JP2014037175A - Control circuit of lighting fixture for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid lights-out or sudden illuminance change of a lighting fixture for vehicle.SOLUTION: A control circuit 1 outputs a voltage signal for controlling a light emission state of a light-emitting device 3 mounted on a lighting fixture for vehicle, and includes: a transistor 21 in which a first terminal is connected to a power source terminal 23, and a first resistance element is connected between the first terminal and the control terminal; a second resistance element and a third resistance element which are connected to each other in series, one end is connected to the first terminal of the transistor 21, and the other end is connected to a reference potential terminal; a shunt regulator 22 in which cathode is connected to the control terminal of the transistor 21, anode is connected to the reference potential terminal, and reference is connected to a node between the second resistance element and the third resistance element; a fourth resistance element and a fifth resistance element which are connected to each other in series, one end is connected to a second terminal of the transistor 21, the other end is connected to the reference potential terminal, in which the circuit outputs voltage of a node between the fourth resistance element and the fifth resistance element as the above voltage signal.

Description

  The present invention relates to an apparatus for controlling the lighting state of a vehicular lamp.

  As a method for controlling a vehicular lamp configured using an LED (light emitting element), a method of controlling the LED by constant current control using a step-up / step-down circuit or a booster circuit is generally used. A prior example of such a step-up / step-down circuit (step-up / step-down DC-DC converter) is disclosed in, for example, Japanese Patent Laid-Open No. 2011-130557 (Patent Document 1).

  By the way, in recent years, an idling stop type vehicle that stops an engine when stopping at an intersection or the like has become widespread. For this reason, the output voltage from the battery mounted on the vehicle decreases for a certain period of time when idling is stopped. At this time, when the LED is controlled by the constant current control as described above, the output voltage and the output current (LED Vf and If) are kept constant even when the input voltage to the control circuit decreases. There is a disadvantage that the input current increases greatly. Although it is conceivable to stop the operation of the control circuit in order to suppress an increase in input current, this is not preferable because the vehicular lamp is turned off at the time of idling stop. On the other hand, it is conceivable to switch the output current to about half when the input voltage becomes below a certain level. In this case, however, the brightness (luminosity) of the illumination light of the vehicle lamp changes greatly in an instant during idle stop. This is not preferable.

JP 2011-130557 A

  A specific aspect of the present invention is to provide a control technique for a vehicular lamp capable of avoiding turning off of the vehicular lamp and a sudden change in luminance.

  A control circuit according to an aspect of the present invention is a control circuit that outputs a voltage signal for controlling a light emission state of a light emitting element mounted on a vehicle lamp, and (a) a first terminal is connected to a power supply terminal. A transistor having a first resistance element connected between the first terminal and the control terminal; and (b) connected in series, one end connected to the second terminal of the transistor and the other end to the reference potential. (C) a cathode is connected to a control terminal of the transistor, an anode is connected to a reference potential terminal, and a reference is connected to the second resistance element and the third resistance element. A shunt regulator connected to a node between them, and (d) a fourth resistance element and a fifth resistor connected in series with each other, having one end connected to the second terminal of the transistor and the other end connected to the reference potential terminal resistance Includes a child, a (e) a control circuit for voltage output as a voltage signal above a node, it is characterized by between fourth resistance element and the fifth resistive element. Here, the “transistor” is, for example, an NPN transistor. In the present specification, when the circuit elements are “connected (connected)”, not only the circuit elements are directly connected but also other circuit elements between the circuit elements. Including the case of intervening.

  According to the above configuration, when the input voltage supplied from the power supply terminal drops below a certain value, the magnitude of the voltage signal can be linearly lowered in conjunction with the input voltage, while the input voltage has a certain value. Higher than that, the magnitude of the voltage signal can be made constant regardless of the input voltage. By driving the light emitting element based on such a voltage signal, it is possible to avoid turning off the vehicular lamp and abrupt brightness change.

  A vehicle lamp system according to an aspect of the present invention is configured to emit light by setting a current value according to the magnitude of a voltage applied from the control circuit, a light emitting element incorporated in the vehicle lamp, and the control circuit. A light emitting element driving device for supplying a driving current to the element is included.

  According to the said structure, it becomes possible to avoid the light extinction of a vehicle lamp, and a rapid illuminance change.

FIG. 1 is a circuit diagram showing a configuration of a vehicular lamp system including a control circuit (control device) according to an embodiment. FIG. 2 is a waveform diagram for explaining the operation of the control circuit.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit diagram showing a configuration of a vehicular lamp system including a control circuit (control device) according to an embodiment. A control circuit 1 shown in FIG. 1 gives a voltage signal as a control signal to an LED driving IC (Integrated Circuit) 2 as a light emitting element driving device, and includes five resistance elements 11, 12, 13, 14, and 15. The transistor 21 and the shunt regulator 22 are included. The control circuit 1 is supplied with an input voltage (+ B) via a power supply terminal 23 from a battery (not shown) mounted on the vehicle. The LED driving IC 2 sets a current value according to the magnitude of the voltage given from the control circuit 1 and supplies a driving current to the light emitting element (LED) 3. The light emitting element 3 is incorporated in the vehicular lamp and emits light with a light intensity corresponding to the magnitude of the drive current supplied from the LED drive IC 2. In addition, although the one light emitting element 3 is shown in FIG. 1, this is only an illustration and the some light emitting element may be connected.

  The transistor (NPN transistor) 21 has a collector (first terminal) connected to the power supply terminal 23 and a resistance element 11 connected between the collector and the base (control terminal).

  The shunt regulator 22 has a cathode connected to the base of the transistor 21, an anode connected to the reference potential terminal 24, and a reference connected to a node 25 between the resistance element 12 and the resistance element 13.

  The resistance element 12 and the resistance element 13 are connected in series, one end of the resistance element 12 is connected to the emitter (second terminal) of the transistor 21, and one end of the resistance element 13 is connected to the reference potential terminal 24. .

  The resistance element 14 and the resistance element 15 are connected in series with each other, and are connected in parallel to the series circuit of the resistance element 12 and the resistance element 13 described above. In other words, the resistance element 14 and the resistance element 15 have one end of the resistance element 14 connected to the emitter of the transistor 21 and one end of the resistance element 15 connected to the reference potential terminal 24. An LED driving IC 2 is connected to a node (output point) 26 between the resistance element 14 and the resistance element 15.

  Next, the operation of the control circuit 1 of this embodiment will be described. FIG. 2 is a waveform diagram for explaining the operation of the control circuit. In FIG. 2, the horizontal axis corresponds to the input voltage, and the vertical axis corresponds to the output voltage (the voltage supplied to the LED driving IC 2).

  When the input voltage (+ B) of the power supply terminal 23 increases, a voltage of almost the same magnitude is applied to both ends of the series circuit of the resistor element 14 and the resistor element 15 via the resistor element 11 and the transistor 21. . This voltage is divided by the resistance element 14 and the resistance element 15, and the divided voltage is supplied as an output voltage to the LED driving IC 2 connected to the node 26 of both. The LED driving IC 2 sets a driving current to be supplied to the light emitting element 3 according to the magnitude of the supplied output voltage. Here, the LED drive IC 2 sets the drive current to the light emitting element 3 to be larger as the supplied voltage is larger, and sets the drive current to the light emitting element 3 to be smaller as the voltage is smaller.

  The emitter voltage of the transistor 21 is set by the shunt regulator 22, the resistance element 12, and the resistance element 13. If the emitter voltage of the transistor 21 is set to 9 V (volts), the input voltage is divided by the resistance element 14 and the resistance element 15 when the input voltage (+ B) is 0 V to 9 V as shown in FIG. The output voltage, which is a voltage, gradually increases, and this output voltage is supplied from the node 26 to the LED driving IC 2. On the other hand, as shown in FIG. 2, when the input voltage (+ B) becomes 9V or higher, the voltage is limited by the shunt regulator 22, so that the emitter voltage of the transistor 21 is fixed at 9V. For this reason, when the input voltage (+ B) is 0V to 9V, the voltage supplied to the LED drive IC 2 gradually increases, so the drive current to the light emitting element 3 increases, and the input voltage (+ B) becomes 9V or more. In this case, a constant driving current is supplied to the light emitting element 3. Conversely, when the input voltage (+ B) decreases between 16V and 9V, the voltage supplied to the LED driving IC 2 is constant at 9V until the input voltage (+ B) reaches 9V. The drive current to the light emitting element 3 is constant. When the input voltage (+ B) becomes 9 V or less, the voltage supplied to the LED drive IC 2 gradually decreases, and accordingly, the drive current to the light emitting element 3 decreases.

  Here, it may be necessary to change the setting of the resistance value of the resistance element 15 according to the brightness rank of the light emitting element 3 or the like. Even in such a case, as shown in FIG. 2, the control circuit 1 of the present embodiment does not change the operating point although the magnitude of the output voltage changes according to the resistance value, and the input voltage (+ B) is 0V to 9V. Until the input voltage (+ B) becomes 10 V or more, the output voltage becomes constant. For this reason, there exists an advantage which can respond easily to the light emitting element 3 of various requirement specifications.

  Thus, according to this embodiment, when the input voltage supplied from the power supply terminal falls below a certain value, the magnitude of the voltage signal can be linearly reduced in conjunction with the input voltage, while the input voltage When the voltage is higher than a certain value, the magnitude of the voltage signal can be made constant regardless of the input voltage. By driving the light emitting element based on such a voltage signal, it is possible to avoid turning off the vehicular lamp and abrupt brightness change.

  In addition, this invention is not limited to the content of embodiment mentioned above, In the range of the summary of this invention, it can change and implement variously. For example, the illustrated circuit configuration is an example, and various additional circuits may be included as long as the configuration and operation according to the present invention are not hindered.

1: Control circuit (control device)
2: LED drive IC
3: LED (light emitting element)
11, 12, 13, 14, 15: Resistance element 21: Transistor 22: Shunt regulator 23, 24: Power supply terminal 25, 26: Node

Claims (3)

A control circuit that outputs a voltage signal for controlling a light emission state of a light emitting element mounted on a vehicle lamp,
A transistor having a first terminal connected to a power supply terminal and a first resistance element connected between the first terminal and the control terminal;
A second resistor element and a third resistor element connected in series with each other, having one end connected to the second terminal of the transistor and the other end connected to a reference potential terminal;
A shunt regulator having a cathode connected to the control terminal of the transistor, an anode connected to the reference potential terminal, and a reference connected to a node between the second resistance element and the third resistance element;
A fourth resistor element and a fifth resistor element connected in series with each other, having one end connected to the second terminal of the transistor and the other end connected to the reference potential terminal;
Including
A vehicle lamp control circuit that outputs a voltage at a node between the fourth resistance element and the fifth resistance element as the voltage signal.   The vehicle lamp control circuit according to claim 1, wherein the transistor is an NPN transistor. A control circuit according to claim 1 or 2,
A light emitting device incorporated in a vehicle lamp;
A light emitting element driving device that sets a current value according to the magnitude of the voltage applied from the control circuit and supplies a driving current to the light emitting element;
A vehicle lamp system.

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