JPH04314641A - Indicator lamp control circuit for vehicle - Google Patents

Abstract

PURPOSE:To provide an indicator lamp control circuit for a vehicle whereby only a small power loss is required at the time of lighting all indicator lamps by always holding fixed brightness of the indicator lamp even when a number of lighting a plurality of the indicator lamps is changed. CONSTITUTION:Indicator lamps 38, 40 are respectively connected in parallel to a line branched from a plus side of a power supply part 36, and in a display part provided with a changeover switch 42 for on-off lighting the indicator lamp 40, a constant voltage circuit 44 is connected to a point D between a branch point C of the above-mentioned line and the indicator lamp 40. A current is allowed to flow in the constant voltage circuit 44, when the indicator lamp 40 is put out, and the constant voltage circuit 44 is actuated so as to prevent the current from flowing in the constant voltage circuit 44 when the indicator lamp 40 is lighted. In this way, fixed potential is always held in each line regardless of a number of lighting the indicator lamps to eliminate a power loss with a small change of illumination intensity.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle indicator lamp control circuit that visually displays the operating status of various parts of a vehicle by blinking a plurality of indicator lamps.

0002

[Prior Art] Conventional vehicle instrument panels are equipped with indicator lamps that visually display the operating status of an air conditioner (A/C) in an easy-to-understand manner by emitting light from a light emitting diode (LED) or a bulb. It is set up.

FIG. 5 is a circuit diagram of a conventional vehicle indicator lamp control circuit. As shown in FIG. 5, a plurality of conventional indicator lamps 10 and 12 are arranged on the instrument panel of a vehicle, and indicate, for example, the strength/weakness of the blower of the air conditioner, the ON/OFF of the air conditioner or the defroster, etc. Visual indication is provided by blinking indicator lamps.

[0004] The plurality of indicator lamps 10, 12
are connected in parallel to the power supply section 14, among which the indicator lamp 10 is always lit, and the indicator lamp 12 blinks when the switch 16 is opened or closed.

[0005]Then, each of the indicator lamps 10,
A constant voltage diode (Zener diode) 18 is disposed between the branch point A of the electric circuit connecting the power supply circuits 12 in parallel and the power supply section 14, and between the point B and the ground via a resistor (R1). There is.

Since the conventional indicator lamp control circuit is constructed in this way, even if the number of indicator lamps lit by opening and closing the switch 16 changes, the current (I1) flows through the constant voltage diode 18, so that B The potential at a point is always kept constant.

[0007]

[Problems to be Solved by the Invention] As described above, in the conventional vehicle indicator lamp control circuit, the indicator lamps 10 and 12 connected in parallel as shown in FIG. A constant voltage diode 18 is connected and operates to maintain the voltage at this point B constant. However, switch 16
When the desired indicator lamps 12 are made to flicker by opening and closing as appropriate, there is a problem in that the voltage across each indicator lamp changes slightly depending on the number of indicator lamps lit, and the illuminance changes.

In particular, when the indicator lamp is a light emitting diode (LED), the illuminance changes even with a voltage change of about 0.01V. Therefore, in conventional indicator lamp control circuits, the display illuminance depends on the number of indicator lamps lit. There was a problem that the image changed so much that appropriate visual display could not be performed.

Further, the voltage regulator diode 1 shown in FIG.
No. 8 has the problem that even when all the indicator lamps are on, the current (I1) flows to keep the potential at point B constant, so there is a power loss even when all the indicator lamps are on.

The present invention has been made to solve the above-mentioned problems, and even if the number of indicator lamps that are turned on among the plurality of indicator lamps changes depending on the operating status of each part of the vehicle, It is an object of the present invention to provide an indicator lamp control circuit for a vehicle in which the brightness of the indicator lamps that are lit is always kept constant and power loss when all the indicator lamps are lit is small.

[0011]

[Means for Solving the Problems] In order to solve the above problems, the vehicle indicator lamp control circuit of the present invention includes a power supply section and a plurality of indicator lamps on an electric path branching from the positive side of the power supply section. A display unit that is connected in parallel and has a changeover switch that turns each indicator lamp on and off individually, and a constant voltage that is connected between the branch point of the electric path and each indicator lamp to maintain a constant voltage therebetween. a circuit, when the indicator lamp is turned off with the changeover switch open, current is passed through the constant voltage circuit, and when the changeover switch is closed and the indicator lamp is turned on, current is not allowed to flow through the constant voltage circuit, It is characterized by keeping the voltage across each indicator lamp constant.

0012

[Operation] According to the indicator lamp control circuit for a vehicle according to the present invention, a plurality of indicator lamps are connected in parallel, and a switch is set between the indicator lamp of the display unit and the branch point, which is equipped with a changeover switch that makes each of the indicator lamps blink individually. The voltage circuits are connected to each other. Then, when the indicator lamp is off, current flows through the constant voltage circuit, and when the indicator lamp is on, current does not flow through the constant voltage circuit.
Since the voltage across each indicator lamp is held constant, the illuminance is kept constant even if the number of indicator lamps lit is increased or decreased.

Furthermore, since no current flows through the constant voltage circuit when all the indicator lamps are lit, it is possible to provide an indicator lamp control circuit with less power loss.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a vehicle indicator lamp control circuit according to the present invention will be described below with reference to the drawings.

FIG. 3 is a circuit diagram of a power supply section in an embodiment of the present invention. As shown in FIG. 3, the power supply unit used in this embodiment includes 12
The oscillation unit 22, the switching control unit 24, and the charge pump unit 26 reduce the power supply voltage of V to 6V without power loss, and the display control unit 28 changes the voltage between daytime and nighttime to display multiple indicators. It is supplied to a display section 30 having a lamp.

The oscillation section 22 uses an astable multivibrator here, and has transistors (Tr1) and (
Tr2) is alternately switched at an oscillation frequency determined by the time constants of the capacitor and resistor. The oscillation unit 22 outputs an AC pulse signal having a constant frequency.

The switching control section 24 switches the current path from the battery power source 20 by alternately switching the two transistors (Tr3) and (Tr4) in accordance with the AC pulse signal output from the oscillation section 22. It is carried out.

The charge pump unit 26 switches the current path by the switching control unit 24, and connects two capacitors (C3
), (C4) are charged in series and discharged in parallel. This allows the 12V battery power supply 20
To lower the power supply voltage to 6V without power loss.

The display control section 28 includes a transistor (T
r5) and (Tr6), and their base terminals have
They are connected to a night light switch 32 that illuminates the entire instrument panel via resistors (R9) and (R10), respectively. A resistor (R13) is connected between the resistors (R9) and (R10) and the night light switch 32 to ground. In addition, a transistor (Tr5),
Bypasses are provided between the emitter and collector of (Tr6) via resistors (R11) and (R12), respectively.

Therefore, during the daytime when the night light switch 32 is open, the transistors (Tr5) and (Tr6) are as follows:
The respective bases fall to the ground via the resistors (R13) and base current flows, so they are turned on, and power is supplied to the display section 30 without passing through the bypass resistors (R11) and (R12).

Furthermore, at night when the night light switch 32 is closed, the transistors (Tr5) and (Tr6) are turned off because the voltage from the power supply 34 is applied to their base terminals, and the base current does not flow. resistance (R11)
, (R12) and is applied to the display section 30.

In this manner, the voltage applied to the indicator lamp of the display section 30 is lower during the night than during the day, thereby increasing the illuminance of the indicator lamp during the day to improve visibility. It can be lowered at night to provide visual display without glare.

FIG. 4 is a block diagram of each component in FIG. 3. As shown in FIG. 4, the power supply section 36 is
The switching control unit 24 lowers the 12V power supply voltage from the battery power supply 20 to 6V without power loss using the oscillation unit 22 and charge pump unit 26, and the display control unit 28 controls the voltage during nighttime and daytime. It is carried out. This controlled voltage is then applied to the next display section 30.

A feature of the present invention is that, by the configuration described below, the display section 30, which is provided with a plurality of indicator lamps that flicker depending on the operating state of the vehicle equipment, has a stable display regardless of the number of indicator lamps lit. Visual display is performed using illuminance to reduce power loss.

FIGS. 1 and 2 are circuit diagrams of a vehicle indicator lamp control circuit according to an embodiment of the present invention. As shown in FIG. 1, the display section connected to the power supply section 36 is connected to the electric circuits separated at the branch point C.
Indicator lamps 38 and 40 consisting of D are connected in parallel. A constant voltage circuit 44 is provided at a point D between the branch point C and the indicator lamp 40, which is provided with a switch 42 and blinks individually.

The constant voltage circuit 44 uses a Zener diode here, and has one terminal connected to the point D and the other terminal grounded. As a result, when the voltage at point D exceeds a predetermined value, a reverse current flows through the Zener diode to maintain the voltage at point D constant.

Furthermore, the indicator lamp 38 is an indicator lamp that is always lit. Next, the operation of this embodiment will be explained.

First, as shown in FIG.
2 is closed, indicator lamps 38 and 40
Both are lit to provide a visual display. At this time, current flows as shown by currents (I2) and (I3) in FIG. 1, but does not flow through the constant voltage circuit 44.

Next, as shown in FIG.
2 is open, the indicator lamp 40 is turned off and only the indicator lamp 38 is lit for visual display. The current flow at this time is the current (
In addition to I2 ), a current (I4 ) flows through the constant voltage circuit 44 to maintain the potential at point D in substantially the same manner as when the indicator lamp 40 of FIG. 1 is turned on.

That is, when the constant voltage circuit 44 is operated as described above, if the voltage at which the Zener effect occurs in the Zener diode of the constant voltage circuit 44 is VD, and the voltage across the indicator lamp 40 is Vd, then Vd ≦V.
Zener diodes may be selected so as to satisfy the relationship D.

As a result, the illuminance of the indicator lamp 38 remains constant even if the number of indicator lamps lit changes as the indicator lamp 40 turns on or off, because the constant voltage circuit 44 works and the voltage across the indicator lamp 38 does not change. Illuminance is kept constant.

Furthermore, in this embodiment, when all the indicator lamps are lit, that is, in the state shown in FIG. 1, no current flows through the constant voltage circuit 44 and power is consumed only for lighting the indicator lamps, which is different from the conventional method. Such power loss is eliminated.

Although the above embodiment has been described with reference to the case where there are two indicator lamps as shown in FIG. 1, the present invention is not limited to this example, and a case where there are three or more indicator lamps produces the same favorable effect as described above.

[0034]

As explained above, according to the vehicle indicator lamp control circuit of the present invention, each of the plurality of indicator lamps connected in parallel to the power supply section and the branch point of the electric circuit can be It is possible to maintain the potential of each circuit at a constant level by providing a constant voltage circuit, allowing current to flow through the constant voltage circuit when the indicator lamp is off, and not allowing current to flow through the constant voltage circuit when the indicator lamp is on. can. Therefore, the illuminance does not change even if the number of indicator lamps lit changes, so that proper visual display can be performed and power loss when all the indicator lamps are lit can be eliminated.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of a vehicle indicator lamp control circuit according to an embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a vehicle indicator lamp control circuit according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a power supply section in an embodiment of the present invention.

FIG. 4 is a block diagram showing each component in FIG. 3;

FIG. 5 is a circuit diagram of a conventional vehicle indicator lamp control circuit.

[Explanation of symbols]

30 Display section 36 Power supply section 38, 40 Indicator lamp 42 Selector switch 44 Constant voltage circuit

Claims (1)

[Claims] 1. A vehicle indicator lamp control circuit that visually displays the operating status of each part of a vehicle by emitting a plurality of indicator lamps, the plurality of indicator lamps being connected to a power supply section and an electric path branching from the positive side of the power supply section. The indicator lamps are connected in parallel, and the indicator lamps are connected between a display unit equipped with a changeover switch that blinks the indicator lamps individually, and a branch point of the electrical path and the indicator lamp equipped with the changeover switch, and the voltage between them is connected. and a constant voltage circuit that maintains a constant voltage, and when the indicator lamp is turned off when the changeover switch is open, current is passed through the constant voltage circuit, and when the changeover switch is closed and the indicator lamp is turned on, current is passed through the constant voltage circuit. An indicator lamp control circuit for a vehicle, characterized in that the voltage across each indicator lamp is kept constant.