JP3520525B2 - Dimming discharge lamp lighting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimming discharge lamp lighting device for continuously dimming a discharge lamp to a low luminous flux region.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG.
A DC voltage obtained by rectifying C by a rectifying circuit RE such as a diode bridge and smoothing by a capacitor C ₀ is applied to the series circuit of the primary winding of the transformer T, the switching element Q ₁ and the resistor R _1, and externally applied. There is known a lighting circuit 1 which adjusts the power supplied to the discharge lamp DL connected to the secondary winding of the transformer T by turning on / off the switching element Q ₁ by the control circuit 2 in accordance with the dimming signal. (U.S. Pat. No. 4,663,570). This lighting circuit 1
Then, the ON period of the switching element Q ₁ or ON
By changing the OFF frequency, as shown in FIG. 11, the current-voltage characteristic of the output from the secondary winding of the transformer T is changed, and the output luminous flux of the discharge lamp DL is adjusted. Here, the differential coefficient (slope) of the output voltage with respect to the output current increases as the ON period is long and the frequency is low (the differential coefficient is generally negative, so the absolute value is small). Further, in this configuration, since the discharge lamp is continuously dimmed to the low luminous flux region, the discharge lamp is hard to be extinguished (F40SP manufactured by General Electric Company, USA).
35).

In order to simplify the description of the circuit configuration shown in FIG. 10, the lighting circuit 1 is a resistance ballast R as shown in FIG. 12, and the discharge lamp DL is connected to the AC power source AC via the resistance ballast R. Consider a circuit configuration in which is connected. In this configuration, changing the ON period and ON / OFF frequency of the switching element Q ₁ is equivalent to changing the resistance value of the resistance ballast R. In addition, current and voltage are considered as effective values. In general, the current-voltage characteristic of the discharge lamp DL is as shown in FIG. 13, the output current of the lighting circuit 1 is the passing current I of the resistance ballast R, and the output voltage V of the lighting circuit 1 is the resistance ballast R. Using the resistance value of
It can be expressed as E-IR (where E is the voltage of the AC power supply AC). Therefore, as shown in FIG. 14, the operating point of the discharge lamp DL can be expressed as an intersection of a straight line representing the current-voltage characteristic of the output of the lighting circuit 1 and a curve representing the current-voltage characteristic of the discharge lamp DL. it can.

Here, the operating points of the discharge lamp DL are P ₁ , P ₂ and P _{3 in} ascending order of current, and the operating points P ₁ ,
Stability will be considered for P ₂ and P ₃ . Also for convenience,
Region a where the current is smaller than point P ₁ , the currents are points P ₁ and P
_The area b is located between ₂ and ₂ , the area c is between the points P ₂ and P _3, and the area d is larger than the point P ₃ .

First, at the point P ₁ , when the change toward the region a, that is, the change in the lamp current in the decreasing direction occurs, the lamp voltage tends to change in the decreasing direction. Therefore, the voltage across the resistor ballast R changes in the increasing direction. To do. Since the resistance value of the resistance ballast R is fixed, if the voltage across the resistance ballast R rises, the passing current I of the resistance ballast R increases and the lamp current changes in the increasing direction. On the other hand, when the lamp current changes toward the region b at the point P ₁ , the lamp voltage tends to increase and the voltage across the resistance ballast R tends to decrease. Therefore, the passing current to the resistance ballast R decreases and the lamp current changes in the decreasing direction. After all, at the point P ₁ , even if the lamp current increases or decreases, a change in the returning direction occurs, so that stable operation can be achieved.

At point P ₂ , when the lamp current decreases and changes toward the region b, the lamp voltage tends to increase, so that the voltage across the resistor ballast R decreases and the output current of the lighting circuit 1 decreases. Changes to decrease. When the lamp current increases and changes toward the region c, the lamp voltage tends to decrease, and the output current of the lighting circuit 1 changes in the increasing direction. That is, when a change occurs in the lamp current, the lighting circuit 1 changes the output current in a direction to increase the change, so that the point P ₂ becomes an unstable operating point.

The point P ₃ can be considered in the same manner as the point P _1, and when the lamp current decreases and changes toward the c region, the output of the lighting circuit 1 increases and the lamp current increases to d. When the change toward the area occurs, the output of the lighting circuit 1 decreases, and the operation point P ₃ operates stably. As is clear from the above consideration, the point P
₁ and P ₃ are stable operating points, and point P ₂ is an unstable operating point.

[0008]

In the above structure, when the resistance value of the resistance ballast R is changed, the slope of the output voltage with respect to the output current of the lighting circuit 1 changes as shown by the broken line in FIG. The output luminous flux of the discharge lamp DL changes. As a singular point in the process of changing the resistance value of the resistance ballast R in this way, as shown in FIG. 16, a curve showing the current-voltage characteristic of the discharge lamp DL and the output current of the lighting circuit 1-
Consider the contacts X ₁ and X ₃ with a straight line (here, the resistance ballast R is the lighting circuit 1; therefore, it is not necessarily a straight line). Each contact X ₁ ,
As is clear from the above consideration, X ₃ is an unstable operating point, and at such an operating point, when some disturbance is applied, the operating point shifts to stable operating points X ₂ and X ₄ .

For example, if the output light flux of the discharge lamp DL is dimmed to a low light flux region by continuously reducing the slope of the current-voltage characteristic of the output of the lighting circuit 1, the dimming amount is continuously adjusted to a certain dimming amount. Although the output light flux decreases, the output light flux suddenly decreases due to the dimming amount, and thereafter, the output light flux continuously decreases again. That is, although the lighting circuit 1 tries to continuously change the dimming amount, the output luminous flux of the discharge lamp DL does not continuously change and is dramatically reduced. In short, if an attempt is made to reduce the lamp current from the contact point X ₁ , the operating point may shift to the point X ₂ . On the contrary, even when the output luminous flux of the discharge lamp DL is increased, when the lighting circuit 1 is continuously changing the dimming amount, the output luminous flux of the discharge lamp DL jumps at a certain dimming amount. To increase. For example, if an attempt is made to increase the lamp current from the contact X ₃ , the operating point shifts to the point X ₄ . Such a jump phenomenon of the output light flux of the discharge lamp DL will be referred to as a jump phenomenon.

The above-mentioned jump phenomenon is caused by the discharge lamp DL.
The larger the absolute value of the slope of the current-voltage characteristic of the discharge lamp DL, the more conspicuous. Discharge lamp DL
The absolute value of the slope of the current-voltage characteristic of is large in the following cases. That is, when the output luminous flux is 20% or less of the rated lighting, when the preheating current of the filament of the discharge lamp DL is small (in FIG. 17, the steeper the rising, the preheating current is smaller), and when the ambient temperature is low ( Figure 1
8, the ambient temperature is lower as the temperature rises steeperly), and the discharge lamp DL has a small tube diameter (a tube thinner than the T8 tube, that is, a tube diameter of 25.4 mm or less). Such a jump phenomenon is a problem that cannot be sufficiently solved by the conventional configuration shown in FIG.

An object of the present invention is to solve the above problems and to prevent jumps in the output light flux of the discharge lamp when the dimming amount is continuously changed in the lighting circuit, and in particular a low light flux. An object of the present invention is to provide a discharge lamp lighting device for dimming that enables continuous dimming even in a region.

[0012]

In order to achieve the above object, the invention of claim 1 comprises a lighting circuit in which the current-voltage characteristic of the output to the discharge lamp is continuously variable, and the current of the discharge lamp is -In a discharge lamp lighting device for dimming, which controls the power supplied to the discharge lamp by changing the position of the intersection of the current-voltage characteristics of the output of the lighting circuit with respect to the voltage characteristics, the lighting circuits are connected in series with each other Both ends of power supply
First choke coil and switch connected between
Equipped with a switching element and connected in parallel with the switching element.
In the OFF period of the switching element,
Parallel connection to the diode and the switching element that flow current
A high-frequency power supply including a first capacitor, and a second
Choke coil, second capacitor and third capacitor
And a discharge lamp on the third capacitor.
It consists of a resonant circuit connected in parallel, and at least the discharge line
Switch for less than 20% of rated light output
The ON period of the switching element to be longer than that during rated lighting
Therefore, it is characterized in that the differential coefficient of the output voltage with respect to the output current of the lighting circuit is set smaller than the differential coefficient of the lamp voltage with respect to the lamp current of the discharge lamp.

The invention of claim 2 is the invention of claim 1.
The differential coefficient of the output voltage with respect to the output current of the lighting circuit is set to be smaller than the differential coefficient of the lamp voltage with respect to the lamp current of the discharge lamp at all of the intersections .

According to a third aspect of the invention, in the first aspect of the invention, the discharge lamp has a tube diameter of 25.4 mm or less. According to a fourth aspect of the present invention, in the first to third aspects of the invention, the high frequency power source is a switching element.
To keep the off period of the child constant and change the on period
Accordingly, characterized in that the power supplied to the discharge lamp is variable.

[0015]

According to the invention of claim 1, at least the discharge run
In the area of less than 20% of the rated light output of the discharge lamp, an unstable point does not occur in the operating point of the discharge lamp, and the output luminous flux of the discharge lamp jumps when the dimming amount by the lighting circuit is continuously changed. The jump phenomenon that would occur does not occur. In particular, although jump phenomenon is likely to occur in the low luminous flux level region, jump phenomenon allows continuous dimming does not occur at the low luminous flux region in the first aspect of the present invention.

[0016] inventions of claim 2, the discharge lamp current - the output of the lighting circuit for the voltage characteristic current - the intersection of the voltage characteristic
A than the differential coefficient of the output voltage to an output current of the lighting circuit for all is set to be smaller than the differential coefficient of the lamp voltage for the lamp current of the discharge lamp, the thus jump phenomenon that to establish such conditions This prevents the continuous dimming.

[0017] The inventions of claim 3, a exemplary embodiment for specific use conditions, continuously for small discharge lamp with a tube diameter by causing tube diameter establishes the above conditions for the following discharge lamp 25.4mm It is possible to adjust the dimming. In the invention of claim 4 , the high frequency power source is a switch
Change the ON period while keeping the OFF period of the switching element constant.
To make the power supply to the discharge lamp variable by
, The resonance condition remains unchanged even in the low luminous flux region, and the second choke coil
Resonant current flows through the coil to prevent the jump phenomenon from occurring.
You can

[0018]

Example (Reference Example 1) In this example , as shown in FIG. 1A, a current limiting element Z as a lighting circuit 1 is inserted between an AC power source AC and a discharge lamp DL. The power supplied to the discharge lamp DL is adjusted by adjusting the impedance of the current limiting element Z. Here, for all intersections of the current-voltage characteristics of the output of the lighting circuit with respect to the current-voltage characteristics of the discharge lamp, the differential coefficient of the output voltage with respect to the output current of the lighting circuit is calculated from the differential coefficient of the lamp voltage with respect to the lamp current of the discharge lamp. In order to satisfy the condition that the current limiting element Z is also set small, the impedance of the current limiting element Z is set as follows. That is, when the voltage of the AC power supply AC is E,
Desired lamp current I in the region where the jump phenomenon occurs
_1, the _I 2, the impedance _Z 1 of the current limiting element Z for _{I 3, Z 2, Z 3} , Z 1 = E /
Set I ₁ , Z ₂ = E / I ₂ , and Z ₃ = E / I ₃ . Regarding the voltage E, as shown in FIG. 1B, a straight line of V = E-IZ (where V is the lamp voltage and Z is the impedance of the current limiting element) is the current-voltage characteristic of the discharge lamp DL. Set so that it intersects the curve at only one point.

If the impedance of the current limiting element Z is set so as to satisfy the above condition, each of the impedances Z ₁ and Z
_The lamp voltage becomes substantially 0 with respect to ₂ and Z ₃ , and the lamp current is restricted only by the current limiting element Z. In addition, each impedance has one operating point, and each operating point becomes a stable operating point, and the jump phenomenon does not occur.

Reference Example 2 In the configuration of Reference Example 1 , it is necessary to set the voltage E of the AC power supply AC high and set the impedance of the current limiting element Z large. Therefore, in this example , as shown in FIG.
As a lighting circuit, a DC power supply DC having a variable output voltage is used as a power supply of a high frequency power supply 1a having a variable output frequency, and a resonance circuit 1b including a choke coil L and a capacitor C between the high frequency power supply 1a and a discharge lamp DL. Is adopted. Here, the output amplitude of the high frequency power supply 1a changes depending on the output voltage of the DC power supply DC. The capacitor C is connected in parallel with the discharge lamp DL, and the choke coil L
Is inserted between one end of the capacitor C and the high frequency power supply 1a.

First, the operation when the voltage of the DC power supply DC is kept constant and only the output frequency of the high frequency power supply 1a is changed will be described. If the discharge lamp DL does not light up when the output frequency of the high frequency power supply 1a is changed, as shown by the solid line in FIG. 3, the output voltage of the lighting circuit (the voltage across the capacitor C at the resonance frequency f ₀ of the resonance circuit 1b). ) Is the highest, and the output voltage decreases as the output frequency moves away from the resonance frequency f ₀ . On the other hand, when the discharge lamp DL is turned on, both ends of the capacitor C are short-circuited and the capacitance component of the resonance circuit 1b is reduced. Therefore, as shown by the alternate long and short dash line in FIG. become. That is, when the output frequency of the high frequency power supply 1a is changed, the output voltage of the lighting circuit becomes lower as the frequency becomes higher.

In the above configuration, as shown in FIG. 3, the output frequency of the high frequency power supply 1a is the resonance frequency f _{0 of the} resonance circuit 1b.
The frequency f ₁ is set to be slightly higher than that, and a high voltage (point A) is applied across the discharge lamp DL to start the discharge lamp DL. When the discharge lamp DL starts, the output voltage of the lighting circuit drops (point B). In order to reduce the output luminous flux from the discharge lamp DL, the output frequency of the high frequency power supply 1a may be increased to lower the output voltage of the lighting circuit.
For example, if the output frequency is set to the frequency f ₂ in FIG. 4 (point C), the output luminous flux of the discharge lamp DL can be lowered.

Here, the stability of the operating point B and the operating point C in the lighting state of the discharge lamp DL will be considered. At the operating point B, there is almost no influence of the capacitor C, so that the operation is similar to that of the ballast using only the choke coil L as described above, and the resistance ballast R in the conventional example has R = 2πfL (however, f Is equivalent to the output frequency of the high frequency power supply 1a). That is, when this operating point B becomes an operating point corresponding to the contacts X ₁ and X ₃ in FIG. 16, a jump phenomenon occurs. However, since the operating point B is set close to the resonance frequency f ₀ and the differential coefficient of the lamp voltage with respect to the lamp current is relatively small, the jump phenomenon is less likely to occur.
After all, the operating point B is substantially the same as the ballast having only the choke coil L, and becomes an unstable operating point.

On the other hand, for the operating point C, the discharge lamp D
Since the impedance of L is large, the output voltage of the lighting circuit is the resonance circuit 1b of the choke coil L and the capacitor C.
Functions as a ballast, and is close to the characteristic when the discharge lamp DL is not lit. Generally speaking, if the lamp current is to increase in this type of resonance circuit 1b,
The capacitive component is weakened and the resonance is weakened, and as a result, the output current is reduced. On the contrary, if the lamp current is to be decreased, the capacitive component becomes stronger and the resonance becomes stronger, so that the output current is increased.
That is, in the ballast using the resonance circuit 1b of the choke coil L and the capacitor C, it is easy to obtain a stable operating point.
However, since the operating point C uses a region in which the change in the output voltage is gentle with respect to the frequency change, it is difficult to obtain such an effect, resulting in an unstable operating point.

From the above consideration, the ballast using the resonance circuit 1b may cause an unstable operating point when used in a region where the lamp impedance is small near the rated lighting,
Even when the input frequency deviates from the resonance frequency f ₀ , an unstable operating point is likely to occur. Conversely, if the lamp impedance is large and the input frequency is used in a region close to the resonance frequency f ₀ when there is no load, it is easy to obtain a stable operating point.

The above findings can be summarized as shown in FIG. That is, it can be said that the region α shown in FIG. 4 is a region where an unstable operating point is easily obtained, and the region β is a region where a stable operating point is easily obtained. Therefore, in order to enable dimming in the region β, the high frequency power source 1
DC power supply DC instead of changing the output frequency of a
The dimming is performed by changing the voltage of (1) to change the output amplitude of the high frequency power supply 1a. If such light control is performed, the jump phenomenon is unlikely to occur. in short,
If dimming is performed in a region close to the resonance frequency f ₀ of the resonance circuit 1b under no load, an unstable operating point does not occur.

FIG. 5 shows a current I flowing in the choke coil L when the output frequency of the high frequency power source 1a is changed to perform dimming.
FIG. 6 shows _L , and FIG. 6 shows a current I flowing through the choke coil L when the output voltage of the DC power supply DC is changed and dimming is performed.
_L is shown. It can be seen that the current I _L is sinusoidal in FIG. 6 and is close to the resonance current at no load, and in FIG.
_It can be seen that _L has a triangular waveform and the choke coil L mainly functions as a ballast. Figure 5
However, in the present state is the jump phenomenon is likely to occur
In the example , the jump phenomenon is unlikely to occur because it is used in the state of FIG.

In the above-mentioned structure, the amplitude of the input voltage to the resonance circuit 1b is controlled by adjusting the output voltage of the DC power supply DC, but the current I _L flowing through the choke coil L which is a current limiting element is controlled. The same effect can be obtained by adopting a configuration that produces a resonance current. For example, an inverter circuit that converts direct current into alternating electric power by connecting a series circuit of at least a pair of switching elements between both ends of a DC power supply and alternately turning on and off the switching elements connected in series is used to turn on the switching elements. The so-called duty control, which controls only the conduction time without changing the OFF frequency, or the so-called asymmetric pulse width control, which shortens the conduction time of one of the switching elements connected in series and lengthens the other, may be adopted. It is possible. Further, even when the output frequency of the high frequency power supply 1a is changed, it may be configured so that the resonance current flows through the resonance circuit 1b.

Furthermore, it is not necessary to use the current I _L flowing through the choke coil L as the resonance current in the entire dimming range, and the region where the absolute value of the derivative of the lamp voltage with respect to the lamp current is particularly large, that is, the rated output luminous flux is If resonance is allowed to flow in the choke coil L only in the region of less than 20%, continuous dimming in the low luminous flux region becomes possible. (Embodiment) This embodiment is an example in which a resonance current is passed through the resonance circuit 1b without changing the power supply voltage of the DC power supply DC, as shown in FIG. High frequency power source 1a includes a switching element Q ₂ to which consisting choke coil L ₁ and the transistor which is connected across the DC power source are connected in series with each other, the diode D ₁ and capacitor C ₁ connected in parallel to the switching element Q ₂ With.
Further, the resonant circuit 1b consists of a series circuit of a choke coil _{L 2} and capacitor _{C 2} and the capacitor _{C 3,} are connected in parallel discharge lamp DL to the capacitor _{C 3.}

In the high frequency power supply 1a having the above structure, the switching element Q ₁ is turned on / off, and in the steady state, it operates as shown in FIG. That is, the OFF period T _OFF of the switching element Q _1, as shown in FIG. 8 (c), the energy stored in the choke coil L ₁ during the ON period of the switching element Q ₁ is released. This released energy is stored in the capacitors C _{1 to} C ₃ and the choke coil L.
₂ , supplied to a resonance circuit including a discharge lamp DL and the like. Therefore, the off period T of the switching element Q _{1
When turned OFF} , as shown in FIG. 8A, the voltage across the switching element Q ₁ (collector-emitter voltage) V _CE is
It changes like a sine wave and has a peak value higher than the power supply voltage V _dc . Voltage across V _CE of the switching device to Q ₁ ON period T _ON the switching element Q ₁ is made to 0V, and the immediately after the start of the ON period T _ON, the collector potential is lower than the emitter potential, 8 through the diode D ₁ (f ), The current I _D flows through the diode D ₁ . When the collector potential becomes higher than the emitter potential, the collector current I _C flows as shown in FIG. 8 (e), the next switching element Q ₁ is kept flowing collector current I _C until clear. Further, during the off period T _OFF of the switching element Q ₁ , as shown in FIG. 8 (g), the charging / discharging current I _C1 flows through the capacitor C ₁ .

Switching element Q ₁ , diode D ₁ ,
The current flowing through the capacitor C ₁ is the switching element Q ₁
It is by the OFF period T _OFF in the choke coil L _1, L ₂ the energy stored in the synthesis and a current I _L2 such as current I _L1 and Figure 8 (b), as shown in FIG. 8 (c) The current I _L1 + I _L2 as shown in FIG. 8D is obtained by switching element Q ₁ , diode D ₁ , capacitor C ₁ for each period.
Flow to each. That is, an alternating current similar to the current I _L2 flowing through the choke coil L ₂ flows through the discharge lamp DL.

When dimming is performed using the circuit configuration shown in FIG. 7, as shown in FIG.
₁ OFF period T _OFF is kept constant and ON period T _ON
And the energy stored in the choke coils L ₁ and L ₂ is changed to adjust the light output of the discharge lamp DL. That is, in the rated lighting shown in FIG. 9A, the ON period T _ON is set longer than in the dimming lighting shown in FIG. 9B. If the dimming control is performed in this way, the resonance condition is not broken, so that the choke coil L
The ₂ flows resonance current _{I L2,} so that the same effect as in Reference Examples 1 and 2 is obtained.

When a sufficient dimming range cannot be secured by adjusting the _ON period T _ON as described above, the method of adjusting the output amplitude by adjusting the input power supply voltage is also used as in Reference Example 1. Good.

[0034]

According to the invention of claim 1, at least the discharge run is performed.
In the area of less than 20% of the rated light output of the discharge lamp, an unstable point does not occur in the operating point of the discharge lamp, and the output luminous flux of the discharge lamp jumps when the dimming amount by the lighting circuit is continuously changed. There is an advantage that the jump phenomenon that occurs does not occur. In particular, the jump phenomenon is likely to occur in the low luminous flux region, but the invention of claim 1 has an advantage that the jump phenomenon does not occur even in the low light flux region and continuous dimming is possible. .

[0035] The inventions of claim 2, the discharge lamp current - the output of the lighting circuit for the voltage characteristic current - the intersection of the voltage characteristic
Since the differential coefficient of the output voltage to an output current of the lighting circuit for all is set to be smaller than the differential coefficient of the lamp voltage for the lamp current of the discharge lamp, thus preventing the jump phenomenon that to establish such conditions The advantage is that continuous dimming can be achieved.

[0036] The inventions of claim 3, a embodiment of specific conditions of use, since the tube diameter is to establish the conditions for the following discharge lamp 25.4 mm, continuously even for small discharge lamp with a tube diameter This has the effect of enabling fine light control. In the invention of claim 4 , the high frequency power source is a switch.
Change the ON period while keeping the OFF period of the ching element constant.
Or varying the power supplied to the discharge lamp by Rukoto
, The resonance condition remains unchanged even in the low luminous flux region, and the second choke coil
Resonant current flows through the coil to prevent the jump phenomenon from occurring.
You can

[Brief description of drawings]

1A and 1B show a reference example 1, where FIG. 1A is a schematic circuit diagram and FIG.
Is an operation explanatory view.

FIG. 2 is a circuit diagram showing a second reference example .

FIG. 3 is an operation explanatory diagram of Reference Example 2;

FIG. 4 is an operation explanatory diagram of Reference Example 2;

FIG. 5 is an operation explanatory diagram of a comparative example.

FIG. 6 is an operation explanatory diagram of Reference Example 2;

FIG. 7 is a circuit diagram showing an example .

FIG. 8 is a diagram illustrating the operation of the embodiment .

FIG. 9 is a diagram illustrating the operation of the embodiment .

FIG. 10 is a schematic circuit diagram showing a conventional example.

FIG. 11 is an operation explanatory diagram of a conventional example.

FIG. 12 is a diagram illustrating the principle of a conventional example.

FIG. 13 is an explanatory diagram showing current-voltage characteristics of a discharge lamp.

FIG. 14 is an operation explanatory diagram of a conventional example.

FIG. 15 is an operation explanatory diagram of a conventional example.

FIG. 16 is an operation explanatory diagram of a conventional example.

FIG. 17 is an explanatory diagram showing a relationship between a preheating current of a discharge lamp and a current-voltage characteristic.

FIG. 18 is an explanatory diagram showing the relationship between the ambient temperature of the discharge lamp and the current-voltage characteristics.

[Explanation of symbols]

AC AC power supply DL discharge lamp Z current limiting element

Claims (4)

(57) [Claims] 1. A lighting circuit, wherein the current-voltage characteristic of the output to the discharge lamp is continuously variable, and the position of the intersection of the current-voltage characteristic of the output of the lighting circuit with respect to the current-voltage characteristic of the discharge lamp is changed. in the discharge lamp lighting device for dimming controlling the power supplied to the discharge lamp by lighting
The circuits are connected in series with each other and connected across the DC power supply.
The first choke coil and switching element
It is equipped with a switching device and connected in parallel.
A current flowing in the opposite direction to the ON period is supplied during the OFF period of the chinging element.
First connected in parallel with diode and switching element
High frequency power supply with capacitor 1 and second choke
Series of coil, second capacitor and third capacitor
Discharge lamp is connected in parallel with the third capacitor.
The resonance circuit is
Switching element for less than 20% of rated output
By setting the ON period of the lamp to be longer than the rated lighting time, the differential coefficient of the output voltage with respect to the output current of the lighting circuit is set to be smaller than the differential coefficient of the lamp voltage with respect to the lamp current of the discharge lamp. Discharge lamp lighting device for light control. 2. The differential coefficient of the output voltage with respect to the output current of the lighting circuit is set to be smaller than the differential coefficient of the lamp voltage with respect to the lamp current of the discharge lamp at all of the intersections . Discharge lamp lighting device for dimming. 3. The discharge lamp lighting device for light control according to claim 1, wherein the discharge lamp has a tube diameter of 25.4 mm or less. 4. The high frequency power supply is a switching element
The discharge lamp for dimming according to any one of claims 1 to 3 power supplied to <br/> discharge lamp by changing the ON period and the off period constant, characterized in that a variable Lighting device.