JPH1032096A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate a lighting miss when a discharge lamp is lighted by starting AC lighting after DC lighting has been kept on for the definite period of time since it was started, and furthermore applying electric power which is the sum of rated electric power and definite electric power, for the period of time which is the sum of the aforesaid hold time and a definite period of time. SOLUTION: A polarity change-over switching circuit 7 keeps on the conditions of turning switching elements 71 and 74 on and switching elements 72 and 73 off for the period of time shorter than TB=T1 , which represents time having elapsed since a discharge lamp 6 was lighted by a signal from a lighting timer 9, and the DC lighting of the lamp 6 is kept on in the direction indicated by an arrow head B. The aforesaid time T1 is set to be the shortest time capable of preventing the occurrence of any lighting miss. Next, an electric power control means 8 keeps on prescribed electric power which is initially indicated electric power for the period of time TB=T2 longer than time T1 . Next, after time T2 has elapsed, control is executed similarly to control in the part, however, control is executed smoothly in such a way that electric power is not abruptly lowered from the initial indicated electric power. And time T2 is also set to be as short as possible. By this constitution, the lamp 6 can thereby be prevented from being missed in lighting directly after starting where a lighting condition is unstable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a discharge lamp such as a headlight of an automobile.

[0002]

2. Description of the Related Art In recent years, the design of automobiles has tended to be more streamlined, and accordingly, compact headlights have been required. If the headlight is made more compact in this way, the light collection efficiency of the lamp will decrease, so a light source with higher efficiency and higher brightness than conventional halogen bulbs will be required. A discharge lamp device using a discharge lamp has been developed. This discharge lamp device is composed of an ultra-small metal halide lamp in which a rare gas, mercury and a metal halide as a luminescent substance are sealed in an arc tube made of quartz glass, and a lighting circuit.

Hereinafter, a conventional discharge lamp lighting device will be described. FIG. 3 shows a configuration and a circuit of a main part of a conventional discharge lamp lighting device. When a switch 1 is turned on, a DC voltage from a battery 2 is boosted to a high voltage by a starting unit 5.
By applying this high voltage, the discharge lamp 6 starts discharging, the DC voltage boosted by the DC / DC converter 3 is converted into an AC voltage by the polarity switching circuit 10 and
Are turned on in alternating current.

The power control means 4 outputs the output voltage V _DC1 of the DC / DC converter 3 for stable lighting of the discharge lamp 6.
The power control is performed for the stable lighting of the discharge lamp 6 while measuring the current _IDC1 .

As the switching elements 101, 102, 103, 104 of the polarity switching circuit 10, field effect transistors (hereinafter referred to as FETs) are used.

[0006] The operation of the discharge lamp lighting device configured as described above will be described. First, when the switch 1 is turned on, a DC voltage from the battery 2 is input to the DC / DC converter 3 and the starting unit 5. The starting means 5 applies a high voltage to the discharge lamp 6 and causes the discharge lamp 6 to start discharging.
A series of controls from the glow discharge to the arc discharge to stable lighting of the discharge lamp 6 are performed by the power control means 4.
In the above series of processes, the polarity switch circuit 1
Numeral 0 denotes a rectangular wave having a frequency of 400 Hz, the polarity of which is inverted, and the discharge lamp 6 is lit by AC.

FIG. 4 is a diagram showing the relationship between the polarity switching immediately after the start of the discharge lamp 6 and the command power control. The AC lighting operation of the discharge lamp 6 is performed by on / off control of the switching elements 101, 102, 103, and 104 in the polarity switching circuit 10. The reason why the AC lighting operation is performed on the discharge lamp 6 is that if the DC lighting is performed, the electrodes of the discharge lamp 6 are significantly deteriorated and the life is shortened.

[0008] Switching elements 101, 1 during AC lighting
The on / off operations of 02, 103, and 104 are as shown in FIG. 5, and the on / off operation is performed by a rectangular wave having a constant frequency of 400 Hz. Further, the switching elements 101 and 10
4 and the switching elements 102 and 103 are on /
The off operation is reversed, so that an AC voltage is applied to the discharge lamp 6. Further, when the on / off operations of the switching elements 101 and 104 and the switching elements 102 and 103 are switched (at the time of polarity reversal), the switching elements 101 and 102 are switched.
And switching element 103 and switching element 10
4 to prevent simultaneous conduction of all switching elements 1
A pause period in which 01 to 104 are turned off is set.

The discharge lamp 6 has a stable
In order to shift to the lighting state, immediately after startup,
The power added to the power, for example, 75 W which is the maximum control power
Is supplied to the discharge lamp 6. After this additional power is applied,
7 (output voltage V_DC) -Indicated power
Stable lighting voltage V from maximum 75W according to characteristics_DC= V _B
Power control up to the rated power of 35 W at the time
A stable light quantity can be obtained in a short time.

When the discharge lamp 6 is turned on in a state where the temperature of the discharge lamp itself is low after a sufficient time has elapsed after turning off the discharge lamp 6 (hereinafter referred to as a cold start), the lamp is turned on from around _VDC = _VA shown in FIG. , The indicated power W _T is the maximum 75 W
It will start the power control from a lower W _A.

When the power control means 4 determines that the output voltage _VDC has dropped and the discharge lamp 6 has started, the power control means 4 calculates the power from the initial command power W _T = 75 W in the table shown in FIG. start the control to lower the output instruction power W _a when the output voltage V _a as shown in point C in FIG. 6- (d). At this time, the switching elements 101 and 104 are on,
The current I flows in the direction shown by the arrow B. Next, the switching elements 101, 104 are switched from on to off, and the switching elements 101, 102, 103, 104
At the point A in FIG. 6- (b) during the rest period when
Although the direction of the current I must be switched, the lighting state of the discharge lamp 6 is unstable immediately after the start of the discharge lamp. In the worst case in the period, the direction of the current I is not switched and the possibility that the discharge lamp 6 is turned off (hereinafter referred to as “lighting mistake”) is increased as shown at point B in FIG.

[0012]

As described above, in the conventional configuration, the direction of the current I is not switched during the AC lighting suspension period immediately after the start, in which the lighting state of the discharge lamp 6 is unstable. In order to perform this, a high voltage is applied to the discharge lamp 6 by the starting means 5.
Has to be re-applied, and the life of the discharge lamp 6 is significantly shortened.

An object of the present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a discharge lamp lighting device in which a lighting mistake does not occur at the start of lighting.

[0014]

In order to achieve this object, a discharge lamp lighting device according to the present invention comprises a D.sub.
A C / DC converter, a polarity switch circuit for converting a DC voltage to an AC voltage, a starting means for applying a high voltage to the discharge lamp to start the discharge lamp, and a voltage and current applied to the polarity switch circuit. Power control means for calculating power and feeding back to the DC / DC converter so as to perform constant power control to a target power; and a lighting time timer for transmitting the time from the start of the discharge lamp to the polarity switching circuit and the power control means. According to the signal of the lighting time timer, the polarity changeover switch circuit keeps the polarity in one direction DC lighting for a fixed time from the start, starts AC lighting after a certain time has elapsed, and the power control means During a period in which a fixed time is added to the lighting holding time, a power output is performed by adding a fixed power to the rated power for maintaining the lighting.

According to this configuration, it is possible to provide a discharge lamp lighting device in which a lighting error does not occur immediately after start-up in which the lighting state of the discharge lamp is unstable.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a DC / DC converter for boosting a DC voltage from a battery, and a full bridge composed of four switching elements converts the DC voltage to an AC voltage. A polarity changeover switch circuit for converting, a discharge lamp connected to a full bridge output of the polarity changeover switch circuit, starting means for applying a high voltage to the discharge lamp to start up the discharge lamp, and the polarity changeover switch circuit. Power control means for calculating power from the voltage and the current and feeding back the DC / DC converter so as to perform constant power control to a target power; and determining the start of the discharge lamp from the voltage applied to the polarity switching circuit, and starting the discharge lamp. A lighting time timer for transmitting the time after the switching to the polarity changeover switch circuit and the power control means. The switch circuit keeps the polarity in one-way DC lighting for a certain period of time from the start, and starts AC lighting after a certain period of time, and the power control means adds a certain period of time to the DC lighting holding period. In order to maintain lighting, a power output is performed by adding a constant power to the rated power. With this configuration, a lighting error does not occur immediately after starting the lighting state of the discharge lamp, which is unstable. The life of the lamp can be long.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a discharge lamp lighting device according to an embodiment of the present invention. In the embodiment of the present invention, the same components as those described in the above-described conventional example are denoted by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, this embodiment comprises a DC / DC converter 3 for boosting a DC voltage from a battery 2 by operating a switch 1, and four switching elements 71, 72, 73, 74. A polarity changeover switch circuit 7 for converting a DC voltage into an AC voltage by a full bridge, a discharge lamp 6 connected to a full bridge output of the polarity changeover switch circuit 7, and applying a high voltage to the discharge lamp 6 to discharge it. Activating means 5 for activating an electric light 6; power control means 8 for calculating power from the voltage and current applied to the polarity switching circuit 7 and feeding back to the DC / DC converter 3 so as to perform constant power control to a target power; Determining the activation of the discharge lamp 6 from the voltage applied to the polarity switch circuit 7,
There is provided a lighting time timer 9 for transmitting the time from the start to the polarity switching circuit 7 and the power control means 8.

The operation of the discharge lamp lighting device configured as described above will be described below. FIG.
(D) is a diagram showing the relationship between polarity switching and command power control of the discharge lamp lighting device according to one embodiment of the present invention. The polarity switching switch circuit 7 switches the polarity of AC lighting in an unstable lighting state immediately after startup. In order to prevent a lighting error from occurring during the idle period of time, the signal of the lighting time timer 9 is set to a value equal to or less than the time T _B = T ₁ from the start of the discharge lamp 6 shown in FIG.
As shown in (d), the switching elements 71 and 74 are turned on, the switching elements 72 and 73 are kept off, and the DC lighting of the discharge lamp 6 in the direction of arrow B in FIG. retention time T ₁ is set to the shortest time that can prevent the lighting error to accelerate the deterioration of too long, as described above the discharge lamp 6 electrodes. For example, as an example, T ₁ is set to about 30 ms. Polarity changeover switch circuit 7 after the DC lighting holding time T ₁ elapses starts alternating current operation, as shown in Figure 2 (d). Next, during the period T _B = T ₂ , which is longer than the DC lighting holding time T _{1, the} power control means 8 suddenly changes to an unstable lighting state immediately after the discharge lamp 6 switches from DC lighting to AC lighting, as shown in FIG. As shown in (c), the initial instruction power of 75 W is held in order to prevent a lighting error that may occur by lowering the instruction power.

Next, after the elapse of the initial designated power holding time T ₂ ,
Similar to the conventional control, control is performed in accordance with the output voltage-instruction power table of FIG. 7, but smooth control is performed so as not to suddenly decrease from the initial instruction power of 75 W. Significantly or shorten the early life deterioration of the discharge lamp 6 The initial indication power holding time T ₂ is also too long, set as short as possible to or can no longer satisfy the flash standards. For example, as an example, T ₂ =
Set to about 60 ms.

As described above, according to the present embodiment, the DC / DC converter 3 for boosting the DC voltage from the battery 2 and the four switching elements 71, 72, 73, 7
4, a polarity switch circuit 7 for converting a DC voltage into an AC voltage by a full bridge, and a discharge lamp 6 connected to a full bridge output of the polarity switch circuit 7.
And a discharge lamp starting means 5 for starting the discharge lamp 6 by applying a high voltage to the discharge lamp 6 and a voltage and a current applied to the polarity switching circuit 7 to perform constant power control to a target power. The power control means 8 which feeds back to the DC / DC converter 3 and the voltage applied to the polarity changeover switch circuit 7 determine the start of the discharge lamp 6, and the time from the start is determined by the polarity changeover switch circuit 7. A lighting time timer 9 for transmitting power control means 8 is provided. The polarity switching switch circuit 7 keeps the polarity in one-way DC lighting for a certain period of time from the start by the signal of the lighting time timer 9 and AC lighting after a certain period of time. And the power control means 8 performs a power output by adding a constant power to a rated power for maintaining the lighting during a period in which the DC lighting holding time is further added with a certain time, so that the discharge is performed. 6 lighting state of the it is possible to prevent the lighting error immediately after the unstable start-up.

[0022]

As described above, the present invention provides a DC / DC converter for boosting a DC voltage, a polarity switching circuit for converting a DC voltage to an AC voltage, and applying a high voltage to the discharge lamp to control the discharge lamp. Starting means for starting, power control means for calculating power from the voltage and current applied to the polarity switch circuit and feeding back to the DC / DC converter so as to perform constant power control to a target power; A lighting time timer for transmitting the time from the polarity changeover switch circuit and the power control means, and the polarity changeover switch circuit by the signal of the lighting time timer keeps the polarity in one direction DC lighting for a certain period of time from the start, After a certain period of time, AC lighting is started, and the power control means adds a certain amount of power to the rated power for maintaining lighting during a period in which a certain amount of time is added to the DC lighting holding time. It was by a structure in which power is output, in which the lighting state of the discharge lamp can be achieved excellent discharge lamp lighting device causing no lighting error immediately unstable startup.

[Brief description of the drawings]

FIG. 1 is a block diagram of a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between polarity switching and command power control of the discharge lamp lighting device.

FIG. 3 is a block diagram of a conventional discharge lamp lighting device.

FIG. 4 is a diagram showing a relationship between polarity switching and command power control of the discharge lamp lighting device.

FIG. 5 is a diagram for explaining the operation of a switching element of the discharge lamp lighting device.

FIG. 6 is a diagram illustrating an operation of the discharge lamp lighting device when a lighting error occurs.

FIG. 7 is a diagram showing a V _DC -instruction power table of the discharge lamp lighting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Switch 2 Battery 3 DC / DC converter 6 Discharge lamp 7 Polarity switch circuit 8 Power control means 9 Lighting time timer

Claims (1)

[Claims] 1. A D for boosting a DC voltage from a battery
A C / DC converter, a polarity switch circuit for converting a DC voltage into an AC voltage by a full bridge composed of four switching elements, a discharge lamp connected to a full bridge output of the polarity switch circuit, Starting means for applying a high voltage to the lamp to start the discharge lamp, and calculating the power from the voltage and current applied to the polarity switch circuit and controlling the DC / DC so as to perform constant power control to the target power.
A power control unit that feeds back to the converter; and a lighting time timer that determines start-up of the discharge lamp based on a voltage applied to the polarity switch circuit, and transmits a time after the start to the polarity switch circuit and the power control unit. In response to the signal of the lighting time timer, the polarity changeover switch circuit keeps the polarity in one-way DC lighting for a certain period of time from the start, starts AC lighting after a certain period of time, and the power control means holds the DC lighting. A discharge lamp lighting device configured to output a power by adding a constant power to a rated power to maintain lighting during a period in which a certain time is added to the time.