TECHNICAL FIELD
[0001] The present invention relates to a lamp lighting control circuit that conducts lighting
of a lamp by using a voltage regulation circuit connected to an electric generator
which rotates in conjunction with an engine.
BACKGROUND OF THE INVENTION
[0002] Conventionally, in some motorcycles for example, an AC voltage is generated by an
electric generator rotating in conjunction with an engine, and the AC voltage is used
to charge a battery as well as to light a lamp such as a headlight.
[0003] Figure 3 shows an example of a control circuit for controlling the battery charging
and lamp lighting. In the shown circuit, an end tap (output terminal) of a coil 2
of a magneto-generator is connected to a power source terminal CH of the control circuit
11, while a battery 3 and a DC load 4 representing various electric equipment are
connected to an output terminal BT of the control circuit 11.
[0004] In the control circuit 11, a battery charge control thyristor SCR1 is provided on
a power line extending between the terminals CH and BT for transmitting positive waves
of the AC voltage input to the power source terminal CH to the output terminal BT.
The battery charge control thyristor SCR1 is controlled by a battery voltage detecting
and controlling circuit 6 for detecting the voltage at the output voltage BT and preventing
overcharge of the battery.
[0005] A lamp (headlight) 5 is connected to a lamp terminal LA of the control circuit 11.
Between the power source terminal CH and the lamp terminal LA of the control circuit
11 is connected a lamp control thyristor SCR2 for transmitting negative waves of the
AC voltage to the lamp 5. Further, a lamp voltage detecting circuit 12 is provided
for keeping the lamp control thyristor SCR2 in an off state when it detects that an
effective (or root mean square value of) voltage of the lamp exceeds a limit value
(for example, 13V), to thereby protect the lamp 5.
[0006] Figure 4 is a waveform diagram showing lamp current control in the above circuit.
The electric generator 2 provides an AC voltage having a sine waveform as shown in
an upper part of Figure 4. As mentioned above, the lamp 5 is supplied only with the
negative voltage waves, of which amplitude and hence the lamp effective voltage increases
with the engine speed. Thus, as shown in the lower waveform in Figure 4, when the
lamp effective voltage exceeds a limit value during one negative voltage half-wave,
because consecutive voltage supply (phantom line in the drawing) could cause an overvoltage,
the next negative voltage half-wave is prevented from being supplied to the lamp (solid
line in the drawing) so that a so-called intermittent voltage supply control is conducted.
[0007] However, this may have a problem that in a low engine speed range, the intermittent
voltage supply control can result in detectable flickering of the lamp. Further, in
the above lamp lighting control circuit, since the lamp voltage may have a substantially
the same peak (absolute) value as that of the AC generator voltage, there may be a
problem that the increase in the generator voltage amplitude with the engine speed
will cause an undesirable increase in the peak value of the lamp voltage, leading
to a shorter operable period of time of the lamp.
[0008] In
FR-A-2 674 382, there is disclosed a lamp lightning control circuit according to the preamble of
claim 1. This document
FR-A-2 674 382 is similar to the prior art circuit described above and discloses a lamp effective
voltage monitoring circuit (25) and an SCR (21) for conducting voltage half-waves
of the AC voltage from the electric generator (10) to the lamp (18), the SCR (21)
reducing the size of the voltage conducted to the lamp to prevent overvoltage.
[0009] In view of such problems of the prior art and the recognition by the inventors, a
primary object of the present invention is to provide a lamp lighting control circuit
for a motor vehicle utilizing an electric generator which rotates in conjunction with
an engine to generate an AC voltage that can suppress the lamp voltage so as to increase
the operable period of time of the lamp.
[0010] A second object of the present invention is to provide a lamp lighting control circuit
for a motor vehicle utilizing an electric generator which rotates in conjunction with
an engine to generate an AC voltage that can prevent detectable flickering of the
lamp as well as prevent overvoltage of the lamp.
[0011] A third object of the present invention is to provide a lamp lighting control circuit
for a motor vehicle utilizing an electric generator which rotates in conjunction with
an engine to generate an AC voltage that can reduce the electric power that the electric
generator has to produce.
[0012] A fourth object of the present invention is to provide such a lamp lighting control
circuit and at low cost.
[0013] According to the present invention, these and other objects are accomplished by providing
a lamp lighting control circuit for lighting a lamp (5) according to the characterizing
part of claim 1.
[0014] In accordance with the invention, the capacitor (C1) is charged only while said switching
device (SCR2) in on and an electric current is flowing through the switching device
(SCR2) and the lamp (5), and is discharged while the switching device (SCT2) is off.
The drive circuit (7b) turns on the switching device (SCR2) after a prescribed delay
(Td) from a point of time (T1) when the negative voltage half-wave of the AC voltage
begins to be generated from the electric generator (2). The predetermined delay (Td)
is set such that the intermittent supply of the negative voltage half-wave to said
lamp (5) is allowed to take place only when a rotational speed of the engine is higher
than a certain rotational speed where the intermittent voltage supply does not cause
perceptible flickering of the lamp (5).
[0015] In this way, although the generated electricity increases with the engine speed,
the reduction in the size of the voltage half-wave can achieve a reduced peak value
of the lamp voltage for a given engine speed and accordingly, the engine speed at
which the generated AC voltage reaches the rate voltage of the lamp can be shifted
to a higher engine speed. This can lead to an extended operable period of time of
the lamp.
[0016] The reduction of the size of the voltage half-wave conducted to the lamp (5) may
be achieved by controlling an amplitude of said voltage half-wave or by delaying start
of conduction of said voltage half-wave to the lamp (5).
[0017] According to the invention, there is provided a lamp lighting control circuit for
lighting a lamp (5) with an AC voltage output from an electric generator (2) which
rotates in conjunction with an engine, comprising: a switching device (SCR2) connected
between the electric generator (2) and the lamp (5); and a drive circuit (7b) for
generating an activation signal for turning on said switching device (SCR2) when either
one of positive and negative voltage half-waves of said AC voltage is generated from
said electric generator (2), wherein said drive circuit (7b) turns on said switching
device (SCR2) after a prescribed delay (Td) from a point of time (T1) when said either
one of said positive and negative half-waves of said AC voltage begins to be generated
from said electric generator (2).
[0018] Preferably, said drive circuit (7b) may comprise a delay circuit, which can be embodied
by a CR time constant circuit (R3, C3). According to a preferred embodiment of the
invention, said switching device consists of a thyristor (SCR2).
[0019] Thus, by delaying the turning on of the thyristor (SCR2) connected between the lamp
(5) and the electric generator (2), it is possible to preferably reduce the size of
the half-wave voltage provided to the lamp (5) and hence reduce the effective lamp
voltage, without an undesirable dissipation of the generated electric power as heat.
[0020] The lamp lighting control circuit may further comprise a lamp effective voltage monitoring
circuit (7a) for monitoring an effective voltage of the lamp (5), wherein said lamp
effective voltage monitoring circuit (7a) prevents an operation of said drive circuit
(7b) when it detects an overvoltage of said lamp (5).
[0021] Such a lamp effective monitoring circuit (7a) can conduct the intermittent voltage
supply control to protect the lamp (5) from an overvoltage. At low engine speed where
the intermittent voltage supply control would cause a detectable flickering of the
lamp (5), however, since the lamp voltage control is preferably achieved by delaying
the turning on of the thyristor (SCR2), the intermittent voltage supply control may
be avoided.
[0022] Other and further objects, features and advantages of the invention will appear more
fully from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Now the present invention is described in the following with reference to the appended
drawings, in which:
Figure 1 is a schematic circuit diagram showing a lamp voltage regulation circuit
(or lamp lighting control circuit) to which the present invention is applied;
Figure 2 is a waveform diagram for showing lamp lighting control according to the
present invention;
Figure 3 is a schematic control circuit diagram for showing conventional lamp lighting
control; and
Figure 4 is a waveform diagram for showing conventional lamp lighting control.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] Figure 1 is a schematic circuit diagram for showing a lamp voltage regulation circuit
according to the present invention. In the drawing, similar parts to those in the
conventional embodiment are denoted with the same reference numerals and the detailed
explanation thereof is omitted.
[0025] As shown in Figure 1, a control circuit 1 comprises the terminals CH, BT and LA to
which the battery 3, DC load, and lamp 5 are connected, respectively, in a similar
fashion to the conventional embodiment. In the control circuit 1, the battery charge
control thyristor SCR1, lamp control thyristor SCR2 and battery voltage detecting
circuit 6 are provided also in a similar fashion to the conventional embodiment. Further,
to the lamp lighting control circuit 7 for controlling a gate of the lamp control
thyristor SCR2 is connected a generator output voltage detecting block 8. Thus, the
lamp control thyristor SCR2, lamp lighting control circuit 7 and generator output
voltage detecting block 8 constitute a lamp voltage regulation circuit.
[0026] Next, an inner configuration of the lamp lighting control circuit 7 is explained.
A transistor Q1 is connected to the gate of the lamp control thyristor SCR2. The transistor
Q1 is adapted to be turned on when another transistor Q2 is turned on. A diode D1
is connected to the power source terminal CH so as to permit an electric current only
toward the power source terminal CH, and via the diode D1, the transistor Q2 and a
transistor Q3 for on/off controlling the transistor Q2 are connected to the terminal
CH. A base of the transistor Q2 is connected to ground via a resistor R1.
[0027] Between the diode D1 and the generator output voltage detecting block 8 is provided
a lamp voltage detection block 7a serving as a lamp effective voltage monitoring circuit.
The above transistor Q3 constitutes an output stage of the lamp voltage detection
block 7a so that turning on of the transistor Q3 causes the transistor Q2 to be turned
off. A transistor Q4 that is turned on while an electric current is flowing through
the lamp 5 is connected to the generator voltage detecting block 8.
[0028] Further, a noise absorbing circuit comprising a capacitor C2 and a resistor R2 is
provided between the base and emitter of the transistor Q1. Similarly, between the
base and emitter of the transistor Q2 are provided a capacitor C3 and a resistor R3
connected in parallel for constituting a CR time constant circuit serving as a delay
circuit 9, which may also function as a noise absorbing circuit. Thus, as shown in
Figure 1, the delay circuit 9 and the transistors Q1, Q2 constitute a drive circuit
7b.
[0029] The lamp voltage detection block 7a in the control circuit 1 detects the lamp effective
voltage based on charging and discharging of a capacitor C1 provided in a base circuit
of the transistor Q3. The capacitor C1 is charged by an electric current flowing through
the transistor Q4 and the generator output voltage detecting block 8 so that the capacitor
C1 is charged only while an electric current is flowing through the lamp 5 and discharged
through a resistor connected thereto in parallel during other period of time. Further,
a zener diode ZD1 is provided between the capacitor C1 and the base of the transistor
Q3 so that a limit value of the lamp effective voltage for prohibiting the turning
on of the thyristor SCR2 is set by a breakdown voltage of the zener diode ZD1, as
described more in detail later.
[0030] An operation of the control circuit 1 constructed as above is explained hereinafter.
When a negative voltage is generated from the electric generator 2, an electric current
first flows to the capacitor C3 in the delay circuit 9 via the resistor R1 so as to
charge the capacitor C3, and after a prescribed delay time defined by the delay circuit
9 (or after a time required for fully charging the capacitor C3) from the generation
of the negative voltage from the electric generator 2, a base current flows to the
base of the transistor Q2 to turn it on. The turning on of the transistor Q2 causes
the transistor Q1 to turn on so that a gate voltage is applied to the lamp control
thyristor SCR2. This turns on the thyristor SCR2, whereby the lamp 5 is lighted.
[0031] In this way, as shown in Figure 2, the lamp voltage (lower waveform) is generated
after a delay time Td has passed from a negative voltage generation timing T1 in the
AC voltage (upper waveform). It should be noted that the delay time Td is determined
so that the magnitude (absolute value) of the AC voltage begins to decrease when the
magnitude of the lamp voltage is still increasing. This results in the lamp voltage
having a smaller peak value (or amplitude) VL
max than a peak value VG
max of the AC voltage (VL
max<VG
max). Also, the period of time during which the voltage is applied to the lamp 5 (or
duration time) is reduced due to the delay time Td. Thus, by delaying the turning
on of the thyristor SCR2 from the negative voltage generation timing T1, a size (amplitude
and duration time) of the voltage half-wave provided to the lamp 5 can be reduced
and accordingly the effective voltage of the lamp 5 can be preferably reduced.
[0032] According to the reduction in size of the voltage half-wave provided to the lamp
5, the amount of electric charge stored in the capacitor C1 in the lamp voltage detection
block 7a by a single wave (a negative wave for lighting the lamp) is also reduced
with respect to the case where the lamp lighting is started without the delay time
Td (phantom line in Figure 2). Thus, at low engine speed where the intermittent voltage
supply control would cause a detectable flickering of the lamp 5a, the voltage of
the capacitor C1 does not reach the breakdown voltage of the zener diode ZD1 and thus,
the intermittent voltage supply control can be avoided at such low engine speed.
[0033] As the engine speed increases higher, the peak value VG
max of the AC voltage from the electric generator 2 increases, which in turn increases
the peak value VL
max of the lamp voltage having the delay time Td relative to the generator voltage. And
at a certain high engine speed, the voltage of the capacitor C1 reaches the breakdown
voltage of the zener diode ZD1 so that the transistor Q3 is turned on. This prevents
the turning on of the transistor Q2 which in turn prevents the thyristor SCR2 from
turning on. Thus, in the control circuit 1 also, the intermittent voltage supply to
the lamp 5 can take place as in the conventional circuit. However, in the control
circuit 1 of the present invention, the intermittent voltage supply control takes
place only at a sufficiently high engine speed range where the frequency of the AC
voltage from the electric generator 2 is sufficiently high and the intermittent voltage
supply control would not cause a detectable flickering of the lamp 5.
[0034] Since the engine speed at which the peak lamp voltage VL
max reaches the rated maximum voltage of the lamp 5 is relatively high, the number of
occasions that the lamp 5 is applied with its rated maximum voltage can be reduced
whereby an extended operable period of time of the lamp 5 is achieved. Further, since
the delay circuit 9 can also function as a noise absorbing circuit for the transistor
Q3 and thus no additional circuit is required, a simple control circuit can be achieved
with a reduced manufacturing cost.
[0035] As described above, according to the present invention, the turning on of the thyristor
SCR2 is controlled by the drive circuit 7b so that the size of the voltage half-wave
(or the amount of electricity) conducted to the lamp 5 is reduced with respect to
the case where the generated electricity, which increases with the engine speed, is
supplied to the lamp 5 directly without delay. This can reduce the peak value of the
lamp voltage for a given engine speed, and the engine speed at which the AC voltage
reaches the rated lamp voltage is shifted to a higher engine speed side, whereby an
extended operable period of time of the lamp 5 is preferably achieved. Further, the
reduction in size of the voltage half-wave conducted to the lamp 5 can reduce the
effective lamp voltage without conducting intermittent voltage supply control. Although
the intermittent voltage supply control to the lamp could take place to protect the
lamp 5 from an excessive generated electric power, such intermittent lamp voltage
supply control will take place only in a high engine speed range where the frequency
of the AC voltage is sufficiently high and the lamp flickering due to the intermittent
lamp voltage supply control can be inconspicuous. Therefore, it is possible to prevent
flickering of the lamp at low engine speed and at the same time to prevent overvoltage
of the lamp at high engine speed.
[0036] The control of the amplitude of the half-wave supplied to the lamp 5 may be achievable
by connecting a resistor between the electric generator 2 and the lamp 5. However,
in such a case, an electric power would be dissipated as heat at the resistor and
this would be undesirable in view of minimizing the electric power that the electric
generator 2 has to produce. In the control circuit according to the invention, the
lamp voltage control can be preferably achieved by delaying the turning on of the
thyristor SCR2 connected between the lamp 5 and the generator 2 without causing an
undesirable dissipation of the generated electric power.
1. A lamp lighting control circuit for lightning a lamp (5) with an AC voltage output
from an electric generator (2) which rotates in conjunction with an engine, comprising:
a switching device (SRC2) connected between the electric generator (2) and the lamp
(5),
a drive circuit (7b) for turning on said switching device (SRC2) when negative voltage
half-wave of said AC voltage is generated from said electric generator (2), and
a lamp effective voltage monitoring circuit (7a) for monitoring an effective voltage
of the lamp (5),
wherein said lamp effective voltage monitoring circuit (7a) comprises a capacitor
(C1) which is charged only while an electric current is flowing through said lamp
(5), and wherein said lamp effective voltage monitoring circuit (7a) prevents an operation
of said drive circuit (7b) only when it detects said voltage of said capacitor (C1)
exceeding a breakdown voltage of a zener diode and allows said operation of said drive
circuit (7b) when said voltage of said capacitor (C1) is below said breakdown voltage,
whereby said negative voltage half-wave of said AC voltage is intermittently supplied
to said lamp (5) for an engine speed higher than a certain engine speed,
characterized in that said capacitor (C1) is charged only while said switching device (SCR2) in on and
an electric current is flowing through said switching device electric current is flowing
through said switching device (SCR2) and said lamp (5), and is discharged while said
switching device (SCR2) is off, and
in that
said device circuit (7b) turns on said switching device (SRC2) after a prescribed
delay (Td) from a point of time (T1) when said negative voltage half-wave of said
AC voltage begins to be generated from said electric generator (2),
wherein said predetermined delay (Td) is set such that said intermittent supply of
said negative voltage half-wave cf said AC voltage to said lamp (5) conducted by said
lamp effective voltage monitoring circuit (7a) is allowed to take place only when
a rotational speed of said engine is higher than a certain rotational speed where
said intermittent voltage supply does not cause perceptible flickering of said lamp
(5).
2. A lamp lightning control circuit according to claim 1, characterized in that said drive circuit (7b) comprises a delay circuit (R1, C3).
3. A lamp lighting control circuit according to claim 2, characterized in that said delay circuit consists of a CR time constant circuit (R1, C3).
4. A lamp lightning control circuit according to claim 1, characterized in that said switching device consists of a thyristor (SCR2).
1. Lampenbeleuchtungs-Steuerschaltkreis zum Beleuchten einer Lampe (5) mit einem Wechselspannungsausgang
von einem Stromerzeuger (2), der sich zusammen mit einem Motor dreht, umfassend:
eine Schaltvorrichtung (SRC2), die zwischen dem Stromerzeuger (2) und der Lampe (5)
angeschlossen ist,
eine Treiberschaltung (7b) zum Einschalten der Schaltvorrichtung (SRC2), wenn eine
negative Spannungshalbwelle der Wechselspannung von dem Stromerzeuger (2) erzeugt
wird, und
einen Lampeneffektivspannung-Überwachungsschaltkreis (7a) zum Überwachen einer Effektivspannung
der Lampe (5),
wobei der Lampeneffektivspannung-Überwachungsschaltkreis (7a) einen Kondensator (C1)
umfasst, der nur geladen wird, während ein elektrischer Strom durch die Lampe (5)
fließt,
und wobei der Lampeneffektivspannung-Überwachungsschaltkreis (7a) einen Betrieb des
Ansteuerschaltkreises (7b) verhindert, nur wenn er erfasst, dass die Spannung des
Kondensators (C1) eine Durchbruchspannung einer Zener-Diode übersteigt, und den Betrieb
des Ansteuerschaltkreises (7b) erlaubt, wenn die Spannung des Kondensators (C1) niedriger
ist als die Durchbruchspannung, wodurch die negative Spannungshalbwelle der Wechselspannung
der Lampe (5) für eine kotorgeschwindigkeit, die höher ist als eine bestimmte Motorgeschwindigkeit,
periodisch zugeführt wird,
dadurch gekennzeichnet, dass der Kondensator (C1) nur geladen wird, während die Schaltvorrichtung (SCR2) eingeschaltet
ist und ein elektrischer Strom durch die Schaltvorrichtung (SCR2) und die Lampe (5)
fließt, und entladen wird, während die Schaltvorrichtung (SCR2) ausgeschaltet ist,
und dass
der Vorrichtungsschaltkreis (7b) die Schaltvorrichtung (SRC2) nach einer vorgegebenen
Verzögerung (Td) ab einem Zeitpunkt (T1), an dem die Erzeugung der negativen Spannungshalbwelle
der Wechselspannung durch den Stromerzeuger (2) beginnt, einschaltet,
wobei die vorherbestimmte Verzögerung (Td) derart eingestellt ist, dass die periodische
Zuführung der negativen Spannungshalbwelle der Wechselspannung zur Lampe (5), die
von dem Lampeneffektivspannung-Überwachungsschaltkreis (7a) ausgeführt wird, nur stattfinden
darf, wenn eine Drehgeschwindigkeit des Motors höher ist als eine bestimmte Drehgeschwindigkeit,
bei der die periodische Spannungszuführung kein merkbares Flimmern der Lampe (5) verursacht.
2. Lampenbeleuchtungs-Steuerschaltkreis nach Anspruch 1, dadurch gekennzeichnet, dass der Treiberschaltkreis (7b) einen Verzögerungsschaltkreis (R1, C3) umfasst.
3. Lampenbeleuchtungs-Steuerschaltkreis nach Anspruch 2, dadurch gekennzeichnet, dass der Verzögerungsschaltkreis aus einem CR-Zeitkonstantenschaltkreis (R1, C3) besteht.
4. Lampenbeleuchtungs-Steuerschaltkreis nach Anspruch 1, dadurch gekennzeichnet, dass die Schaltvorrichtung aus einem Thyristor (SCR2) besteht.
1. Circuit de commande d'allumage de lampe pour allumer une lampe (5) avec une sortie
de tension alternative provenant d'un générateur électrique (2) qui tourne en conjonction
avec un moteur, comprenant :
un dispositif de commutation (SRC2) connecté entre le générateur électrique (2) et
la lampe (5),
un circuit d'excitation (7b) pour mettre sous tension ledit dispositif de commutation
(SRC2) lorsqu'une demi-onde de tension négative de ladite tension alternative est
générée par ledit générateur électrique (2), et
un circuit de surveillance de tension efficace de lampe (7a) pour surveiller une tension
efficace de la lampe (5),
dans lequel ledit circuit de surveillance de tension efficace de lampe (7a) comprend
un condensateur (C1) qui est chargé seulement pendant qu'un courant électrique circule
à travers ladite lampe (5),
et dans lequel ledit circuit de surveillance de tension efficace de lampe (7a) empêche
un fonctionnement dudit circuit d'excitation (7b) seulement lorsqu'il détecte que
ladite tension dudit condensateur (C1) dépasse une tension de claquage d'une diode
Zener et permet ledit fonctionnement dudit circuit d'excitation (7b) lorsque ladite
tension dudit condensateur (C1) est inférieure à ladite tension de claquage, de manière
à ce que ladite demi-onde de tension négative de ladite tension alternative soit fournie
par intermittence à ladite lampe (5) pour une vitesse de moteur supérieure à une certaine
vitesse de moteur,
caractérisé en ce que ledit condensateur (C1) est chargé seulement pendant que ledit dispositif de commutation
(SCR2) est sous tension et un courant électrique circule à travers ledit dispositif
de commutation (SCR2) et ladite lampe (5), et est déchargé pendant que ledit dispositif
de commutation (SCR2) est hors tension, et
en ce que
ledit circuit de dispositif (7b) met sous tension ledit dispositif de commutation
(SRC2) après un retard spécifié (Td) à partir d'un instant (T1) où ladite demi-onde
de tension négative de ladite tension alternative commence à être générée par ledit
générateur électrique (2),
dans lequel ledit retard prédéterminé (Td) est réglé de telle sorte que ladite fourniture
intermittente de ladite demi-onde de tension négative de ladite tension alternative
à ladite lampe (5) effectuée par ledit circuit de surveillance de tension efficace
de lampe (7a) est autorisée à avoir lieu seulement lorsqu'une vitesse de rotation
dudit moteur est supérieure à une certaine vitesse de rotation où ladite fourniture
de tension intermittente ne provoque pas un scintillement perceptible de ladite lampe
(5).
2. Circuit de commande d'allumage de lampe selon la revendication 1, caractérisé en ce que ledit circuit d'excitation (7b) comprend un circuit de retard (R1, C3),
3. Circuit de commande d'allumage de lampe selon la revendication 2, caractérisé en ce que ledit circuit de retard consiste en un circuit à constante de temps CR (R1, C3).
4. Circuit de commande d'allumage de lampe selon la revendication 1, caractérisé en ce que ledit dispositif de commutation se compose d'un thyristor (SCR2).