JP4288812B2 - Optical beacon vehicle transmitter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vehicular transmission device, and more particularly to a vehicular transmission device that transmits data to a communication device provided outside the vehicle using light.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an optical beacon vehicle transmission device is known as a device that transmits light to a communication device mounted on a vehicle and provided near a road using light.
[0003]
[Problems to be solved by the invention]
The present invention does not use a normally used in-vehicle battery as a power source for a transmission device for an optical beacon vehicle, uses an independent and built-in power source (that is, a battery) provided separately from this, and The purpose is to reduce the number of uses.
[0004]
[Means for Solving the Problems]
The present invention is driven by a battery provided separately from the in-vehicle battery, includes a capacitor between the battery and the LED for data transmission, and opens and closes the switch circuit provided between the capacitor and the LED. A transmitter for an optical beacon vehicle that controls supply of current to an LED, further comprising a DC / DC converter between the battery and the capacitor , and the DC / DC converter and the A second switch circuit is further provided between the capacitor and the capacitor, and the second switch circuit is opened when the LED emits light . By doing so, the number of batteries used for the power source can be reduced, and a large amount of electrical energy can be stored in the capacitor so that a large current can be instantaneously supplied to the LED. Further, the second switch circuit is opened at the time of the LED light emission, and the DC / DC converter and the capacitor are separated, so that the load of the DC / DC converter varies due to the LED light emission. It is possible to prevent fluctuations. In the present invention, the current flowing during light emission, it is also effective to limit using the constant current circuit, also effective to add a switch circuit between the battery and the DC / DC converter for use in power It is.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
The transmitter for an optical beacon vehicle is usually powered from an in-vehicle battery, but considering the complexity of installation work and the instability of the power source resulting from voltage fluctuations in the in-vehicle battery, Independent drive with a built-in power source (ie battery) is desired. The same applies when one vehicle transmitter is shared by a plurality of vehicles.
[0006]
FIG. 5 shows a circuit of a light emitting unit of a general in-vehicle battery-driven optical beacon vehicle transmitter.
In order to give the amount of light necessary for transmission to an optical beacon (roadside machine), it is necessary to use a plurality of LEDs as shown in FIG. 5, and a current of several hundred mA is instantaneously applied to each LED. Need to flow. At this time, the forward voltage generated in the LED is about 2-3V.
[0007]
If the in-vehicle battery of the circuit of FIG. 5 is replaced with a battery separately provided, for example, circuits as shown in FIGS. 6 and 7 are conceivable.
The LED series type shown in FIG. 6 requires less current supplied from the battery. However, the forward voltage generated in the LED is added, and a higher power supply voltage is required, and many batteries need to be connected in series.
In the LED parallel type of FIG. 7, it is not necessary to increase the number of batteries in terms of voltage. However, since a large amount of current supplied from the battery is required, it is necessary to connect many batteries in parallel.
[0008]
In order to reduce the number of batteries in the LED series type of FIG. 6, consider a method of increasing the voltage by inserting a DC / DC converter between the battery and the LED light emitting circuit as shown in FIG. It was.
However, this method still requires a large number of batteries to extract the necessary current.
[0009]
In order to reduce the number of batteries in the LED parallel type of FIG. 7, a method of interposing a capacitor between the battery and the LED light emitting circuit as shown in FIG. 9 was considered. This method pays attention to the fact that the time during which the LED emits light is shorter than the time when the LED does not emit light, and aims to store the necessary current by charging the capacitor with a battery when not emitting light. It is.
However, in order to secure the current required for light emission, a large-capacity capacitor is required, and the large-capacitance capacitor has a very large equivalent series resistance or a large leakage current. The goal of reducing was not achieved.
In other words, when the equivalent series resistance is large, the voltage drops when a large current is passed through the capacitor, and a large number of batteries are still necessary to secure the voltage necessary for LED driving.
In addition, when there is a large amount of leakage current, it is necessary to charge the capacitor frequently in order to secure the current required for LED driving, and it is necessary to connect many batteries in parallel.
[0010]
After trial and error as described above, the present inventors have found a method for reducing the number of batteries used for the power source by interposing a DC / DC converter and a capacitor between the battery and the LED light emitting circuit.
[0011]
As an example, FIG. 1 shows the case of six LEDs and two batteries.
The voltage was boosted by a DC / DC converter to reduce the number of series batteries, and by interposing a capacitor, the current that could be extracted from the power source could be instantaneously increased, and the number of parallel batteries was reduced.
The DC / DC converter and the capacitor can be interposed in the reverse order.
However, there is an advantage that the capacity of the capacitor can be reduced by increasing the voltage of the battery of the power supply with the DC / DC converter and interposing it so as to charge the capacitor.
Normally, the switch circuit 1 is left open and the capacitor C is charged.
When light emission (transmission) is necessary, the switch circuit 1 is closed and a current is supplied to the LED to emit light.
After the light emission is finished, the switch circuit 1 is opened to recharge the capacitor.
[0012]
FIG. 2 shows another embodiment in which a switch circuit 2 is added between the DC / DC converter and the capacitor in the circuit of FIG.
In the switch circuit 2, when the power source boosted by the DC / DC converter is shared by other circuits, the power source voltage may fluctuate greatly due to fluctuations in the load of the DC / DC converter during light emission. In order to prevent this, the DC / DC converter and the capacitor are separated from each other during light emission. Also, if the capacitor is fully charged and no further charging is required, disconnecting the DC / DC converter from the capacitor will cause leakage current in the capacitor, which will require unnecessary charging. It can also be prevented.
However, in this case, it is necessary to recharge the capacitor in advance when light emission is required. At this time, the capacity of the capacitor C needs to be determined so that the terminal voltage of the capacitor does not fall below the forward voltage of the LEDs in series at the end of light emission.
[0013]
FIG. 3 shows another example in which the current flowing during light emission is limited using a constant current circuit. If necessary, by driving the constant current circuit, the current flowing during light emission can be made constant, and the light emission output can be stabilized.
[0014]
FIG. 4 shows another embodiment in which a switch circuit 3 is added between a battery and a DC / DC converter.
If the DC / DC converter is always driven, it consumes a current alone. Therefore, when charging of the capacitor is unnecessary, the switch circuit 3 separates the battery and the DC / DC converter. Is.
[0015]
【The invention's effect】
As described above, the optical beacon vehicle transmitter is driven by a battery provided separately from the on-board battery, and a DC / DC converter and a capacitor are interposed between the battery and the LED light emitting circuit, Even if the number of batteries of the power supply is reduced, the optical beacon vehicle transmitter can be effectively operated.
[Brief description of the drawings]
FIG. 1 shows an example of a light emitting unit of a battery-driven light beacon vehicle transmission device of the present invention.
FIG. 2 shows an example of a light emitting unit of a battery-driven light beacon vehicle transmission device of the present invention in which a switch circuit is added between a DC / DC converter and a capacitor.
FIG. 3 shows an example of a light emitting unit of the battery-driven light beacon vehicle transmission device of the present invention in which the current flowing during light emission is limited by a constant current circuit.
FIG. 4 shows an example of a light emitting unit of the battery-driven light beacon vehicle transmission device of the present invention in which a switch circuit is added between the battery and the DC / DC converter.
FIG. 5 shows an example of a light emitting unit of a general optical beacon vehicle transmission device.
FIG. 6 shows an example of a light emitting unit of a series-type battery-powered beacon vehicle transmitter.
FIG. 7 shows an example of a light emitting unit of a parallel type battery-driven light beacon vehicle transmission device.
FIG. 8 shows an example of a light emitting unit of a battery-powered light beacon vehicle transmission device of a series system to which a DC / DC converter is added.
FIG. 9 shows an example of a light emitting unit of a parallel-type battery-powered light beacon vehicle transmission device to which a capacitor is added.

Claims (3)

It is driven by a battery provided separately from the in-vehicle battery, a capacitor is provided between the battery and the LED for data transmission, and the LED is opened and closed by opening and closing a first switch circuit provided between the capacitor and the LED. An optical beacon vehicle transmitter for controlling the supply of current to the vehicle,
A DC / DC converter is further provided between the battery and the capacitor ;
And a second switch circuit is further provided between the DC / DC converter and the capacitor.
The optical beacon vehicular transmitter, wherein the second switch circuit is opened when the LED emits light.   The transmitter for an optical beacon vehicle according to claim 1, wherein a current that flows when the LED emits light is limited using a constant current circuit.   The transmitter for an optical beacon vehicle according to claim 1, wherein a switch circuit is added between a battery provided separately from the vehicle battery and a DC / DC converter.

Images