JP3188873B2 - Lighting device for discharge lamp - Google Patents

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 metal halide lamp, and more particularly to an improvement in the lighting performance of the lamp.

[0002]

2. Description of the Related Art FIG. 1 is a diagram showing typical discharge current and voltage characteristics of a discharge lamp such as a metal halide lamp.
FIG. 2 is a view showing a general lighting device of a discharge lamp.

[0003] Lighting of this type of lamp is first performed by an igniter.
By (4), a high voltage pulse is supplied to break down between the electrodes of the bulb and start the discharge. This corresponds to the region near OA in FIG.

The high voltage pulse required for breakdown is usually several kV or more. An unstable period that begins following the breakdown of the ramp (referred to as a primary takeover, typically lasting a few microseconds to a few tens of microseconds; FIG. 1B
Shown by dots. ), The lamp enters the glow discharge stage, and the glow voltage is substantially constant. The glow voltage varies depending on the characteristics of the lamp, but is usually about 150 to 200 V.

[0005] The discharge holding voltage required for maintaining the discharge is supplied from the DC power supply (1). Transition energy to the glow discharge is generated by the charging voltage stored in the capacitor (3), it is well known in the (1/2) CV ^2. Here, C indicates the capacity of the capacitor, and V indicates the charging voltage.

[0006] Sufficient energy is required to immediately shift to arc discharge (secondary takeover) after shifting to glow discharge. That is, as the electrodes are heated by the heat of the glow discharge and the thermionic current increases, the arc discharge can be started over the barrier from the glow to the arc.

In the prior art, the capacitor (3) plays a large role not only for lighting the lamp but also as a smoothing capacitor for reducing high-frequency ripple current after arc discharge. This is because the downconverter (2) has a high frequency (tens of KHz
This is a ripple component generated due to switching at several hundred KHz), because smoothing is required to reduce the risk of arc instability due to acoustic resonance of the lamp (5). Typically, the ripple content is 5% or less, and 0.1 μF to 10 μF is generally used for smoothing.

The down converter (2) is a high-frequency inverter. The down converter (2) converts the output voltage and the output current to (7),
Detected by (6), operated by arithmetic circuit (8), fed back to downconverter (2) via pulse width modulation circuit (9), and operated to control pulse width of downconverter (2) Let me.

The power supplied from the down converter (2) is mainly for power control for a slow lamp voltage change after the transition to the arc discharge, but the power is controlled so that an appropriate energy can be supplied even in the glow discharge stage. It is believed that the converter (2) can be controlled and can supply a glow current of typically several hundred mA.

However, since the capacity of the condenser (3) used for smoothing is large, the operation of the downconverter (2) cannot respond to the rapid operation from breakdown of the lamp (5) to arc discharge, and the glow discharge stage , Almost no continuous power can be supplied from the down converter (2) to the lamp (5). In other words, the current from the downconverter (2) is temporarily charged in the capacitor (3), so that the current cannot be immediately supplied to the lamp (5).

In practice, the charging voltage of the capacitor (3) shifts to arc discharge by the energy discharged to the lamp. This energy is instantaneously high, but not continuous, and thus often fails the arcing, gradually heating the electrode while reciprocating between breakdown and the area of glow and secondary takeover, and reaches the arcing.

The number of reciprocations depends on the performance of the lamp itself. That is, in FIG. 1, points B, D, E
Lamps with high voltage levels at points F and F have poor lighting properties and reciprocate many times. Each time the lamp reciprocates, a high-voltage pulse is supplied between the electrodes of the lamp, and the inner wall of the lamp is covered with tungsten as an electrode material by sputtering, and the lumen output is reduced. Even if the charging energy is increased by unnecessarily increasing the capacity of the capacitor (3), the lighting performance of the lamp hardly changes.

[0013]

SUMMARY OF THE INVENTION Accordingly, there is provided a lighting device capable of improving the lighting performance of a lamp and enabling a quick transition from breakdown to glow discharge and further to arc discharge.
The challenge is to improve the life span of the luminous flux maintenance characteristics by minimizing the spatter.

[0014]

According to a first aspect of the present invention, there is provided a lighting device for a discharge lamp, which is required for transition from a glow discharge stage to an arc discharge.
Stored in the capacitor as energy supplied to the
A lighting device for a discharge lamp that does not depend on the charge
DC power supply (1), down converter (2) for controlling power of discharge lamp (5), capacitor circuit (10), igniter
(4), the equivalent capacity of the capacitor circuit (10) can be changed, and the equivalent capacity of the capacitor circuit (10)
At the start of lighting of (5), the discharge lamp (5) has a small capacity necessary and sufficient to generate the energy necessary for shifting from breakdown by the igniter (4) to glow discharge.
Is set to be changed to a large capacity necessary for reducing the high-frequency ripple component of the downconverter (2) after the transition from the glow discharge to the arc discharge.

The energy supplied to the lamp required for the quick transition to the arc in the glow discharge stage is downconverted.
It depends on the power control by (2). For this reason, at startup, a capacitor circuit should be used so as not to hinder the response of power control.
Minimize the equivalent capacitance of (10) and downconverter
It shall be the minimum necessary for the closed loop stability of (2). Also the first
The value is set to the minimum necessary for maintaining the glow discharge from the next takeover.

After the shift to the arc discharge, the equivalent capacitance of the capacitor circuit (10) is increased to effectively work as a smoothing capacitor, and the high frequency ripple current is reduced.

The term "after the transition to the arc discharge" as used herein may be literally after the transition to the arc discharge, and is not limited to simultaneous with or immediately after the transition to the arc discharge. Therefore, a case where the equivalent capacity is changed after a lapse of a predetermined time (for example, several seconds) from the shift is naturally included in the present invention. This is the same in the following inventions.

The lighting device of discharge lamp of claim 2, the glow discharge
Supply to lamps required for transition from electric phase to arc discharge
Depends on the charge stored in the capacitor as energy
There is no discharge lamp lighting device, including a DC power supply (1),
Down converter (2) that controls the power of the discharge lamp (5)
, A capacitor circuit (10), and an igniter (4), the equivalent capacity of the capacitor circuit (10) can be changed, and the equivalent capacity of the capacitor circuit (10) is 100 pF at the start of lighting of the discharge lamp (5). After the discharge lamp (5) shifts from the glow discharge to the arc discharge, the discharge lamp (5) is set to 0.1 μF to 10 μF.
It is set to be changed to μF.

According to the present invention, in the device of the first aspect, a suitable range is specified as an equivalent capacitance of the capacitor circuit.

A lighting device for a discharge lamp according to a third aspect is the first aspect.
Alternatively, in the device according to claim 2, the capacitor circuit (10) has a capacity of 10
0pF to 0.1μF small capacitor (15) and 0.1μF to 10μF
The large capacity capacitor (14) is connected in parallel, and the large capacity capacitor (14) can be cut off from the circuit by the switching means. Before that, it is in a cut-off state.

According to the present invention, the equivalent capacitance of the capacitor circuit is changed to an appropriate capacitance at each time by connecting and disconnecting a large-capacity capacitor among the capacitors connected in parallel.

A lighting device for a discharge lamp according to a fourth aspect is the first aspect of the invention.
Or The apparatus of claim 2, wherein, the capacitor circuit (10)
Is a 0.1μF to 10μF large-capacity capacitor (14) and a small-capacity capacitor (15) connected in series.
The capacitance of (15) is selected so that the equivalent capacitance of the series circuit with the large-capacity capacitor (14) is 100 pF to 0.1 μF, and the small-capacity capacitor (15) can be short-circuited by switching means. , Characterized by being short-circuited after transition to arc discharge at the time of lamp lighting.

According to the present invention, the equivalent capacitance of the capacitor circuit is changed to an appropriate capacitance at each time by connecting and short-circuiting a small-capacity capacitor among the capacitors connected in series.

The lighting device of discharge lamp of claim 5, the glow discharge
Supply to lamps required for transition from electric phase to arc discharge
Depends on the charge stored in the capacitor as energy
There is no discharge lamp lighting device, including a DC power supply (1),
Down converter (2) that controls the power of the discharge lamp (5)
, A capacitor circuit (10), and an igniter (4) .The capacitor circuit has a capacitor (14) having a capacity of 0.1 μF to 10 μF and a resistor (17) connected in series, and the resistor (17) is a switching means. And the lamp is short-circuited after transition to arc discharge.

The present invention does not switch the equivalent capacitance of the capacitor circuit, but controls the charging current of the capacitor (14) by the resistance, and secures the current supply to the lamp until the transition to the arc discharge. At the same time, after the transition to the arc discharge, the resistor is short-circuited in order to effectively use the capacitor (14) for smoothing.

According to a sixth aspect of the present invention, there is provided the lighting device for a discharge lamp according to the third, fourth or fifth aspect, wherein the switching means includes a switch circuit (16) and a timer circuit (20) set for a predetermined time. It is characterized by the following.

According to the present invention, the connection, disconnection, and short-circuit of the capacitor or the connection and short-circuit of the resistor in each of the above-mentioned inventions are performed by a switch circuit (16) controlled by a timer. According to this, by setting the timer, it is possible to change the equivalent capacitance of the capacitor circuit or short-circuit the resistor with good timing after the transition to the arc discharge.

The lighting device of discharge lamp of claim 7, Gro
-The lamp required to transition from the discharge stage to arc discharge
It depends on the charge stored in the capacitor as the supplied energy.
Lighting device for a discharge lamp that does not
And a down converter that controls the power of the discharge lamp (5)
(2), a capacitor circuit (10), and an igniter (4)
The capacitor circuit is a capacitor with a capacitance of 0.1μF to 10μF (14)
And the thermistor (18) are connected in series.

The present invention is similar to the fifth embodiment in that the resistors are basically arranged in series and the charging current of the capacitor is controlled. The resistance value is reduced by temperature using a thermistor.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to preferred embodiments.

[Embodiment 1] FIG. 3 is a diagram showing this embodiment. The lamp (5) is, for example, a 150W, 75V metal halide lamp as an example. The DC power supply (1) needs an output open-circuit voltage (OCV) higher than the required sustaining voltage before the lamp breaks down, and usually 200 to 400V is appropriate.

The DC power supply (1) is supplied to the down converter (2). The down converter (2) is a switching element (1
1), diode (12), choke coil (13),
It forms a step-down chopper circuit of a typical switching power supply. Choke coil is 0.39 as an example
mH.

The output of the down converter (2) includes a voltage detection circuit (7) for detecting an output voltage and a current detection circuit (6) for detecting an output current. The detected voltages and currents are calculated by an arithmetic circuit (8). ) And through a pulse width modulation circuit (9),
It is fed back to the switching element (11).

The down converter (2) has a high frequency (several tens KHz
The switching is performed at several hundred KHz, and the output voltage and the output current detected are calculated and the pulse width is controlled by the pulse width modulation circuit (9) in order to supply a constant power after the lamp is stably operated.

The power supplied from the down converter (2) is mainly controlled by power after arc discharge, but the down converter (2) is controlled so that appropriate energy can be supplied even in the glow discharge stage. Is controlled to supply a glow current of typically several hundred mA.

If an arc discharge occurs, the lamp voltage becomes lower than the discharge maintaining voltage of the glow discharge. Therefore, a down converter that can control the output voltage to be lower than the voltage supplied from the DC power supply is suitable. The down-converter output whose output power is controlled is connected to a lamp (5) via an igniter (4). To turn on the lamp, first, a high voltage pulse is supplied by the igniter (4) to break down between the electrodes of the bulb and start discharging. In FIG. 1, it corresponds to the region near OA, and the high-voltage pulse required for breakdown is usually several kV.
It is a single pulse system of 3030 kV.

An unstable period that starts following the breakdown of the ramp (5) (point B in FIG. 1 and will be referred to as a primary takeover, typically lasting for a few microseconds and tens of microseconds) ), The lamp (5) enters the glow discharge stage (region D in FIG. 1), and the glow voltage is almost constant, usually about 200V.

The energy for glow discharge is the charge voltage stored in the discharge capacitor (15) (1/2) CV ²
It is represented by Where C is the capacitance of the capacitor (as an example
0.01 μF), and V indicates a charging voltage (300 V as an example). One example of discharge energy is (1/2) × 0.01 × 10 ⁻⁶ × 30
0 ² = 450 μJ.

Here, the capacity of the discharge capacitor (15) is low enough not to hinder the power response of the downconverter (2), and is not too low so as to quickly achieve glow discharge from the first takeover. To make a proper choice. Typically, 100 pF to 0.1 μF is appropriate.

The discharge capacitor (15) also functions as a so-called bypass capacitor that suppresses a component of the high voltage of the igniter returning via the lamp, and prevents the switching element from being damaged and destroyed.
Further, the capacitor (15) also functions as an integrating circuit for making the feedback loop of the downconverter (2) a stable system. Thereafter, sufficient energy is required to immediately shift to arc discharge (beyond the secondary takeover at point F in FIG. 1).

That is, as the electrodes are heated by the heat of the glow discharge and the thermionic current increases, the arc discharge can be started over the barrier from the glow to the arc. FIG.
Corresponds to the area of EFG. Continuous power is required to reach stable arc discharge quickly over this region, and a down converter with a quick response of power control
Can be supplied from (2). For this purpose, the smoothing capacitor (14) (0.1 to 10 μF) normally used for removing ripples is not connected.

As a result, the feedback system of the downconverter (2) can follow a rapid transient change in voltage from a glow discharge region of several hundred volts to an arc discharge of several tens of volts, and sufficient continuous glow power can be supplied. A quick transition to arc discharge can be achieved.

The glow power is, for example, 150 V to 30
Supply 100-150W at 0V. Immediately after the transition to arc discharge, gas discharge is the main, and the voltage is low, approximately 10 to 20V. If mercury and halide metal working as plasma inside the lamp (5) evaporate enough, the voltage will reach the rated 75V,
The rated 150W is supplied.

After the transition to the arc discharge, the change is slow and takes about one minute, for example, to reach the rated voltage. In FIG. 3, (1
4) is a smoothing capacitor for reducing high-frequency ripple current after arc discharge. This is a down converter
(2) is a problem of a ripple generated due to switching at a high frequency (several tens of KHz to several hundred KHz), and needs to be smoothed to reduce a risk of arc instability due to acoustic resonance of the lamp. Typically, the ripple content is 5% or less, and 0.1 to 10 μF is generally used for smoothing.

A switch circuit (16) disconnects the smoothing capacitor (14) from the down-converter output before arc discharge to maintain good lamp lighting, and connects to the down converter (2) after arc discharge. To remove ripples and perform stable operation without acoustic resonance.

The timer (20) is set to, for example, about 3 seconds, and the switch circuit (16) is shut off during the set time of the timer (20) from the start of the operation of the igniter (4), so that the rapid arc discharge of the lamp is performed. Achieve the transition to

Embodiment 2 The equivalent capacity of the capacitor circuit (10) is switched to a small capacity of 100 pF to 0.10 μF until the transition to arc discharge is achieved, and a large capacity of 0.1 to 10 μF after arc discharge. Can be considered other than the above.

FIG. 4 is a diagram showing the capacitor circuit of the present embodiment. The configuration other than the capacitor circuit (10) is the same as that of the first embodiment.
Is the same as Capacitor circuit (10) has a large capacity of 0.1μF
~ 10μF capacitor C ₁ (14) and small capacitor C
₂ ) The capacitor (15) is connected in series, and the capacitance of the capacitor (15) is 100 PF or less of the equivalent capacitance Cs of the series circuit with the capacitor (14).
0.1 μF was selected, and after the lamp was turned on, the capacitor (15) was short-circuited by the switch circuit (16).

Where Cs = (C ₁ × C ₂ ) / (C ₁ + C ₂ )
Becomes

In this embodiment, the same effects as in the first embodiment can be obtained.

Embodiment 3 Embodiments 1 and 2 above
Although the equivalent capacitance of the capacitor circuit is changed, the present embodiment and the fourth embodiment described below achieve the same object by controlling the charging current of the capacitor by using a resistor.

FIG. 5 is a diagram showing a capacitor circuit of this embodiment. Capacitor circuit is large capacity 0.1μF ~ 10μF
The resistor (17) is connected in series with the capacitor (14) of
Due to the time constant, the response speed of the down converter is increased in the glow discharge stage. In other words, by controlling the charging current of the capacitor, the current supplied from the down converter (2) to the lamp is ensured.

After the arc discharge, the resistor 17 is short-circuited to operate as a smoothing capacitor for removing ripples. In this embodiment, the short circuit of the resistor (17) is controlled by the timer (2
0), performed by the switch circuit (16).

The configuration other than the capacitor circuit (10) is the same as that of the first embodiment.
Is the same as

[Embodiment 4] FIG. 6 is a diagram showing a capacitor circuit of the present embodiment. The capacitor circuit (10) has a large capacity of 0.1 μF to 10 μF.
(14) is connected in series with a thermistor (18) having a negative characteristic, and the time constant of the thermistor (18) due to the initial resistance increases the response speed of the downconverter in the glow discharge stage. After the arc discharge, heat is generated by the high-frequency current flowing through the thermistor (18), the resistance of the thermistor (18) becomes low, and the capacitor (14) operates as a smoothing capacitor for removing ripples.

The structure other than the capacitor circuit (10) is the same as that of the first embodiment.

[0057]

As described above, according to the present invention, the transition from breakdown at the time of lamp operation to glow discharge and arc discharge can be improved and optimized, and the reciprocating operation of the lighting process can be minimized. It is possible to provide a lighting device in which blackening is reduced and a luminous flux maintenance ratio with respect to life is good.

[Brief description of the drawings]

FIG. 1 is a diagram showing typical discharge current and voltage characteristics of a discharge lamp such as a metal halide lamp.

FIG. 2 is a diagram showing a conventional discharge lamp lighting device.

FIG. 3 is a diagram showing a discharge lamp lighting device according to the first embodiment.

FIG. 4 is a diagram illustrating a capacitor circuit of the lighting device according to the second embodiment.

FIG. 5 is a diagram illustrating a capacitor circuit of a lighting device according to a third embodiment.

FIG. 6 is a diagram illustrating a capacitor circuit of a lighting device according to a fourth embodiment.

[Explanation of symbols]

 (1) DC power supply (2) Down converter (4) Igniter (5) Discharge lamp (6) Current detection circuit (7) Voltage detection circuit (8) Operation circuit (9) Pulse width modulation circuit (10) Capacitor circuit (11 ) Switching element (12) Diode (13) Choke coil (14) Large capacitor (smoothing capacitor) (15) Small capacitor (16) Switch circuit (17) Resistance (18) Thermistor (20) Timer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-234685 (JP, A) JP-A-10-241875 (JP, A) JP-A 8-213180 (JP, A) 26199 (JP, U) JP-A-2-14698 (JP, U) JP-A-4-99697 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) H05B 41/14-41 / 298

Claims (7)

(57) [Claims] 1. Transition from glow discharge to arc discharge
To supply energy to the lamp needed for the condenser
A lighting device for a discharge lamp that does not depend on the stored charge
Therefore, a DC power supply (1), a down converter (2) for controlling the power of the discharge lamp (5), a capacitor circuit (10), and an igniter
The equivalent capacity of the capacitor circuit (10) can be changed, and the equivalent capacity of the capacitor circuit (10) is changed from breakdown by the igniter (4) to glow discharge when the discharge lamp (5) starts lighting. The discharge lamp (5) reduces the high-frequency ripple component of the downconverter (2) after the discharge lamp (5) shifts from the glow discharge to the arc discharge. A lighting device for a discharge lamp, which is set so as to be changed to a large capacity necessary for the discharge lamp. 2. Transition from glow discharge stage to arc discharge
To supply energy to the lamp needed for the condenser
A lighting device for a discharge lamp that does not depend on the stored charge
Therefore, a DC power supply (1), a down converter (2) for controlling the power of the discharge lamp (5), a capacitor circuit (10), and an igniter
(4), the equivalent capacitance of the capacitor circuit (10) can be changed, and the equivalent capacitance of the capacitor circuit (10) is 100 pF to 0.1 μF at the start of lighting of the discharge lamp (5). 0.1μ after the lamp (5) transitions from glow discharge to arc discharge
A discharge lamp lighting device, which is set to be changed to F to 10 μF. The capacitor circuit (10) has a small capacitor (15) of 100pF to 0.1μF and a large capacitor (14) of 0.1μF to 10μF connected in parallel, and the large capacitor (14) is switched. Means, which can be disconnected from the circuit by the means, and become a connected state after the transition to the arc discharge at the time of lamp lighting, and is in a disconnected state before that. 3. The lighting device for a discharge lamp according to 2. 4. A capacitor circuit (10) includes a large capacity capacitor (14) and a small capacity capacitor (15) of 0.1 μF to 10 μF connected in series, and the capacity of the small capacity capacitor (15) is a large capacity capacitor. The equivalent capacitance of the series circuit with (14) is 100 pF to 0.1
μF, and the small-capacitance capacitor (15) can be short-circuited by switching means, and is short-circuited after transition to arc discharge at the time of lamp lighting. Claim 2
A lighting device for a discharge lamp as described in the above. 5. The transition from the glow discharge stage to the arc discharge.
To supply energy to the lamp needed for the condenser
A lighting device for a discharge lamp that does not depend on the stored charge
Therefore, a DC power supply (1), a down converter (2) for controlling the power of the discharge lamp (5), a capacitor circuit (10), and an igniter
(4), the capacitor circuit has a capacitor (14) and a resistor (17) having a capacity of 0.1 μF to 10 μF connected in series,
(17) The lighting device for a discharge lamp, wherein the lighting device can be short-circuited by the switching means and short-circuited after the lamp shifts to arc discharge. 6. A lighting device for a discharge lamp according to claim 3, wherein the switching means includes a switch circuit and a timer circuit set for a predetermined time. 7. Transition from glow discharge stage to arc discharge
To supply energy to the lamp needed for the condenser
A lighting device for a discharge lamp that does not depend on the stored charge
Therefore, a DC power supply (1), a down converter (2) for controlling the power of the discharge lamp (5), a capacitor circuit (10), and an igniter
A lighting device for a discharge lamp, comprising: (4) a capacitor circuit in which a capacitor (14) having a capacitance of 0.1 μF to 10 μF and a negative characteristic thermistor (18) are connected in series.