JPS6141773B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel headlamp switching circuit, and particularly to a headlamp that is used by switching between a main light and a auxiliary light.
To provide a novel headlamp switching circuit that dims the main light gradually, not instantaneously, when switching from the main light to the auxiliary light, allowing the driver's eyes to adapt to changes in brightness and light distribution. That is.

Conventionally, switching from the main light to the auxiliary light in an automobile headlamp was simply done by switching the daymer switch, cutting off the current flowing through the main light and simultaneously supplying current to the auxiliary light. I was worried. Therefore, in such headlights, when the daymer switch is switched from the main light to the auxiliary light, the brightness of the headlight rapidly decreases and the light distribution changes rapidly. As a result, the driver's eyes are unable to adapt to the sudden changes in brightness and light distribution, resulting in a sudden sensation of darkness, and until the driver's eyes adjust to the darkness, he or she cannot see anything. The problem was that it was extremely dangerous.

Therefore, the present invention has developed a novel system in which when the switch is switched from the main lights to the auxiliary lights, the main lights dim gradually instead of instantaneously, allowing the driver's eyes to adjust to changes in brightness and light distribution. This is intended to provide a headlamp switching circuit, which includes a control voltage generation circuit whose output voltage gradually changes using a switching signal from the main lamp to the auxiliary lamp as a trigger, and a control voltage generation circuit that receives the output voltage of the control voltage generation circuit and generates a main lamp. It is characterized by comprising a current supply circuit that supplies the main light with a pulse current of a constant cycle whose pulse width gradually becomes narrower after switching from the light to the auxiliary light.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The headlamp switching circuit of the present invention will be described in detail below with reference to embodiments shown in the accompanying drawings.

FIG. 1 and FIG. 2 are for explaining an example of implementation of the headlamp switching circuit of the present invention. In FIG. 1, B is a battery whose negative electrode is grounded. LS is a lamp switch for flashing the headlights, and one of its terminals a and battery B's positive terminal +
It is connected to the. ML ₁ and ML ₂ are a pair of main lights connected in parallel with each other, and SL ₁ and SL ₂ are a pair of auxiliary lights connected in parallel with each other, and one end of these two parallel circuits is connected to each other in parallel. lamp switch LS
is connected to the other terminal b. Note that the main light here refers to a light source for emitting a driving beam, and the auxiliary light refers to a light source for emitting a passing beam. The main light and the auxiliary light may be provided in separate lamps, or may be provided in the same lamp or even within the same pulse. DS is a daymer switch for switching between the main light and the auxiliary light, and one of the switching terminals X is connected to a pair of main light _ML1 and
The other switching terminal Y is connected to the other end of the parallel circuit consisting of the pair of auxiliary lights SL ₁ and SL _{2 ,} and the common terminal Z is grounded.

SG is a control voltage generation circuit, whose input terminal 1 is connected to the auxiliary light side switching terminal Y of the daymer switch DS, and when the voltage applied to input terminal 1 (switching detection voltage) V _SW is "high" is the voltage at output terminal 2, that is, the output voltage V _CON is the voltage at battery B, E
It is kept at the same height as the When the switching detection voltage V _SW changes from "high" to "low", the output voltage V _CON gradually decreases. 3 is the ground terminal of the control voltage generation circuit SG,
4 is a power supply terminal, which is connected to terminal b of the lamp switch LS.

SC is a switching circuit for supplying a constant cycle pulse current to the main light after switching from the main light to the auxiliary light, and after switching from the main light to the auxiliary light, the main light _ML1 , The current _IML supplied to _ML2 is switched. The switching circuit SC is a control voltage generation circuit
The control voltage generation circuit is controlled by the SG output voltage V _CON , and the energization time in one switching cycle is controlled by the SG output voltage V CON.
It is designed to be approximately proportional to the SG output voltage V _CON . Reference numeral 5 denotes an input terminal, which is connected to the output terminal 2 of the control voltage generation circuit SG. Reference numeral 6 denotes an output terminal, which is connected to a connection point between the main lights ML ₁ and ML ₂ and the main light side switching terminal X of the daymer switch DS. Reference numeral 7 denotes an input terminal receiving an output voltage V _VD of a control voltage detection circuit VD, which will be described later. When this output voltage V _VD becomes "low", the switching circuit SC becomes non-conductive.
8 is a ground terminal.

VD is a control voltage detection circuit that detects the output voltage V _CON of the control voltage generation circuit SG _. ) When V CON is higher than E _S , no detection signal is generated and there is no electrical effect on the switching circuit SC, and when V _CON is lower than E _S , the output terminal becomes "low". The switching circuit SC is made non-conductive. 9 is the input terminal of the control voltage detection circuit VD, which is the input terminal of the control voltage generation circuit SG.
is connected to the output terminal of 10 is an output terminal connected to the input terminal 7 of the switching circuit SC. 11 is a ground terminal, and 12 is a power terminal, which is connected to terminal b of the lamp switch LS.

The operation of this headlamp switching circuit will be explained below.

(1) Turn on the lamp switch and turn on the daymer switch.
When the DS is placed on the main light side.

In this case, battery B, lamp switch
LS, main light ML ₁ , ML ₂ and daymer switch DS
A closed circuit is formed by this, current I _ML flows through the main lights ML ₁ and ML ₂ , and the main lights ML ₁ and ML ₂ are turned on.

In this case, the same potential as the positive terminal + of the battery B is applied to the input terminal 1 of the control voltage generation circuit SG via the lamp switch LS and the auxiliary lights SL ₁ and SL ₂ , and the switching detection voltage V _SW is "high". I'm keeping it.

(2) When the daymer switch DS is switched to the auxiliary light side (t ₀ ).

In this case, battery B, lamp switch
A closed circuit is formed by the LS, the auxiliary lights SL ₁ and SL ₂ , and the dimer switch DS, and the auxiliary lights SL ₁ and SL ₂ are turned on.

At the same time, the short-circuit condition caused by the dimmer switch DS on the output side of the switching circuit SC is released, so the switching circuit is connected to the main lights ML ₁ and ML ₂ .
Current I _ML begins to flow depending on the switching state of SC. Therefore, even immediately after the daymer switch DS is switched, the main light is turned off as shown in Figure 2.
A current I _ML flows through ML ₁ and ML ₂ . As described above, the switching circuit SC switches the current _IML at a constant cycle, and the energization time in one switching cycle is made approximately proportional to the output voltage V _CON of the control voltage generation circuit SG.
The current I _ML flowing through the main lights ML ₁ and ML ₂ after switching from the main light to the auxiliary light becomes a pulse current with a constant period having a pulse width W _P proportional to the output voltage V _CON .

By the way, at the switching time _t0 of the dimmer switch DS, the output voltage V _CON of the control voltage generation circuit SG
Since is approximately the same height as the power supply voltage E, the pulse width W _P of the pulse current I _ML controlled by the output voltage V _CON is relatively wide at that point. After that, the input terminal 1 of the control voltage generation circuit SG is grounded by switching the daymer switch DS, and the switching detection voltage V _SW changes from "high" to "low", which is used as a trigger for control. The output voltage V _CON of the voltage generating circuit SG gradually decreases, and the pulse width W _P of the pulse current I _ML gradually narrows accordingly. Therefore, the brightness of the main lights HL ₁ and HL ₂ gradually decreases.

Then, the output voltage V _CON of the control voltage generation circuit SG
When becomes lower than the preset reference value E _S ,
At that time _t1 , the output voltage V _VD of the control voltage detection circuit VD
changes to “low”. Then, the switching circuit SC becomes non-conductive and remains in that state, so that no current is supplied to the main lights ML ₁ and ML ₂ . Therefore, the main lights ML ₁ and ML ₂ are completely turned off.

In addition, in this embodiment, after switching from the main light to the auxiliary light, the lamp switch is disconnected from the battery B.
Current I _M supplied to main lights ML ₁ and ML ₂ via LS
_L is switched at a constant cycle by a switching circuit SC, and as a result, a pulse current I _ML at a constant cycle is supplied to the main lights ML ₁ and ML ₂ . Therefore,
The switching circuit SC functions as a current supply circuit that supplies pulsed current to the main lights ML ₁ and ML ₂ . However, various means can be considered for supplying pulse current to the main lights ML ₁ and ML ₂ , and the above-mentioned switching circuit can be used as the current supply circuit.
Not limited to SC.

Also, in this embodiment, the control voltage generation circuit
The initial value of the SG output voltage V _CON is set high, and after switching from the main light to the sub light, the output voltage V _CON gradually decreases, and after the switch, the main light ML ₁ ,
The pulse width W _P of the pulse current I _ML flowing through ML ₂ is made narrower as the output voltage V _CON decreases. However, the initial value of the output voltage V _CON of the control voltage generation circuit SG is set low, for example 0, and the output voltage V _CON increases after switching from the main lamp to the auxiliary lamp. The pulse width W _P of the pulse current I _ML supplied to the main lights ML ₁ and ML ₂ from the output voltage V _C
It may be made narrower as _{the ON} level increases.

As described above, the headlamp switching circuit of the present invention includes a control voltage generating circuit whose output voltage gradually changes using a switching signal from the main lamp to the auxiliary lamp as a trigger, and a control voltage generating circuit that receives the output voltage of the control voltage generating circuit. , consists of a current supply circuit that supplies the main light with a pulse current of a constant cycle that gradually narrows the pulse width after switching from the main light to the auxiliary light, so when the main light is switched from the main light to the auxiliary light A pulse current is supplied by the current supply circuit to the main light, and the main light continues to be lit for a while even after switching. Then, as the pulse width of the pulse current gradually narrows, its average value gradually decreases, and the main light gradually dims accordingly. Therefore, when the switch is switched from the main light to the auxiliary light, the headlight slowly changes from the brightness and light distribution of only the main light to the brightness and light distribution of only the auxiliary light. Therefore, the driver's eyes can adapt well to the changes in brightness and light distribution, and when switching from the main light to the auxiliary light, as in the case of a conventional simple dimmer switch, the driver's eyes will be able to adapt well to the changes in brightness and light distribution, and the driver will be able to see ahead when switching from the main light to the auxiliary light. There is no danger of falling into a state where you cannot see anything at all.

Further, a control voltage detection circuit is provided to detect the output voltage of the control voltage generation circuit, and when the output voltage of the control voltage circuit reaches a preset reference value intermediate in magnitude between the initial value and the final value, the detection circuit detects the output voltage of the control voltage generation circuit. By causing the current supply circuit to stop supplying current to the main lamp based on the detection signal generated from the It can completely cut off unnecessary current flowing through the main light, eliminating unnecessary battery consumption. In other words, when the pulse width of the pulse current flowing through the main light narrows and the average current falls below a certain value, the temperature of the filament decreases, visible light is no longer emitted from the filament, and the pulse current flowing through the main light is wasted. However, the control voltage generation circuit can completely cut off such wasteful current _IML and reduce the consumption of battery B.

Next, specific examples of the control voltage generation circuit SG, switching circuit SC, and control voltage detection circuit VD that constitute the headlamp switching circuit of the present invention will be explained.

Figure 3 shows an example of the control voltage generation circuit SG, which includes a diode _D1 , a capacitor C1, a resistor _{R1 ,} and a PNP transistor that constitute a Miller integration circuit.
It consists of Tr ₁ and diode D ₂ . Capacitor C ₁
and resistor R ₁ are connected in series to form a charging/discharging circuit, and the capacitor C ₁ side terminal of this charging/discharging circuit is connected to the base of transistor Tr ₁ , and the other terminal is drawn out to ground terminal 3. . The output point of this charging/discharging circuit, that is, the connection point between the capacitor C ₁ and the resistor R ₁ is connected to the collector of the transistor Tr ₁ and is also drawn out to the output terminal 2. And the anode of diode _D2 is connected to transistor _Tr1
At the base of , the cathode is connected to the emitter of Tr ₁ . This transistor Tr ₁ functions as an amplifier of the Miller integration circuit, and the diode D ₂ functions to flow the discharge current of the capacitor C ₁ . The cathode of the diode D ₁ is connected to the output point of the Miller integration circuit, and the anode of the diode D ₁ is drawn out to the input terminal 1.

This control voltage generation circuit SG operates as follows.

When the switching detection voltage V _SW is "high", that is, when the power supply voltage E is applied to the input terminal 1, substantially the same voltage as the power supply voltage E is applied to the output terminal ₂ via the diode D1. At that time, the collector and emitter of the PNP transistor Tr ₁ are at substantially the same potential, so they are non-conductive, and the capacitor C ₁ is not charged.

Next, when the switching detection voltage V _SW becomes "low", that is, when the input terminal 1 becomes the ground potential, the diode D ₁ becomes non-conductive, and the output terminal 2 becomes in a state where it is not electrically influenced by the input terminal. And the capacitor
The base current of transistor Tr ₁ flows through the charging/discharging circuit consisting of C ₁ and resistor R ₁ , and transistor Tr ₁ is turned on. Therefore, the transistor Tr ₁ is connected to the resistor R ₁
collector current flows. And the transistor
As the capacitor _C1 is charged by the base current of _Tr1 , the base current decreases, and accordingly, the collector current of the transistor _Tr1 also gradually decreases. As the collector current decreases, the terminal voltage of the resistor _R1 , that is, the voltage V _CON of the output terminal 2 of the control voltage generating circuit SG, decreases linearly as shown in FIG.

In addition, the switching detection voltage V _SW changes from “low” to “high”
When the voltage changes to , the charged capacitor _C1 is discharged through the diode _D2 .

Figure 4 shows an example of the switching circuit SC,
FIG. 5 is a time chart for explaining the operation of the circuit SC.

This switching circuit SC consists of a control circuit CC and an output circuit OC controlled by the control circuit CC, and the control circuit CC is composed of a pulse generation circuit PG.
, a sawtooth wave generating circuit STG, a comparator circuit COM, and a flip-flop FF. The pulse generating circuit PG generates a constant cycle pulse voltage V _P as shown in FIG. 5, and this voltage V _P is applied to the set input terminal S of the flip-flop FF. The pulse width of this pulse voltage V _P is set to be narrow within the operable range of the flip-flop FF. Sawtooth wave generation circuit STG is a pulse generation circuit
This circuit generates a sawtooth voltage V _ST that is triggered by the pulse voltage V _P generated by PG and applied to one input terminal of the comparator circuit COM. The sawtooth voltage V _ST has a waveform that rises relatively slowly in a straight line from 0 to the power supply voltage E, and then rapidly drops to 0, and its period is determined by the pulse generation circuit.
It is equal to the cycle of the pulse voltage V _P generated by PG, and is synchronized with the pulse voltage V _P. The comparison circuit COM compares the output voltage V _CON of the control voltage generation circuit SG applied to the input terminal 5 with the sawtooth voltage V _ST generated by the sawtooth wave generation circuit STG.
COM output voltage V _CON is control voltage generation circuit SG
When the output voltage V _{CON of} is higher than the sawtooth voltage V _ST , the output voltage becomes "low", and vice versa, the output voltage becomes "high". This output voltage V _COM is applied to the reset input terminal R of flip-flop FF. The flip-flop FF is a so-called RS type flip-flop circuit that is set by the pulse voltage V _P generated by the pulse generator PG and reset by the output voltage V _CON of the comparator circuit COM, and its output voltage V _FF is applied to the output circuit OC. applied. This flip-flop FF is set by a pulse voltage V _P having an extremely narrow pulse width, and is configured so that it can be inverted in response to a reset signal immediately after being set.

The operation of this control circuit CC will be explained below.

When the output voltage V _P generated by the pulse generating circuit PG changes from "low" to "high", flip-flop FF enters the set state at _ta , and its output voltage V _FF becomes "high". Also, at that time, the sawtooth voltage V _ST starts rising from 0 at t _a . At this point, the sawtooth voltage V _ST is lower than the output voltage V _CON of the control voltage generating circuit SG, so the output voltage V _CON of the comparator circuit COM is "low". Note that the voltage V _P generated by the pulse generation circuit PG changes from "low" to "high" and then immediately changes from "high" to "low".

The sawtooth voltage _VST increases and the control voltage generation circuit
When the output voltage of SG exceeds V _CON , the _comparator circuit
The output voltage V _CON of COM changes from "low" to "high", thereby resetting flip-flop FF and causing its output voltage V _FF to change from "high" to "low". and the sawtooth voltage V _ST
When it reaches the power supply voltage E, it drops rapidly and becomes 0 by the time the pulse voltage V _P rises next, that is, when it changes from "low" to "high", and one cycle of operation is completed. This operation is repeated thereafter.

In such a control circuit CC, the time t _ab required for the sawtooth voltage V _ST to rise from 0 and reach the same voltage as the output voltage V _CON of the control voltage generation circuit SG is determined by the height of the output voltage V _CON . Approximately proportionally, the higher the output voltage V _CON is, the later the timing at which the flip-flop FF is reset by the output voltage V _CON of the comparator circuit COM is delayed. Therefore, when the control voltage generation circuit SG output voltage V _CON has just started to decrease and is relatively high, such as V _CON1 , the pulse width W _P1 of the output voltage V _FF1 of the flip-flop FF is wide, and As the output voltage V _CON becomes extremely low, such as V _CON2 , over time, the pulse width W _P2 also becomes extremely narrow. Note that V _CON1 indicates the waveform of the output voltage of the comparator circuit COM when the output voltage of the control voltage generation circuit SG is V _CON1 , and V _COM2 indicates the waveform of the output voltage of the comparator circuit COM when the output voltage is V _CON2 . show.

Output circuit OC that constitutes switching circuit SC
consists of an output transistor Tr ₂ and resistors R ₂ and R _3. The base of the transistor Tr ₂ is connected to the output terminal Q of the flip-flop FF via the resistor R ₂ , and the resistor R is connected between the base and the emitter. ₃ are connected. The collector, base, and emitter of the transistor Tr ₂ are drawn out to an output terminal 6, an input terminal 7, and a ground terminal 8, respectively.

The base of this transistor Tr ₂ has a control circuit
Output voltage V of flip-flop FF that constitutes CC
_FF is applied through resistor R ₂ and transistor Tr ₂
is in a conductive state when the output voltage V _FF is "high" and is in a non-conductive state when the output voltage V _FF is "low". The current I _ML flowing through the main lamps ML ₁ and ML ₂ is switched by this transistor Tr ₂ . I _ML1 in Figure 5 is the control voltage generation circuit SG
The main light when the output voltage of is V _CON1
The waveform of the current flowing through ML ₁ and ML ₂ is shown, and I _ML2 is the main lamp when the above output voltage is V _CON2 .
The waveform of the current flowing through ML ₁ and ML ₂ is shown.

In this way, the switching circuit SC generates a pulse-like output voltage V _FF of a constant period having a pulse width W _P proportional to the output voltage V _CON of the control voltage generation circuit SG.
Since the output circuit OC is controlled by the control circuit CC that generates the voltage, the current _IML flowing through the main lights ML ₁ and ML ₂ becomes a pulsed current with a constant period, and the control voltage generation circuit SG detects the switching. When the output voltage V _CON gradually decreases triggered by the voltage V _SW , the pulse width W _P of the pulse current I _ML gradually narrows accordingly.

Furthermore, when the voltage at the input terminal 7 of the switching circuit SC becomes "low", the transistor of the output circuit OC
Tr ₂ becomes non-conductive and no current flows to the main lights ML ₁ and ML ₂ .

FIG. 6 shows an example of the control voltage detection circuit VD, which includes a PNP transistor Tr ₃ ,
It consists of an NPN transistor Tr ₄ and resistors R ₄ , R ₅ , R ₆ , and R ₇ . Resistors R ₄ and R ₅ are connected in series to form a voltage divider circuit, one terminal of this voltage divider circuit is connected to the power supply terminal 11, the other terminal is connected to the ground terminal 12, and the resistor R ₄ The connection point between R5 and _R5 is connected to the emitter of transistor _Tr3 . The resistance ratio of this voltage dividing circuit determines the reference voltage E _S . In addition, the output voltage V _CON of the control voltage generation circuit SG
When the voltage decreases from the power supply voltage E and reaches the reference voltage E _S , the output voltage V _VD of the control voltage detection circuit VD becomes “low”. The base of the transistor Tr ₃ is drawn out to the input terminal 9 and connected to the base of the transistor Tr ₄ via a collector resistor R ₆ . A resistor _R7 is connected between the base and emitter of the transistor _Tr4 , and its collector is connected to the input terminal 10.
In addition, the emitters are each led out to a ground terminal 12.

In this control voltage detection circuit VD, when the voltage at the input terminal 9, that is, the output voltage V _CON of the control voltage generation circuit SG is higher than or substantially equal to the reference voltage E _S , no base current flows through the transistor Tr ₃ , so the transistor Tr ₃ is not conductive. Therefore, no current is supplied from the collector of transistor Tr ₃ to the base of transistor Tr ₄ ,
Transistor Tr ₄ also does not conduct. In this case, the output voltage V _VD of the control voltage detection circuit VD has no effect on the switching circuit SC.

Then, the output voltage V _CON of the control voltage generation circuit SG
When becomes lower than the reference voltage E _S (t ₁ in Fig. 2), the base current flows to the transistor Tr ₃ , and the transistor
Tr ₃ conducts. Then, a current is supplied from the transistor Tr ₃ to the base of the transistor Tr ₄ through the resistor R ₆ , and the transistor Tr ₄ becomes conductive, so that the input terminal 10 becomes approximately at ground potential. When the input terminal 10 becomes approximately the ground potential, the base of the transistor Tr ₂ of the output circuit OC becomes approximately the ground potential, so even if the output voltage V _FF of the flip-flop FF is "high", the transistor Tr ₂ is non-conductive. becomes. As a result, the current I _ML flowing through the main lights ML ₁ and ML ₂
is blocked.

According to such a control voltage detection circuit VD, after switching from the main light to the auxiliary light of the daymer switch DS,
When the output voltage V _CON of the control voltage generation circuit SG decreases and becomes approximately equal to the reference voltage E _S , the main lamp ML ₁ ,
The current I _ML flowing through ML ₂ can be completely cut off, thereby reducing the consumption of battery B. That is, the pulse current I flowing through the main lights ML ₁ and ML ₂
When the pulse width W _P of _ML becomes narrower and its average current becomes less than a certain value, the temperature of the filaments of the main lights ML ₁ and ML ₂ decreases, and visible light is no longer emitted from the filaments. Therefore, from then on, the main lights ML ₁ , ML ₂
The pulse current I _ML flowing through is wasted, but such wasted current I _M is eliminated by the control voltage generation circuit VD.
It is possible to completely shut off _L and reduce consumption of battery B.

By the way, in the above-mentioned headlamp switching circuit, the main light turns on simultaneously with the auxiliary light for a while after switching from the main light to the auxiliary light, so the headlight becomes brighter than normal at that time. Therefore, if such a situation occurs when an oncoming vehicle approaches very closely, there is a risk that the driver of the oncoming vehicle will be dazzled by the headlights of the oncoming vehicle.

In order to eliminate such a fear, Fig. 7 shows that when an oncoming vehicle gets very close, when switching from the main light to the auxiliary light, the main light does not turn on after the switch, and also This figure shows an example of the implementation of the headlight switching circuit of the present invention, which stops lighting the main lights if an oncoming vehicle approaches very closely after switching to the auxiliary lights. In this figure, parts common to the embodiments shown in FIGS. 1 and 2 are not shown.

VD' is a control voltage detection circuit, which is constructed by providing the control voltage detection circuit VD shown in FIG. 6 with an input terminal 13 derived from the base of a transistor _Tr4 .

PD is a light detection circuit that detects light from an oncoming vehicle.This light detection circuit PD consists of a light receiving element CdS and a resistor.
It consists of R ₈ , R ₉ and a PNP transistor Tr ₅ . The light receiving element CdS has a characteristic that the resistance value decreases as the amount of light received increases, and is provided to receive light from an oncoming vehicle. The light receiving element CdS and the resistor _R8 are connected in series to form a voltage dividing circuit, and the terminal on the light receiving element CdS side of this voltage dividing circuit is connected to the ground terminal 14.
The resistor _R8 side terminal is led out to the power supply terminal 15, and the connection point between the light receiving element CdS and the resistor _R8 is connected to the base of the transistor _Tr5 . The emitter of transistor Tr ₅ is drawn out to power supply terminal 15, and the collector is connected to output terminal 1 via resistor R ₉ .
It is pulled out to 6. And this output terminal 1
6 is connected to the input terminal 13 of the control voltage detection circuit VD'. In addition, the power terminal 15 is a lamp switch.
Connected to terminal b of LS.

In this light detection circuit PD, when the amount of light from an oncoming vehicle exceeds a preset reference value, the resistance value of the light receiving element CdS decreases, and the base potential of the transistor Tr ₅ decreases.
Tr ₅ is turned on.

Therefore, when there is no light from an oncoming vehicle or when the amount of light from an oncoming vehicle does not reach the reference value, the resistance value of the light receiving element CdS and the base potential of the transistor Tr ₅ do not decrease sufficiently, and the transistor Tr ₅ remains off, so the photodetection circuit PD does not electrically affect the control voltage detection circuit VD'.

Then, when the amount of light from the oncoming vehicle exceeds the above reference value, the transistor Tr ₅ is turned on as described above, so that the base of the transistor Tr ₄ of the control voltage detection circuit VD' is connected from the transistor Tr ₅ through the resistor R ₉ . A current is supplied to the transistor Tr4, and the transistor _Tr4 is turned on. As a result, the output voltage of the control voltage detection circuit VD' becomes "low" and the transistor Tr ₂ of the switching circuit SC whose input terminal 7 is connected to the output terminal 10 is turned off, so that the main lamps ML ₁ and ML ₂ The pulse current I _ML does not flow through the main lights ML ₁ and ML 2 and the main lights ML 1 and ML ₂ are completely turned off.

In this photodetector circuit PD, the reference value is the resistance
It is determined by the resistance value of _R8 and the characteristics of the light receiving element CdS, and if the reference value is set to an appropriate value,
For example, even if the switching timing is delayed and the driver of an oncoming vehicle is already close enough to be dazzled by the headlights of those vehicles when switching from the main lights to the auxiliary lights. After switching, the main lights ML ₁ and ML ₂ go out immediately.
Also, if an oncoming vehicle approaches very closely after switching from the main light to the secondary light, the main light after switching
Lighting of ML ₁ and ML ₂ is stopped. Therefore,
It is possible to prevent the driver of an oncoming vehicle from being dazzled by the headlights.

According to the headlight switching circuit of the present invention having such a light detection circuit, the light detection circuit detects light from an oncoming vehicle, and detection occurs when the amount of light is greater than a preset reference value. The signal can stop the current supply circuit from supplying current to the main lights, so if an oncoming vehicle is already very close when switching from the main lights to the auxiliary lights, the main lights will stop supplying current to the main lights. The light doesn't turn on. Furthermore, if an oncoming vehicle approaches very closely after switching from the main light to the auxiliary light, the lighting of the main light after the switch is stopped. Therefore, it is possible to reliably prevent the driver of an oncoming vehicle from being dazzled by the headlights.

By the way, sudden changes in brightness and light distribution caused by switching from main lights to auxiliary lights can lead to dangerous driving conditions when the car is running faster than a certain speed. When the traveling speed is slower than the constant speed, there is no need to prevent sudden changes in brightness or light distribution, and therefore there is no need to turn on the main light after switching from the main light to the auxiliary light. Therefore, the pulsed current flowing through the main lamp in such a case becomes a wasted current, unnecessarily increasing battery consumption.

Figure 8 shows that in order to prevent such unnecessary current from flowing, the vehicle's running speed is detected and if it is below a certain value, that is, a reference value, the current is supplied after switching from the main light to the auxiliary light. SD is an example of a vehicle speed detection circuit that stops the circuit from supplying current to the main lights.
This shows that.

This vehicle speed detection circuit SD is a vehicle speed sensor SSE, a resistor
It consists of R ₁₀ , R ₁₁ , R ₁₂ , R ₁₃ , capacitors C ₂ , C ₃ , diodes D ₃ , D ₄ and NPN transistor Tr ₆ . The vehicle speed sensor SSE consists of a rotor ROT that rotates with the rotation of the vehicle's axle and a reed switch LES. is magnetized. Also, the reed switch LES is a rotor.
The rotor is located close to the ROT.
It turns on when located inside the magnetic field on the surface of the ROT, and turns off when located outside the magnetic field. Therefore, as the car runs, the rotor
When the ROT rotates, the reed switch LES turns on.
The switching cycle becomes shorter as the vehicle speed increases. One terminal of the reed switch LES of this vehicle speed sensor SSE is led out to the ground terminal 17, and the other terminal is connected to one terminal of the resistor _R10 . The other terminal of the resistor R ₁₀ is led out to the power supply terminal 18 . Vehicle speed sensor SSE
One terminal C of a capacitor C ₂ is connected to the connection point between the capacitor C 2 and the resistor R ₁₀ , and the other terminal of the capacitor C ₂ is connected to the cathode of the diode D ₃ and the anode of the diode D ₄ . The anode of the diode _D3 is drawn out to the ground terminal 17. The cathode of the diode D ₄ is connected to the base of the transistor Tr ₆ via the resistor R ₁₁ , and the cathode of the diode D ₄
A capacitor is connected between the cathode of the
C ₃ is connected. The emitter of the transistor Tr ₆ is drawn out to the ground terminal 17, and the collector is connected to the anode of the diode D ₅ and one terminal of the resistor R ₁₃ . The other terminal of the resistor R ₁₃ is led out to the power supply terminal 18 , and the cathode of the diode D ₅ is led out to the output terminal 19 . A resistor _R12 is connected between the base and emitter of the transistor _Tr6 . The power supply terminal 18 is connected to the terminal b of the lamp switch LS, and the output terminal 1
9 is connected to the input terminal 13 of the control voltage detection circuit VD' shown in FIG.

This vehicle speed detection circuit SD operates as follows.
When the reed switch LES of the vehicle speed sensor SSE is on, the potential of one terminal C of the capacitor C ₂ becomes the ground potential, and therefore the capacitors C ₂ and C ₃ are not charged. When the reed switch LES of the vehicle speed sensor SSE changes from on to off, a resistor is connected to the power supply terminal 18.
Current is supplied to R ₁₀ , capacitor C ₂ , diode D ₄ and capacitor C ₃ to charge capacitors C ₂ and C ₃ . The terminal voltage of capacitor C ₃ at that time is determined by the capacitance ratio of capacitors C ₂ and C ₃ . Next, reed switch LES of vehicle speed sensor SSE
When the capacitor _C2 changes from off to on, the reed switch LES of the vehicle speed sensor SSE
and is discharged very quickly through diode _D3 , the voltage at the terminals of capacitor _C2 suddenly changes to zero and diode _D4 is cut off. On the other hand, capacitor _C3 discharges relatively slowly through resistors _R11 and _R12 , and its terminal voltage decreases relatively slowly. Thereafter, the above-described operation is repeated in accordance with the switching operation of the vehicle speed sensor SSE.

By the way, the reed switch of the vehicle speed sensor SSE
When the switching period of LES is long, use a capacitor.
The lower the terminal voltage of _C3 and the shorter its switching period, the higher the terminal voltage of capacitor _C3 . That is, when the switching period is relatively long, the time interval from when the reed switch LES of the vehicle speed sensor SSE changes from off to on until it changes from on to off is relatively long. Therefore, the capacitor charged when the reed switch LES is off
_C3 can be substantially fully discharged through resistors _R11 and _R12 while the reed switch LES is turned on and remains in that state. Then, when the capacitor C ₃ is substantially sufficiently discharged, the reed switch LES is switched from on to off, and the capacitors C ₂ and C ₃ are charged. Therefore, in this case the capacitor
The terminal voltage of _C3 is a relatively low voltage determined by the ratio of capacitances of capacitors _C2 and _C3 . Therefore, the base voltage of the transistor Tr ₆ does not reach the level required to turn the transistor Tr ₆ on, so the transistor Tr ₆ is turned off. In this case, a resistor R ₁₃ and a diode are connected from the power supply terminal 18.
A current flows to the base of the transistor Tr ₄ via D ₅ , the output terminal 19 and the input terminal 13 of the control voltage detection circuit VD'. Therefore, the control voltage detection circuit
The output terminal 10 of VD' becomes ground potential, the transistor Tr ₂ of the switching circuit SC to which the input terminal 7 is connected to the output terminal 10 is turned off, and the main lamps ML ₁ ,
No current flows through ML ₂ .

However, when the vehicle speed exceeds a preset reference value and the switching cycle of the vehicle speed sensor SSE switch becomes shorter than a certain value, the capacitors C ₂ and C ₃ that were charged when the switch was off
Of these, C ₂ has almost completely discharged (the discharge circuit of capacitor C ₂ does not include any particular resistance element, so the discharge ends in a very short time), but the resistor R ₁₁ of capacitor C ₃ Charging will be started at a time when discharging has not progressed much through _R12 . That is, the discharge of the capacitor _C3 is not completed and the charge remains, and the capacitor C3 is discharged without a significant drop in the terminal voltage. Therefore, capacitor C ₂
The voltage division ratio between _C3 and C3 changes, and the terminal voltage of capacitor _C3 increases. As a result, the base voltage of the transistor Tr ₆ also becomes high, so the transistor Tr ₆ is turned on. Then, the anode side of the diode _D5 becomes the ground potential, and the diode _D5 is cut off, so that the vehicle speed detection circuit SD does not have any electrical influence on the control voltage detection circuit VD'.

Therefore, if the reference value is set to an appropriate value, even if the brightness or light distribution changes suddenly due to switching from the main light to the auxiliary light, the speed will be low enough that there is no risk of danger. When driving, when switching from the main light to the auxiliary light, the main light ML ₁ , ML ₂ after the switch
Since the pulse current _IML is not supplied to the battery B, consumption of the battery B can be reduced.

According to the headlight switching circuit of the present invention having the vehicle speed detection circuit as described above, the vehicle speed detection circuit detects the traveling speed of the automobile, and when the traveling speed is smaller than a preset reference value, the problem occurs. The detection signal causes the current supply circuit to stop supplying current to the main lights, so there is no need to prevent sudden changes in brightness or light distribution due to switching from main lights to auxiliary lights when the vehicle is running at a low speed. In this case, no current flows through the main lights ML ₁ and ML ₂ after the switching. Therefore, consumption of battery B can be reduced.

[Brief explanation of the drawing]

1 and 2 show an example of implementation of the headlamp switching circuit of the present invention. FIG. 1 is a circuit diagram showing the entire circuit, FIG. 2 is a time chart for explaining the circuit operation, and FIG. The figure is a circuit diagram showing a specific example of a control voltage generation circuit constituting the headlamp switching circuit of the present invention.
FIG. 4 is a circuit diagram showing a specific example of the current supply circuit, FIG. 5 is a time chart for explaining the operation of the current supply circuit shown in FIG. 4, and FIG. 6 is a circuit diagram of the control voltage detection circuit. A circuit diagram showing a specific example, FIG. 7 is a circuit diagram showing an example of a light detection circuit and a control voltage detection circuit in an example of the headlight switching circuit of the present invention equipped with a light detection circuit, and FIG. 8 is a circuit diagram showing a vehicle speed detection circuit. FIG. 3 is a circuit diagram showing an example of a vehicle speed detection circuit in an example of the headlamp switching circuit of the present invention. Explanation of symbols SG...Control voltage generation circuit, SC...
...Current supply circuit, CC...Control circuit, OC...Output circuit, VD, VD'...Control voltage detection circuit, PD...
Light detection circuit, SD...Vehicle speed detection circuit.

Claims (1)

[Claims] 1. A control voltage generation circuit whose output voltage gradually changes using a switching signal from the main light to the auxiliary light as a trigger;
It is characterized by comprising a current supply circuit that receives the output voltage of the control voltage generation circuit and supplies the main light with a pulse current having a constant cycle such that the pulse width gradually narrows after switching from the main light to the sub light. Headlight switching circuit. 2. A control circuit in which a current supply circuit receives an output voltage from a control voltage generation circuit and generates a pulse having a pulse width corresponding to the magnitude of the output voltage at a constant cycle, and an output circuit controlled by the control circuit. A headlamp switching circuit according to claim 1, characterized in that the circuit comprises: 3. A control voltage generation circuit whose output voltage gradually changes as a switching signal and trigger from the main light to the auxiliary light,
a current supply circuit that receives the output voltage of the control voltage generation circuit and supplies the main light with a pulse current having a constant period such that the pulse width gradually narrows after switching from the main light to the sublight; and the control voltage generation circuit. a control voltage detection circuit that detects the output voltage of the output voltage and generates a detection signal when the output voltage reaches a preset reference value intermediate in magnitude between the initial value and the final value, the control voltage detection circuit A headlamp switching circuit characterized in that the detection signal causes the current supply circuit to stop supplying current to the main lamp. 4. A control circuit in which the current supply circuit receives the output voltage of the control voltage generation circuit and generates a pulse having a pulse width corresponding to the magnitude of the output voltage at a constant cycle, and an output circuit controlled by the control circuit. A headlamp switching circuit according to claim 3, characterized in that the circuit comprises: 5 A control voltage generation circuit whose output voltage gradually changes using a switching signal from the main light to the auxiliary light as a trigger;
A current supply circuit that receives the output voltage of the control voltage generation circuit and supplies the main light with a pulse current of a constant period whose pulse width gradually becomes narrower after switching from the main light to the auxiliary light; and a current supply circuit that supplies light from an oncoming vehicle to the main light. and a light detection circuit that detects the amount of light and generates a detection signal when the amount of light is greater than a preset reference value, and the detection signal of the light detection circuit causes the current supply circuit to supply current to the main lamp. A headlight switching circuit characterized in that the circuit is configured to stop the headlight. 6. A control circuit in which a current supply circuit receives an output voltage from a control voltage generation circuit and generates a pulse having a pulse width corresponding to the magnitude of the output voltage at a constant cycle, and an output circuit controlled by the control circuit. A headlamp switching circuit according to claim 5, characterized in that the circuit comprises: 7 A control voltage generation circuit whose output voltage gradually changes using a switching signal from the main light to the auxiliary light as a trigger;
A current supply circuit that receives the output voltage of the control voltage generation circuit and supplies the main light with a pulse current of a constant period whose pulse width gradually becomes narrower after switching from the main light to the sub-light, and a current supply circuit that detects the vehicle speed and detects the vehicle speed. and a vehicle speed detection circuit that generates a detection signal when the vehicle speed detection circuit is smaller than a preset reference value, and the detection signal of the vehicle speed detection circuit causes the current supply circuit to stop supplying current to the main lamp. A headlight switching circuit characterized by: 8. A control circuit in which a current supply circuit receives an output voltage from a control voltage generation circuit and generates a pulse having a pulse width corresponding to the magnitude of the output voltage at a constant cycle, and an output circuit controlled by the control circuit. A headlamp switching circuit according to claim 7, characterized in that the circuit comprises: