JPH0340398A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To enhance the power factor with a simple and small additional circuitry by inserting a capacitor in parallel with or series to the primary or secondary winding of a booster transformer, which boosts the pressure of high frequency electric power and supplies it to a discharge lamp. CONSTITUTION:Commercial AC power is fed from a terminal 10 to generate a high frequency voltage by a self-exciting oscillator circuit of lower type, and it is reduced to approx. 8V in the same phase and emitted from secondary windings 34, 39, 40 of a reduction transformer 17. This is sent to booster transformers 42-45 via transmission lines 41, 42, and upon boosting to a specified voltage, is fed to discharge lamps 70-72. In this constitution drop of the power factor due to influence of the inductance of the reduction transformer and booster transformer is compensated by inserting capacitors 58-61 in parallel with or series to primary windings 46-49 or secondary windings 50-53, 54-57 of the transformers 42-45. Thus the power factor can be enhanced with a simple and small additional circuitry.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention inputs commercial AC power, converts it into a voltage, current, etc. suitable for stabilizing a discharge lamp such as a fluorescent lamp, and supplies the converted electric power to the discharge lamp. The present invention relates to a discharge lamp lighting device.

(Prior Art) In order to stably light a discharge lamp, such as a fluorescent lamp, by inputting commercial AC power, so-called electromagnetic ballasts have traditionally been widely used, and recently electronic ballasts have also been used. ing.

An electromagnetic ballast uses commercial AC power (for example, 50Hz).

100V) and boosts the voltage to a voltage suitable for lighting fluorescent lamps, etc.Furthermore, since fluorescent lamps, etc. exhibit a so-called negative characteristic in which impedance rapidly decreases when lighting starts, the output current is limited and the voltage is increased to a voltage suitable for lighting fluorescent lamps etc. It supplies power to other devices.

The electromagnetic ballast is an improved version of the electromagnetic ballast, which is large and heavy. That is, to explain an example of its configuration, input commercial AC power is once rectified and then passed through an inverter to AC of 20kHz, 300V, and the output current is limited to supply power to a fluorescent lamp. By increasing the frequency from 50 Hz to 20 kHz, the transformer etc. can be made smaller, and the volume can be reduced by about 30% compared to the electromagnetic ballast described above. As this inverter,
Usually, a frequency of about 10 kHz to 300 kllz is used.

Regarding this electronic ballast, in order to reduce the cost of cables used for wiring between the power supply and fluorescent lamps, etc. and to ensure safety in the event of an accident, the voltage is stepped down to, for example, 20kHz, 24V and placed near the fluorescent lamp. A discharge lamp lighting device has been proposed in which the voltage is increased to 300V or the like, which is suitable for lighting a fluorescent lamp, using a booster circuit placed near the fluorescent lamp (Japanese Patent Laid-Open No. 1-21894). (see official bulletin). This allows for low voltage wiring, as well as
It has the advantage that only two wirings are required (four wirings are required in normal wiring). If this method is adopted, it is necessary to provide the booster circuit near a fluorescent lamp or the like, but since the frequency is high, for example, 20 kHz, the booster circuit can be small and lightweight.

(Problems to be Solved by the Invention) However, as described above, there is a problem in that when the electronic ballast once lowers the voltage and then increases the voltage again, the power factor deteriorates significantly.

The present invention aims to solve this problem and improve the power factor using a simple and compact additional circuit while maintaining the advantage of low voltage wiring.

(Means for Solving the Problems) A discharge lamp lighting device of the present invention includes an AC power generation circuit that inputs commercial AC power and generates AC power of a predetermined high frequency, and an AC power generation circuit that generates the AC power from the AC power generation circuit. It has a step-down transformer that steps down and takes out the voltage, and a step-up transformer that is connected to the secondary side of the step-down transformer and steps up the AC power and supplies it to the discharge lamp, and the step-up transformer has a primary winding of the step-up transformer. Alternatively, it is characterized by comprising a capacitor in series or parallel with the secondary winding.

Here, the above-mentioned predetermined high frequency is, for example, the above-mentioned 10K
This refers to a frequency of about Hz to 300kHz, but this depends on the selected circuit elements and circuit system, and therefore is not limited to frequencies within the above range.
It refers to various high frequencies used in so-called electronic ballasts, which are considerably higher in frequency than the frequency of commercial AC power.

(Function) As mentioned above, discharge lamps such as fluorescent lamps generally have negative characteristics, and therefore it is necessary to limit the current flowing into these discharge lamps. As methods for carrying out this current limitation, there are known methods that use a magnetic leakage transformer and methods that use the impedance of a choke coil or a capacitor. However, in the past, if a method using the impedance of a choke coil or a capacitor was adopted, the lighting device would become extremely large, so a method using a magnetic leakage transformer was common.

Since the present invention uses a high frequency of, for example, 20 kHz, there are no methods other than using a magnetic leakage transformer to limit the current flowing into a fluorescent lamp, etc., even if the dimensions of the lighting device are considered. , I first realized that a method using the impedance of a capacitor could also be adopted,
In addition, when the voltage is stepped up after being stepped down, a capacitor is inserted in series or parallel with the winding of the step-up transformer to compensate for the drop in power factor caused by the inductors of the step-down and step-up transformers, thereby improving the power factor. It made me realize that it is possible.

That is, since the discharge lamp lighting device of the present invention includes a capacitor in series or parallel with the primary winding or secondary winding of the step-up transformer, a decrease in power factor due to the influence of the inductors of the step-down transformer and the step-up transformer can be compensated for. As a result, the power factor is greatly improved, and it also becomes compatible with the negative characteristics of discharge lamps.

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

FIG. 1 is a circuit diagram of an embodiment of the discharge lamp lighting device of the present invention.

Commercial AC power (for example, 100VA
c.

50Hz) is input, and the noise filter 11. Surge killer 12. After passing through the full-wave rectifier circuit 13 and further having its waveform shaped by the capacitor 14, it passes through the choke coil 15 to the coil 1B that constitutes the Royer self-excited oscillation circuit.
The signal is input to the Royer self-excited oscillation circuit from the intermediate terminal tea of the primary winding 16 of the transformer 17.

Further, a capacitor 18 is connected in parallel with the choke coil 15, and a parallel resonant circuit is formed by the choke coil 15 and the capacitor 18B. The power passing through this parallel resonant circuit is NPN via resistor 20.21)
The resistor 20. It is also supplied to the base 24c of the NPN transistor 24 via the resistor 23. Also, both bases 22c of these two transistors 22 and 24,
24C, the winding 25 of the transformer 17 is connected between them. The emitters 2 of these two transistors 22°24
2a and 24a are grounded. Also the collectors 22b of these two transistors 22,24.

24b is connected to each end lea, 16b of the coil 1B. Furthermore, these collectors 22b, 2
A waveform shaping capacitor 26 is connected between the terminals 4b and 4b.

Furthermore, cathodes 27b and 28b of diodes 27 and 28 whose anodes 27a and 28a are grounded are connected to each of these collectors 22b and 24b in order to prevent reverse voltage from being applied to the transistors 22 and 24.

The power induced in the winding 29 of the transformer 17 is transferred to the resistor 30.
, a full-wave rectifier circuit 31, the waveform is shaped by a capacitor 32, and then a diode 33. Bases 22c, 24c of transistors 22.24 via resistors 21.23
It is connected to the. This circuit consists of a transistor 22゜2
This is for bias adjustment of the bases 22c and 24c of No. 4.

In the Royer self-help oscillation circuit configured as described above, when the transistor 22 first starts to turn on, the transformer 17 is excited by its collector current, and the transistor 22 is suddenly turned on.

When the magnetic core of transformer 17 reaches saturation, transistor 22
is turned off, and this turning off generates a back electromotive force in the transformer 17, turning on the transistor 24. Self-help oscillation continues by repeating this process. Here, this Royer-type self-help oscillation circuit oscillates at about 20 kHz. Here, due to the switching delay time of the two transistors 22, 24, these two transistors 22, 24 may turn on at the same time. At this time, among the primary windings 16 of the transformer 17, the windings on both sides of the intermediate terminal 18c excite the magnetic cores of this transformer F in opposite directions, so the transformer 17 loses its function as an inductor. At this moment, a rush current attempts to flow into the two transistors 22 and 24. Therefore, by making the anti-resonant frequency of the parallel resonant circuit 19 approximately equal to the repetition frequency of this inrush current, the current flowing into this Royer 2 self-excited oscillation circuit is limited, and the transistors 22 and 24 are controlled by the inrush current. Destruction or heat generation that would affect the lifetime of the transistors 22, 24 due to this inrush current is prevented or reduced.

Here, the voltage between both sides of the primary winding 6 of the transformer 17 is approximately 400 to 500V (peak voltage), and the secondary winding 34 of the transformer 17 steps down this voltage to approximately 8V.

In addition, a transformer 35 is connected in parallel with the primary winding 16 of the transformer 17.
Each secondary winding 37.38 of the transformer 17 is connected to each secondary winding 39.40 of the transformer 17.
4 and in phase with each other, approximately 8 V (actual value) is excited, and thus approximately 24 V is excited between the transmission lines 41, 41.

This transmission line 41.41 is connected to the primary windings 46 to 49 of each of the four step-up transformers 42 to 45 arranged in the vicinity of the four fluorescent lamps 70 to 73 in the negative column, respectively. One end of each of the next windings 50 to 53 50a to 53
aoov is excited between a and each intermediate terminal 50c to 53e. This 300v is supplied to the fluorescent lamp 7 through capacitors 58 to B1 connected in series with the secondary windings 50 to 53.
0 to 73. Moreover, 5V is excited between each intermediate terminal 50c-53c and each other end 50b-53b of the secondary windings 50-53, and in the windings 54-57. This 5
v is for preheating the fluorescent lamps 70 to 73.

FIG. 2A is a graph a1 representing the change in the input current flowing through the power transmission line 41, 41 and inputted to each step-up transformer 42-45 with respect to the capacitance ff1C of the capacitors 58-61 shown in FIG. 1. Graph b1 showing changes in the fluorescent lamp input current input to 70 to 73, and graph C showing changes in efficiency η (equal to the power factor) defined below.
FIG. However, the vertical axis shows only the efficiency η in %. Here, the efficiency η is defined as the voltage value (24V) of the transmission line 41.41.

Each step-up transformer 42 to 4 flowing through the transmission line 41.41
When the current value for one fluorescent lamp 5 is A, the voltage value applied to each fluorescent lamp 70-73 is V, and the value of the fluorescent lamp input current input to each fluorescent lamp 70-73 is AL, , ·AL η1 −V Since each step-up transformer 42 to 45 generates little heat, it is approximately equal to the power factor.

When optimal capacitors 58 to 61 having a capacitance C0 are connected, the efficiency η becomes approximately 90%, which is a very good value. In addition, the capacitors 58 to 61 allow the fluorescent lamps 70 to 73 to
Due to the negative characteristic of , overcurrent to the fluorescent lamps 70 to 73 is also prevented.

FIG. 2B shows each step-up transformer 42 to 45 in FIG.
Instead of inserting a capacitor in series in the secondary winding of the field voltage transformer 42 to 45, the voltage flowing through the electric transmission lines 41, 41 and the step-up transformer 42 to Graph a I showing the change in the input current input to 45, graph b' showing the change in the fluorescent lamp input current input to each of the fluorescent lamps 70 to 73, and graph C' showing the change in efficiency η. FIG. No matter how you adjust the leakage magnetic flux, only very low efficiency (power factor) can be obtained.

Note that the above embodiment is an example in which capacitors 58 to 61 are connected in series to the secondary windings 50 to 53 of each step-up transformer 42 to 45; The primary windings 46 to 49 may be connected in series, and the secondary windings 46 to 49 or the secondary windings 50
~53 may be connected in parallel.

(Effects of the Invention) As explained in detail above, the discharge lamp lighting device of the present invention includes a capacitor in series or parallel with the primary winding or secondary winding of a step-up transformer, so that wiring is possible at a low voltage. By using a simple and compact additional circuit, while maintaining the advantage that it is possible to reduce the power consumption, the decrease in power factor due to the influence of the inductors of the step-down and step-up transformers is compensated for, and the power factor is greatly improved, while also improving the negative characteristics of the discharge lamp. Also suitable.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the discharge lamp lighting device of the present invention, and FIG. 2A is a diagram showing the relationship between the capacitance C of the capacitor inserted in series with the secondary winding of the step-up transformer, and the voltage applied to the step-up transformer by hand. Figure 2B is a graph showing the change in the input terminal of the step-up transformer; graph b1 showing the change in the output current from the step-up transformer; Graph a1 showing the change in the input current input to the step-up transformer with respect to the interval of the gap intentionally created in the magnetic core of the step-up transformer instead of inserting a capacitor in series in the line A1 of the output current from the step-up transformer Graph b showing changes and efficiency η
It is a figure which showed the graph C showing the change of.

Claims (1)

[Scope of Claims] An AC power generation circuit that inputs commercial AC power and generates AC power of a predetermined high frequency; a step-down transformer that steps down and extracts the AC power from the AC power generation circuit; and a step-up transformer connected to the secondary side to step up the AC power and supply it to the discharge lamp, and the step-up transformer has a capacitor connected in series or parallel with the primary winding or secondary winding of the step-up transformer. A discharge lamp lighting device characterized by comprising: