JP3136108B2 - Lighting device for discharge lamp - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a discharge lamp, and more particularly to a lighting device having a push-pull type inverter.

[0002]

2. Description of the Related Art Generally, in a lighting device for a discharge lamp using a push-pull type inverter, as shown in FIG. 6, a rectifier is connected to an AC input from a commercial AC power supply 11 via a line filter 12 as shown in FIG. The DC power supply circuit 15 is formed by connecting the circuit 13 and the partial smoothing type circuit or the step-up type power factor correction circuit 14, and the push-pull type inverter 16 is operated by the DC voltage to light the discharge lamp FL. Here, the boosting power factor improving circuit 14 uses, for example, Motorola Corporation's MC33262P to increase the input power factor and obtain a constant DC voltage.

A push-pull type inverter 16 includes a pair of switching elements (transistors) Q ₁ and Q ₂ which are connected in a push-pull manner and are turned on and off alternately, and a DC power supply circuit 15 via the switching elements Q ₁ and Q ₂ . An oscillation transformer 18 having a primary winding P (P ₁ and P ₂ ) having both ends connected to the negative electrode side and an intermediate point Pm connected to the positive electrode side of the DC power supply circuit 15 is provided.
The discharge lamp FL is turned on by the boosted high-frequency power obtained from the next winding S.

Here, the input side of the oscillation transformer 18 is usually divided into two parts with an intermediate tap M corresponding to an intermediate point Pm and connected in series with each other as shown in a circuit diagram of FIG. Two windings P ₁ and P ₂ ,
Oscillating circuit by the capacitor C _1, C ₂ connected in parallel thereto is formed, the windings P _1, P _2, as shown in FIG. 8
As shown in schematically sectional view, one winding P ₁ (on the side closer to the iron core 181) surrounding the inner one of the core 181 is wound, after intermediate tap M is derived, the outer ( other winding P ₂ is wound on the far side) the iron core 181.

[0005]

In the lighting device for a discharge lamp having the above-described push-pull type inverter, the number of turns depends on the shape of the primary windings P ₁ and P ₂ of the oscillation transformer 18. Are equal to each other,
There is a problem that a considerable difference occurs between the respective self-inductances.

That is, the sectional area of an elongated cylindrical solenoid or annular endless solenoid is a, the length is b, and the total number of turns is n.
Then, when a current i flows through the coil of the solenoid, the magnetic field H generated therein becomes H = ni / b [A / m], so that the magnetic permeability inside the coil is μ = μ _S μ ₀ ( μ
₀ ; vacuum permeability, μ _S ; relative permeability), the magnetic flux density B, the magnetic flux φ, the linkage flux N, and the self-inductance L
Are represented by the following equations.

[0007]

(Equation 1)

In a lighting device having a conventional push-pull type inverter, the primary winding P of the oscillation coil 18 is used.
_As described above, ₁ and P ₂ are wound around the inside and outside of the iron core 181, respectively. Therefore, if the cross-sectional areas are a ₁ and a ₂ , naturally, a ₁ <a ₂ Therefore, assuming that the self-inductances of these windings P ₁ and P ₂ are L ₁ and L ₂ respectively,

[0009]

(Equation 2)

Therefore, L ₁ <L ₂ .

In order to eliminate the difference in self-inductance L _1, L ₂ such windings P _1, P ₂ are conventionally experimentally slightly increase either the number of turns of each winding P _1, P ₂ There was a problem that it was necessary to adjust by reducing or reducing. Here, the self inductances L ₁ , L ₂ of P ₁ , P _{2
If the two} are different, the oscillation state becomes unbalanced, and especially at the end of the life of the discharge lamp, that is, at the time of half-wave discharge in the emissionless state, the switching element of the inverter is damaged. Therefore, it is necessary to provide a separate protection circuit.

The present invention has been made in view of such circumstances, and the number of turns of each winding is adjusted as in the related art while using an oscillation transformer in which the primary winding is divided into two windings by an intermediate tap. The self-inductance of each winding can be made substantially equal without the need to adjust the number of turns, so that the push-pull inverter can continue to oscillate in a state where it is always balanced on both poles. An object of the present invention is to provide a lighting device for a discharge lamp that can prevent breakage of each switching element at the end of life of the discharge lamp without providing the lighting device.

[0013]

A structure for achieving the above object will be described with reference to FIGS. 1 to 3 showing an embodiment. A pair of switching elements Q1, Q2 that are pull-connected and alternately turned on and off, and both ends of the primary winding P are connected to the negative electrode side of the DC power supply circuit 5 through the respective switching elements Q1, Q2. A lighting device for a discharge lamp including a push-pull inverter having an oscillation transformer 8 having a positive electrode side of the DC power supply circuit 5 connected to an intermediate point Pm obtained by dividing the pair of windings P into two, 8 is composed of two leakage transformers 80a and 80b, and the primary winding P of the oscillation transformer 8 is
Is further divided into two on both sides of the intermediate point Pm, and two windings are arranged on both sides of the intermediate point Pm. Then, the one P ₁₁ on one side of the two windings P _11, P ₁₂ of the midpoint Pm, other P ₂₂ of two windings P _21, P ₂₂ on the other side of the midpoint Pm is, one leakage transformer the iron core 81a of 80a, the midpoint one winding P ₁₁
There windings P ₂₂ intermediate points other side is wound so as to be located on the outside on the inside and two windings of the other side of the midpoint Pm P
_21, and one P ₂₁ of P _22, the other P ₁₂ on one side of the two windings P _11, P ₁₂ of the midpoint Pm is, the core 81b of the other leakage transformer 80b, the winding of its midpoint other side P ₂₁ is characterized by the windings P ₁₂ of the midpoint on one side on the inside is wound so as to be positioned on the outer side.

[0014] According to the above present invention, the primary winding of the oscillating transformer 8 has one end winding from side P _11, winding P _12, the midpoint Pm, winding P _21, winding P ₂₂ order are connected in series, as shown in FIG. 3, the winding P ₁₁ and the winding P ₂₂ iron core 81a of one of the leakage transformer 80a, the winding P ₂₂ is the outer winding P ₁₁ is on the inside wound so as to be positioned, and the core 81b of the winding P ₂₁ and the winding P ₁₂ and the other leakage transformer 80b, winding P ₁₂ winding P ₂₁ is on the inside
Is wound so as to be located outside, so that the intermediate point P
The cross-sectional areas of the windings on both sides of m can be made substantially equal to each other.

[0015] That is, the pair of side winding P ₁₁ and P ₁₂ across the midpoint Pm has one of the windings P ₁₁ are wound on the inner side of the leakage transformer 80a, other winding P ₁₂ another While being wound outside the leakage transformer 80b of
The windings P ₂₁ and P ₂₂ on the opposite side of the intermediate point Pm
The pair one winding P ₂₁ is a leakage transformer 80b
Inside of, other winding P ₂₂ is a leakage transformer 80a
Is wound around the outside of each of the leakage transformers 80a.
80b and by the same shape and dimensions each including an iron core, each winding _{P 11, P 12, P 21} , P and their respective cross-sectional areas each equal turns a ₁₁ of _22, a ₁₂ and,
Assuming that a ₂₁ and a ₂₂ , a ₁₁ ≒ a ₂₁ <a ₁₂ ≒ a _22. However, a pair of two windings P ₁₁ and P ₁₂ on each side of the intermediate point Pm, and P ₂₁ the sum of the cross-sectional area of the P ₂₂ becomes _{a 11 + a 12 ≒ a 21} + a 22.

Accordingly, each of these windings P ₁₁ , P ₁₂ ,
The self-inductances of P ₂₁ and P ₂₂ are represented by L ₁₁ ,
When L ₁₂ , L ₂₁ , and L ₂₂ , L ₁₁ + L ₁₂ 21L ₂₁ + L ₂₂ holds, and the self-inductances of the primary windings on both sides of the intermediate point Pm can be made substantially equal.

[0017]

FIG. 1 is an overall circuit configuration diagram of an embodiment of the present invention, and FIG. 2 is a detailed circuit configuration diagram showing an oscillation transformer 8 extracted therefrom.

An AC input from a commercial AC power supply 1 is connected to a full-wave rectifier 3 and a boost type power factor correction circuit 4 via a line filter 2 to increase the input power factor and convert it to a constant DC voltage. Is done. An electric field capacitor 51 for smoothing is connected in parallel to the boosting power factor correction circuit 4. These by forming a direct current power source circuit 5 for the inverter 6. The smoothed DC output is supplied to the inverter 6 via the constant current inductor 52.

The inverter 6 is a push-pull type inverter, and includes two switching transistors Q ₁ and Q ₂ which are push-pull connected to each other, an oscillation transformer 8 having an intermediate tap M, and a primary winding of the oscillation transformer 8. The main components are _two capacitors C ₁ and C ₂ inserted in parallel to the line.

The oscillation transformer 8 is actually composed of two leakage transformers 80a and 80b, and the primary winding of the oscillation transformer 8 has an intermediate point P.
m on both sides of the intermediate tap M provided at
Divided into a total of four windings P ₁₁ , P ₁₂ , P ₂₁ and P
₂₂ is divided into, which are serially connected in the order of P _11, P _12, center tap M, P _21, P _22. Then, two of each of the four primary windings are wound around the two leakage transformers 80a and 80b, respectively, to form respective primary windings. Further, the secondary winding of the oscillating transformer 8 is divided into two, has a their respective secondary windings are each winding S ₁ and S ₂ are wound around the two leakage transformer 80a, 80b, As shown in FIG. 2, these are connected in series, and both ends thereof are connected to the discharge lamp FL.

The winding P divided on one side of the intermediate tap M₁₁
And P₁₂Pair has one of its windings P ₁₁But leakage tiger
The other winding P₁₂Is another
It is wound around the leakage transformer 80b. Also, inside
Winding P divided on the other side of the intermediate tap M_{twenty one}And P_{twenty two}Pair of
Is one of the windings P_{twenty one}Is leakage transformer 80b
And the other winding P_{twenty two}To the leakage transformer 80a
Each is wound.

The two leakage transformers 8
Both ends of the oscillating transformer 8 consisting 0a and 80b, i.e. beginning and end of the winding P ₂₂ of the winding P ₁₁ is connected to each of the two collectors of the transistors Q _1, Q ₂ mentioned above, respectively, the respective transistors Each emitter of Q ₁ and Q ₂ is connected to the negative side of the DC power supply circuit 5. The intermediate tap M of the oscillation transformer 8 is connected to the positive side of the DC power supply circuit 5.

Further, the bases of the transistors Q _1, Q _2, with each end of the feedback winding T ₁ of the oscillating transformer 8 is connected, the base of each transistor Q _1, Q ₂ is, Like the tertiary winding T ₂ of the oscillating transformer 8, the electric field capacitor and the diode D _1, D ₂ rectifies the voltage is stepped down by the third winding T _2, to direct current the rectified voltage by smoothing It is connected to a main base energizing current supply circuit 9 comprising 91 and the like.

Now, each of the leakage transformers 80 described above will be described.
The winding positions of each primary winding with respect to a and b are shown in FIG.
(A) and (B) show schematic sectional views. That is, the core 81a of the leakage transformer 80a
Winding P ₁₁ is wound directly wound, winding P ₂₂ is wound on the outer side with respect to. Further, with respect to the iron core 81b of the other leakage transformer 80b, winding P ₂₁ is wound directly wound, winding P ₁₂ is wound on the outside thereof.

Here, in this example, each leakage
Cores 81a and 81 of transformers 80a and 80b
b have the same shape and size as each other, and
P₁₁, P ₁₂, P_{twenty one}, P_{twenty two}Have the same number of turns. Follow
And each of these windings P₁₁, P₁₂, P _{twenty one}, P_{twenty two}The cross section of
Each a₁₁, A₁₂, A_{twenty one}, A_{twenty two}Then, each iron core 81
a or 81b, the winding P wound inside
₁₁And P_{twenty one}Cross section a₁₁And a_{twenty one}Are approximately equal to each other,
In addition, each iron core 81a or 81b is wound outward.
Winding P₁₂And P_{twenty two}Cross section a₁₂And a_{twenty two}Is
Become substantially equal to each other, and a₁₂And a_{twenty two}Each
Rea₁₁And a_{twenty one}Larger than.

Next, the operation of the above embodiment of the present invention will be described. When the power switch of the commercial AC power supply 1 is turned on, full-wave rectification is performed by the full-wave rectifier 3 and input to the boosting power factor correction circuit 4. DC voltage output from the circuit is a constant voltage inductor 52, flowing a weak current through the starting resistance R ₀ in the base circuit of a pair of transistors Q _1, Q _2. As a result, _one of the pair of transistors Q ₁ and Q ₂ conducts, and the oscillation transformer 8 (80a, 80b)
Coupled with the voltage being applied to the primary winding current on both sides of the winding P ₁₂ and P _11, and one of P ₂₁ and P ₂₂ across the intermediate tap M of the primary winding of the oscillating transformer 8 Flows. As a result, a voltage is induced in the secondary windings S ₁ and S ₂ of the oscillation transformer 8 and at the same time, a pair of transistors Q ₁ and
It is induced voltage in the feedback winding T ₁ which is connected to the base circuit of Q _2, one transistor which has been conducting nonconductive and feedback winding so as to conduct the transistors were non-conductive earlier feedback from T ₁ is applied. In this manner, the pair of oscillation transistors Q ₁ and Q ₂ alternately perform on / off operations.

On the other hand, a stepped down voltage is induced in a winding T ₂ wound around a part of the primary side of the oscillation transformer 8, and this voltage is full-wave rectified by rectifiers D ₁ and D ₂ , and an electric field capacitor is provided. A DC base energizing current is supplied to the bases of the transistors Q ₁ and Q ₂ via the resistors R _{1 to} R _4, which are smoothed by the resistor 91. The inverter 6 quickly reaches normal oscillation by the supply of the base current from the main base energizing current supply circuit 9. The discharge lamp FL is immediately turned on by the high frequency secondary output of the inverter 6.

[0028] Now, in the above oscillation, the one transistor Q ₁ is turned on, Q ₂ is off, [the DC power supply circuit 5 positive → intermediate tap M → winding P ₁₂ → winding P ₁₁
→ transistor Q ₁ → negative electrode of DC power supply circuit 5] conducts, and current flows through this path. On the other hand, when transistor Q ₁ is off and Q ₂ is on,
The positive electrode → an intermediate tap M → winding P ₂₁ → winding P ₂₂ → negative electrode of the transistor Q ₂ → DC power source circuit 5] becomes conductive, a current flows in this path, the secondary winding S ₁ by this repetition,
The discharge lamp FL is driven by a high frequency induced in S _2.

In such an operation, as described above, since a ₁₁ ≒ a ₂₁ <a ₁₂ ≒ a ₂₂ and the number of turns of these windings is the same, the windings P ₁₁ , P ₁₂ , P ₂₁ , and P ₂₂ , where L ₁₁ , L ₁₂ , L ₂₁ , and L ₂₂ , respectively, are L ₁₁ + L ₁₂ ≒ L ₂₁ + L ₂₂ , and a pair of windings through which a current flows in each of the conduction states described above. the sum of the self-inductance value of P ₁₁ and P _12, and P ₂₁ and P ₂₂ are substantially equal to each other. Therefore,
The oscillation circuit continues the oscillation state in a balanced state.

It should be particularly noted in the above embodiment of the present invention that the primary winding of the oscillation transformer 8 divided into a total of four windings has an intermediate tap M without adjusting the number of turns. This is the point where the self-inductance on both sides of the pin is inevitably substantially equal, and it is possible to continue oscillation in a very stable and balanced state without going through the conventional work of adjusting the number of turns. Electric light FL
The transistor Q ₁ , Q ₂ is not likely to be damaged even during a half-wave discharge in an emission-less state at the end of its life.

Table 1 is a table showing the results of actually assembling the oscillation transformer 8 shown in the above-described embodiment of the present invention and actually measuring the self-inductance of each part.
Here, in this [Table 1], A indicates the total value of inductances L ₁₁ + L ₁₂ of the windings P ₁₁ and P ₁₂ , and B indicates the winding P ₂₁
Indicates the total value L ₂₁ + L ₂₂ of the inductance of the P ₂₂ and. In addition, the ratio of the difference of inductance,

[0032]

(Equation 3)

Is calculated by

[0034]

[Table 1]

As is apparent from Table 1, the difference between the inductances of the windings on both sides of the intermediate tap M is described.
The percentage is very small, incidentally, in the oscillation transformer of the illustrated conventional structure in FIG. 7, the ratio ratio of this difference is usually 1.5%
It is about.

In the embodiment of the present invention shown in FIG. 1, the measurement result of the voltage waveform between XX 'in FIG. 1 is as shown in FIG. 4, and the stable and balanced oscillation state is shown. It was confirmed to continue.

In addition, when the oscillation transformer 8 is constituted by the two leakage transformers 80a and 80b, the following effects can be obtained. That is, since the surface area per unit volume of the oscillation transformer 8 is increased, the heat radiation effect is increased. In addition, with the recent diversification of discharge lamps (fluorescent lamps), a variety of inverters for lighting the lamps are required, and existing ferrite cores that are commercially available are used. In order to satisfy the specified specifications, satisfactory test results may not be obtained with a single oscillation transformer as in the past, but by dividing the oscillation transformer into two transformers, the degree of freedom in design is increased. And various specifications can be satisfied by using a commercially available ferrite core.

In the above embodiment, an example using the boosting power factor correction circuit 4 and the electric field capacitor 51 has been described. Instead, a partial smoothing circuit as shown in FIG. Although an example in which a circuit may be used and the oscillation control of the push-pull type inverter 6 is of a self-excited type has been described, it is needless to say that this can be separately excited.

[0039]

As described above, according to the present invention, an oscillation transformer in a discharge lamp lighting device using a push-pull type inverter is constituted by two leakage transformers and a primary winding of the oscillation transformer. Is further divided into two parts on both sides of the intermediate point. One pair of two windings on each side of the intermediate point is placed inside one of the leakage transformer cores and the other is placed on the other side. Since it is wound outward, the self-inductance of the windings on both sides of the middle point of the primary winding can be made substantially equal to each other without fine adjustment of the windings, and a stable and balanced state Thus, a lighting device that continues to oscillate can be easily obtained. As a result, even in the emissionless state of the discharge lamp, the switching element of the inverter can be prevented from being destroyed without requiring a special protection device, which greatly contributes to cost reduction.

Further, since the oscillation transformer is divided into two leakage transformers, the surface area per unit volume increases and the temperature rise can be reduced, and at the same time, various types of ferrite cores that can be easily obtained on the market are used. It has become possible to construct an inverter that can handle a variety of discharge lamps.

[Brief description of the drawings]

FIG. 1 is an overall circuit configuration diagram of an embodiment of the present invention.

FIG. 2 is a detailed circuit diagram showing the oscillation transformer 8 extracted and shown.

FIG. 3 is a schematic sectional view showing a winding position of a primary winding of the oscillation transformer 8 with respect to iron cores 81a and 81b of leakage transformers 80a and 80b.

FIG. 4 is a graph showing actual measurement results of an oscillation waveform according to the embodiment of the present invention (collector voltages of Q ₁ and Q ₂ ).

FIG. 5 is a circuit diagram showing a configuration example of a partial smoothing circuit that can be used in place of the boost type power factor correction circuit in the present invention.

FIG. 6 is a circuit diagram illustrating a configuration example of a conventional discharge lamp lighting device using a push-pull inverter.

7 is a circuit configuration diagram in the vicinity of the oscillation transformer 18 of FIG.

FIG. 8 is a schematic cross-sectional view showing a winding position of a primary winding with respect to an iron core of an oscillation transformer in a conventional push-pull inverter.

[Explanation of symbols]

2 Line filter 3 Full-wave rectifier 4 Boost type power factor improvement circuit 5 DC power supply circuit 51 Electrolytic capacitor 52 Constant current inductor 6 Push-pull type inverter 8 Oscillation transformer 80a, 80b Leakage transformer 9 Main base energizing current supply circuit M Middle tap P _11, the primary winding Q _1, Q ₂ transistors P _12, P _21, P ₂₂ oscillating transformer 8

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05B 41/24-41/298

Claims (1)

(57) [Claims] 1. A pair of switching elements which are mutually push-pull connected and which are alternately turned on and off, and both ends of a primary winding are connected to a negative electrode side of a DC power supply circuit via the respective switching elements. A lighting device for a discharge lamp including a push-pull type inverter having an oscillation transformer whose positive electrode side of the DC power supply circuit is connected to an intermediate point where the primary winding is divided into two, wherein the oscillation transformer has two oscillation transformers. The primary winding of the oscillation transformer is further divided into two parts on both sides of the intermediate point, and two windings are arranged on both sides of the intermediate point.
And one of the two windings on one side of the intermediate point and the other
The other of the two windings on one side is
The winding on one side of the intermediate point is inside and the other
Is wound so that the side winding is located on the outside, and
One of the two windings on the other side of the point and the two
The other of the windings is the iron core of the other leakage transformer
The winding on the other side of the intermediate point is
A lighting device for a discharge lamp, wherein the wire is wound so that the wire is located outside.