JP3201757B2 - Discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention converts a voltage, a current, etc., suitable for stably lighting a discharge lamp, such as a fluorescent lamp, provided with a high-frequency oscillation circuit. The present invention relates to a discharge lamp lighting device for supplying an electric lamp.

(Prior art) In order to stably turn on a discharge lamp, for example, a fluorescent lamp,
Conventionally, so-called electromagnetic ballasts have been frequently used, and recently, electronic ballasts have also been used.

The electromagnetic ballast uses commercial AC power (for example, 50 Hz, 100
V) to increase the voltage to a level suitable for lighting a fluorescent lamp or the like, and furthermore, the fluorescent lamp or the like exhibits a so-called negative characteristic in which the impedance rapidly drops when the lighting is started. It supplies power to lamps and the like.

The electronic ballast is an improvement of the electromagnetic ballast because the electromagnetic ballast has a large size. That is, to explain an example of the configuration, the input commercial AC power is once rectified and then converted to, for example, 20 kHz, 300 V AC power by a high-frequency oscillation circuit, for example, a Royer type self-excited oscillation circuit, and the output current is limited to supply power to the fluorescent lamp. By increasing the frequency from 50 Hz to 20 kHz, the transformer and the like can be made smaller, and the volume can be reduced to about 30% as compared with the electromagnetic ballast. As this high frequency oscillation circuit, one having a frequency of about 10 KHz to 300 KHz is usually used.

 Hereinafter, a lower type self-excited oscillation circuit will be described as an example.

FIG. 6 is a circuit diagram showing a basic circuit configuration of a Royer type self-excited oscillation circuit.

The emitters 1a and 2a of the two NPN transistors 1 and 2 are grounded. Collectors 1b, 2 of the two NPN transistors 1,2
b is connected to each end 4a, 4b of the primary winding 4 of the transformer 3. The bases 1c, 2 of the two NPN transistors 1, 2
c is connected to each end 5a, 5b of the winding 5 of the transformer 3. One end of the power supply 80 is grounded and the other end is connected to the intermediate terminal 4c of the temporary winding 4 of the transformer 3 via the choke coil 7. Here, the transformer 3 is configured to have an appropriate leakage magnetic flux between the primary winding 4 and the secondary winding 6 of the transformer 3 so as to conform to the negative characteristics of a fluorescent lamp or the like. The secondary winding 6 is connected to a fluorescent lamp (not shown).

In the lower-type self-excited oscillation circuit configured as described above, if the transistor 1 first starts to be turned on by some trigger, the transformer 3 is excited and the transistor 1 is quickly turned on. When the magnetic core of the transformer 3 reaches saturation, the transistor 1 is turned off. When the core is turned off, a back electromotive force is generated in the transformer 3 and the transistor 2 is turned on. Oscillation continues by this repetition.

Here, the two transistors 1 and 2 may be turned on at the same time due to the switching delay time of the two transistors 1 and 2. At this time, among the primary windings of the transformer 3, the windings on both sides of the intermediate terminal 4c excite the magnetic core of the transformer 3 in opposite directions, so that the transformer 3 loses its function as an inductor. At this moment, an inrush current tries to flow into the two transistors 1 and 2 at this moment. The choke coil 7 limits the current flowing into the lower type self-excited oscillation circuit,
To prevent the transistors 1 and 2 from being destroyed.

Further, when this lower type self-excited oscillation circuit is used as a ballast for lighting a fluorescent lamp, a capacitor 8 may be connected between both collectors 1b and 2b of the two transistors 1 and 2.
The Royer-type self-excited oscillation circuit basically oscillates with a rectangular wave. However, the connection of the capacitor 8 causes the oscillation waveform to approach a sine wave, so that the heat generation of the transistors 1 and 2 can be reduced. The life of an electronic ballast using a self-excited oscillation circuit can be extended.

(Problems to be Solved by the Invention) For example, the Royer-type self-excited oscillation circuit is an oscillation circuit suitable for an electronic ballast (discharge lamp lighting device), but even if the choke coil 7 and the capacitor 8 are connected. There is still a problem that heat generation is large.

The present invention has been made in view of the above circumstances, and has as its object to provide a discharge lamp lighting device in which the above-described heat generation is further reduced by providing a simple additional circuit in a high-frequency oscillation circuit known so far for a discharge lamp lighting device. It is assumed that.

(Means for Solving the Problems) The discharge lamp lighting device of the present invention is a discharge lamp lighting device provided with various high-frequency oscillation circuits such as a Royer system, a Johnsen system, a half-bridge system, and a modified forward system.
A parallel resonance circuit is provided between a power supply for supplying power to the high-frequency oscillation circuit and the high-frequency oscillation circuit, the parallel resonance circuit limiting an inrush current flowing from the power supply to the high-frequency oscillation circuit. .

Here, the high-frequency oscillation circuit is, for example, the above-described 10 KH
A circuit that oscillates at a frequency of about z to 300 KHz, but this depends on the selected circuit element and circuit method, and is not limited to the frequency within the above range, and the frequency of commercial AC power It refers to various high-frequency oscillation circuits used in so-called electronic ballasts, which are considerably higher in frequency.

(Operation) In the discharge lamp lighting device of the present invention, a capacitor is connected in parallel with a current limiting coil (for example, choke coil 7 in FIG. 4) connected between a power supply and a high-frequency oscillation circuit to form a parallel resonance circuit. By forming such a structure to prevent an inrush current, the oscillation waveform further approaches a sine wave, thereby reducing the heat generation of the transistor and further extending the life of the discharge lamp lighting device. In addition, a humming sound may be generated from the current limiting coil due to the distortion of the oscillating waveform. However, since the oscillating waveform is further improved, the humming sound is prevented or reduced.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram for explaining the principle of a lower type self-excited oscillation circuit according to one embodiment of the present invention. The same elements as those in FIG. 6 are denoted by the same reference numerals as in FIG. 6, and description thereof will be omitted.

1, a capacitor 9 is connected in parallel with the choke coil 7, and the choke coil 7 and the capacitor 9 form a parallel resonance circuit. As is well known, the parallel resonance circuit has a high impedance for frequencies within a predetermined range around a predetermined resonance frequency. Therefore, by setting the capacitance of the capacitor 9 so that the resonance frequency of the parallel resonance circuit becomes an appropriate frequency, only the rush current can be effectively used without obstructing the supply of power from the power supply 6 to the lower type self-excited oscillation circuit. Is prevented, the waveform is improved,
Heat generation of the transistors 1 and 2 is reduced.

FIG. 2 is a circuit diagram showing a specific embodiment of the discharge lamp lighting device of the present invention.

Commercial AC power (for example, 100VAC, 50Hz) from terminals 10,10
Is input, passes through a noise filter 11, a surge killer 12, and a full-wave rectifier circuit 13, and is further somewhat shaped by a capacitor 14, and then passes through a choke coil 15 to form a coil (transformer) constituting a Loyer-type self-excited oscillation circuit. The primary terminal of the 17th winding is input to the lowier type self-excited oscillation circuit from the intermediate terminal 16c. A capacitor 18 is connected in parallel with the choke coil 15.
Are connected, and the choke coil 15 and the capacitor 18 form a parallel resonance circuit 19 which is a feature of the present invention. The power passing through the parallel resonance circuit 19
, And is also supplied to the base 24c of the NPN transistor 24 via the resistors 20 and 23. The winding 25 of the transformer 17 is connected between the bases 22c and 24c of these two transistors 22 and 24. The emitters 22a, 24a of these two transistors 22, 24 are grounded. The collectors 22b, 24b of these two transistors 22, 24
Are connected to one ends 16a and 16b of the coil 16, respectively. A waveform forming capacitor 26 is connected between the collectors 22b and 24b. Furthermore, each of these collectors 22b, 24
b, a diode 27, whose anodes 27a, 28a are grounded, to prevent reverse voltage from being applied to the transistors 22, 24.
28 cathodes 27b, 28b are connected. Here, this lowier type self-excited oscillation circuit oscillates at about 20 KHz.

The electric power excited by the winding 29 of the transformer 17 passes through a resistor 30, a full-wave rectifier circuit 31, and is shaped by a capacitor 32.
They are connected to 2,24 bases 22c and 24c. This circuit is for adjusting the bias of the bases 22c and 24c of the transistors 22 and 24. Here, the voltage across the primary winding 16 of the transformer 17 is approximately
400 to 500 V (peak voltage), and the secondary winding 34 of the transformer 17 reduces this voltage to about 8 V (effective value). Also, the primary windings 37, 38 of the transformers 35, 36 are connected in parallel with the primary winding 16 of the transformer 17, and the respective secondary windings 39, 40 have the same phase as the secondary winding 34 of the transformer 17. About 8V each (effective value)
Is excited, and therefore, about 24 V is excited between the transmission lines 41, 41.

The transmission lines 41, 41 are, for example, four fluorescent lamps 42.
To each of the four transformers 42-
45 are connected to the primary windings 46 to 49, and 300 V is excited between one ends 50a to 53a of the secondary windings 50 to 53 and the intermediate terminals 50c to 53c. The 300V is connected to the fluorescent lamps 70 to 60 via the capacitors 58 to 61 connected in series with the secondary windings 50 to 53.
Supplied to 73. Also, each intermediate terminal 50 of the secondary windings 50 to 53
between c-53c and each terminal 50b-53b, and windings 54-57
5V is excited. This 5V is for preheating the filaments of the fluorescent lamps 70 to 73.

FIG. 3 is a graph showing an example of the correspondence between the capacitance C of the capacitor 18 of the parallel resonance circuit 19 and the heating temperature (difference from the normal temperature) of the transistors 22 and 24 in the circuit shown in FIG. . The inductance of the choke coil 15 is fixed.

When only the choke coil 15 is used without connecting the capacitor 18, a temperature rise of about 45 ° C. is observed. Connecting predetermined capacitor of capacitance C ₀ in parallel with the choke coil 15, the temperature increase is only about 10 ° C.. In this experiment, the predetermined capacitance C ₀ is such that the resonance frequency of the parallel resonance circuit 19 is about
Oscillation frequency of about 40 KHz and lowier type self-excited oscillation circuit
It was about twice as high as 0 KHz. This is presumably because the switching of the two transistors 22 and 24 occurs twice in one cycle of the Royer's self-excited oscillation circuit. However, it is not necessary to always set the resonance frequency of the parallel resonance circuit to twice the oscillation frequency. For example, when switching from the state where the transistor 22 is turned on to the state where the transistor 24 is turned on, an inrush current is generated. However, in the opposite case, that is, when switching from the state in which the transistor 24 is turned on to the state in which the transistor 22 is turned on, in a circuit configuration in which an inrush current does not occur, the resonance frequency of the parallel resonance circuit is It is conceivable that it is better to match the frequency.

The illumination of the fluorescent lamp 70 to 73 when the capacitance C of the capacitor 18 exceeds a predetermined value C ₁ is caused a phenomenon that decreases. Therefore, it is considered appropriate to connect the capacitor somewhat smaller capacity near or than the capacitance C _0. Also,
A capacitor having a capacity close to the predetermined capacity C _0, beat sound of the choke coil 19 is also no longer occurs.

Note that the heat generation of the transistors 22 and 24 can be reduced to some extent by connecting the choke coil 19 having a large inductance without connecting the capacitor 18. However, if a choke coil having a large inductance and a small size is used, the heat generated by the choke coil itself becomes a problem, and if a choke coil having a large inductance is manufactured while suppressing the heat generation, the size becomes extremely large, which is not practical.

Figure 4 is the collector of the transistor 22 or transistor 24 shown in FIG. 2 - is a diagram showing an example of emitter voltage V _CE and the collector current I _C of the waveform.

The solid line in the figure corresponds to the case where not connecting the capacitor 18 in parallel with the choke coil 15, a broken line corresponds to the case of connecting a capacitor 18 having a predetermined capacitance C _0. The waveform is improved when the capacitor 18 is connected as compared with the case where the capacitor 18 is not connected.

Although all of the above embodiments are examples using a Royer-type self-excited oscillation circuit, the present invention is not limited to a high-frequency oscillation circuit using a Royer method. Both bases 1 of transistors 1 and 2
It is basically the same as the Royer type self-excited oscillation circuit described above except that a transformer magnetically coupled to the collector circuit is added between a and 2a. The present invention can be applied similarly to the Royer method.

FIG. 5 is a circuit diagram for explaining the principle of a modified forward self-excited oscillation circuit to which the present invention is applied. Circuit elements and the like functionally corresponding to the Royer-type self-excited oscillation circuit shown in FIG. 1 are indicated by adding dashes to the numbers given in FIG.

The other end of the power supply 80 ', one end of which is grounded, is connected to the collector 1b' of the transistor 1 'via a parallel resonance circuit composed of a choke coil 7' and a capacitor 9 '. One end 4a ', 4b' of a primary winding 4 'of a transformer 3' is connected to the emitter 1a 'of the transistor 1' and the collector 2b 'of the transistor 2'. The emitter 2a 'of the transistor 2' is grounded. A waveform improving capacitor 8 'is connected in parallel with the primary winding 4'. Bases 1c ', 2c'- of two transistors 1', 2'-
A winding 5 'of a transformer 3' is connected between the emitters 1a 'and 2a'. A diode 81 connected between the collectors 1b 'and 2b' of the two transistors 1 'and 2' and a diode 82 connected between the emitters 1a 'and 2a' of the two transistors 1 'and 2' Transistors 1 ',
This is for preventing reverse voltage of the transistor 2 '. The transformer 3 'is configured to have an appropriate leakage flux between the primary winding 4' and the secondary winding 6 'so as to conform to the negative characteristics of the fluorescent lamp. Are connected to a fluorescent lamp (not shown).

In the modified forward self-excited oscillation circuit configured as described above, the two transistors 1 'and 2' alternately turn on and off alternately and oscillate at, for example, about 20 KHz, similarly to the lower self-excited oscillation circuit described above. Also, as in the case of the aforementioned Loyer-type self-excited oscillation circuit, the two transistors 1 'and 2' may be turned on at the same time. At that time, an inrush current tries to flow from the power supply 80 '. The rush current is prevented by the parallel resonance circuit composed of the capacitor 9 'and the transistors 1', 2 'are prevented from being broken or heated.

Although all of the above embodiments have been described using a fluorescent lamp as an example,
The present invention can be similarly applied to lighting devices for other discharge lamps such as a neon tube.

(Effect of the Invention) As described in detail above, the discharge lamp lighting device of the present invention includes the parallel resonance circuit that limits the rush current flowing from the power supply to the Royer-type self-excited oscillation circuit, so that the waveform is improved. As a result, the heat generation of the transistor can be considerably suppressed, the life of the discharge lamp lighting device is considerably extended, and the reliability is improved. In addition, the growling noise of the coil constituting the parallel resonance circuit is reduced or eliminated.

[Brief description of the drawings]

FIG. 1 is a circuit diagram for explaining the principle of a lower type self-excited oscillation circuit according to one embodiment of the present invention, and FIG. 2 is a circuit diagram showing a specific embodiment of a discharge lamp lighting device of the present invention. FIG. 3 is a graph showing an example of the correspondence between the capacitor capacitance of the parallel resonance circuit and the heat generation temperature of the transistor in the circuit shown in FIG. 2, and FIG. 4 is a graph showing the collector of the transistor shown in FIG. diagram showing an example of emitter voltage V _CE and the collector current I _C of the waveform, Fig. 5, a principle explanatory circuit diagram of a modification forward type self-excited oscillation circuit according to the present invention, FIG. 6 is a Royer type FIG. 2 is a circuit diagram showing a basic circuit configuration of a self-excited oscillation circuit. 1,1 ′, 2,2 ′, 22,24 …… NPN transistor 3,3 ′, 17,35,36,42,43,44,45 …… Transformer 7,7 ′, 15 …… Choke coil 9, 9 ', 18 …… Capacitor for parallel resonance circuit 42,43,44,45 …… Fluorescent lamp

Continuation of the front page (56) References JP-A-57-141898 (JP, A) JP-A-57-135688 (JP, A) JP-A-56-157261 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) H05B 41/24-41/298

Claims (1)

(57) [Claims] 1. A power supply circuit for rectifying an AC power supply, a high-frequency oscillation circuit having two transistors that alternately turn on and off, and the two power supply circuits provided between the power supply circuit and the high-frequency oscillation circuit. A discharge lamp lighting device comprising: a current limiting coil configured to limit an inrush current flowing from the power supply circuit to the two transistors when the transistors are simultaneously turned on, wherein a capacitor is connected in parallel with the current limiting coil. A discharge lamp lighting device, wherein a parallel resonance circuit is formed, and the capacitance of the capacitor is set such that the resonance frequency of the parallel resonance circuit is one or two times the oscillation frequency of the high-frequency oscillation circuit.