the voltage V3, and input to the boost control IC. The resistors R2, R3 and R4 determine the amplification factor of the operational amplifier Q1. Therefore, the operational amplifier Q1,
The resistors R2, R3 and R4 form the voltage detection circuit 7 of FIG. In the boost control IC, the input V
3 and the internal reference voltage 5 are compared, and the duty ratio of the transistor Tr of the booster circuit 4 is controlled so that they are equal to each other without enduring. Boost control I
The oscillator 12 in C determines the cycle of repeating ON / OFF of the transistor Tr, and the PWM amplifier 13 plays a role of determining the duty ratio and driving the transistor Tr.

For example, when the voltage of the battery 3 drops for some reason, the voltage V2 drops first, and at the same time the LED
The current I flowing through 9 decreases and the voltage V1 of the resistor R1
Also decreases. Then, the voltage V3 also drops, so that there is a difference from the reference voltage 5 in the boost control IC. In order to eliminate this difference in the step-up control IC, control works in the direction of increasing the duty ratio of the transistor Tr, and eventually the voltage V2 rises and stabilizes at a value before changing.

In this circuit, the voltage V1 is controlled to be constant, so that the current I flowing through the LED 9 is I
= V1 / R1 and is constant. That is, the constant current circuit is formed by the resistor R1.

If the value of the voltage V1 is not increased more than necessary, the heat generated in the resistor R1 can be suppressed and wasteful heat generation can be reduced. For example, when all eight LEDs are connected in parallel as in a conventional circuit and a resistor is used for each current limitation, when the electric power that is the heat source generated in the resistor is calculated,
Power supply voltage is 12V, LED forward voltage Vf is 2V, L
Since the voltage applied to each resistor is 12V-2V = 10V when the current flowing through the ED is 0.02A, the total resistance power is 10V × 0.02A × 8 (pieces) = 1.6W. On the other hand, when the voltage applied to the resistor R1 in the circuit of FIG. 2 is controlled so that the voltage V1 is 1 V and the current flowing through the LED is also 0.02 A, it becomes 1 V × 0.02 A = 0.02 W It is extremely less than the conventional circuit.

Further, even if the forward voltage Vf changes due to the variation in the characteristics of the LED 9, the voltage V1 is constant and the variation is absorbed by the change in the boosted voltage V2. This is the LED
Even if the forward voltage Vf of 9 fluctuates to the smaller one, the resistance R
This means that the heat of 1 does not increase.

Further, comparing the overall efficiency, when eight former LEDs are connected in parallel, the power consumed by the LEDs is 2V × 0.02A × 8 (piece) = 0.32W Since the input power from is a small amount for the control circuit, it is neglected. 12V × 0.02A × 8 (parallel) = 1.92W Therefore, the efficiency is 0.32 / 1.92 × 100 = 16.7 (%) Becomes On the other hand, in the circuit of FIG. 2, the power consumed by the LED 9 is 2V × 0.02A × 8 (pieces) = 0.32W, and the power consumed by the resistor R1 is 1V × 0.02A = 0.02W If the efficiency of the circuit 4 is 70%, the input voltage from the power supply is also (0.32W + 0.02W) /0.7=0.48W, ignoring the control circuit portion. It is 0.48 × 100 = 66.7 (%), which means that the efficiency is much higher than that of the conventional circuit.

As described above, in the vehicle rear combination lamp device of the present embodiment, it is possible to prevent wasteful heat generation, and even if the forward voltage Vf of the LED varies, it is absorbed by the change in the boosted voltage V2. As a result, it is possible to prevent the heat generation amount of the constant current circuit from increasing, and the efficiency is much higher than that of the conventional parallel circuit.

In the present embodiment, the chopper method is used as the method of boosting the power supply voltage, but there are various methods of boosting, and any method including the charge pump method and the transformer method is used. May be.

The configuration, shape, quantity, material, size, connection relationship, etc. of the other parts of the vehicle rear combination lamp device are not limited to those in this embodiment.

[0029]

As described above, in the vehicle rear combination lamp device according to the invention of claim 1, a light emitting diode is used as a light source, and a plurality of the light emitting diodes are connected in series to boost the power source voltage. The light is applied by applying a voltage.

Normally, the voltage of the automobile battery is about 12V.
The forward voltage of the light emitting diode is about 2V. Therefore, when the LEDs are arranged in series and turned on, the limit is six. Therefore, the LEDs are rearranged from the conventional parallel to the serial, and a booster circuit is provided between the LEDs arranged in series with the battery to increase the voltage.
It is now possible to cope with the increase in the number of. by this,
Since there are two wires between the power source and the LED unit, workability can be improved and cost can be reduced. In addition, since the LEDs of the same size are arranged in series, the same amount of current flows through all the LEDs, so variations in brightness among the LEDs are suppressed, and even if the power supply voltage fluctuates, the voltage applied to the LEDs is also controlled by the booster circuit. Therefore, the brightness does not fluctuate.

In this way, the vehicle rear combination lamp device can be provided in which the number of wirings is reduced, the brightness of the light emitting diode is made uniform, and the fluctuation of the brightness can be prevented.

According to a second aspect of the present invention, there is provided a vehicle rear combination lamp device according to the first aspect, wherein the light emitting diodes connected in series are driven with a constant current and a variable voltage is applied.

In this vehicle rear combination lamp device, in addition to arranging the LEDs in series to boost and apply the power supply voltage, a constant current circuit is added for constant current driving. Then, a variable voltage is applied so that this constant current matches the forward current of the LED. by this,
In addition to the effect described in claim 1, the voltage applied to the constant current circuit or the like is reduced, the heat generation amount in this portion is small, and heat is generated only in this portion. The amount of heat generated is also reduced and the efficiency is improved.

In this way, the vehicle rear combination lamp device can minimize the heat generation of the circuit, reduce the number of wires, make the brightness of the light emitting diode uniform, and prevent the brightness from varying.

In the vehicle rear combination lamp device according to a third aspect of the present invention, in the configuration of the second aspect, the circuit for the voltage boosted from the power supply voltage has a constant current circuit and a voltage detection circuit for the constant current circuit. The variable voltage is applied to the plurality of light emitting diodes as a voltage boosted from the power supply voltage as low as possible so that the voltage detected by the voltage detection circuit can cause the plurality of light emitting diodes to emit light. To do.

In addition to the effect of the second aspect, in the vehicle rear combination lamp device, a constant current circuit for driving the LED at a constant current and a voltage detection circuit for detecting the voltage applied to the constant current circuit are provided. Have Then, the magnitude of the variable voltage is changed so that the voltage detected by the voltage detection circuit becomes as low as possible enough to cause the plurality of light emitting diodes to emit light, and the voltage is applied. As a result, the amount of heat generated in the constant current circuit decreases, and heat is generated only in this portion, so that the amount of heat generated in the entire device also decreases and efficiency improves.

In this way, a vehicle rear combination lamp device which can more reliably minimize the heat generation of the circuit, reduce the number of wires, make the brightness of the light emitting diodes uniform, and prevent the brightness from varying. Become.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an outline of a circuit of a vehicle rear combination lamp device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a more detailed circuit of the vehicle rear combination lamp device according to the exemplary embodiment of the present invention.

FIG. 3 is a circuit diagram showing an example of a conventional vehicle rear combination lamp device.

[Explanation of symbols]

1 Rear combination lamp device for vehicles 9 Light emitting diode (LED)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F21Q 1/00 HF term (reference) 3K073 AA02 AA21 AA27 AA43 AA83 AA84 AB03 BA02 BA08 BA20 CF12 CF18 CG01 CG14 CG16 CG54 CJ17 CL11 3K080 AA01 BA07 BE07

Claims (3)

[Claims] 1. A light emitting diode for a light source, wherein a plurality of the light emitting diodes are connected in series, and a voltage boosted from a power supply voltage is applied to the plurality of the light emitting diodes to illuminate. Rear combination lamp device. 2. The vehicle rear combination lamp device according to claim 1, wherein the light emitting diodes connected in series are driven with a constant current and a variable voltage is applied. 3. A circuit for a voltage boosted from the power supply voltage has a constant current circuit and a voltage detection circuit for the constant current circuit,
The variable voltage is applied to the plurality of light emitting diodes as a voltage detected by the voltage detection circuit as low as possible to cause the plurality of light emitting diodes to emit light. Vehicle rear combination lamp device.