JPS6031077B2 - discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device that is capable of lighting a discharge lamp using an AC power source with a voltage close to the lamp voltage.

The discharge lamp lighting device shown in FIG. 1 is a premise of the present invention, and is a lighting circuit for a discharge lamp having a lamp voltage close to the power supply voltage.
3 is an inductive ballast, 3 is a discharge lamp connected to the AC power source 1 via the ballast 2, and 4 is a switch circuit connected in parallel with the discharge lamp 3.

This switch circuit 4 is closed for a certain period of time every half cycle of the power supply voltage to allow current to flow through the ballast 2, and after accumulating electromagnetic energy in the inductance of the ballast 2, the switch circuit 4 is opened and the electromagnetic energy is Energy is applied to the power supply voltage and applied to the discharge lamp 3 to light it. The operation of this discharge lamp lighting device will be explained using the waveform diagram shown in FIG. 2. FIG. 2 shows a case where the discharge lamp 3 is in a steady lighting state, and now consider the case where the lamp current 11 becomes zero and the lamp voltage VI becomes zero at time to. At this time, the power supply voltage Vo is applied to both sides of the discharge lamp 3, but the direction of this voltage is as a result of the lamp current 11 being a lagging current because the ballast 2 is inductive.
This is the opposite of the ramp fin pressure VI just before. If the switch circuit 4 is configured so that when the direction of the voltage across the discharge lamp 3 is reversed and reaches a certain constant voltage, the switch circuit 4 detects this state and closes, the lamp current 11 becomes zero. The switch circuit 4 at the same time, that is, at substantially the same time.
is closed. A short-circuit current ls then flows through the ballast 2, accumulating electromagnetic energy in the inductance within the ballast 2. This switch circuit 4 is provided with a control function that detects this and opens the switch circuit 4 when the short circuit current ls increases to a predetermined value. Therefore, time t,
When the short circuit current ls reaches a predetermined value, the switch circuit 4 is opened. At this time, the discharge lamp 3 is lit again by the pulse voltage Vp generated across the ballast 2, and the lamp current 11 flows. Since this lamp current 11 becomes a lagging current as described above, it continues to flow for a while even if the direction of the fin pressure of the fin source voltage Vo is reversed. During this time, a substantially constant lamp voltage VI following the pulse voltage Vp appears at both ends of the discharge lamp 3.
During this period, the switch circuit 4 remains open. When the lamp current 11 becomes zero, the same operation is repeated in the reverse cycle. Incidentally, the operational problem in such a discharge lamp lighting device may be considered to be the reliability of the re-ignition operation.

In other words, since the power supply voltage Vo is extremely close to the lamp voltage VI, the lamp current 11 must surely increase after re-ignition with the pulse voltage Vp, and in order to transition to a normal lighting state, Certain conditions are necessary. In a normal lighting circuit, sufficient power supply voltage is provided, so the lamp current will definitely increase after re-ignition, but depending on the power supply voltage being low or other external conditions, the lamp current will not increase and the lamp will reach the glow region. It may become stable or the discharge may stop. This phenomenon is not observed even in the circuit shown in Fig. 1, and in particular, the power supply voltage Vo is close to the lamp voltage VI, which is 50 to 70% compared to a normal lighting circuit.
Since only a voltage of 100 mL is applied, the situation is such that a state in which discharge is not possible or a glow discharge becomes stable is more likely to occur than in a normal case. The reason why such a phenomenon occurs can be considered as follows. That is, the ions and electrons, which are charged particles, existing in the discharge lamp 3 at the time when the lamp current 11 becomes zero, rapidly decrease due to recombination, and at the time L' when the pulse voltage yp is applied. It almost ceases to exist.
The number of ions and electrons is the time from time Uto to time Chi,
That is, the longer the time T during which the switch circuit 4 is closed, the shorter the time T becomes. When a pulse voltage Vp is applied to the discharge lamp 3 in which ions and electrons are diluted in this way, the remaining electrons are accelerated and collide with the metal atoms present in the discharge lamp 3, ionizing them. Forming plasma. In order for this plasma to grow and form an arc discharge, current supply from the AC power supply 1 is essential. However, since this lighting circuit is equipped with a ballast 2,
The rise of the current supplied from the AC power source 1 is extremely vague. Therefore, in order for the current to increase, enough ions and electrons generated by the pulse voltage yp need to remain until the current reaches a certain level. In normal lighting circuits, there is no discharge pause period, so the next half-cycle discharge starts before the half-cycle discharge current reaches zero and ions and electrons have not yet disappeared, and the power supply voltage is also sufficient. Since the high voltage is applied, such problems do not occur. By the way, the lamp current 11
Considering the case where there are not enough ions and electrons in the discharge lamp at the time of rise, the difference between the number of ions and electrons that disappear due to recombination in the discharge lamp and the number of newly supplied ions and electrons. Depending on the situation, the transition to arc discharge may be prevented and the discharge may become stable in the glow discharge region, or even glow discharge may not be maintained and the discharge may stop. Basically, the reason for this state is that, as mentioned above, in a state where the pulse voltage Vp disappears and only the power supply voltage Vo is applied, the lamp current 11 increases to a certain level for a finite period of time. , this is because a sufficient amount of ions and electrons cannot exist, and individual external factors include insufficient energy in the pulse voltage yp and insufficient absolute amount of remaining ions and electrons due to a long pause period of the lamp current 11. ,
Various factors can be considered, such as insufficient absolute amount of generated ions and electrons due to low metal vapor pressure, and insufficient rising current due to low power supply voltage Vo. In this way, in the lighting device shown in Fig. 1, the superficial reason why discharge is not possible or stable discharge occurs in the glow discharge region is due to a decrease in the power supply voltage Vo and a decrease in the ambient temperature. It is clear that this is due to insufficient energy injection and a drop in metal vapor pressure after the voltage Vp disappears. In view of the above-mentioned circumstances, the present invention aims to provide a discharge lamp lighting circuit that can reliably re-ignite and maintain discharge without being greatly influenced by conditions such as power supply voltage and ambient temperature. .

Therefore, in the present invention, when the lamp current becomes zero and a current flows through the switch circuit, the pulse voltage generated when the short circuit current is cut off is used to simply add energy to the ions and electrons remaining in the discharge lamp at that point. In addition to giving a certain amount of energy, part of that energy is stored in the capacitor circuit, and the charge stored in the capacitor circuit is released as a pulse current to the discharge lamp, which has become conductive due to the ions and electrons formed by the pulse voltage. By forming a large amount of ions and electrons in the discharge lamp to provide excessive inductivity, the lamp provides time for the current supplied from the power source to increase, thereby ensuring reliable lighting.

3 and 4 show the circuit configuration and operating waveforms of the discharge lamp lighting device according to the present invention, where 6 is a capacitance circuit composed of, for example, a capacitor 51 and impedances 52 and 53;
p indicates a pulse current resulting in discharge of the capacitive circuit 5, and Vd indicates a drop voltage caused by the presence of excess charged particles.

Note that the other symbols are the same as those in FIGS. 1 and 2, so the explanation will be omitted. In the lighting circuit having such a configuration, the lamp current 11 becomes zero at a certain time, and the switch circuit 4
is closed and a short circuit current ls flows, and at time t, the switch circuit 4 is opened to cut off the short circuit current ls and a pulse voltage Vp is obtained. Everything up to this point is exactly the same as in the case of FIG. The pulse voltage Vp charges the capacitor circuit 5 to its peak value, while the discharge lamp 1 gives energy to the remaining ions and electrons, accelerates them, and causes them to collide with metal atoms, as in the case of Fig. 1. Ionizes to form plasma.
When the discharge lamp 3 is rapidly turned on in this way, the charge stored in the capacitive circuit 5 is immediately discharged through the discharge lamp 3, and at this time, a pulse current m corresponding to the amount of stored charge flows as part of the lamp current 11. . And this pulse current l
Ions and electrons approximately proportional to p are formed in the discharge lamp 3, and at this time the discharge lamp 3 exhibits extremely high inductivity, and therefore the lamp voltage Vp is a significantly low voltage, that is, a drop lower than the normal lamp voltage Vp. Indicates voltage Vd. Ions and electrons formed excessively by the pulse current lp are
It soon disappears due to recombination, but during this time, the current supplied from the AC power source 1 via the ballast 2 increases, transitioning to normal arc discharge, and the normal lamp current 11 begins to flow. Accordingly, the lamp voltage VI also returns to the normal voltage. When one cycle of normal lamp current 11 is completed and the current becomes zero, the next cycle is repeated. The drop voltage Vd appearing in FIG. 4 is evidence that excessive charged particles are generated in the discharge lamp 3 by the pulse current lp and excessive conductivity is obtained. However, in a discharge lamp lighting device that relights the discharge lamp by applying a pulse voltage after the end of the rest period, it plays an important role in ensuring reliable lighting. That is, the capacitor circuit 5 in FIG. 3 supplies sufficient pulse current to excessively increase the conductivity of the discharge lamp 3 at least temporarily during the re-ignition operation of the discharge lamp 3 when the switch circuit 4 is opened. To this end, the capacitive circuit 5 must have a short-circuit current ls that is sufficient to supply a pulse current that can temporarily form excessive charged particles in the discharge lamp 3. The storage capacity must be secured by the pulse voltage generated when the circuit is cut off. FIG. 5 shows the circuit configuration according to the present invention applied to a case where a crab light lamp is used as a discharge lamp.

In the figure, 1 is an AC power supply, 21 is a choke coil used as a ballast, 31 is a crab light lamp used as a discharge lamp, 4 is a switch circuit, 51 is a capacitor as a capacitance circuit, 6 is a child heating circuit, and 7 is a It is a rectifier circuit. The switch circuit 4 includes, for example, a thyristor 41 and a transistor 42 connected in series, and a trigger thyristor 43 connected between the base and emitter of the transistor 42. Resistors 44 and 45 constitute a trigger circuit of thyristor 41 and transistor 42, respectively, and resistor 46 is connected in series with transistor 42 as an impedance for voltage detection, and supplies a trigger voltage to trigger thyristor 43. A diode 47 connected in series with the resistor 46 and in parallel with the trigger thyristor 43 compensates for the on-voltage of the trigger thyristor 43 and prevents the transistor 42 from discharging due to the on-voltage of the trigger thyristor 43. be. The operation of this switch circuit 4 is controlled by the crab light lamp 31.
The operation will be explained using FIG. 6. That is,
In the steady lighting state, the time ratio at which the lamp current 1 becomes zero.

Then, the voltage applied to the switch circuit 4 becomes zero once.
Then, at this time, the lamp voltage VI is switched to the power supply voltage Vo. Therefore, at this time, Tsuyoshiji. This means that the operation mode of the switch circuit 4 has been newly reset. When the power supply voltage Vo is applied to the switch circuit 4,
The thyristor 41 and the transistor 42 each have a resistor 44
, 45 turns on immediately after the time. As a result, the thyristor 41, the transistor 42
, the choke coil 2 through the diode 47 and the resistor 46.
A short circuit current ls flows which gradually increases to 1. When the current reaches a predetermined value and the terminal voltage of the resistor 46 rises to a certain value, the base voltage of the transistor 42 reaches the breakover voltage of the trigger thyristor 43, and the trigger thyristor 43 is turned on. Therefore, transistor 4
2 is turned off at time t, and subsequently the thyristor 41 is also turned off by the current flowing from its gate to the resistor 45. At this time, the pulse voltage yp generated in the choke coil 21 is applied to both ends of the crab light lamp 31 at the same time as the capacitor 51 is charged to its peak value. Then, energy is given to the ions and electrons remaining in the crab light lamp 31 to further increase the number of ions and electrons, thereby restoring the conductivity of the crab light lamp 31. When conductivity is imparted to the full-length lamp 31, the charge charged in the capacitor 51 is released, and this discharge current appears as a pulse current lp.
As a result, excessive ions and electrons temporarily exist within the crab light lamp 31, causing a decrease in the lamp voltage VI.
The depth of this drop in voltage Vd from the normal lamp voltage VI is proportional to the amount of excess ions and electrons. These excess ions and electrons disappear due to recombination etc. as time passes, but during this time the current flowing through the choke coil 21 increases and the normal lamp current 11 increases.
form. Excess ions and electrons are removed by this lamp current 1
This is necessary to ensure the rise of 1. This is because there are no excessive ions or electrons, the conductivity of the full-body light lamp 31 is extremely low, and the number of thermoelectrons emitted as a current from the electrodes of the crab light lamp 31 is small, a condition in which the cage current can increase. This is because there is a high possibility that the conductivity of the full-length light lamp 31 will be lost if this is not done. When the current reaches a normal value, the lamp voltage VI also returns to normal, and normal lighting is maintained. During this time, the lamp voltage VI is applied to the switch circuit 4, but the trigger thyristor 43 remains on, and current flows through the resistors 44 and 45, but the loss in the switch circuit 4 is large enough for the resistor 44. Since the value can be selected, it is possible to set it to a small value. Note that the heating circuit 6 is a well-known technique necessary when using the crab light lamp 31, and is a circuit that causes a heating current to flow through the filament at the starting stage when the AC power source 1 is applied.

The operation of this circuit is controlled by a preheating control circuit 62 that turns on a preheating thyristor 61 for a certain period of time, and causes a preheating current to flow through the thyristor 41 in the switch circuit 4. It can be operated in parallel with generation. By the way, the third
When a discharge lamp is lit using the basic circuit shown in the figure, it is generally predicted that the reliability of the lighting operation and the influence of the pulse eagle pressure Vp on the lighting life depend on the operating conditions.

Therefore, the present inventor conducted experiments using the lighting device using the crab light lamp shown in FIG. It was revealed that the pulse current affects the characteristics more substantially than the pulse voltage. Figure 7 shows the tapal current l versus the rated current le of the crab light lamp 31.
It shows the relationship between the ratio of peak values of p (hereinafter referred to as peak value ratio) and the lighting probability of the total light lamp 31.

That is, it can be seen that when the peak value of the pulse current lp is changed while keeping the input power constant, the lighting operation is not performed reliably in a range where the peak value is low, and the probability of lighting the backlight lamp 31 decreases. As is clear from the figure, if the peak value ratio falls below about 1.3 tones, problems may arise in practice. The reason for this is clearly a lack of ions and fins due to a lack of current. The crab light lamp 31 used in the experiment was 40 watts and had a rated current of 0.43 hiro, and the capacitor that obtained a pulse current of 1.8 times the peak value ratio was 330 mf. This capacitor 51 constitutes an LC resonant circuit with the power supply frequency as its natural frequency with the choke coil 21, and applies the resonant voltage generated across the capacitor to the crab light lamp 31, which is a so-called resonant lighting circuit. I think it has become clear from the explanation of the operation so far that they are essentially different,
The pulse voltage and pulse current in the actual operating waveform are extremely small, on the order of several tens of seconds, and are different from general resonance circuit operation. FIG. 8 shows the incidence of blackening at the tube end of the crab light lamp 31.

Generally, the electrodes of crab light lamps are hot cathodes made of metal oxides, and when the metal oxides are scattered due to ion bombardment, they react with the mercury sealed in the crab light lamps and adhere to the tube wall, producing a black to yellow color. This stain is generally called blackening. This darkening is due to the causes mentioned above, and it is known that the occurrence of darkening is approximately proportional to the lifespan.
According to the figure, the peak value ratio is about 3. It can be seen that when a pulse current lp that exceeds the fan level flows, the incidence of blackening becomes extremely high. This is because a large amount of excess ions are generated and the conductivity of the crab light lamp 31 becomes good, so that a large current flows before the electrode temperature rises, and the operating conditions for hot cathode discharge change as if they were cold cathode lamps. Because it operates like an electric discharge, mercury oxide is formed and adheres to the tube tube, creating a yellow stain. In this way, in a lighting device that maintains lighting by applying a pulse voltage to re-ignite the discharge lamp after a period of rest occurs in the discharge current, the discharge lamp remains lit after it has been extinguished. It can be seen that applying a pulsed current to restore conductivity is effective. moreover,
It is practically preferable to set a lower limit for the pulse current to ensure reliability of operation, and to set an upper limit to ensure longevity. Obviously, similar characteristics are expected for discharge lamps using hot cathodes. In addition, in this example, since the charge in the capacitor is directly discharged into the discharge lamp, there is a nearly proportional relationship between the peak value of the pulse current and the capacitor capacity, but if the capacitor capacity is large and the peak value is too large, an appropriate It is also possible to lower the peak value by inserting impedance. FIG. 9 shows the change in the pulse current peak value when a resistor is inserted in series with the capacitor 5 in the circuit of FIG. In this way, the capacitor 51
By inserting an appropriate impedance in series or parallel with the peak value ratio, it is possible to select an appropriate value for the peak value ratio. As explained in detail above, the present invention provides a lighting device including a switch circuit in parallel with a discharge lamp that is closed for a certain period of time after the discharge of each half cycle of the discharge lamp is completed, and a capacitor circuit is provided in parallel with the discharge lamp. When the discharge lamp is re-ignited by applying a pulse voltage generated when the switch circuit is opened to this capacitor circuit, the charge of the capacitor circuit charged with the pulse voltage is used to re-ignite the discharge lamp. It has the function of immediately discharging using the conductivity of the discharge lamp generated by operation, and temporarily increasing the conductivity of the discharge lamp excessively with a pulsed current.

Therefore, even in a lighting device in which there is a rest period in the discharge current every half cycle, and the charged particles in the discharge lamp need to be re-ignited in a state where they have significantly decreased, they are temporarily stored in this capacitive circuit. Excessive charged particles are generated by the pulsed current caused by the accumulated charge, and the conductivity of the discharge lamp is increased excessively.As a result, the conductivity of the discharge lamp can be ensured for a sufficient period of time for the current from the power supply to rise, resulting in stable lighting. It has the effect of maintaining movement. In addition, ensuring excessive conductivity in the discharge lamp using this pulsed current has the effect of relatively easily correcting adverse conditions when lighting the discharge lamp, such as a drop in power supply voltage or a drop in ambient temperature, and is extremely useful in practice. .

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a discharge lamp lighting device which is the premise of the present invention.
Fig. 2 is a waveform diagram showing the lighting state, Fig. 3 is a basic circuit diagram of the present invention, Fig. 4 is a waveform diagram showing the lighting state, and Fig. 5 is a waveform diagram showing the lighting state.
Figure 6 is a circuit diagram showing a specific example, Figure 6 is a waveform diagram showing its lighting state, Figure 7 is a characteristic diagram showing the relationship between lighting probability and pulse current of the example shown in Figure 5, and Figure 8. Similarly, FIG. 9 is a characteristic diagram showing the relationship between the blackening incidence rate and the pulse current, and FIG. 9 is a characteristic diagram showing the relationship between the pulse current and the series resistance. As shown in the figure, 1 is an AC power supply, 2 is a ballast, 3 is a discharge lamp,
4 is a switch circuit, 5 is a capacitor circuit, 6 is a child heat circuit, Vo
is the power supply voltage, Vp is the pulse voltage, VI is the lamp voltage, V
d is the fill-in voltage, 11 is the lamp current, ls is the short circuit current,
lp is a pulse current. GA'Outside the figure 2 figure 3 figure 4 figure 5 figure 5 figure 7 figure 7 figure 8 figure

Claims (1)

[Claims] 1. A discharge lamp connected in series to an AC power source via an inductive ballast, a capacitor circuit connected in parallel with the discharge lamp, and after each half cycle of discharge of the discharge lamp ends. a switch circuit that is closed for a period of time, said capacitive circuit providing a pulsed current sufficient to at least temporarily increase the electrical conductivity of the discharge lamp during a restriking operation of the discharge lamp when the switch circuit is opened. A discharge lamp lighting device characterized by having a function that allows 2. The discharge lamp lighting device according to claim 1, wherein a fluorescent lamp is used as the discharge lamp, and a preheating circuit that operates only when the fluorescent lamp is started is provided in parallel with the switch circuit. 3. The discharge lamp lighting according to claim 2, wherein the peak value of the pulse current is selected to be approximately 1.5 to 3.5 times as large as the rated current of the fluorescent lamp. Device.