JP2003168591A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lighting device which can be adapted to like kinds of discharge lamps substantially equivalent in rated lamp current and different in rated lamp output from each other and can adjust a light output ratio substantially uniformly at every discharge lamp without causing fading-out, flickering and abnormal oscillation. <P>SOLUTION: The lightening device is equipped with a lamp current fixing means for keeping a lamp current at an optional illumination level unchanged even when any of like kinds of discharge lamps La substantially equivalent in rated lamp current and different in rated lamp output from each other is connected. Therefore, output voltage-output current characteristics in an illumination range from rated lighting to lower limit of illumination can be made characteristics near a substantially perpendicular straight line that inclination becomes almost infinite, and so illumination that the light output ratio is kept substantially unchanged over the whole illumination range from rated lighting to lower limit of illumination is feasible even when any of the like kinds of discharge lamps La is lighted, and flickering and fading-out in the vicinity of the lower limit of the illumination can be prevented. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device which is suitable for the same type of discharge lamps having substantially the same rated lamp current and different rated lamp powers and which is capable of dimming any of the discharge lamps.

[0002]

2. Description of the Related Art As shown in FIG. 13, a DC output of a DC power supply 1 is converted into a high frequency output by an inverter unit 2 and supplied to a discharge lamp La through a resonance circuit 3 of an inductor L1 and a capacitor C1. A discharge lamp lighting device that dims the discharge lamp La by controlling the operating frequency and on-duty ratio of the inverter unit 2 by the dimming unit 4 according to a dimming signal given from the outside to adjust the high frequency output. Has been provided (hereinafter, referred to as "conventional example 1").
However, in this prior art example 1, when the high-frequency output of the inverter unit 2 is reduced to near the lower limit of the dimming range, the discharge lamp La easily flickers or disappears, so the dimming is too deep (the light output is low). I couldn't.

Therefore, there has been proposed a discharge lamp lighting device capable of deeper dimming by lowering the lower limit of the dimming range while suppressing the flicker and extinction as described above (hereinafter referred to as "conventional example 2"). ). In this conventional example 2, in addition to the inductor L1 and the capacitor C1 which are connected in series between the output terminals of the inverter unit 2 as shown in FIG. 14, a connection point between the inductor L1 and the capacitor C1 and one end of the discharge lamp La are provided. The capacitor C2 is connected in series to the resonance circuit 3 to form the resonance circuit 3. By adding the capacitor C2,
It becomes easy to design so that the operating frequency (lower limit operating frequency) fDim of the inverter unit 2 near the lower limit of the dimming range and the no-load resonance frequency f0 of the resonant circuit 3 become substantially the same, and the inverter unit near the lower limit of the dimming range becomes easier. There is an advantage that the output voltage of No. 2 (no-load secondary voltage) is increased to suppress flickering and fading, and deeper dimming becomes possible.

By the way, recently, discharge lamps of the same kind having substantially the same rated lamp current and different rated lamp power, for example, compact fluorescent lamps FHT24, FHT32, FHT42 (JIS C among fluorescent lamps exclusively for high frequency lighting) (JIS C
7601), a discharge lamp lighting device is provided. Curves a and b in FIG. 15 show the lamp voltage-lamp current characteristics of the same type of discharge lamps A and B, respectively, and curves a to d in FIG. 15 are discharge lamp lighting devices in which the discharge lamps A and B are compatible lamps ( The output voltage-output current characteristics of the inverter unit 2) are shown respectively. The curve a
Shows the lower limit of dimming, and curves b and c show the output voltage-output current characteristics in the dimming range when rated lighting is performed. Further, by changing the operating frequency of the inverter unit 2, the output voltage-output current characteristics are changed as shown by the curves a to d, and the intersections of the curves a to d and the curves a and b are the discharge lamps A and B.
It becomes the operating point of.

Here, as described above, in order to prevent flickering and disappearance near the lower limit of dimming, the inverter unit 2
Since the lower limit operating frequency fDim and the no-load resonance frequency f0 of the resonance circuit 3 are substantially matched (fDim≈f0) to increase the no-load secondary voltage, the output voltage-output current characteristic at the dimming lower limit is As shown by the curve d in FIG. 15, the characteristic (constant current characteristic) is close to a substantially vertical straight line having a substantially infinite inclination. The output voltage-output current characteristics of the discharge lamp lighting device differ depending on the output voltage of the DC power supply 1, the circuit configuration of the resonance circuit 3, the constant setting of circuit elements, the dimming control method of the dimming unit 4, and the like.

In this way, when the lower limit operating frequency fDim of the inverter section 2 and the no-load resonance frequency f0 of the resonance circuit 3 are substantially matched, the lamps when the discharge lamps A and B are dimly lit at the dimming lower limit. Although the currents are substantially equal, the output voltage-output current characteristic at the operating frequency fFull at the rated lighting has a smaller slope than that at the time of dimming as shown by the curve a in FIG. 15, so the lamp currents of the discharge lamps A and B are The difference between
That is, in the case of the above-mentioned conventional example 2 which is suitable for the same kind of discharge lamps having different rated lamp powers and which suppresses the flicker and extinction at the lower limit of dimming, the rated light output and the actual light output of each discharge lamp at the time of rated lighting. However, there is a problem in that the difference in light output ratio during dimming varies among the discharge lamps.

On the other hand, by detecting the lamp current and feedback-controlling the output of the inverter unit so that the lamp current corresponds to the dimming signal, the fluctuation of the instantaneous value of the lamp current is suppressed, thereby causing the problem of the above-mentioned conventional example 2. There is provided a discharge lamp lighting device that solves the above problem (see, for example, Japanese Patent Laid-Open No. 9-251899).

FIG. 16 shows a schematic configuration of the discharge lamp lighting device (hereinafter referred to as "conventional example 3") described in the above publication.
In the conventional example 3, the commercial power source 101 is replaced with the high frequency power source 102.
Is converted into high frequency power by the high frequency power supply 102, and the high frequency current supplied from the high frequency power supply 102 to the discharge lamp of the load circuit 103 is detected by the current detection circuit 105. The lamp current signal Sa detected by this detection circuit 105 and the light control section A feedback control circuit 107 generates a control signal Se for controlling the high frequency power supply 102 by a dimming signal Sb input from 111.
In the feedback control circuit 107, the lamp current signal Sa and the dimming signal Sb are subtracted by the subtractor 108, and the error signal Sc is amplified by the error amplification circuit 109. The amplified signal Sd and the dimming signal Sb are further added by the adder 112 to form a control signal Se. In addition, the adder 112 and the error amplification circuit 1
The switch 113 is provided between the switch 11 and
The connection / disconnection of 3 is performed by the dimming signal Sb and the reference signal generator 1.
It is switched by a comparison circuit 115 such as a comparator that compares the value of the operation switching dimming level signal Sf output from the controller 14.

Thus, in the above-mentioned conventional example 3, when the value of the lamp current signal Sa is the same as the dimming signal Sb, the error signal S
Since c becomes 0 and the output of the error amplification circuit 109 is also 0, the dimming signal Sb is directly input to the high frequency power supply 102 as the control signal Se. When the lamp current signal Sa is smaller than the dimming signal Sb, the error signal Sc is generated, amplified by the error amplification circuit 109, and further added to the dimming signal Sb to form the control signal Se. It is input to the high frequency power supply 102. In this way, the dimming signal Sb
The lamp current signal Sa by performing feedback control according to
To prevent flicker of the discharge lamp by suppressing fluctuations in the instantaneous value of the lamp current.

Further, the operation switching dimming level signal Sf output to the comparison circuit 115 is a signal serving as a reference value for determining at which dimming level the feedback control is started and stopped, and this signal The comparison circuit 1 judges whether the value is larger or smaller than the dimming signal Sb.
Activate 15. In this conventional example 3, as shown in FIG. 17, the value of the operation switching dimming level signal Sf is compared with the dimming level of the dimming signal Sb (light output ratio when the light output during rated lighting is 100%). Is set within the range of approximately 40 to 60%. That is, when the dimming level is approximately 40% or less, problems such as extinction and flicker of the discharge lamp at a low temperature are likely to occur, and when the dimming level is approximately 60% or less, individual differences (for example, individual differences that occur when the discharge lamp lighting device is commercialized). There may be variations in the components) and the dimming level is almost 50
When the value is%, the need for feedback control is low, it is preferable that the range in which wasteful feedback control is omitted is wider, and because it is possible to sufficiently deal with the flicker of the discharge lamp, etc. It is most effective to stop the feedback control when it is between 60%.

According to the prior art example 3, when the dimming signal Sb reaches a preset value (for example, when the dimming level is 50% or more), the switch 113 is opened to stop the feedback control. Therefore, the lamp current signal Sa only needs to be detected from the current detection circuit 105 only within a limited range (0 to 50% of the dimming level), and thus even the lamp current signal Sa unnecessary for feedback control is detected. By eliminating the need for detection and narrowing the detection range, the dynamic range can be relatively widened, the detection accuracy of the lamp current signal can be improved, and the noise resistance can also be improved.

[0012]

By the way, the output voltage-output current characteristics of the conventional example 1 shown in FIG. 13 are as shown by the curves ad in FIG. 18, and the discharge lamp A of the same kind as described above, When dimming B, rated lighting (dimming level 100
%), The lamp currents for the same dimming signal (dimming level) are almost equal, but when the dimming is deep (dimming level is small), the output voltage-output current characteristics (curve c) of the discharge lamp lighting device are shown. ) And the lamp voltage-lamp current characteristic (curve B) of the discharge lamp A are lost, and the discharge lamp A may be extinguished. Further, the feedback control of the lamp current as in the conventional example 3 does not make sense to the region where the discharge lamp A goes out, and the dimmable range is inevitably narrowed (shallow).

On the other hand, in the conventional example 2, the disappearance does not occur near the dimming lower limit, but if the feedback control as in the conventional example 3 is performed, the gain of the feedback control near the dimming lower limit is shown in FIG. Is large, the output response of the discharge lamp by the feedback control circuit 107 becomes excessive, and the feedback control circuit 10
7 may cause abnormal oscillation. For example, if the discharge becomes unstable near the lower limit of dimming and the instantaneous value of the desired lamp current corresponding to the dimming signal decreases slightly, the feedback control circuit 107 increases the lamp current. However, if the gain is large, the lamp current will increase more than necessary. As a result, the feedback control circuit 107 operates in the direction of decreasing the lamp current this time. However, since the gain is also large, the lamp current decreases more than necessary, and the feedback control causes a large variation in the instantaneous value of the lamp current. This will encourage flicker. In the conventional example 2, the output voltage-output current characteristic at the lower limit of dimming has the constant current characteristic as shown by the curve d in FIG.
In a low temperature environment, the discharge is likely to become unstable particularly near the lower limit of dimming, and therefore a slight fluctuation of the lamp current that is not perceived as a flicker should be caused by the feedback control circuit 107 as shown in FIG. It can increase and cause flicker. Therefore, it is usually desirable that the peak value of the lamp current is substantially constant even at the lower limit of dimming as shown in FIG.

In the conventional example 3, the dimming level is 5
In the case of 0% or more, the feedback control circuit 107 does not perform the feedback control, so that the difference in the lamp current between the discharge lamps A and B is large with respect to the desired lamp current according to the dimming signal near the rated lighting. Therefore, the difference between the rated light output of each discharge lamp and the actual light output becomes large, and the light output ratio during dimming varies among the discharge lamps. This is not preferable in a discharge lamp lighting device that is compatible with the same type of discharge lamps having different rated lamp powers.

The present invention has been made in view of the above circumstances, and an object thereof is to be compatible with discharge lamps of the same kind having rated lamp currents substantially equal to each other and rated lamp powers different from each other, and extinguishing, flickering, and abnormalities. An object of the present invention is to provide a discharge lamp lighting device capable of dimming the light output ratio of each discharge lamp substantially constant without causing oscillation.

[0016]

In order to achieve the above object, the invention of claim 1 is an inverter section for converting a DC output of a DC power supply into a high frequency output, and a resonance circuit connected to an output terminal of the inverter section. And a load unit including a discharge lamp, a dimming unit that adjusts a high-frequency output supplied to the load unit to dimm the discharge lamp, and a discharge lamp of the same type having different rated lamp currents and different rated lamp powers. It is characterized in that it is provided with a lamp current stabilizing means for making the lamp current substantially constant at any dimming level in any connected condition.
It can be applied to the same type of discharge lamps that have almost the same rated lamp current and different rated lamp powers, and can adjust the light output ratio of each discharge lamp to a substantially constant level without flicker, flickering, or abnormal oscillation. it can.

According to a second aspect of the present invention, in the first aspect of the present invention, the lamp current constant means is a resonance set so that the operating frequency of the inverter section at an arbitrary dimming level substantially matches the no-load resonance frequency. It is characterized by comprising a circuit, and the lamp current constant means can be realized with a simple circuit configuration.

According to a third aspect of the present invention, in the second aspect, the load section includes a resonance circuit including an inductor and a capacitor connected in series between the output terminals of the inverter section, and the capacitor of the resonance circuit has a discharge lamp. Are connected in parallel, and the same operation as the invention of claim 2 is achieved.

According to a fourth aspect of the present invention, in the second aspect of the present invention, the load section has an inductor and a first capacitor connected in series between output terminals of the inverter section, and the discharge lamp and the first capacitor are connected in parallel with the first capacitor. The two capacitors are connected in series, and the resonance frequency of the resonance circuit can be increased to widen the dimming range.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the load section has a third capacitor and a switch element connected in series in parallel with the second capacitor, and the switch element opens and closes according to a dimming level. The resonance frequency of the resonance circuit can be increased and the dimming range can be expanded by closing the switch element.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the lamp current stabilizing means detects the lamp current and controls the inverter section so that the detected lamp current has a desired level. Therefore, the fluctuation of the instantaneous value of the lamp current can be suppressed.

According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the load section includes a resonance circuit composed of an inductor and a capacitor connected in series between the output terminals of the inverter section, and the capacitor of the resonance circuit has a discharge lamp. Are connected in parallel, and the same operation as the invention of claim 6 is achieved.

According to an eighth aspect of the present invention, in the load section, the inductor and the first capacitor are connected in series between the output ends of the inverter unit, and the discharge lamp and the first capacitor are connected in parallel with the first capacitor. The two capacitors are connected in series, and the resonance frequency of the resonance circuit can be increased to widen the dimming range.

According to a ninth aspect of the present invention, in the eighth aspect of the present invention, the load section has a third capacitor and a switch element connected in series in parallel with the second capacitor, and the switch element opens and closes in accordance with a dimming level. The resonance frequency of the resonance circuit can be increased to widen the dimming range.

A tenth aspect of the present invention is characterized in that, in any one of the second to ninth aspects, the light control means changes the operating frequency of the inverter section. Has the same effect.

The invention according to claim 11 is the invention according to any one of claims 2 to 9, characterized in that the light control means changes the on-duty ratio of the inverter section. Has the same effect as.

According to a twelfth aspect of the present invention, in any one of the second to ninth aspects of the invention, the light control means changes the output voltage of the DC power source. Has the same effect.

A thirteenth aspect of the present invention is characterized in that, in any one of the second to ninth aspects of the invention, the light control means changes the operating frequency of the inverter section and the output voltage of the DC power source. The same operation as any of the above inventions is achieved.

A fourteenth aspect of the present invention is characterized in that, in any one of the second to ninth aspects, the light control means changes the on-duty ratio of the inverter section and the output voltage of the DC power source. The same effect as any of the inventions of 9 is exhibited.

According to a fifteenth aspect of the invention, in the invention of the second, tenth or thirteenth aspect, the light output at the rated lighting is 100%.
In this case, the operating frequency of the inverter section is substantially matched with the no-load resonance frequency of the resonant circuit within the dimming range of the light output ratio of 40% to 60%, and abnormal oscillation of the inverter section can be prevented.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION First, the basic configuration of the present invention will be described. As shown in FIG. 1, the discharge lamp lighting device of the present invention includes an inverter unit 2 for converting a DC output of a DC power supply 1 into a high frequency output, a resonance circuit 3 connected to an output end of the inverter unit 2 and a discharge lamp La. Any of the load section including the load section, the dimming section 4 for adjusting the high-frequency output supplied to the load section to dimm the discharge lamp La, and the discharge lamp La of the same kind having substantially the same rated lamp current and different rated lamp power. And a lamp current fixing means for making the lamp current substantially constant at an arbitrary dimming level even when the lamp is connected. As the discharge lamps La of the same type having substantially the same rated lamp current and different rated lamp powers, compact fluorescent lamps FHT42, FHT32, F among fluorescent lamps exclusively for high frequency lighting are used.
The HT24 is exemplified, but the invention is not limited to this.

Curves A, B and C in FIG. 2 are the three types of discharge lamps La (FHT42, FHT32, FHT).
24) shows the lamp voltage-lamp current characteristics of 24). Similarly, curves a to d in FIG. 2 are output voltage-output current characteristics of the discharge lamp lighting device (inverter unit 2). Curve a is at rated lighting, curve d is the lower limit of dimming, and curves b and c are The characteristics in the dimming range are shown.
However, it is ideal that the output voltage-output current characteristic of the inverter unit 2 is a straight line with an infinite slope all over the dimming range, but in reality, the breadth of the dimming range and the lamp current stabilizing means are concrete. Depending on the specific configuration, all the characteristics do not necessarily become a straight line of infinity in the entire dimming range.

In the present invention, the output voltage-output current characteristic in the dimming range from the rated lighting to the dimming lower limit is
The lamp current stabilizing means provides a characteristic (constant current characteristic) close to a substantially vertical straight line having an almost infinite slope as shown by the curves a to d in FIG. Therefore, when any of the above three types of discharge lamps La (FHT42, FHT32, FHT24) is lit, the rated lighting (dimming level 100
%), It is possible to perform dimming with the light output ratio substantially constant over the entire dimming range from the dimming lower limit, and furthermore, it is possible to prevent flickering and extinction near the dimming lower limit.

An embodiment in which the above-mentioned lamp current stabilizing means is embodied will be described below.

(Embodiment 1) FIG. 3 shows a schematic configuration of this embodiment, and FIG. 4 shows the output voltage-output current characteristics (curves a to e) of the inverter section 2 of this embodiment and the above-mentioned three types. Discharge lamp La (FHT42, FHT32, FHT
24) Lamp voltage-lamp current characteristics (curves a, b,
C) is shown. In the present embodiment, the operating frequency f of the inverter unit 2 at the dimming level near the center of the dimming range or slightly closer to the dimming lower limit than the center is the no-load resonance frequency f0.
The characteristic is that the lamp current stabilizing means is constituted by the resonance circuit 3 set so as to substantially match with.

As shown in FIG. 3, the inverter section 2 has a conventionally well-known half-bridge type structure in which a pair of switching elements Q1 and Q2 made of MOSFETs are connected in series between the output terminals of a DC power source 1. The resonance circuit 3 is connected to the low-side switching element Q2 via a DC cut capacitor C _D , and the control circuit 2a alternately switches the switching elements Q1 and Q2 to convert the DC output of the DC power supply 1 into a high-frequency output. To do. Control circuit 2
a adjusts the operating frequency of the inverter unit 2 (the switching frequency of the switching elements Q1 and Q2) in accordance with a dimming signal given from the outside to vary the high frequency power supplied to the discharge lamp La through the resonance circuit 3. It is a thing.
The resonance circuit 3 is composed of an inductor L1 and a capacitor C1 connected in series, and the discharge lamp La is connected to both ends of the capacitor C1.
Are connected in parallel. By appropriately setting the inductance value of the inductor L1 and the capacitance value of the capacitor C1, the no-load resonance frequency f0 of the resonance circuit 3 is adjusted near the center of the dimming range, or slightly below the dimming lower limit of dimming. It is set to match the operating frequency f of the inverter unit 2 at the level. That is, since the lamp voltage is lower in the rated lighting than in the vicinity of the lower limit of dimming, if the slopes of the output voltage-output current characteristics of the inverter unit 2 are the same, each discharge lamp (FHT42, FHT32, FHT2
The resonance frequency f0 of the resonance circuit 3 is set as described above in consideration of the fact that the difference in the lamp current of 4) is small and the variation width of the light output with respect to the lamp current is smaller than near the dimming lower limit. .

Thus, according to the present embodiment, the closer to the operating frequency of the rated lighting and dimming lower limit, that is, the resonance circuit 3
Although the slope of the output voltage-output current characteristic of the inverter unit 2 becomes smaller (gradient) as it goes farther from the resonance frequency f0 of FIG. Even if the above feedback control of the lamp current is not used, the light output ratio of each discharge lamp (FHT42, FHT32, FHT24) can be adjusted to be substantially constant without extinguishing, flickering, or abnormal oscillation.

(Embodiment 2) FIG. 5 shows a schematic configuration of this embodiment, and FIG. 6 shows the output voltage-output current characteristics (curves a to e) of the inverter section 2 of this embodiment and the above-mentioned three types. Discharge lamp La (FHT42, FHT32, FHT
24) Lamp voltage-lamp current characteristics (curves a, b,
C) is shown. In this embodiment, a capacitor C2 and a discharge lamp La are connected in series at both ends of the capacitor C1, and the resonance circuit 3 is formed by an inductor L1 and two capacitors C1 and C2.
Is configured, and other configurations are common to the first embodiment. That is, also in the present embodiment, the inductance value of the inductor L1 and the capacitors C1 and C2 are
By appropriately setting the capacitance value of, the unloaded resonance frequency f0 of the resonance circuit 3 is set to the operating frequency f of the inverter unit 2 at the dimming level near the center of the dimming range or slightly near the dimming lower limit than the center. Match.

In the resonance circuit 3 in this embodiment, there are two resonance frequencies depending on the load fluctuation. That is, the equivalent load resistance RLa of the discharge lamp La increases as the dimming depth increases (the dimming level decreases) and no load (RLa =
In the case of ∞), the resonance frequency (no-load resonance frequency) f01 is determined by the inductor L1 and the capacitor C1. On the other hand, if the dimming is made shallow (the dimming level is made large), the equivalent load resistance RLa becomes small, and the resonance frequency f02 in the case of load short circuit (RLa = 0) is the inductor L1 and the capacitor C.
1, C2. Since there are two resonance frequencies f01 and f02 of the resonance circuit 3 as described above, the slope of the output voltage-output current characteristic of the inverter unit 2 in the vicinity of the rated lighting is nearly infinite as compared with the first embodiment. It can have a constant current characteristic.

Since this embodiment is configured as described above, each discharge lamp (FHT42, FHT32, FHT24) covers a wider dimming range than that of the first embodiment.
The light output ratio can be adjusted to be substantially constant every time.

(Embodiment 3) FIG. 7 shows a schematic configuration of this embodiment. The present embodiment is characterized in that the capacitor C3 and the switch element SW are connected in series with the capacitor C2 in parallel, and the switch element SW is opened / closed according to the dimming level by the control circuit 2a. Two
Is common with.

Thus, in the state where the switch element SW is opened by the control circuit 2a, the resonance circuit 3 including the inductor L1 and the capacitors C1 and C2, which is the same as that of the second embodiment, is used.
However, in the state where the switch element SW is closed, there is another unloaded resonance frequency f03 because the resonance circuit 3 including the inductor L1 and the capacitors C1, C2 and C3 is formed. Become. The control circuit 2a turns on the switch element SW when the dimming level is high in accordance with the dimming signal input from the outside, and turns off the switch element SW when the dimming level is low.

In the present embodiment, the unloaded resonance frequency f01 of the resonance circuit 3 is set near or at the center of the dimming range by appropriately setting the inductance value of the inductor L1 and the capacitance value of the capacitor C1. By matching the operating frequency f of the inverter unit 2 at a dimming level slightly closer to the lower limit of dimming and setting the inductance value of the inductor L1 and the capacitance values of the capacitors C1, C2, C3 appropriately, By matching the load resonance frequency f03 with the operating frequency f of the inverter unit 2 at the dimming level closer to the rated lighting than the center of the dimming range, the discharge lamps (FHT42) over a wider dimming range than in the second embodiment. , FHT32, F
The light output ratio can be adjusted to be substantially constant for each HT24).

(Fourth Embodiment) FIG. 8 shows a schematic configuration of the present embodiment. The present embodiment is provided with a current detection circuit 5 that detects a lamp current, and a feedback control circuit 6 that feedback-controls the inverter unit 2 so that the lamp current detected by the current detection circuit 5 reaches a desired level. It is characterized in that the current detection circuit 5 and the feedback control circuit 6 constitute a lamp current constant means. However, the same components as those in the second embodiment are designated by the same reference numerals and the description thereof will be omitted. In the present embodiment, the AC power supply AC is full-wave rectified by the diode bridge DB, and the inductor L2, the diode D1, the switching element Q3, the smoothing capacitor C0, and the switching element Q are used.
The DC power supply 1 is shown as an example in which a DC voltage of a desired level is obtained by a conventionally known step-up chopper circuit composed of a control circuit 1a for switching control of the DC power supply 3. However, the configuration of the DC power supply 1 is not limited to this. It is not something that will be done.

The current detection circuit 5 detects the lamp current flowing through the discharge lamp La and outputs a lamp current signal according to the level of the detected lamp current. The feedback control circuit 6 includes an operational amplifier OP, and an inverting input terminal (-) of the operational amplifier OP.
The lamp current signal is input to the non-inverting input terminal (+) via the resistor Rs, and a signal (dimming control signal) obtained by amplifying the difference from the reference voltage Vr input to the non-inverting input terminal (+) via the resistor Rc is output to the inverter unit 2. Output to the control circuit 2a. Further, a capacitor Cf is provided between the inverting input terminal and the output terminal of the operational amplifier OP.
Is connected to a parallel circuit of a resistor Rf and an operational amplifier O
The gain of P is determined by the proportional integration gain of the capacitor Cf and the resistors Rf and Rs, and the low frequency ripple is reduced by the parallel circuit of the capacitor Cf and the resistor Rf.
Further, the reference voltage Vr of the feedback control circuit 6 is increased / decreased to a voltage level according to the dimming level by a dimming signal provided from the outside (dimmer 7).

On the other hand, the control circuit 2a of the inverter section 2 is
It is composed of an integrated circuit for so-called PWM (pulse width modulation), and variably controls the operating frequency f of the inverter unit 2 according to the dimming control signal given from the feedback control circuit 6.
Specifically, when a positive dimming control signal is output from the feedback control circuit 6 when the lamp current signal is lower than the reference voltage Vr, the operating frequency f is reduced to increase the lamp current and release it. By increasing the light output of the electric lamp La, conversely, when the negative dimming control signal is output from the feedback control circuit 6 when the lamp current signal is higher than the reference voltage Vr, the operating frequency f is increased. The lamp current is reduced to reduce the light output of the discharge lamp La. In this way, the feedback control circuit 6 is arranged so that the lamp current detected by the current detection circuit 5 matches the current value according to the dimming level instructed by the dimmer 7.
Since the feedback control is performed by, the fluctuation of the instantaneous value of the lamp current can be suppressed and the flicker of the discharge lamp La can be prevented.

Here, the output voltage-output current characteristics (curves a to d) of the inverter section 2 of the present embodiment and the lamp voltages of the same kind of discharge lamps A and B having substantially the same rated lamp current and different rated lamp powers- Lamp current characteristics (curve a, b)
Are shown in FIG. Now, assuming that the no-load resonance frequency f0 of the resonance circuit 3 is substantially matched with the operating frequency f of the inverter section 2 at the dimming lower limit, the dimming level becomes large and the operating frequency f becomes higher than the no-load resonance frequency f01. Since the slope of the output voltage-output current characteristic of the inverter unit 2 decreases as the value decreases, if the inverter unit 2 is operated at the same operating frequency f with respect to an arbitrary dimming signal (dimming level), each discharge lamp is discharged. Although the lamp currents of A and B are different from each other, in the present embodiment, the feedback control circuit 6 performs feedback control so that the lamp current becomes a desired lamp current according to the dimming signal. The lamp current of each of the discharge lamps A and B can be made substantially constant with respect to the signal.

In the present embodiment, as in the second embodiment, the no-load resonance frequency f01 of the resonance circuit 3 is near the center of the dimming range or at the dimming level slightly closer to the dimming lower limit than the center. 2 operating frequency f
However, specifically, as shown in FIG. 10, the inverter unit 2 when the dimming level is 40% and 60% is used.
For operating frequencies f40 and f60 of
It is desirable to set the no-load resonance frequency f01 so that ≦ f40. That is, if the no-load resonance frequency f01 is set within the above range while avoiding the vicinity of the lower limit of dimming, where the discharge is likely to be unstable, the feedback control circuit 6 performs feedback control because the lamp current can be made constant to some extent. Even if the gain is made relatively small, the lamp current can be made constant and abnormal oscillation of the inverter unit 2 can be prevented.

In the above-described first to fourth embodiments, the output of the inverter unit 2 is adjusted by changing the operating frequency f by the control circuit 2a. However, the switching element Q1,
The output is adjusted by changing the on-duty ratio of Q2, and the discharge lamp La is dimmed.
Without switching the circuit configuration of the resonance circuit 3 like
The output voltage-output current characteristic in the dimming range from the rated lighting to the lower limit of dimming should be a constant current characteristic close to a substantially vertical straight line having a substantially infinite slope as shown by the curves a to d in FIG. You can The switching frequency is set near the no-load resonance frequency f0 of the resonance circuit 3.

(Fifth Embodiment) FIG. 11 shows a schematic configuration of the present embodiment. The present embodiment is characterized in that the DC power supply 1 is composed of a conventionally known two-stone step-up / down chopper circuit, and the discharge lamp La is dimmed by changing the output voltage of the DC power supply 1 according to the dimming signal. There is. However, since the circuit configurations of the inverter unit 2 and the resonance circuit 3 are the same as those of the second embodiment, the description thereof will be omitted.

The step-up / step-down chopper circuit is obtained by adding a switching element Q4 and a diode D2 to the preceding stage (input side) of the step-up chopper circuit in the fourth embodiment, and the switching elements Q3 and Q4 are switching-controlled by the control circuit 1a. Thus, a desired DC voltage Vdc higher or lower than the power supply voltage (peak value) of the AC power supply AC is obtained. The step-up / step-down chopper circuit having such a circuit configuration is well known in the art, and thus detailed description of the operation is omitted.

If the control circuit 1a lowers the switching frequency of the switching elements Q3 and Q4 (or increases the on-duty ratio), the output voltage V of the DC power supply 1 is increased.
If dc increases and the switching frequency is increased (or the on-duty ratio is decreased), the output voltage Vdc decreases,
Along with this, the high-frequency power supplied from the inverter unit 2 to the discharge lamp La is also increased or decreased, so that the discharge lamp La is dimmed. The unloaded resonance frequency f of the resonance circuit 3
01 is set to match the operating frequency f of the inverter unit 2 near the center of the dimming range or at a dimming level slightly closer to the dimming lower limit than the center.

The present embodiment is configured as described above, and discharge lamps of the same kind (FHT42, FHT32, FH) having substantially the same rated lamp current and different rated lamp powers are used.
The value of the lamp current with respect to the dimming signal can be made substantially equal every T24), and the light output can be dimmed to be substantially constant. In addition,
In the case where the output characteristic of the inverter unit 2 changes depending on the ambient temperature, the current detection circuit 5 described in the fourth embodiment.
By combining the feedback control circuit 6 and the feedback control circuit 6, the same output characteristics can be obtained at both normal temperature and low temperature.

The DC power supply 1 is configured by the boost chopper circuit described in the fourth embodiment, and the control circuit 1a changes the switching frequency (or the on-duty ratio) of the switching element Q3 in accordance with the dimming signal and discharges it. The light La is dimmed, and the feedback control circuit 6 controls the inverter unit 2
If the configuration is such that the lamp current is feedback-controlled by controlling the operating frequency of, the amount of change in the output voltage Vdc can be small by the feedback control, so that stable operation is possible without using a two-stone buck-boost chopper circuit with many parts. It can be dimmed.

(Sixth Embodiment) FIG. 12 shows a schematic configuration of the present embodiment. In the present embodiment, the DC power supply 1 is configured by a step-up chopper circuit, and the discharge lamp La is dimmed by changing the output voltage of the DC power supply 1 according to the dimming signal and changing the operating frequency of the inverter unit 2. There is a feature in doing it. However, since the circuit configurations of the inverter unit 2 and the resonance circuit 3 are the same as those of the first embodiment, the description thereof will be omitted.
Further, the no-load resonance frequency f0 of the resonance circuit 3 is made to coincide with the operating frequency f of the inverter unit 2 at the dimming level near the center of the dimming range or slightly closer to the dimming lower limit than the center.

The control circuit 1a adjusts the output voltage Vdc of the DC power supply 1 by changing the switching frequency (or on-duty ratio) of the switching element Q3 according to the dimming signal, and at the same time, the control circuit 2a responds to the dimming signal. By changing the on-duty ratio of the switching elements Q1 and Q2, the output is adjusted and the discharge lamp La is dimmed. Also in the case of the present embodiment, the output voltage-output current characteristic in the dimming range from the rated lighting to the dimming lower limit is set to a substantially vertical straight line having an almost infinite slope as shown by the curves a to d in FIG. The constant current characteristics can be made close to each other, and the lamp current of the same type of discharge lamp can be made substantially constant with respect to an arbitrary dimming signal.

Further, since the dimming control for varying the output voltage Vdc of the DC power source 1 and the dimming control for varying the on-duty ratio of the inverter unit 2 are performed, the operation of each dimming control is suppressed. Therefore, there is an advantage that the circuit design margin is increased. For example, if only the dimming control for varying the output voltage Vdc of the DC power supply 1 is required, it is necessary to configure the DC power supply 1 with the step-up / down chopper circuit as in the fifth embodiment. A sufficient dimming range can be ensured even if is constituted by a boost chopper circuit, and the circuit configuration can be simplified. When the output characteristic of the inverter unit 2 changes depending on the ambient temperature, the same output characteristic can be obtained at room temperature or at low temperature by combining the current detection circuit 5 and the feedback control circuit 6 described in the fourth embodiment. .

[0058]

According to the invention of claim 1, an inverter section for converting a DC output of a DC power supply into a high frequency output, a load section including a resonance circuit and a discharge lamp connected to an output end of the inverter section, and a load section are provided. Arbitrary dimming regardless of whether dimming means for adjusting the supplied high-frequency output to dimm the discharge lamp or discharge lamps of the same kind with different rated lamp currents and different rated lamp power are connected. Since the lamp current constant means for making the lamp current at the level substantially constant is provided,
It can be applied to the same type of discharge lamps that have almost the same rated lamp current and different rated lamp powers, and can adjust the light output ratio of each discharge lamp to a substantially constant level without flicker, flickering, or abnormal oscillation. The effect is that you can do it.

According to a second aspect of the present invention, in the first aspect of the present invention, the lamp current constant means is a resonance set so that the operating frequency of the inverter section at an arbitrary dimming level substantially matches the no-load resonance frequency. Since it is composed of a circuit, there is an effect that the lamp current constant means can be realized with a simple circuit configuration.

According to a third aspect of the present invention, in the second aspect, the load section includes a resonance circuit including an inductor and a capacitor connected in series between the output terminals of the inverter section, and the capacitor of the resonance circuit has a discharge lamp. Since they are connected in parallel, the same effect as the invention of claim 2 is obtained.

According to a fourth aspect of the present invention, in the second aspect of the present invention, the load section has an inductor and a first capacitor connected in series between the output terminals of the inverter section, and the discharge lamp and the first capacitor are connected in parallel with the first capacitor. Since the two capacitors are connected in series, there is an effect that the resonance frequency of the resonance circuit can be increased to widen the dimming range.

According to a fifth aspect of the present invention, in the load section, the third capacitor and the switch element are connected in series in parallel with the second capacitor, and the switch element opens and closes according to the dimming level. Therefore, there is an effect that the resonance frequency of the resonance circuit can be increased and the dimming range can be expanded by closing the switch element.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the lamp current stabilizing means detects the lamp current and controls the inverter section so that the detected lamp current has a desired level. There is an effect that the fluctuation of the instantaneous value of the current can be suppressed.

According to the invention of claim 7, in the invention of claim 6, the load part comprises a resonance circuit composed of an inductor and a capacitor connected in series between the output terminals of the inverter part, and the capacitor of the resonance circuit is provided with a discharge lamp. Are connected in parallel, the same effect as the invention of claim 6 is obtained.

According to the invention of claim 8, in the invention of claim 6, the load part is such that the inductor and the first capacitor are connected in series between the output terminals of the inverter part, and the discharge lamp and the first capacitor are connected in parallel with the first capacitor. Since the two capacitors are connected in series, there is an effect that the resonance frequency of the resonance circuit can be increased to widen the dimming range.

According to a ninth aspect of the present invention, in the load section, the third capacitor and the switch element are connected in series in parallel with the second capacitor, and the switch element opens and closes according to the dimming level. Therefore, there is an effect that the dimming range can be widened by increasing the resonance frequency of the resonance circuit.

According to a tenth aspect of the present invention, in the invention according to any one of the second to ninth aspects, since the dimming means changes the operating frequency of the inverter section, the same effect as the invention according to any of the second to ninth aspects. Play.

The invention according to claim 11 is the same as the invention according to any one of claims 2 to 9 in the invention according to any one of claims 2 to 9 because the light control means changes the on-duty ratio of the inverter section. Produce an effect.

According to a twelfth aspect of the present invention, in the invention of any one of the second to ninth aspects, the dimming means changes the output voltage of the DC power source. Play.

According to a thirteenth aspect of the present invention, in the invention of any one of the second to ninth aspects, the dimming means changes the operating frequency of the inverter section and the output voltage of the DC power source. The same effect as that of the invention can be obtained.

According to a fourteenth aspect of the present invention, in the invention according to any one of the second to ninth aspects, the dimmer changes the on-duty ratio of the inverter section and the output voltage of the DC power source.
The same effects as those of the invention of any one of claims 2 to 9 are achieved.

According to a fifteenth aspect of the present invention, in the second or tenth or thirteenth aspect of the invention, the light output at the rated lighting is 100%.
Since the operating frequency of the inverter section is substantially matched with the no-load resonance frequency of the resonant circuit within the dimming range of 40% to 60% of the light output ratio, the abnormal oscillation of the inverter section can be prevented. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a basic configuration of the present invention.

FIG. 2 is a diagram showing an output voltage-output current characteristic of the same as above and a lamp voltage-lamp current characteristic of each discharge lamp which is adapted to the above.

FIG. 3 is a schematic configuration diagram showing a first embodiment.

FIG. 4 is a diagram showing an output voltage-output current characteristic of the same as above and a lamp voltage-lamp current characteristic of each discharge lamp which is adapted to the above.

FIG. 5 is a schematic configuration diagram showing a second embodiment.

FIG. 6 is a diagram showing an output voltage-output current characteristic of the same as above and a lamp voltage-lamp current characteristic of each discharge lamp which is adapted to the above.

FIG. 7 is a schematic configuration diagram showing a third embodiment.

FIG. 8 is a schematic configuration diagram showing a fourth embodiment.

FIG. 9 is a diagram showing an output voltage-output current characteristic of the same as above and a lamp voltage-lamp current characteristic of each discharge lamp which is adapted to the above.

FIG. 10 is a diagram showing the relationship between the operating frequency of the inverter unit, the unloaded secondary voltage, and the optical output in the above.

FIG. 11 is a schematic configuration diagram showing a fifth embodiment.

FIG. 12 is a schematic configuration diagram showing a sixth embodiment.

FIG. 13 is a schematic configuration diagram showing a first conventional example.

FIG. 14 is a schematic configuration diagram showing a second conventional example.

FIG. 15 is a diagram showing an output voltage-output current characteristic of the same as above and a lamp voltage-lamp current characteristic of each discharge lamp conforming to the above.

FIG. 16 is a schematic configuration diagram showing a third conventional example.

FIG. 17 is a diagram showing the relationship between the optical output ratio (dimming level) and the feedback control gain in the above.

FIG. 18 is a diagram showing an output voltage-output current characteristic of Conventional Example 1 and a lamp voltage-lamp current characteristic of each discharge lamp which is adapted to the above.

FIG. 19 is an operation explanatory diagram of Conventional Example 3.

FIG. 20 is an operation explanatory diagram of Conventional Example 3.

[Explanation of symbols]

1 DC power supply 2 Inverter section 3 resonance circuit 4 Light control section La discharge lamp

Continued front page    (72) Inventor Tomohiro Sasakawa             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company (72) Inventor Katsunobu Hamamoto             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company F term (reference) 3K072 AA02 AB09 AC02 AC11 BA05                       BB10 CA03 DB03 DD03 DD04                       DE02 GA02 GB03 GB12 GC04                       HA05 HA06 HA10                 3K098 CC24 CC26 CC41 CC60 DD01                       DD22 DD35 DD36 DD37 DD43                       EE03 EE20 EE32 EE40 FF04                       GG02 GG10

Claims (15)

[Claims] 1. An inverter unit for converting a DC output of a DC power supply into a high frequency output, a load unit including a resonance circuit and a discharge lamp connected to an output end of the inverter unit, and a high frequency output supplied to the load unit. Therefore, the lamp current at any dimming level can be omitted regardless of whether the dimming means for dimming the discharge lamp and the discharge lamp of the same kind having different rated lamp currents and different rated lamp powers are connected to each other. A discharge lamp lighting device, comprising: a constant lamp current constant means. 2. The lamp current stabilizing means comprises a resonant circuit set so that the operating frequency of the inverter section at an arbitrary dimming level is substantially equal to the no-load resonant frequency. Discharge lamp lighting device. 3. The load section includes a resonance circuit including an inductor and a capacitor connected in series between output terminals of the inverter section, and a discharge lamp is connected in parallel to the capacitor of the resonance circuit. Item 2. The discharge lamp lighting device according to item 2. 4. The load part comprises an inductor and a first capacitor connected in series between output terminals of the inverter part, and a discharge lamp and a second capacitor connected in series with the first capacitor in parallel. The discharge lamp lighting device according to claim 2. 5. The load section, wherein a third capacitor and a switch element are connected in series in parallel with the second capacitor, and the switch element is opened / closed according to a dimming level. Discharge lamp lighting device. 6. The discharge lamp lighting device according to claim 1, wherein the lamp current stabilizing means detects the lamp current and controls the inverter unit so that the detected lamp current has a desired level. 7. The load section includes a resonance circuit including an inductor and a capacitor connected in series between output terminals of the inverter section, and a discharge lamp is connected in parallel to the capacitor of the resonance circuit. Item 7. The discharge lamp lighting device according to item 6. 8. The load part comprises an inductor and a first capacitor connected in series between output terminals of the inverter part, and a discharge lamp and a second capacitor connected in series with the first capacitor in parallel. The discharge lamp lighting device according to claim 6. 9. The load section, wherein a third capacitor and a switch element are connected in series in parallel with the second capacitor, and the switch element is opened / closed in accordance with a dimming level. Discharge lamp lighting device. 10. The discharge lamp lighting device according to claim 2, wherein the dimming means changes the operating frequency of the inverter section. 11. The discharge lamp lighting device according to claim 2, wherein the light control means changes the on-duty ratio of the inverter section. 12. The discharge lamp lighting device according to claim 2, wherein the light control means changes the output voltage of the DC power supply. 13. The discharge lamp lighting device according to claim 2, wherein the light control means changes the operating frequency of the inverter section and the output voltage of the DC power supply. 14. The discharge lamp lighting device according to claim 2, wherein the light control unit changes the on-duty ratio of the inverter unit and the output voltage of the DC power supply. 15. The operating frequency of the inverter section is made substantially equal to the no-load resonance frequency of the resonance circuit within the dimming range of 40% to 60% of the light output ratio when the light output at the rated lighting is 100%. The discharge lamp lighting device according to claim 2, 10 or 13, wherein.