JP2000215991A - Rectangular wave lighting device for disharge lamp, and rectangular wave lighting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small and highly efficient lighting device where heat loss due to on-resistance of a full bridge inverter is greatly reduced, by setting first and second switch means in a cut-off state during a starting period, and releasing first and fourth switching elements from a lamp starting circuit system. SOLUTION: Heat loss of a full bridge inverter 3 is provided using a timer means 20 effectively. Output of the timer means 20 is first supplied to switch means 16, 17, and SW1 and SW2 are cut off during a starting period. Second, during the starting period added with a delay time, generation from a pulse generating circuit is stopped to hold a Low level, switching elements Q2, Q3 are in a conductive state, and switching elements Q1, Q4 are in a cut-off state. Thus, high voltage is not impressed onto all power MOSFETs of switching elements Q1-Q4 even during starting of the lamp. After a prescribed time, rectangular wave lighting is provided. Therefore, elements that have low pressure resistance and low heat loss can be used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectangular wave lighting device and a rectangular wave lighting method for a discharge lamp such as a metal halide lamp, and provides a small and highly efficient lighting device by greatly reducing the heat loss of a full-bridge inverter. In addition, it relates to the improvement of the lighting performance of the lamp.

[0002]

2. Description of the Related Art As a lighting device for a discharge lamp such as a metal halide lamp by AC lighting, a rectangular wave of a low frequency is usually employed in order to prevent an acoustic resonance phenomenon. FIG. 4 is a circuit diagram showing a conventional rectangular wave lighting device for lighting such a discharge lamp.

Here, the basic configuration of the lighting device is to convert the chopper output of the down converter (2) having a current limiting or constant power control function into a rectangular wave current by a full bridge inverter (3) to stably light the discharge lamp. is there.

[0004] For lighting this kind of lamp, first, a high voltage pulse is supplied by an igniter (4) to break down between the electrodes of the bulb and start discharging. Following breakdown, a transition is made to arc discharge via a glow discharge stage. The sustaining voltage required for sustaining the discharge is supplied from the DC power supply (1) (usually 200 to 400 V).

[0005] The DC power supply (1) is supplied to a down converter (2). The down converter is a kind of DC-DC converter, and a step-down type chopper method is typically used in order to control a transition from a high discharge sustaining voltage at the time of starting a lamp to a low arc discharge voltage.

This circuit detects an output voltage and an output current with a voltage detection circuit (7) and a current detection circuit (6), respectively, in order to supply a constant power after the lamp is stably turned on, and an arithmetic circuit (8) And feeds back to the downconverter via the pulse width modulation circuit (9), and the switching element Qd (11) controls the pulse width of the downconverter (2). This output voltage corresponds to a lamp voltage represented by DC.

[0007] The DC output of the downconverter is provided with a full-bridge inverter of switching elements Q1 (23), Q2 (24), Q3 (25), and Q4 (26) on the load side to provide a full-bridge drive circuit (1).
0) through the drive signal from the pulse generation circuit (21),
The switching elements Q2, Q3 and Q1, Q4 are alternately turned on and off alternately, and the lamp is turned on in a rectangular wave AC. The frequency of the square wave is to prevent the acoustic resonance phenomenon,
Usually, 50 to 500 Hz is adopted.

[0008] The rectangular wave lighting device of a discharge lamp lights a rectangular wave at a constant frequency in a normal lighting state, but for a few seconds immediately after the lamp is started (referred to as Ts, typically 0.5).
(~ 3 seconds), it is common to release the rectangular wave and perform DC lighting to minimize starting errors.

For example, the switching elements Q2 (24) and Q3 (25) of a full-bridge inverter are turned on, and Q1 (23) and Q4 (26) are held off. Therefore, during the period before the transition to the arc discharge at the time of starting the lamp, a high potential of the discharge maintaining voltage is applied between the drain and source of the switching elements Q1 (23) and Q4 (26) in the cutoff state.

In recent years, power MOSFETs that require a small amount of drive power for full-bridge inverters are generally used. Power MOSFET drain-source voltage V _DSS
The rating of the voltage applied when starting the discharge lamp is 200 to 400
In consideration of V, a high withstand voltage of 400 V or more is applied.

However, since the on-resistance of the high-voltage power MOSFET is high, the heat loss of the full-bridge inverter is large, and a large heat sink is required for air cooling, which contributes to an increase in the size of the lighting device.

[0012]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a compact and highly efficient lighting device which greatly reduces heat loss due to the on-resistance of a full-bridge inverter, and to improve the lighting performance of a lamp. Aim.

[0013]

According to the present invention, when the lamp is operated stably, the output voltage becomes low (for example, 50 to 100 V) and the power MO becomes low.
Attention is paid to the fact to become a drain-to-source voltage is also equally low voltage applied between the SFET, lamp and a circuit such that the voltage high specific is not applied between the drain and the source at the time of start-up, the drain-source voltage V _DSS rating Can use a power MOSFET as low as about 200V. The specific configuration is as follows.

According to a first aspect of the present invention, there is provided a rectangular lamp lighting device for a discharge lamp, comprising: a DC power source; a down converter for controlling power of the discharge lamp; and an output of the down converter. A smoothing capacitor (14), a full-bridge inverter (3) that converts the output of the downconverter (2) into a square-wave current, and a full-bridge drive circuit ( 10) and a rectangular wave lighting device of a discharge lamp including a pulse generation circuit (21) for sending a pulse signal to a full bridge drive circuit (10),
The full-bridge inverter (3) is a first switch means (16)
And a series circuit composed of first and third switching elements (23) and (25), and a series circuit composed of second and fourth switching elements (24) and (26) including second switch means (17). A discharge lamp (5) is connected between the connection point of the first and third switching elements and the connection point of the second and fourth switching elements via an igniter (4). And the first and fourth switching elements and the second and third switching elements.
The switching elements are driven by a full-bridge drive circuit (10) alternately to turn on and off, and during a predetermined starting period immediately after the lamp is started, the full-bridge drive circuit is released from reset and the second and third switching elements are turned on. Condition, first
And a timer means (20) for fixing the fourth switching element to a cut-off state, wherein the first and second switch means (16) and (17) are turned off during the start-up period.
And the fourth switching elements (23) and (26) are released from the lamp starting circuit system.

The rectangular wave lighting device for a discharge lamp according to the present invention also emits a rectangular wave at a constant frequency in a normal lighting state similarly to the conventional lighting device. In order to minimize it, the rectangular wave is released and DC lighting is performed.

For example, the switching elements Q2 and Q3 of the full-bridge inverter are turned on, and the switching elements Q1 and Q4 are held off. In the case of the prior art, a high potential of the discharge sustaining voltage is applied between the drain and the source of Q1 and Q4 in the cut-off state until the transition to the arc discharge at the time of starting the lamp. Since the switching elements Q1 and Q4 are opened from the full bridge circuit by the switching means, no high voltage is applied.

After the start-up period Ts, the switching elements Q1 and Q4 are connected again to the full bridge circuit, and the operation shifts from DC lighting to regular rectangular wave lighting. Starting period Ts
If the lamp shifts to arc discharge within the period and the lamp is turned on normally, the voltage applied to all the elements Q1 to Q4 is a low voltage of 200 V or less.

Therefore, the full-bridge inverter 4
The drain-source voltage of the power MOSFET as a switching element can be a low-rated one (for example, a 200 V type).

As a result, since a power MOSFET having a low on-resistance can be used, the loss of the full-bridge inverter can be minimized. Further, since heat generation is small, the heat sink can be downsized to provide a compact lighting device.

As the timer means (20), any means other than a timer may be used as long as it can generate an appropriate timing. For example, a control circuit such as a microcomputer or a logic may be used.

According to a second aspect of the present invention, there is provided the rectangular wave lighting device for a discharge lamp according to the first aspect, wherein the setting of the starting period and the control of the opening and closing of the first and second switch means (16) and (17) are performed. It is characterized in that the same timer means (20) is also used.

In this case, the timer means (20) provided for providing the starting period is replaced with the switch means (16) and (17).
Therefore, the number of components can be reduced and a simple circuit can be realized.

According to a third aspect of the present invention, there is provided a rectangular wave lighting device for a discharge lamp according to the first or second aspect, wherein the reset of the full-bridge driving circuit is canceled after a predetermined delay time has elapsed after the starting period has ended. (22).

According to this, it is possible to effectively prevent the operation of the full bridge from being started at the moment when the switch means is turned on, the output of the full bridge from being cut off, and the lamp from being turned off.

According to a fourth aspect of the present invention, there is provided a rectangular wave lighting device for a discharge lamp according to the first, second, or third aspects.
The smoothing capacitor (14) is supported via the first or second switch means, and during the start-up period, the down converter is used.
It is characterized by being released from (2).

According to this, it is possible to make the smoothing capacitor (14) not connected to the down-converter output during the lamp starting period Ts without increasing the number of switch means.

According to a fifth aspect of the present invention, there is provided a rectangular wave lighting device for a discharge lamp according to any one of the first, second, third, and fourth devices, in which the lamp is not turned on within a starting period. A non-lighting detection means (27) for stopping the signal of (1).

According to a sixth aspect of the present invention, there is provided a rectangular wave lighting device for a discharge lamp, wherein the output of the non-lighting detecting means (27) stops the switching of the pulse width modulation circuit (9).

According to these, if the lamp does not light during the starting period, this is detected, the pulse width modulation circuit (9) is shut down, and the switching of the down converter (2) is stopped. Can be.

According to a seventh aspect of the present invention, there is provided a method for lighting a rectangular wave of a discharge lamp, comprising the steps of: providing a DC power supply and a full-bridge inverter having two sets of switching elements driven to be turned on and off alternately; A rectangular wave lighting method of a discharge lamp in which a discharge lamp is lit by a current, wherein during a predetermined starting period immediately after the discharge lamp is lit, one set of switching elements of a full-bridge inverter (3) is turned on for DC lighting. And the other set of switching elements is fixed in the cut-off state and released from the lamp starting circuit system.After the starting period, the set of switching elements fixed in the cut-off state is connected to the lamp starting circuit system, and the The bridge drive circuit is released from reset and shifts to rectangular wave lighting.

According to an eighth aspect of the present invention, there is provided a method for lighting a rectangular wave of a discharge lamp, wherein a set of switching elements fixed in a cut-off state after a lapse of a starting period is connected to a lamp starting circuit system. It is characterized in that the reset of the full bridge drive circuit is released after the delay time has elapsed.

In the method of lighting a rectangular wave of a discharge lamp according to the present invention, a rectangular wave is lit at a constant frequency in a normal lighting state, and the rectangular wave is turned on in a starting period Ts immediately after the lamp is started in order to minimize starting mistakes. Release and perform DC lighting.

During the start-up period Ts, the switching elements Q1 and Q4, which are cut off, are released from the full bridge circuit by the switching means, so that no high voltage is applied. Therefore, the drain-source voltage of the power MOSFET, which is the switching element of the full-bridge inverter, can be low in rating, and a power MOSFET with low on-resistance can be used, so that the loss can be reduced.

If the full-bridge driving circuit is reset after the delay time has elapsed, the full-bridge operation starts at the moment when the switch is turned on, the full-bridge output is cut off, and the lamp is turned off. This can be effectively prevented.

[0035]

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

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing one embodiment of a rectangular wave lighting device for a discharge lamp according to the present invention.

As the discharge lamp (5), for example, 150
A W, 75V AC lighting metal halide lamp was used.

The DC power supply (1) has an output open-circuit voltage (OCV) higher than the discharge sustaining voltage required before the lamp breaks down.
Is required, and usually 200 to 400 V is applied.

The DC power supply (1) is supplied to the down converter (2). The down converter (2) is a switching element (1
It consists of 1), a diode (12) and a choke coil (13) to form a typical step-down chopper circuit of a switching power supply. Choke coil is 0.39mH as an example
It is. The voltage detection circuit (7) that detects the output voltage and the current detection circuit that detects the output current are provided at the output of the downconverter.
(6), and the detected voltage and current are calculated by the arithmetic circuit
It is input to (8) and fed back to the switching element (11) via the pulse width modulation circuit (9).

The down converter (2) has a high frequency (several tens of KHz
(Several hundred KHz), and in order to be able to supply constant power after stable lighting of the lamp, the detected output voltage and output current are calculated and the pulse of the down converter (2) is calculated by the pulse width modulation circuit (9). Operate to control the width. The voltage detection circuit (7) is simply a resistor R2 (28), R
The voltage is divided and output according to 3 (29). For the current detection circuit (6), a low resistance Rl of, for example, 1Ω or less is generally used.

A smoothing capacitor (14) is provided between the output terminal (positive electrode side) of the choke coil (13) of the down converter and the reference potential.
Is connected. This is to reduce the risk of arc instability due to acoustic resonance of the lamp by suppressing the ripple component that occurs because the downconverter (2) switches at high frequency (several tens to several hundreds of kHz). is there. Typically, the ripple content is less than 5%, with 0.1 μF to 10 μF being commonly used.

The DC output (potential is equivalent to the lamp voltage) of the down converter is applied to the switching element Q1 (2
3), Q2 (24), Q3 (25), and Q4 (26) are supplied to a full-bridge inverter (3). The output terminal (positive electrode side) of the choke coil of the down converter is firstly connected to the drain of Q1 and secondly to the drain of Q2 via SWl of the switch means (16).

The reference potential side of the down converter is connected to the sources of Q3 and Q4 via a current detection circuit. One between the output of the choke coil and the reference potential is the Q1 source.
The drain of Q3 is connected to connect a SW1-Q1-Q3 circuit, and the other is connected to the source of Q2 and the drain of Q4 via SW2 to form a Q2-SW2-Q4 circuit.

The output of the full-bridge inverter (3), ie, Q
A discharge ramp (5) is connected between the sources of 1 and Q2 via an igniter. A signal from the pulse generation circuit (21) is supplied to each of the gates Q1 to Q4 via the full bridge drive circuit (10). Full bridge drive circuit is an inverted driver
(35), (36) and non-inverting drivers (37), (38) are Q
3, connected to the gates of Q2, Q1, and Q4.

Thus, when the lamp is stably operated, Q2 and Q3
And Q1 and Q4 are alternately turned on and off alternately, and the lamp is turned on by rectangular wave AC. Usually, a frequency of 50 to 500 Hz is adopted as the frequency of the pulse generation circuit.

A bypass capacitor (15) is inserted between the output of the full-bridge inverter (3) and the input of the igniter (4). This serves as a capacitor that suppresses the component that the high voltage of the igniter returns via the lamp, and prevents the switching element from being damaged and destroyed.

To turn on the discharge lamp (5), first, a high voltage pulse is supplied by the igniter (4) to break down between the electrodes of the bulb and start discharging. The high-voltage pulse required for breakdown is typically a single pulse of several KV to 30 kV. Following the breakdown of the lamp, the lamp enters a glow discharge phase (the glow voltage is almost constant and is usually around 200 V) and transitions to arc discharge.

The rectangular wave lighting device for a discharge lamp according to the present invention has a constant frequency in a normal lighting state, but minimizes starting mistakes for a few seconds (Ts, typically 0.5 to 3 seconds) immediately after starting the lamp. In order to change the frequency, the rectangular wave is released and DC lighting is performed. This start period is generated by the timer means (20).

The present invention is to effectively utilize the timer means (20) to reduce the heat loss of the full-bridge inverter (20) which is another object. Because of this date, the output of the timer means is firstly switched by a switch means (1
6) and (17), and SWl and SW2 are cut off during the starting period Ts.

Secondly, the pulse signal is supplied to the pulse generating circuit (21) via the delay circuit (22), and a period in which a delay time (referred to as Td, for example, about 100 ms) is added to the starting period Ts is as follows. Stop the oscillation of the pulse generation circuit and keep it at the low level.
As a result, the switching element Q during the period of (Ts + Td)
2 and Q3 are made conductive, and the switching elements Q1 and Q4 are kept cut off. As a result, all power MOs of Q1 to Q4
No high voltage is applied to the SFET even when the lamp is started.

After the period Ts, SWl (16) and SW2 (17) become conductive,
The switching elements Q1 and Q4 are connected to the full bridge circuit, and after the elapse of the delay time Td, the pulse generation circuit (21) operates again to shift to regular rectangular wave lighting. Here, the function of the delay circuit (22) is to prevent the full bridge operation from starting at the moment when SW1 (16) and SW2 (17) are turned on, thereby preventing the full bridge output from being shut off and the lamp from being turned off. That's why.

Third, the output of the timer means is input to the non-lighting detection circuit (27). This is to shut down the pulse width modulation circuit (9) and stop the switching of the down converter (2) when the discharge lamp (5) does not reach the arc discharge during the period of Ts and fails to light. .

Thus, when the lamp is not lit, the starting period T
After s, the high voltage of the DC power supply is prevented from being applied between the drain and the source of Q1 to Q4.

FIG. 2 shows the starting timing of the present invention. Here, (a) is the output of the timer means, which is at the low level during the starting period Ts. (b) is a delay circuit output,
The output of the timer means is delayed by the delay time Td.
(c) is an output of the non-lighting detection circuit, which becomes low level when the lamp is normally lit during the Ts period, and becomes high level after the Ts period when the lamp is not lit.

The non-lighting detection circuit (27) will be described by taking a lamp of 150 W and a lamp voltage range of 50 to 100 V as an example. In the case of such a lamp, for example, the non-lighting determination level is set to 120V. Resistor connected to downconverter output (30)
The voltage is divided by (31) and input to the non-inverting input of the comparator (32). For example, 5 V is connected to the inverting input side as a reference power supply (33). For example, if R4 = 240KΩ and R5 = 10KΩ, the comparator output becomes High level at the judgment level of about 120V or more, and after Ts, if the lamp is not lit, the AND element (34) will be at High level if it is High level. It is output and makes the pulse width modulation circuit shut down.

(D) shows the output timing of the full-bridge inverter. If the discharge lamp (5) lights up normally within the starting period Ts, the state shifts from DC to rectangular wave lighting after Ts + Td. When the lamp is not lit, the pulse width modulation circuit (9) is shut down after the elapse of the starting period Ts, and the output of the full-bridge inverter becomes a no-signal state.

Embodiment 2 FIG. 3 is a circuit diagram showing another embodiment of the rectangular wave lighting device according to the present invention.

Compared with the first embodiment, the smoothing capacitor (1
Only the connection method of 4) is different. Therefore, only the different part will be described, and the description of the circuit having the same operation as the first embodiment will be omitted.

The smoothing capacitor (14) is connected to the switch means SWl
It is connected between the output terminal (positive pole side) of the choke coil of the down converter (2) and the reference potential via (16). Therefore, the smoothing capacitor is not connected to the down-converter output during the starting period Ts at the time of starting the lamp.

In other words, the efficiency of the full-bridge inverter (3) can be improved and the connection switching of the smoothing capacitor (14) can be shared by the SWl (16) without increasing the number of switching means. This embodiment is based on the previously filed invention (Japanese Patent Application No.
The method for improving the lighting performance of a 0-290777 discharge lamp) is applied to the discharge lamp square wave lighting device of the present invention.

Thus, when starting the lamp, several hundreds
The feedback system of the down-converter can follow the sudden change of the voltage from the glow discharge region of V to the arc discharge of several tens of volts, and it can supply sufficient continuous glow power to achieve the quick transition to arc discharge. be able to. Glow power is 100-150W at 150V-300V as an example
Supply. After the elapse of the starting period Ts, SWl (16) is turned on, and the smoothing capacitor (14) is connected to the output of the down converter (2).

Immediately after the transition to the arc discharge, gas discharge is mainly performed, and the voltage is low and is about 10 to 20 V. If the mercury and halide metal working as plasma inside the discharge lamp are sufficiently vaporized, the voltage will reach the rated 75V and the rated 150W will be supplied. After the transition to arc discharge, the change is slow, for example
It takes about one minute to reach the rated voltage.

As described above, after the lamp is turned on, the down converter is switched at a high frequency (several tens KHz to several hundred KHz), thereby suppressing the ripple generated and reducing the risk of arc instability due to the acoustic resonance of the lamp. Need to be smoothed. Typically, the ripple content is 5% or less, and 0.1 to 10 μF is generally used for smoothing.

[Test] As an example, a rectangular wave lighting device of a discharge lamp of 50 W to 100 V and a constant power of 150 W was prototyped, and the efficiency was measured in the conventional example and the present embodiment, and the heat loss of the full-bridge inverter of the present embodiment was reduced. The effect was confirmed.

Table 1 shows the switching elements used in the full-bridge inverter.

[0066]

[Table 1]

[0067]

[Table 2] From Table 2, it can be seen that the improvement effect is particularly large when the output lamp voltage V _O is low. Therefore, it can be said that the effect is particularly large for a discharge lamp having a short arc length and a low lamp voltage.

[0068]

As described above, according to the present invention, a switching element of a full-bridge inverter uses a low withstand voltage element because a high voltage peculiar to a lamp is not supplied at the time of starting a lamp, that is, an element with extremely small heat loss. Can be
A highly efficient and compact rectangular wave lighting device can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit according to a first embodiment.

FIG. 2 is a diagram showing timing at the time of starting.

FIG. 3 is a diagram illustrating a circuit according to a second embodiment.

FIG. 4 is a diagram showing a circuit of a conventional lighting device.

[Explanation of symbols]

(1) DC power supply (2) Down converter (3) Full bridge inverter (4) Igniter (5) Discharge lamp (6) Current flow detection circuit (7) Voltage detection circuit (8) Arithmetic circuit (9) Pulse width modulation circuit (PWM) (10) Full bridge drive circuit (11) Down converter switching element (12) Diode (13) Choke coil (14) Smoothing capacitor (15) Bypass capacitor (16), (17) Switching means (20) Timer means (21) Pulse generation circuit (22) Delay circuit (23), (24), (25), (26) Switching element of full-bridge inverter (27) Non-lighting detection circuit (28), (29), ( 30), (31) Resistance (32) Comparator (33) Reference power supply (34) AND circuit (35), (36) Inverting driver (37), (38) Non-inverting driver

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K072 AA13 AC01 AC20 BA05 BB01 CA05 CA16 DA00 DD06 DE02 DE05 DE06 GA03 GB18 GC04 HA09 3K082 AA01 AA61 AA62 AA74 AA77 BA02 BA04 BA24 BA33 BC23 BD03 BD04 BD23 BD26 BD31 BE01 BE04 BE10 BE10 5H007 AA03 AA06 BB03 CA02 CB02 CB04 CB05 CC03 CC12 DB03 DC02 DC05 EA02 FA09 GA01

Claims (8)

[Claims] A down converter (2) for controlling power of a direct current power supply (1), a discharge lamp (5), a smoothing capacitor (14) for smoothing an output of the down converter, and a down converter (2). A full-bridge inverter (3) that converts the output to a square-wave current, a full-bridge drive circuit (10) that drives the switching elements of the full-bridge inverter (3), and a pulse that sends a pulse signal to the full-bridge drive circuit (10) A rectangular wave lighting device for a discharge lamp including a generating circuit (21), wherein a full-bridge inverter (3) includes a first switch means (16).
And a series circuit composed of first and third switching elements (23) and (25), and a series circuit composed of second and fourth switching elements (24) and (26) including second switch means (17). An igniter (4) between the connection point of the first and third switching elements and the connection point of the second and fourth switching elements.
And a discharge lamp (5) is connected thereto. The first and fourth switching elements and the second and third switching elements are driven by a full-bridge drive circuit (10) alternately to conduct and cut off. During a predetermined starting period immediately after starting the lamp, the full bridge drive circuit is reset and the second and third switching elements are released.
Timer means (20) for fixing (24) and (25) in a conductive state and first and fourth switching elements (23) and (26) in a cut-off state, wherein the starting period is the first and second switching elements. Switch means (16), (17)
Is turned off to release the first and fourth switching elements (23) and (26) from the lamp starting circuit system. 2. The same timer means is used for setting the starting period and controlling the opening and closing of the first and second switch means (16) and (17).
2. The rectangular wave lighting device for a discharge lamp according to claim 1, wherein the operation is performed also as (20). 3. A delay means (22) for releasing the reset of the full-bridge drive circuit after a predetermined delay time has elapsed after the start-up period has ended.
Or a rectangular wave lighting device for a discharge lamp according to claim 2. 4. The smoothing capacitor (14) is supported via first or second switch means, and is opened from the down converter (2) during a starting period. Claim 1, Claim 2 or Claim 3
A rectangular wave lighting device for a discharge lamp as described in the above. 5. A non-lighting detecting means (27) for stopping a signal to a full bridge inverter (3) when a lamp does not light up during a starting period. 5. A rectangular wave lighting device for a discharge lamp according to claim 3, wherein 6. The rectangular wave lighting device for a discharge lamp according to claim 5, wherein the output from the non-lighting detection means stops the switching of the pulse width modulation circuit. 7. A rectangular discharge lamp for lighting a discharge lamp with a rectangular wave current by a DC power supply (1) and a full-bridge inverter (3) having two sets of switching elements driven to be turned on and off alternately. In a wave lighting method, for a predetermined starting period immediately after the discharge lamp is turned on, one set of switching elements of the full-bridge inverter (3) is fixed in a conductive state in order to perform DC lighting, and the other set of switching elements is turned on. Fixed to the cut-off state and released from the lamp starting circuit system.After the starting period, connect the set of switching elements fixed to the cut-off state to the lamp starting circuit system. A method for lighting a rectangular wave of a discharge lamp. 8. A set of switching elements fixed to a cut-off state after a lapse of a starting period is connected to a lamp starting circuit system, and after a lapse of a predetermined delay time, a full-bridge driving circuit is released from reset and shifts to rectangular wave lighting. 8. The method for lighting a rectangular wave of a discharge lamp according to claim 7, wherein: