JPH01167988A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To make it unnecessary to provide a no-load countermeasure and to increase the degree of freedom of design by dividing either a coil or a capacitor of an LC resonance circuit, and feeding a resonance current or a preheating current to the respective filaments of a discharge lamp through the divided coils or capacitors separately. CONSTITUTION:Capacitors C3 and C4 for resonance are provided, and while one side capacitor C3 is connected between a capasitor C2 and the negative electrode of a DC power source E through a filament F1, the other side capacitor C4 is connected between the capacitor C2 and the negative electrode of the DC power source E through a filament F2. In other works, a capacitor for resonance and a capacitor for preheating are provided to the filament F1 and to the filament F2 respectively. As a result, since there is no resonance loop at the no-load condition by removing a discharge lamp 1, it is not necessary to provide the no-load countermeasure. Furthermore, since the preheating and the resonance capacitors C3 and C4 are provided, the degree of freedom of design can be increased.

Description

[Detailed description of the invention] [1! Technical Field 1 The present invention relates to a discharge lamp lighting device fi which lights a discharge lamp at high frequency.
It is related to.

[Background I] There are various methods for lighting discharge lamps at high frequencies, but among them, there is one that uses series resonance between a coil and a capacitor (hereinafter referred to as LC series resonance) without using a transformer. FIG. 8 shows a discharge lamp lighting device for lighting an electric lamp at high frequency. This discharge lamp lighting device uses a modified bar 7 bridge imperter 2, and by connecting the discharge lamp 1 in parallel with the capacitor C9 for LC series resonance, a high voltage is applied to both ends of the capacitor CI due to resonance. This makes it easier to start the discharge lamp 1. In addition, in this discharge lamp lighting device, by connecting the discharge lamp 1 to both ends of the capacitor C1, the discharge lamp 1
It also has the advantage of being able to preheat the filament (F), F2. The inverter 2 operates using a DC power source E obtained by rectifying and smoothing a commercial power source, and switching elements Q, , Q are connected in series to both ends of this DC power source E.
2 are alternately turned on and off by a control circuit 3 to light the discharge lamp 1 at high frequency. Incidentally, the switching elements Q, , Q: are connected with gunpah diodes D 1 , , D 2 in antiparallel, respectively. Load circuit 4 connected to this inverter 2 output
゛ is charged when the discharge lamp 1 and the capacitor C9, the coil L1 which constitutes a series resonant circuit together with the above-mentioned capacitor C1, and the switching element Q of the inverter 2 are conductive, and when the switching element Q2 is conductive, it is charged in the reverse direction to the load circuit 4゛. capacitor c2 used as a constant voltage power supply that flows a current of
It consists of Note that the capacitance of the capacitor C2 is selected to be sufficiently larger than the capacitance of the capacitor C1 so as not to affect the resonance between the coil L1 and the capacitor C1.

When the discharge lamp 1 starts discharging, after the switching element Q1 becomes conductive, a voltage is applied to the discharge lamp 1 via the coil L I s capacitors C, C2, and at the same time as the switching element Q1 is connected and disconnected, the switching element Q2 is turned on. When conductive, the electric charge stored in the capacitor c2 is discharged through the coiled capacitor c5 and the switching element Q2, and a voltage of opposite polarity is applied to the discharge lamp 1. In this discharge lamp lighting device, switching element Q2 of inverter 2
By repeating the above operation through alternate conduction, high-frequency power is supplied to the discharge lamp 1.

An advantage of this method is that there is no need for no-load countermeasures because there is no resonance loop during so-called no-load when the discharge lamp 1 is removed. For example, in a discharge lamp lighting device shown in FIG. 9 that lights multiple discharge lamps 1 to which a plurality of the load circuits 4 are connected, even if several discharge lamps 1 are disconnected,
The remaining discharge lamps 1 have the great advantage of being normal rated 7α lamps.

By the way, in a discharge lamp lighting device using LC series resonance as shown in FIG. and the constant of capacitor C1 is approximately determined. However, there is a limit to the capacitance value of the capacitor CI, and the value of the capacitor C5 cannot be increased beyond a certain value. In other words, in this system, the capacitor C1 is the filament of the discharge lamp 1) F, , F2
The resonant current of the capacitor CI always flows as a preheating current of the filament F, F2.

This current is hereinafter referred to as the constant preheating current. When the capacitance of the capacitor C1 increases, this constant preheating current increases, power loss in the filament Fl ff F 2 increases, and circuit efficiency worsens. It causes the lifespan to be shortened. This drawback is particularly apparent in the case of lighting multiple discharge lamps 1 as shown in FIG. In this way, with the circuit system shown in FIG. 8, depending on conditions such as the switching frequency and the type of discharge lamp 1, the capacitance of the resonance capacitor C5 is limited, which makes it difficult to design the circuit. The disadvantage is that the degree of freedom is small. In other words, this resonance capacitor C9 is the filament F of the discharge lamp 1.

This is due to the fact that it also serves as a capacitor for preheating F2.

In addition, in the circuit system shown in the vJ8 diagram, the resonance capacitor C1
Since it is difficult to set the capacitance large, the switching frequency of the switching elements Q, , Q2 is set to f11 filter ■, 1
If f is the resonance frequency determined by the inductance of the inductance and the capacitance of the capacitor C3, then r+<ro... (1) L: The inductance of the coil C1: The capacitance of the coil C1. In addition, in this circuit system, the LC resonance conditions are different before and after the start of discharge, and a slow-phase current flows through the switching elements Q, , Q during normal lighting. If this is shown for switching Q, the switching element Q
, the current rcx is as shown in FIG. In addition, the same figure also shows the switching element Q and the Nigaru voltage ■3.
This is also an indication. In the circuit of FIG. 8, when the switching element Q is made conductive by the output of the control circuit 3, first a forward current flows through the Gumper diode D-2, and then a current flows through the switching element Q1. However, discharge lamp 1 has reached the end of its life, and both or one of the filament lamps (F)
When the active material of , , F is completely peeled off, the state becomes light load or close to no load, and if the circuit of FIG. 8 is separately excited, the switching frequency f0 remains unchanged, so the switching element Q1 ．． As shown in Fig. 11(a), a phase-advanced current flows through Q2, and the switching elements Q, ,Q
There is also the possibility that this may lead to the disadvantage of increased stress. This problem also occurs in the multiple discharge lamp lighting device shown in FIG.

In short, the circuit type discharge lamp lighting device shown in Fig. 8 does not require no-load measures, and when lighting multiple lamps, the remaining discharge lamps 1 can be lit normally even if several lamps are disconnected. On the other hand, since the capacitance of capacitor C1 cannot be increased, the degree of freedom in design is reduced, and this also reduces the resonant frequency f of the LC series resonant circuit. switching frequency f
1 cannot be set too high, and when the discharge lamp 1 reaches the end of its lifespan, a phase-advanced current flows through the switching elements Q, . Note that the above is not limited to the modified bar 7 bridge inverter 2 like the circuit in FIG.
This applies to all inverters having a configuration like the load circuit 4'' shown in the figure, such as the bar 7 pritzno inverter.

[Objective of the Invention 1 The present invention has been made in view of the above-mentioned points, and its purpose is to eliminate the need for no-load countermeasures, provide a large degree of freedom in design, and reduce the risk of discharge lamps reaching the end of their lifespan. An object of the present invention is to provide a discharge lamp lighting device in which a switching frequency can be set higher than a resonant frequency of an LC series resonant circuit so that a phase-advanced current does not flow through a switching element even if the LC series resonant circuit is used.

[Disclosure of the Invention] (Structure) The present invention includes an inverter that converts a DC power source into a high-frequency voltage, and a load circuit including a discharge lamp connected to the inverter output and equipped with an LC resonant circuit consisting of a coil and a capacitor. In a discharge lamp lighting device that lights a discharge lamp at high frequency by applying a high voltage caused by resonance of a resonant circuit to the discharge lamp, either the coil or the capacitor of the LC resonant circuit is divided into each filament of the discharge lamp. A resonant current or preheating current is passed through the filament individually through a coil or capacitor, and by passing the resonant current and preheating current individually through the filament, there is no need for no-load countermeasures and there is a greater degree of freedom in design. Largely, the switching frequency can be set higher than the resonant frequency of the LC series resonant circuit so that phase-advanced current does not flow through the switching element even when the discharge lamp reaches the end of its life.

(Example 1) FIG. 1 shows an example of the present invention. In the following description, descriptions of parts having the same configuration as those in FIG. 8 will be omitted, and only parts that are characteristic of this embodiment will be described. This embodiment has the following characteristics in the load circuit 4.

In other words, in this embodiment, the resonance capacitor C3 in FIG.
, one capacitor C is connected between the capacitor C2 and the negative electrode of the DC power supply E via the filament F+, and the other capacitor C4 is connected to the negative pole of the DC power supply E via the filament F2. It is connected between the capacitor C2 and the negative pole of the DC power supply E via the capacitor C2. Therefore, in this embodiment, capacitors for resonance and preheating are provided for the filaments F1 and F2, respectively. Note that even with this VT structure, there is no resonance loop when there is no load due to detachment of the discharge lamp 1, so it still has the advantage of not requiring no-load countermeasures like the circuit shown in FIG.

Moreover, the capacitors Cx and C4 for preheating and resonance are 2
This method has a greater degree of freedom in setting than conventional methods. This point will be specifically explained below.

Let the filament resistances of the filaments F, , F, of the discharge lamp 1 be R, , R2, respectively, and since the discharge lamp 1 can be approximated to a resistance while lit, the discharge lamp 1 can be set to the load resistance RL.
Then, the circuit of FIG. 8 can be equivalently represented by the circuit of FIG. 12. and the desired switching frequency v!
At t r +, the rated tube current of the discharge lamp 1 ■. The constants of the resonance coil L1 and capacitor C1 in which the current flows are respectively L + + CI, and the current flowing through the coil L and capacitor C1 during lighting is I Lll I C+. In this case, the currents I, I2 flowing through the filament resistors R, R2, respectively, are the lamp currents I-, and
If the respective constant preheating currents in the filament F, F2 are I Plt I F2, I p+ = I P2 = I c, - (4) according to the above equation (3). Here, consider the power loss WI due to the constant preheating current in the filament (Fl-F2). Filament resistance R,,R
Since 2 are almost equal, it is safe to set R,=R2=R...(5). (4)? From formula (5), the power loss W is W, = R, I Ip, l 2 + R21 Ip, l 2 =
2 RI I QI I 2-(6). Also,
Considering the LC resonance frequency f0. Now, suppose the expression (
7) It is assumed that the power loss W in the filament F2 due to the constant preheating current I Plt I F2 is large. In this case, in order to reduce the power loss W1 without changing the switching frequency f, the capacitor C,
There is no choice but to reduce the capacitance of the coil, and as a result, the inductance of the coil also becomes smaller. At this time, the inductance of the resonance coil L is L1゛, and the capacitor C is
The capacitance of 1 is CI', and the resonant frequency at this time is f
.

゛, (However, C1'< CIt L +'< L +
), and the resonant frequency f. becomes high, and Ll>
There is a risk that f.

By the way, if the present invention shown in FIG. 1 is used and equivalently shown in the same manner as in FIG. 8, the result will be as shown in FIG. v&2. Note that the capacitor C at the switching frequency f1
,,C, has a capacitance of C,,C.

Binding, C,=C2+C,...(9). Therefore, r c+ = I C3+ I C4・= (1,0)
At this time, T LI= I o+ I C3+ I C4-(11
)11=I0+IC5...(12) I2=10+■o,...(13
)IPI"IC:l...
(14) I P2= I c--(15) Therefore, the power loss W2 due to the constant preheating current is ==R(l
ICj + 2+I IC4121"' (16) Here, since I C1f r C3t I C4 are in phase, each is proportional to the capacitance value of the capacitor. In other words, (
14), (15), (16) to (6), (9), (19) to (20), by using the present invention, the power loss is always less than half that of the conventional example. When C1=C4, it becomes the minimum compared to the conventional example, and in this case it becomes 1/4. Alternatively, according to equations (17) and (18), the constant preheating current also becomes smaller. Also, the resonance frequency f at this time. Considering ゛, from equations (7) and (9), =f,
...(21) From equations (8) and (2), fo''<fo' - (22) (22)
The equation shows that the circuit system according to the present invention can set the resonant frequency lower than the conventional system.

To summarize the meanings of equations (21) and (22) above, the circuit system according to the present invention has capacitors C3-C1
By appropriately designing the power loss caused by the constant preheating current, it is possible to significantly reduce the power loss caused by the constant preheating current, so compared to the conventional method, it is possible to apply constants for resonance inductance and capacitance, which could not be applied with the conventional method shown in Figure 8. This is a method with a large degree of freedom in design. This makes it easier to set the resonant frequency lower than the conventional method, making it easier to set the switching frequency higher than the resonant frequency, and even when the discharge lamp reaches the end of its life, phase-advanced current flows through the switching element. It becomes easier to prevent the flow from flowing, and the reliability of the device also improves.

Note that the above also applies to multiple lamp lighting devices for various discharge lamps 1 in which a plurality of load circuits 4 are connected in parallel.

FIG. 3 shows a specific circuit of the above embodiment. In this circuit,
A DC power source E is obtained by voltage doubler rectifying and smoothing a commercial power source AC using a voltage doubler rectifier and smoothing circuit 5 composed of diodes Di-D- and capacitors c, . . . . Also, the control circuit 3
The switching regulator for RC (TL494 etc.) 6
The mutually opposing outputs of this IC6 are connected to an output transformer T2, T2 and a switching element Q3 consisting of a MOSFET. The date signal is applied as a date signal to switching elements Q, Q2 made up of MOSFETs via an output circuit made up of transistors Q- and the like.

Incidentally, in the above explanation, the case where the capacitors C3t and C4 are divided into parts for resonance and preheating of each filament (F+-Fz) was explained, but as shown in FIG. It is also possible to divide it into parts and connect them.

(Example 2) FIG. 5 shows another example of the present invention. In this embodiment, the present invention is applied to a case where there is not a single discharge lamp, but two discharge lamps 14, 1□ are connected in series.

The coil and capacitor C2 are capacitors for the coil and power supply of the LC series resonant circuit as in the above embodiment. Note that in this embodiment, resonance capacitors C3 to C
2 is unique in how it is connected. That is, capacitor C6
is connected to the power supply side of the filament (F) of the discharge lamp 11, -FI2, and the capacitor C7 is connected to the filament (F) of the discharge lamp 1□.
21 t F is connected to the power supply side of 2□, and the capacitor C5 is connected to the filament of discharge lamp 11)
□ filler line) Connect to the non-power supply side of F2□. With this configuration, the two filaments of the negative discharge lamp 1 are F I l ff F + 2 or 1 F2+tF
If you focus on 2□, you will see two filamen) F II
-F 12 or F 21 t F 2□ will each be equipped with a capacitor for resonance and preheating. Therefore, the resonant loop during no-load is eliminated by detachment of either discharge lamp 11 or 1□, so no-load countermeasures are required. Furthermore, as explained in the above embodiment, since the power loss due to constant preheating current can be significantly reduced, the degree of freedom in design is greater than when the conventional method as shown in Fig. 8 is applied to this embodiment. is thick.For this reason, it is easy to set the switching frequency higher than the resonant frequency, and even if the discharge lamps 11, 1 It becomes easier to prevent current from flowing, and the reliability of the device also improves.

In the case of this embodiment as well, as shown in FIG. 6, a coil can be used in place of the capacitor and divided into parts.

(Example 3) FIG. 7 shows still another example of the present invention. In this embodiment, the present invention is applied when the inverter 2 has a so-called full-frontal configuration, and the resonance capacitors C, , C
, are connected in substantially the same manner as in the above-mentioned embodiment, and the same effects as in the above-mentioned embodiment can be expected. In the above embodiments, a modified bar 7 bridge inverter or a full-bridge inverter is used as the inverter 2, but other single-stone inverters, bar 7
Needless to say, a bridge inverter or the like may be used. Furthermore, in the embodiment described above, it is possible to easily make the preheating currents of the pair of filaments of the discharge lamp unbalanced, so that movement stripes of the discharge lamp 1 can be prevented and flickering of light emission can also be prevented.

[Effects of the Invention 1] As described above, the present invention divides either the fill or the capacitor of the LC resonant circuit, and individually supplies the resonance current or preheating current to each filament of the discharge lamp through the divided coil or capacitor. Since it is a sink, there is no resonance loop when there is no load due to disconnection of the discharge lamp,
Therefore, there is no need for no-load measures, and by appropriately designing the actance of the LC resonant circuit, power loss due to constant preheating current can be significantly reduced. This has the effect of increasing the degree of freedom in design. Furthermore, with this increased degree of freedom in design, the switching frequency can be set higher than the resonant frequency of the LC series resonant circuit so that phase-advanced current will not flow through the switching element even at the end of the discharge lamp's life. This has the advantage that stress is not applied to the switching elements and the reliability of the device is improved.

[Brief explanation of the drawing]

The first leap is a circuit diagram of an embodiment of the present invention, Figure 2 is a similar circuit as above, Figure 3 is a specific circuit as above, and Figure 4 is a circuit diagram when the capacitor and coil as above are replaced. , FIG. 5 is a circuit diagram of another embodiment of the present invention, FIG. 6 is a circuit diagram when the same capacitor and coil are replaced, and FIG. 7 is a circuit diagram of still another embodiment of the present invention. Fig. 8 is a circuit diagram of a conventional example, Fig. 9 is a circuit diagram when the same as above is used as a multi-lamp lighting circuit,
tJtJ10 and 11 are the same operation explanatory diagrams as above, and the first
FIG. 2 is an equivalent circuit diagram of FIG. 8. 1 is a discharge lamp, 2 is an inverter, 4 is a load circuit, L is a coil, C, C4 are capacitors, F, F2 are filaments, and E is a DC power supply. Agent Patent Attorney Ishi 1) Chief 7 Figure 5 Figure 6 Figure 7 Figure 10 - Figure 11 ↑ Figure 12 Procedural amendment (voluntary)

Claims (1)

[Claims] (1) An inverter that converts DC power into high frequency voltage,
A discharge lamp that is equipped with a load circuit including a discharge lamp connected to an inverter output and equipped with an LC resonant circuit consisting of a coil and a capacitor, and applies a high voltage due to the resonance of the LC resonant circuit to the discharge lamp to light the discharge lamp at high frequency. The lighting device is characterized in that either the coil or the capacitor of the LC resonant circuit is divided, and a resonant current or preheating current is individually passed through the divided coil or capacitor to each filament of the discharge lamp. discharge lamp lighting device.