JPH10112396A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make possible utilization of only advantages of a current dimming system and a pulse dimming system by providing a dimming circuit operated by a current dimming system when a discharge lamp is lit in excess of a specified current value of a rated maximum current value or less and operated by a pulse dimming system when the discharge lamp is lit below a specified current value. SOLUTION: A lighting device employing a thermal cathode fluorescent tube 10 has a direct current power supply PS1 for device driving and a variable direct current power supply PS2 for dimming and is constituted by a circuit including a pulse dimming additional circuit, a tube current detection circuit, and a dimming signal inverting amplifier. The variable direct current power supply PS2 for dimming outputs 0V when dimming degree is set to the darkest and +5V when dimming degree is set to the brightest. When a dimming signal level is below a specified value by means of dimming operation, a pulse is generated by the pulse dimming additional circuit. At this time, a tube current is attenuated according to a pulse width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimming circuit for a backlight such as a large-screen liquid crystal display and a discharge lamp lighting device such as a hot cathode fluorescent tube used for other purposes.

[0002]

2. Description of the Related Art Conventionally, a hot cathode fluorescent tube as a discharge lamp has
Along with cold cathode fluorescent tubes and the like, they are used for backlight illumination of liquid crystal displays and light tables for film inspection.

The principle of light emission of a hot cathode fluorescent tube is as follows.
A voltage is applied to the filament electrode by a heater circuit to heat it. Then, thermoelectrons are emitted from the electron-emitting substance applied to the filament, and the temperature in the tube rises. With this temperature rise, the gas pressure of the mercury vapor sealed in the tube rises. At this time, due to the electric field applied to the tube, ionization of the mercury vapor gas near the filament progresses, and discharge in the tube (conduction state) is started. Due to this discharge, ultraviolet rays are emitted from the mercury vapor, and the ultraviolet rays excite phosphors coated in the tube to cause light emission.

As a method for changing the light quantity of the hot cathode fluorescent tube, a current dimming method and a pulse dimming method are known as shown in FIG. The "current dimming method" is a method of changing the input DC voltage or input current of an inverter circuit with a DC-DC converter or the like and changing the current of a fluorescent tube connected to the inverter transformer secondary side to perform dimming. (See, for example, JP-A-61-195599).

In the "pulse dimming method", the oscillation operation of the inverter circuit is forcibly turned ON / OFF, and the ON period and the O
This is a method of performing light control by changing the ratio of the FF period (this is referred to as “duty ratio”).

In this system, a fixed frequency PWM system in which the ratio of the ON period and the OFF period of the dimming pulse is changed according to the level of the dimming signal, and an ON period in which the ON period is fixed and the oscillation frequency is changed. And a frequency dimming (PFM) system in which dimming is performed by changing the duty ratio in the OFF period (for example, see Japanese Patent Application Laid-Open No. 5-198348).

[0007]

However, in the current dimming method, unnecessary radiation (noise) at the time of dimming is small, noise of components such as a transformer and a choke coil is small, and a tube current is detected. In many cases, feedback constant current control is performed. Therefore, there is an advantage that the tube current is stable against a change in temperature or a change with time, but there are the following problems.

That is, one of the problems is that the light control range is narrow. That is, as a property of the fluorescent tube, when the dimming is darkened and the tube current is reduced, a problem that the discharge becomes unstable and the light is cut off at a low temperature easily occurs.

Generally, the dimming range is 1 in the current dimming method.
The limit is about 00% to 50% (see FIG. 1B).

Another problem is that when the luminance is reduced by the dimming circuit, the input voltage of the inverter circuit decreases, the inverter output voltage decreases, the voltage applied to the tube decreases, and the tube current decreases. Is to decrease.

When the tube current is small, the luminance of the tube surface is called a thermometer effect on the high voltage input side and the low potential side of the tube due to the stray capacitance between the tube and surrounding metals such as a reflector. A luminance gradient occurs. In a backlight-equipped liquid crystal display screen, the so-called shading phenomenon in which the left and right luminances become non-uniform becomes a problem (see FIG. 2A).

In the pulse dimming method, since the luminance of the tube is determined by the duty ratio of the inverter circuit by forcibly turning on / off the inverter circuit, if the ratio of the ON period is reduced and the OFF period is lengthened, It has the advantage that light can be adjusted to a range where the luminance is dark (about 10% of the maximum luminance) while maintaining a state where the inclination of the tube luminance is small (FIG. 2B, FIG. 1).
(C)).

However, the pulse dimming method has the following problems. That is, one of the problems is ON / OFF for dimming.
Is a frequency in the audible frequency band of about several hundred Hz to 2 KHz, so that a groan sound is generated from components such as a transformer coil and the sound is harsh.

Further, the pulse dimming is performed by the O
N / OFF is repeated at the cycle of the burst pulse, and a large voltage is applied to the tube when the tube is turned on, that is, when the tube is turned on. In other words, a voltage having a large amplitude is always applied to the tube in a pulsed manner at the cycle of the burst pulse (see FIG. 3).

Accordingly, a large amount of high-frequency electromagnetic noise is radiated from the pipe and the wiring of the pipe, and noise is likely to occur in other electronic devices. In particular, since pulse dimming is performed even in a high power range and high luminance range, the influence of noise is great.

Furthermore, in the case of pulse dimming, constant current control for feeding back the tube current is not performed in many cases. Therefore, the change in the tube current due to the difference in temperature or the aging of the tube is large, and the luminance is greatly disturbed.

In view of the above problems, an object of the present invention is to provide a discharge lamp lighting device provided with a dimming circuit that can make use of only the advantages of the current dimming method and the pulse dimming method.

[0018]

To achieve the above object, according to the present invention, in a discharge lamp lighting device having a dimming circuit, the dimming circuit is configured so that the discharge lamp is equal to or less than a rated maximum current value. The present invention proposes a discharge lamp lighting device that operates in a current dimming mode when the lamp is lit above a predetermined current value, and operates in a pulse dimming mode when the discharge lamp is lit below the predetermined current value.

According to the discharge lamp lighting device, when the discharge lamp is lit with a predetermined current value equal to or less than the rated maximum current value, for example, about 50% of the rated maximum current value, the dimming of the discharge lamp is performed by the current control. Dimming is performed by the constant current control by operating in the light system, and when the dimming degree is set so that the discharge lamp luminance becomes dark, the dimming is performed by operating in the pulse dimming system.

According to a second aspect of the present invention, in the discharge lamp lighting device according to the first aspect, the dimming circuit performs current dimming by applying a DC signal obtained by amplifying the dimming signal to a constant current control loop. A discharge lamp lighting device which performs pulse dimming by applying a pulse current or a voltage to the constant current control loop is proposed.

According to the discharge lamp lighting device, when the discharge lamp is lit beyond a predetermined current value equal to or less than the rated maximum current value, the DC signal obtained by amplifying the dimming signal by the dimming circuit is supplied to the constant current control loop. When the discharge lamp is lit at a predetermined current value or less, the pulse current or the voltage is applied to the constant current control loop by the light control circuit to perform the pulse light control.

According to a third aspect of the present invention, in the discharge lamp lighting device according to the second aspect, the pulse voltage waveform applied to the constant current control loop for pulse dimming is adjusted to a set input dimming signal level. Accordingly, a discharge lamp lighting device having a pulse width modulation that outputs a pulse having a duty ratio of 0 to about 50% or a waveform in which the pulse width modulation and the pulse amplitude modulation are used in combination is proposed.

According to the discharge lamp lighting device, when pulse dimming is performed by the dimming circuit, an input dimming signal level is used as a pulse voltage waveform applied to the constant current control loop for pulse dimming. , A pulse width modulation waveform that outputs a pulse having a duty ratio of 0 to about 50%, or a waveform in which the pulse width modulation is combined with the pulse amplitude modulation is used.

According to a fourth aspect of the present invention, there is provided a discharge lamp lighting device according to any one of the first to third aspects, wherein the discharge lamp is a hot cathode fluorescent tube.

According to the discharge lamp lighting device, a hot cathode fluorescent tube is used as the discharge lamp.

According to a fifth aspect of the present invention, there is provided a discharge lamp lighting device according to any one of the first to third aspects, wherein the discharge lamp is a cold cathode fluorescent tube.

According to the discharge lamp lighting device, a cold cathode fluorescent tube is used as the discharge lamp.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is an electric circuit diagram showing the first embodiment of the present invention, in which a hot cathode fluorescent tube is used as a discharge lamp. In the figure, reference numeral 10 denotes a hot cathode fluorescent tube (hereinafter, simply referred to as “tube”). Usually, a hot cathode fluorescent tube lighting device is provided with a so-called sequence circuit such as a heater circuit for heating filaments provided at both ends inside the tube and a timer circuit for stopping the operation of the heater circuit for a predetermined time. However, these are not shown because they are well known to those skilled in the art and need not be described in the present application.

PS1 is a DC power supply for driving the device. P
S2 is a variable DC power supply for dimming, and outputs 0 V when the dimming degree is set to the darkest and +5 V when the dimming degree is set to the brightest. IC1 is a PWM control circuit composed of an integrated circuit. This IC1, transistor Q
1, a diode D1, an inductance L1 and a capacitor C2 constitute a step-down DC-DC converter 20. That is, the DC-DC converter 20 functions to reduce the driving DC power supply voltage value to a predetermined value.

Inductance L2, resistors R13, R1
4, an inverter circuit 30 is constituted by the transistors Q2 and Q3, the capacitor Cr and the transformer T1.

The capacitor Cb is a current limiting element for preventing a current exceeding a predetermined value from flowing through the tube 10, that is, a ballast capacitor. Diodes D2, D3, resistor R1
5, R16 and capacitor C3 detect the tube current and
A tube current detection circuit 80 for converting a feedback voltage to the C-DC converter 20 is configured.

The IC2 and the resistors R1 to R4 are a dimming signal inverting amplifier 40 for inverting and amplifying the dimming signal. IC
3, a capacitor C4, and resistors R17 to R21 form a rectangular wave (pulse) oscillation circuit 50. The integrating circuit 60 integrates the resistor R22 and the capacitor C5 into a sawtooth wave by integrating the pulse wave. The IC 4 and the resistors R25 and R26 constitute a PWM circuit 70. This will be described later. In addition, IC
3. The IC4 uses a so-called open collector output comparator.

The DC-DC converter 20 has a drive power supply P
A voltage is supplied from S1 to the second terminal of IC1 ((2) of IC1 in FIG. 4), and when the switch including the transistor Q1 is in the ON state, the supply voltage is half-wave rectified by the diode D1, and is rectified by the inductance L1. The AC component is cut and smoothed by the capacitor C2, and the output is supplied to the inverter circuit 30.

The inverter circuit 30 converts the DC voltage supplied from the DC-DC converter 20 into transistors Q2 and Q2.
The AC voltage is converted by the oscillator Q3, the voltage is increased by the transformer T1, and the tube 10 is lit by the high AC voltage. The current (tube current) flowing through the tube 10 due to the discharge is detected by the tube current detection circuit 80 described above, and the PW in the DC-DC converter 20 is detected.
It is fed back to IC1 which is an M control circuit.
Control is performed so that a constant current flows through the tube 10.

The rectangular wave oscillation circuit IC3 generally oscillates a rectangular wave (pulse wave) at a frequency at which pulse dimming is performed.
This oscillation frequency is generally set to about 100 Hz to 1 KHz so that flicker of the tube 10 is not noticeable. The square wave output from the comparator IC3 is R2
2 and a capacitor C5 to form a sawtooth wave, a DC component is cut by a capacitor C6, and resistors R23 and R24
And then input to the minus input side of the IC 4 of the PWM circuit.

The dimming signal from the dimming DC power supply PS2 is
The voltage is input to the minus input side of the dimming amplifier IC2 in the range of 0 to + 5V. The dimming signal is inverted by IC2,
Through the resistor R7, the aforementioned PWM control circuit (IC1)
Applied to the feedback loop.

The lighting device operates under constant current control.
When the dimming signal level is at the maximum, the output voltage of the IC 2 becomes the minimum (about 0.6 V). At this time, since a current flows from the feedback loop to the IC2 side through R7, the voltage on the feedback loop side drops, and conversely, the inverter circuit operates in a direction to increase the tube current, and the brightness of the tube 10 becomes maximum. At this time, the output voltage of the dimming amplifier IC2 is lower than the DC level of the sawtooth wave biased by the resistors R23 and R24. Operates in dimming mode.

When the dimming degree is reduced, the dimming amplifier I
Since the output voltage of C2 increases and acts to lower the feedback voltage, the tube current decreases and the brightness of the tube 10 decreases. At this time, if the output voltage level of IC2 applied to the plus side input of IC4 through resistor R25 becomes higher than the level of the sawtooth voltage biased with a DC bias preset by the values of R23 and R24, IC
4 is at a high level and outputs a pulse waveform voltage. The pulse voltage becomes a PWM output having a larger pulse width as the output voltage level of the IC 2 is higher, that is, as the dimming signal input voltage level is lower.

Since the open collector load resistor R26 of the IC 4 is connected to the output of the IC 2 (before the resistor R25), the PWM output voltage changes in pulse width and pulse amplitude. That is, pulse amplitude modulation (PAM) is performed simultaneously. PWM (pulse width modulation)
When PAM (Pulse Amplitude Modulation) is used together, the switching from current dimming to pulse dimming is performed smoothly rather than steeply.

That is, the pulse voltage having a relatively narrow pulse width and a small amplitude outputted from the comparator IC4 is cut off the DC component by the capacitor C7, the amplitude is adjusted by the resistor R5, and the error amplifier (the capacitor C1 and the resistor C1) of the PWM control circuit is adjusted. R8), and is mixed with the dimmed feedback signal coming from R6.

The pulse voltage from R5 is slightly integrated by the feedback capacitor C1 of the error amplifier, and its waveform is dull. As a result, the current dimming waveform so far becomes a waveform that has been subjected to amplitude modulation at the frequency of pulse dimming ((3) in FIG. 5D).

When the dimming is further reduced, a current waveform similar to the pulse dimming operation as shown in (4) of FIG. 5D is obtained.
When the dimming degree is set to be the darkest, that is, when the dimming signal level is the minimum, the output voltage of the dimmer amplifier IC2 becomes the maximum (+5 V), the current flowing from the IC2 side to R7 becomes the maximum, and the tube brightness is increased. Is the darkest.

At this time, the output voltage level of IC2 applied to the plus input side of IC4 through R25 becomes maximum,
The IC 4 outputs a pulse waveform having a duty of about 50%, which is compared with a sawtooth voltage to which a DC bias has been previously set in R23 and R24 ((5) in FIG. 5C). The output of IC4 is applied to the feedback loop through C7 and R5, and the inverter circuit operates almost in the same manner as the pulse dimming method. At this time, ON
The tube brightness is minimized by pulse dimming having a short period and a long OFF period ((5) in FIG. 5D).

As described above, in the present embodiment, the dimming of the discharge lamp is operated by the current dimming method at the dimming degree of the brightness which is set normally, and the dimming degree is set so that the tube brightness is darkened. In this case, it operates by pulse dimming. That is, in the current dimming method, the tube current is detected and the PWM on the input side of the inverter circuit is detected.
The constant current control is performed by returning to the control circuit to change the output voltage of the DC-DC converter, and the dimming of the discharge lamp is performed by changing the DC level of the dimming signal applied to the constant current control loop. Will be

When the level of the dimming signal falls below the set value by the dimming operation, a pulse is generated from the pulse dimming addition circuit including the rectangular wave oscillation circuit, the integration circuit, and the PWM circuit. That is, according to the degree of dimming, the pulse width is 0 to 50% (0% at the time of high luminance, and the pulse starts to be emitted at a set value equal to or less than the medium luminance.
(Set so that the duty becomes about 50% at the minimum luminance), and the output voltage is applied to the constant current control loop. At this time, the tube current attenuates according to the pulse width. Thus, when the luminance is set high by the dimming operation, the operation is performed by the current dimming method, and when the luminance is set low, the same operation as the pulse dimming method is executed (see FIG. 5).

Thus, according to the present embodiment, it is possible to increase the dimming range of the lamp. For example, when a discharge lamp such as a hot cathode fluorescent tube is used as a backlight of the screen, the screen is low. Since the brightness can be increased, it can be used in a dark place. Further, it is possible to cope with an application in which the brightness of the screen is reduced in an energy saving mode or the like. That is, it is possible to expand the brightness adjustment range of the same level as that of the pulse dimming method, while basically using the current dimming method.

When the brightness of the lamp is higher than the level normally used, the mode is switched from pulse dimming to current dimming. Therefore, the generation of noise radiated from the lamp and the lamp wiring is smaller than that of the conventional pulse dimming method. And become smaller. That is, when the lamp brightness is high, the noise level of the electromagnetic wave is lower than that of the conventional pulse dimming method.

Further, in the conventional current dimming circuit, when the luminance of the lamp is low, a luminance gradient phenomenon that the luminance on the high voltage output side becomes high on the lamp tube surface is observed. The slope is improved and less noticeable. That is, the level can be made substantially the same as the characteristic of the conventional pulse dimming method.

In the conventional pulse dimming method, since constant current control of the lamp current is not performed, the lamp current changes due to factors such as changes in the ambient temperature and changes over time in the lamp, and the screen brightness changes. However, in this method, since the constant current control is effective even during the pulse dimming, the tube current and the luminance are stable with respect to the change in the ambient temperature. That is, the stability of the tube current is superior to that of the conventional pulse modulation method.

The switching operation between the current dimming and the pulse dimming can be performed smoothly by using the pulse width modulation and the pulse amplitude modulation for the pulse dimming signal waveform.

Further, since the rising and falling waveforms of the pulse dimming are made duller than those of the conventional pulse dimming, the generation of hot spots at the tube electrode portion is suppressed, and the emission of the emitter applied to the electrode portion is reduced. Scattering can be prevented, and the effect on lamp life during pulse dimming can be reduced. Further, for the same reason, the radiation of electromagnetic waves is small even in a state of low luminance as compared with the pulse dimming method.

As described above, the present embodiment is not simply a collection of the two conventional dimming systems, but incorporates a new system to extract only the advantages of both conventional systems.
Furthermore, there is a remarkable effect that constant current control can be performed even during pulse dimming.

Next, a second embodiment of the present invention will be described. FIG. 6 is an electric circuit diagram showing the second embodiment of the present invention. This embodiment is different from the first embodiment in that the DC-D
The C converter 20 is replaced with a well-known step-up chopper system. Other configurations are the same as those of the first embodiment, and the same effects as those of the first embodiment were obtained.

Next, a third embodiment of the present invention will be described. FIG. 7 is an electric circuit diagram showing a third embodiment of the present invention. In the present embodiment, when a plurality of tubes 10 are provided,
In this case, the lights are turned on in parallel by a plurality of (corresponding to the number of tubes) DC-DC converters and a plurality of inverter circuits. The basic configuration for tube lighting and dimming is in principle the same as in the first embodiment.

As various examples of the embodiment of the present invention, the following design changes are possible.

(1) Components of Rectangular Wave Oscillation Circuit In addition to the above-described comparator IC, a multivibrator,
A blocking oscillation circuit, an oscillation circuit using a logic gate, and an oscillation circuit using a timer IC can be used.

(2) In the case where the polarities of the dimming signals are different The dimming voltage when the luminance is minimum by the dimming operation is set to + 5V,
The maximum luminance can be set to 0V. In this case, the dimmer does not perform the inverting operation.

(3) The non-inverting input side of the error amplifier of the PWM control circuit (IC1) can be used.

In some PWM control ICs, the error amplifier input terminal has both + (plus) and-(minus) polarities. In this case, the non-inverting input side (minus side) of the input terminal is used. In this case, the input polarity of the PWM circuit (IC4) in the pulse dimming addition circuit is used in reverse.

(4) The dimming PWM control may be performed on the ground side of the switching elements (Q2, Q3) of the inverter circuit.

(5) In the embodiment, the hot cathode fluorescent tube lighting device is disclosed. However, the present invention can be applied to a cold cathode fluorescent tube lighting device and other lighting devices for discharge tubes.

[0062]

As described above, according to the first aspect of the present invention, the dimming range of the discharge lamp can be increased. For example, a discharge lamp such as a hot cathode fluorescent tube can be used as a backlight for a screen. In this case, the brightness of the screen can be reduced, so that it can be used in a dark place. Further, it is possible to cope with an application in which the brightness of the screen is reduced in an energy saving mode or the like. That is, it is possible to expand the brightness adjustment range of the same level as that of the pulse dimming method, while basically using the current dimming method. Furthermore, when the brightness of the discharge lamp is higher than the level normally used, the mode switches from pulse dimming to current dimming, and the noise radiated from the discharge lamp and its wiring is less than that of the conventional pulse dimming method. And become smaller. That is, when the discharge lamp luminance is high, the noise level of the electromagnetic wave is smaller than that of the conventional pulse dimming method. Also,
In the current dimming circuit of the related art, when the luminance of the discharge lamp is low, a luminance gradient phenomenon that the luminance on the high voltage output side becomes higher on the discharge lamp tube surface was observed, but in the present invention, the luminance gradient is improved. And become inconspicuous. That is, the level can be made substantially the same as the characteristic of the conventional pulse dimming method.

According to the second aspect of the present invention, in addition to the above-described effects, when the discharge lamp is lit beyond a predetermined current value equal to or less than the rated maximum current value, the DC light obtained by amplifying the dimming signal by the dimming circuit. When a signal is applied to the constant current control loop to perform current dimming and the discharge lamp is lit at the predetermined current value or less, a pulse current or voltage is applied to the constant current control loop by the dimming circuit. Since pulse dimming is performed, in the conventional pulse dimming method, constant current control of the discharge lamp current is not performed, so that the discharge lamp current changes due to factors such as changes in the ambient temperature and the aging of the discharge lamp. However, the present invention has a problem that the screen luminance changes, but in the present invention, since the constant current control is effective even at the time of pulse dimming, the tube current and the luminance are stable with respect to the change in the ambient temperature.

According to the third aspect of the present invention, in addition to the above effects, when pulse dimming is performed, input dimming is performed as a pulse voltage waveform applied to the constant current control loop for pulse dimming. Since a pulse width modulation waveform that outputs a pulse having a duty ratio of 0 to about 50% or a waveform in which the pulse width modulation and the pulse amplitude modulation are used in accordance with the signal level is used, current dimming and pulse dimming are performed. The light switching operation can be performed smoothly, and only the advantages of both the conventional current dimming method and the pulse dimming method are brought out. Further, there is a remarkable effect that the constant current control can be performed even during the pulse dimming. .

According to the fourth aspect, in addition to the above-described effects, the light control between the hot cathode fluorescent lights can be smoothly performed.

According to the fifth aspect, in addition to the above effects, the dimming between the cold cathode fluorescent lights can be performed smoothly.

[Brief description of the drawings]

FIG. 1 shows a tube current waveform in a conventional current dimming method and a pulse dimming method.

FIG. 2 is a diagram showing a luminance distribution of a tube in a case of a current dimming method and a case of a pulse dimming method.

FIG. 3 is a voltage waveform diagram in an oscillation circuit of an inverter circuit.

FIG. 4 is a tube current waveform diagram according to a dimming degree in the lighting device of the present invention.

FIG. 5 is an electric circuit diagram according to the first embodiment of the present invention.

FIG. 6 is an electric circuit diagram according to a second embodiment of the present invention.

FIG. 7 is an electric circuit diagram according to a third embodiment of the present invention.

[Explanation of symbols]

10 hot-cathode fluorescent tube, 20 DC-DC converter, 3
0: inverter circuit, 40: dimming signal inverting amplifier, 50
... Square wave oscillation circuit, 60 ... Integration circuit, 70 ... PWM circuit, 80 ... Tube current detection circuit, Cb ... Ballast capacitor, IC1 ... PWM control circuit, PS1 ... Device driving DC power supply, PS2 ... Dimming variable DC power supply .

Claims (5)

[Claims] 1. A discharge lamp lighting device having a dimming circuit, wherein the dimming circuit operates in a current dimming mode when the discharge lamp is lit by exceeding a predetermined current value equal to or less than a rated maximum current. A discharge lamp lighting device, which operates in a pulse dimming mode when the lamp is turned on at a value equal to or less than the predetermined current value. 2. The dimming circuit according to claim 1, further comprising: applying a DC signal obtained by amplifying the dimming signal to a constant current control loop to perform current dimming; and applying a pulse current or voltage to the constant current control loop to perform a pulse. 2. The discharge lamp lighting device according to claim 1, wherein dimming is performed. 3. A pulse for outputting a pulse having a duty ratio of 0 to about 50% according to a set input dimming signal level, wherein the pulse voltage waveform applied to the constant current control loop for pulse dimming is controlled. 3. The discharge lamp lighting device according to claim 2, wherein the waveform is a waveform obtained by performing width modulation or a combination of the pulse width modulation and the pulse amplitude modulation. 4. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is a hot cathode fluorescent tube. 5. The discharge lamp lighting device according to claim 1, wherein the discharge lamp is a cold cathode fluorescent tube.