JP2600638Y2 - Lighting circuit for vehicle discharge lamps - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a lighting circuit for a discharge lamp for a vehicle having a control function of reducing the control power when the battery voltage drops, in which the control power is excessively reduced and the lighting of the discharge lamp cannot be maintained. It is an object of the present invention to provide a novel lighting circuit for a discharge lamp for a vehicle, which can be controlled so as not to fall into a state.

[0002]

2. Description of the Related Art In recent years, small metal halide lamps have attracted attention as light sources replacing incandescent light bulbs.
After boosting the battery voltage by the booster circuit,
2. Description of the Related Art There is known an AC conversion circuit that converts an AC voltage into a sine wave or a rectangular wave AC voltage and then applies the AC voltage to a metal halide lamp.

[0003] With respect to the lighting control of the discharge lamp, after performing control for shortening the starting time or restarting time at the initial lighting or relighting, the control is shifted to constant power control for keeping the control power constant in a stable state. There are things that let me do that.

[0004]

By the way, if the constant voltage control is to be maintained even if the battery voltage is reduced for some reason, the battery current increases, and the heat generation due to the power loss of the lighting circuit increases. There are problems such as strict specifications for the maximum rated current of the component parts, and problems such as burden on the battery and adverse effects on another circuit using the battery as a power source.

Therefore, it is conceivable to perform control so as to reduce the control power when the battery voltage is lowered. However, if the control power is too low, it becomes difficult to maintain the lighting of the discharge lamp, or if the control power is lower than a certain power value. There is a disadvantage that the re-ignition voltage increases and the life of the discharge lamp is shortened.

[0006]

In order to solve the above-mentioned problems, a lighting circuit for a vehicle discharge lamp according to the present invention has a control circuit for performing power control including constant power control of the discharge lamp and a battery. in the lighting circuit of the vehicular discharge lamp that is to be able to perform the lighting control of the discharge lamp to regulate the control power of the discharge lamp by detecting a voltage to a power lower than the predetermined power with a decrease of the battery voltage, controlled Electric power
However, it does not fall below the lower limit that can maintain the lighting of the discharge lamp.
A lower limit regulating means for regulating a decrease in control power.
When the battery voltage falls below the reference value, the control power is released.
Is fixed at the lower limit value of.

[0007]

Therefore, according to the present invention, there is provided a lower limit regulating means for regulating the control power not to fall below the lower limit when the battery voltage falls below the reference value. By keeping the control power from dropping too much, it is possible to maintain the lighting of the discharge lamp and prevent the life of the discharge lamp from being shortened.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the lighting circuit for a vehicle discharge lamp according to the present invention will be described below with reference to the illustrated embodiment. In the illustrated embodiment, the present invention is applied to a lighting circuit of a rectangular wave lighting system.

FIG. 1 schematically shows a lighting circuit 1, in which a battery 2 is connected between DC voltage input terminals 3, 3 '.

Reference numerals 4 and 4 'denote DC power supply lines, and a lighting switch 5 is provided on one of the plus lines 4.

A relay contact 6 a is provided on the positive line 4, and is opened and closed by a power-off relay circuit 6. That is, the power cutoff relay circuit 6 is provided to cut off the supply of the battery voltage to the subsequent circuit when an abnormality is detected in the circuit, and is controlled by an abnormality detection signal from an abnormality detection circuit (not shown).

Reference numeral 7 denotes a DC booster circuit, the positive side input terminal of which is connected to the output side terminal of the relay contact 6a, and the other ground side input terminal of which is connected to the DC voltage input terminal 3 '.

The DC booster circuit 7 is provided for boosting the battery voltage.
The configuration of a C-DC converter is used, and the boosting control is performed by a control circuit described later.

Reference numeral 8 denotes a DC-AC converter circuit, which is provided at a stage subsequent to the DC booster circuit 7 and converts a DC voltage sent from the DC booster circuit 7 into a rectangular wave AC voltage. The DC-AC conversion circuit 8 includes, for example, 2
A bridge type driving circuit composed of a pair of FETs is used.

Reference numeral 9 denotes an igniter circuit, which is arranged at the subsequent stage of the DC-AC conversion circuit 8 and has AC output terminals 10, 1;
Between 0 ', a metal halide lamp 11 with a rated power of 35W
Are connected.

Reference numeral 12 denotes a control circuit for controlling the output voltage of the DC booster circuit 7. The control circuit 12 controls the output voltage of the DC booster circuit 7 detected by the voltage detector 13 provided between the output terminals of the DC booster circuit 7. A corresponding voltage detection signal is input.

A current detection signal corresponding to the output current of the DC booster circuit 7 is converted into a voltage by a current detector 14 provided on a ground line connecting the DC booster circuit 7 and the DC-AC converter circuit 8. The data is input to the control circuit 12 in the form.

In this embodiment, the metal halide lamp 1 is used.
Although a signal corresponding to the lamp voltage or lamp current of 1 is obtained from the output stage of the DC booster circuit 7, it is a matter of course that a configuration for directly detecting these signals may be employed.

The control circuit 12 generates a control signal corresponding to the above detection signal and sends it to the DC boosting circuit 7 to control the output voltage, thereby performing power control in accordance with the starting state of the metal halide lamp 11. The start time and the restart time of the lamp are shortened and the control is promptly shifted to the constant power control. The V (voltage) -I (current) control unit 15 and the PWM (pulse width modulation) control unit 16 Having.

The VI control unit 15 is configured to control the lighting of the metal halide lamp 11 based on a control curve that defines the relationship between the lamp voltage and the lamp current.
When a detection signal related to the output voltage of the DC booster circuit 7 is sent from the voltage detection unit 13, a current command value corresponding to the detection signal is calculated, and this is compared with an actual current value to perform PWM control on the command signal. The data is sent to the unit 16.

The control curve is, for example, a constant power control area (a linear approximation to the power curve of the rated power) through a transition area from a control area in which power is supplied several times the rated power of the metal halide lamp 11 at the beginning of lighting. A power control program that shifts to a control line or the like is used.

The PWM control unit 16 generates a signal whose pulse width is varied in response to a command signal from the VI control unit 15 and transmits this signal to a control signal to the semiconductor switch element of the DC booster circuit 7 (this "PS").

Reference numeral 17 denotes a low power control unit, which lowers a control power value related to constant power control according to the battery voltage when the battery voltage falls below a predetermined value.
It is provided to regulate the lower limit so that the control power value does not fall below the lower limit value when the battery voltage becomes extremely low.

That is, if the metal halide lamp 11 is controlled at a certain power value or less, the lighting becomes unstable and the lighting cannot be maintained, or the re-ignition voltage increases to shorten the lamp life. A power value that does not occur is checked in advance for the metal halide lamp 11, and the control power value is set to this value.

FIG. 2 shows a path from the VI control unit 15 to the PWM control unit 16 and a configuration example of the low power control unit 17 together. The specific configuration of the VI control unit 15 is not shown because it does not relate to the gist of the present invention.

The output signal of the VI control unit 15 is sent to the PWM control unit 16 via an amplifier using an operational amplifier 18.

As shown in the figure, an operational amplifier 18 constituting an inverting amplifier circuit by a feedback resistor 19 has an inverting input terminal connected to an output terminal 15 of a VI control unit 15 via a resistor 20.
a, and a predetermined reference voltage (referred to as “E1”) is supplied to the non-inverting input terminal.

A general-purpose IC for a switching regulator is used for the PWM control unit 16, and an error amplifier, an oscillator, a comparator, a reference voltage source, and the like are packaged therein.

The output signal of the operational amplifier 18 is input to the error amplifier 21 inside the IC shown in FIG. 2 via a resistor at a minus input terminal thereof, and a predetermined reference voltage (this Is referred to as “E2”.)
Is supplied, and when the input voltage to the error amplifier 21 increases, the duty cycle of the output signal PS decreases, and as a result, control is performed so that the output voltage of the DC booster circuit 7 decreases.

The low power control section 17 comprises an amplifier 22 using an operational amplifier and an ideal diode circuit 23.

The amplifier 22 is configured as an inverting amplifier circuit using an operational amplifier 24. A battery voltage (referred to as “+ B”) is applied to a non-inverting input terminal of the operational amplifier 24 via resistors 25 and 26. A predetermined reference voltage (this is referred to as “E3”) is supplied to the inverting input terminal via the resistor 27.

The resistor 28 is a feedback resistor.

The output of the amplifier 22 is the ideal diode circuit 2
3 is sent to the non-inverting input terminal of the operational amplifier 29.

Reference numeral 30 denotes a diode, the anode of which is connected to the inverting input terminal of the operational amplifier 29;
The output terminal 15 a of the VI control unit 15 is connected via a resistor 31 and a resistor 20, and the cathode thereof is connected to the output terminal of the operational amplifier 29.

Reference numeral 32 denotes a capacitor, which is an operational amplifier 29
Are inserted between the inverting input terminal and the output terminal.

As described above, the output line of the low power control unit 17 is a branch line of the main control line from the VI control unit 15 to the PWM control unit 16, and its current (this is referred to as "I1
7 ") affects the signal level of the main control line.

However, according to the above circuit, when the battery voltage is within the normal range, the output voltage of the amplifier 22 is large, so that the ideal diode circuit 23 is reverse-biased (I17 = 0), and the VI control is performed. The output of the unit 15 is sent to the operational amplifier 18 as it is.

At the time of constant power control, the potential of the inverting input terminal of the operational amplifier 18 (this is referred to as "V18") is controlled so as to be substantially equal to E1, and E1-V18 is controlled by the PWM controller 16.
Of the control signal P
The duty cycle of S is varied so that the control power is controlled to be constant.

That is, when a control line obtained by linear approximation to a constant power curve is used, control is performed so that the value of an equation obtained by linearly combining the output voltage and output current of the DC booster circuit 7 at a certain ratio is constant. For example, when the output current of the DC booster circuit 7 increases, control is performed such that the duty cycle of the control signal PS is reduced to reduce the output voltage of the DC booster circuit 7.

Assuming that the battery voltage drops during such constant power control, the amplifier 2 of the low power control unit 17
2, the current I17 starts to flow, which causes the VI control unit 15 to output the operational amplifier 1
Since the signal level of the control signal 8 is pulled down, the duty cycle of the control signal PS is reduced, and the output voltage is controlled to decrease.

The magnitude of the current I17 is determined by the magnitude of the battery voltage.
7, the power control is performed such that the control power decreases as the battery voltage decreases.

Then, the battery voltage has a certain lower limit (E
Corresponds to 3. ), The output voltage of the amplifier 22 becomes substantially zero and becomes constant, I17 settles down to a constant value, and the control power reaches the lower limit value (this is described as “PL”).

FIG. 3 is a graph of the description so far, in which the horizontal axis represents the battery voltage “+ B”, and the vertical axis represents the control power (this is described as “P”) and the current I17. It shows these relationships.

The range in which the battery voltage is equal to or higher than the predetermined value BN indicates the normal range of the battery voltage (however, not including the overvoltage range exceeding the upper limit).
When the battery voltage becomes less than N, I17 increases as the battery voltage decreases, and the control power P decreases. However, when the battery voltage falls below a certain voltage BL, the control power P decreases to the lower limit value P.
It turns out that it does not become less than L.

FIG. 4 shows the change of the battery current with respect to the battery voltage. The horizontal axis indicates the battery voltage "+ B", and the vertical axis indicates the battery current (this is "B").
i ". ) To show the relationship between the two.

In the normal range of the battery voltage, the battery current Bi is small, and when the battery voltage is less than BN and is not less than BL, the battery current Bi is substantially constant. When the battery voltage is less than BL, the battery current Bi becomes large. I understand.

As described above, even if the battery voltage decreases, the low power control is performed so that the battery current does not increase in order to suppress power loss and heat generation until the power value reaches the predetermined lower limit value PL. Is extremely reduced, the control power is controlled so as not to be lower than the lower limit value, and the control for maintaining the lighting of the discharge lamp is performed.

[0048]

[Effects of the Invention] As is apparent from the above description, according to the present invention, when the battery voltage drops to some extent, the lighting control is performed at a low power according to the battery voltage, but the battery voltage drops. If the battery power drops, the lower limit is imposed so that the control power does not become lower than the lower limit, so that the discharge lamp is kept lit and the battery current increases when the battery voltage drops without shortening the life of the discharge lamp. Can be suppressed.

The above-described embodiment is merely an embodiment of the present invention, and the technical scope of the present invention should not be construed as being narrow only by this embodiment. For example, in the above-described embodiment, an example is shown in which the present invention is applied to a lighting circuit of a rectangular wave lighting system. However, the present invention is not limited to this and can be applied to a lighting circuit of a sine wave lighting system.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an outline of a lighting circuit of a vehicle discharge lamp of the present invention.

FIG. 2 is a circuit diagram showing a main part of the present invention.

FIG. 3 is a graph schematically showing a relationship between a battery voltage, control power, and current I17 in the present invention.

FIG. 4 is a graph schematically illustrating a relationship between a battery voltage and a battery current in the present invention.

[Explanation of symbols]

 1 lighting circuit for vehicle discharge lamp 12 control circuit 17 lower limit regulating means

Continuation of the front page (56) References JP-A-4-12496 (JP, A) JP-A-4-155796 (JP, A) JP-A-5-21186 (JP, A) JP-A-5-174984 (JP JP-A-5-213109 (JP, A) JP-A-6-111955 (JP, A) JP-A-6-119981 (JP, A) JP-A-6-140174 (JP, A) 6-140175 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 41/14-41/29 B60Q 1/04

Claims (1)

(57) [Scope of request for utility model registration] A control circuit for performing power control including constant power control of a discharge lamp, and detecting a battery voltage to regulate a control power of the discharge lamp to a power lower than a prescribed power according to a decrease in the battery voltage. In a lighting circuit of a vehicle discharge lamp capable of performing the lighting control of the discharge lamp, the control power becomes lower than a lower limit value at which the lighting of the discharge lamp can be maintained.
Lower limit regulating means to regulate the decrease in control power so that
Provided to control when battery voltage falls below the reference value
A lighting circuit for a vehicular discharge lamp, wherein the power is fixed to the lower limit .