JPH0658831B2 - Discharge lamp lighting device - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

 The present invention relates to a discharge lamp lighting device.

[Prior art]

FIG. 7 shows a series circuit of an inductance element L and a preheating type discharge lamp l such as a fluorescent lamp, and filaments f ₁ and f _{2 of the} discharge lamp l.
A conventional example of a discharge lamp lighting device that supplies AC power to a discharge lamp 1 by using a load circuit RL composed of a capacitor C ₂ connected to the non-power source end side of the above as a load. Next, the above conventional example will be described. In this conventional example, the DC power source E
Is connected to a series circuit of switching elements Q ₁ and Q ₂ of the inverter circuit 2, and a capacitor C ₁ is connected to the switching element Q _2.
The load circuit RL is connected in parallel via. The control circuit 1 is for alternately turning on and off the switching elements Q ₁ and Q ₂ , and the diodes D ₁ and D ₂ are freewheeling diodes. The relationship between the capacity of the capacitor C _{1 and} the capacity of the capacitor C ₂ is C ₁ >> C ₂ , and the capacitor C ₁ does not participate in the resonance of the load circuit RL. Next, the operation of the conventional example will be described based on the waveform chart of FIG. First, the control circuit 1 causes the switching elements Q ₁ , Q
It is assumed that each ON section of ₂ is controlled equally. At first, the switching frequency f of the switching elements Q ₁ and Q ₂ is the resonance frequency fo of the series circuit of the inductance element L and the capacitor C _2. And higher than, the inductance element L, filaments f ₁ by the series resonance current of the capacitor C _2, f ₂
When the switching frequency f is gradually brought closer to the resonance frequency fo after sufficiently preheating, the voltage across the discharge lamp 1 rises, and the discharge lamp 1 is started and lit. As shown in FIG. 8 (a), the capacitor C ₁ has an E in the direction of arrow X in FIG.
The voltage of / 2 is charged, and as a result, the load circuit RL is
The alternating voltage V _RL as shown in FIG. A resonance current I _L determined by a load circuit RL as shown in FIG. 8 (d) flows through the inductance element L, and the discharge lamp 1 has a lamp current Il and a lamp voltage Vl shown in FIGS. 8 (f) and 8 (g). Get AC power consisting of. 8B shows the currents I _Q1 and I _D1 of the switching element Q ₁ and the diode D ₁ , and FIG. 8C shows the inter-terminal voltage V _Q1 of the switching element Q ₁ .

[Problems to be Solved by the Invention]

The conventional example shown in FIG. 7 has the following problems. That is, as shown in FIG. 9, when the discharge lamp 1 is detached, the voltage between the terminals A and B connecting the discharge lamp 1, that is, the so-called no-load secondary voltage V _02, becomes abnormally large. The above phenomenon will be specifically described with reference to FIGS. 9 and 10. FIG. 9 is an equivalent circuit when the discharge lamp 1 is detached, that is, when there is no load. Essentially, when there is no load, the impedance between the terminals A and B connecting the discharge lamp l becomes infinite, the loop through which the current I _L of the inductance element L flows disappears, and the no-load secondary voltage V ₀₂ is shown in FIG. The waveform is the same as the AC voltage V _RL applied to the load circuit RL shown in (b), and the effective value of the no-load secondary voltage V ₀₂ is V _{02 (RMS)} ≈E / 2 ... (1). However, in reality, since there is a small stray capacitance Co between the wirings between the terminals A and B, the inductance element L and the stray capacitance Co cause LC series resonance, so that the inductance element L is shown in FIG. The resonance current I _L as shown flows, and as a result, the no-load secondary voltage V ₀₂ is the AC voltage V _{RL in} which the resonance voltage between the inductance elements L due to the series resonance of the inductance element L and the stray capacitance Co is applied.
The waveform is as shown in FIG. 7C, and the unloaded secondary voltage V ₀₂
There was a problem that the effective value of was very large compared to E / 2 shown in Eq. (1). Actual resonance voltage I _L
Has a resistance R due to wiring or the like in the loop in which the resonance current I _L shown in FIG. Further, if the effective value of the no-load secondary voltage V ₀₂ is large, the lighting equipment may require an interlock function as a ground terminal or a lighting device in the electrical equipment, and the cost of the lighting equipment and the lighting device becomes high. There was a problem. First
FIG. 0 (a) shows the voltage V _C1 across the capacitor C ₁ . Since the stray capacitance Co has a very small capacitance value as compared with the capacitor C ₂ , it does not affect the operation in the presence of the discharge lamp l. The present invention has been made in view of the above problems, and it is possible to increase the secondary voltage at no load due to the stray capacitance between the terminals connecting both ends of the discharge lamp even at the time of no load due to disconnection of the discharge lamp. An object of the present invention is to provide a discharge lamp lighting device that can be suppressed.

[Means for Solving the Problems]

The present invention relates to a DC power supply, an inverter circuit that includes a pair of switching elements that alternately turn on and off and that converts the voltage of the DC power supply into an AC power supply and outputs the same, and an inductance element that is energized by the output of the inverter circuit. In a discharge lamp lighting device comprising a series circuit of a preheating type discharge lamp and a load circuit forming a resonance circuit with a capacitance element connected to the non-power source side of the filament of the discharge lamp, the discharge lamp is eliminated from the load circuit. When no load is applied, the impedance element that suppresses generation of an excessive resonance voltage in the inductance element due to the resonance action of the stray capacitance existing between the wirings connecting both ends of the discharge lamp and the inductance element is the first impedance element. In the resonance circuit including the inductance element, the inductor is connected from the connection end to which the discharge lamp is connected. Which are connected in a direction coming close to the element.

[Work]

However, in the discharge lamp lighting device of the present invention, when the discharge lamp is separated from the load circuit, that is, when there is no load, the stray capacitance existing between the terminals connecting both ends of the discharge lamp and the series resonance of the inductance element in the load circuit. The impedance element that suppresses the generation of an excessive resonance voltage in the inductance element is connected in a direction closer to the inductance element than the connection end to which the discharge lamp is connected in the resonance circuit including the inductance element. Therefore, the so-called no-load secondary voltage increase between the terminals connecting the discharge lamp can be suppressed.

【Example】

Hereinafter, the present invention will be described in detail with reference to examples. FIG. 1 shows a circuit configuration of one embodiment. In this embodiment, in the conventional example shown in FIG. 7, a capacitor C ₃ in parallel with the discharge lamp 1 is provided between terminals A and B connecting both ends of the discharge lamp l,
An impedance circuit Z ₁ consisting of a series circuit of a resistor R ₁ is connected as an impedance element. Here, since the capacitor C ₃ uses a capacitor having a lower capacity than the capacitor C ₂ , and the resistor R ₁ is set to a value larger than the impedance of the discharge lamp l, the impedance circuit Z ₁
Is very large compared to the impedances of the discharge lamp 1 and the capacitor C ₂ , and does not affect the resonance operation of the load circuit RL while the discharge lamp 1 is lit. Therefore, while the discharge lamp 1 is lit, the embodiment circuit shown in FIG. 1 is shown in FIGS. 8 (f) and 8 (g) in the discharge lamp 1 as in the prior art circuit shown in FIG. Obtain high frequency AC power. Next, when the discharge lamp 1 is disconnected and there is no load, the load circuit RL is composed of the impedance circuit Z ₁ , a parallel circuit of the stray capacitance Co between the terminals A and B, and a series circuit of the inductance element L. It The waveform of each part and the waveform of the unloaded secondary voltage V ₀₂ in this case are shown in FIG. At the time of no load, a rectangular wave-shaped high frequency AC voltage V _RL as shown in FIG. 2B is applied to the load circuit RL. Since the impedance circuit Z ₁ has the resistance R ₁ that serves as a damping element in the resonance circuit, the load circuit RL in the no-load condition performs damping vibration. In other words, the impedance element Z and the stray capacitance Co are connected by connecting the impedance circuit Z ₁ in parallel to the stray capacitance Co between the wirings.
The series resonance due to is caused to be a damping vibration, and as a result, as shown in FIG. 2 (d), a minute current I _L that causes the damping vibration flows through the inductance element L. Therefore, since the voltage generated in the inductance element L during the damping vibration of the load circuit RL is small, the waveform of the unloaded secondary voltage V ₀₂ becomes the waveform shown in FIG. 2 (c), and its effective value is also E / 2. Therefore, the increase of the no-load secondary voltage V ₀₂ can be prevented. Further, the impedance circuit Z ₁ added for reducing the unloaded secondary voltage V ₀₂ is a series circuit of a capacitor C ₃ and a resistor R ₁ connected between terminals A and B connecting the discharge lamp l. , A voltage waveform corresponding to the alternating current of the discharge lamp 1 is generated as the voltage V _R1 across the resistor R ₁ . When the filament f ₁ or f _{2 of the} discharge lamp l is abnormally lit at the end of its life, the voltage V _R1 becomes larger than that in the normal state. This is the lamp voltage Vl (3rd
It is shown in FIG. 3 together with the waveform of FIG. As shown in FIG. 3 (b), the voltage V _R1 is a voltage at which the end of life of the discharge lamp l can be detected. As shown in FIG. 4, the resistor R ₁ is connected in series with resistors R ₂ and R _3. The detection voltage V _R obtained by rectifying and smoothing the voltage across the resistor R ₃ obtained by dividing the voltage V _R1 by the diode D ₃ , the capacitor C ₄ , and the resistor R ₄ is the end of the lamp life of the discharge lamp l. It can be adopted as a detection voltage that can be detected. Therefore, the impedance circuit Z
There is also an effect that _one may also serve as the detection circuit of the lamp end of life. Of course, the resistance of the impedance circuit Z ₁ is the resistance R ₁
You may comprise only. 2A shows the voltage V _C1 across the capacitor C ₁ , and FIG. 3A shows the normal lighting, B shows the abnormal lighting of the filament f _{1 at} the end of its life, and C shows the filament f ₂ . Abnormal lighting at the end of life, d indicates abnormal lighting at the end of life of the filaments f ₁ and f ₂ , respectively. Particularly, by appropriately setting the constants of the resistor R ₁ and the capacitor C ₁ , the voltage across the points A and B at no load, that is, the oscillating voltage superimposed on the no-load secondary voltage V ₀₂ , in other words, no effect that an oscillating voltage which is generated in the inductance element L when the load can be obtained as a voltage across the resistor R _1, it can be detected that the discharge lamp l became unloaded off the voltage across the resistor R ₁ There is also. FIG. 5 shows a circuit of another embodiment of the present invention. In this embodiment, in the conventional circuit shown in FIG. 7, an impedance circuit Z ₂ composed of a capacitor C ₃ is connected in parallel with an inductance element L as an impedance element. Since the capacitor C ₃ is a low-capacity capacitor and has a very large impedance with respect to the impedance of the inductance element L, the discharge lamp
When l is on, high-frequency AC power as shown in FIGS. 8 (f) and 8 (g) is obtained from the discharge lamp l as in the conventional circuit shown in FIG. Next, when the discharge lamp 1 is disconnected and there is no load, the load circuit RL is a series circuit of the parallel circuit of the capacitor C ₃ and the inductance element L and the stray capacitance Co between the terminals A and B. FIG. 6 shows the waveform of each part and the waveform of the no-load secondary voltage V ₀₂ when there is no load. Load circuit R when no load
A rectangular wave-shaped high-frequency AC voltage V _RL as shown in FIG. 6B is applied to L. The currents I _C3 and I _C0 flowing through the capacitor C ₃ and the stray capacitance Co respectively are as shown in FIGS. 6 (e) and 6 (f). This current I _C3 , I _C0
Both are resonance currents, and their phases are shifted by 180 ° C. The current I _L shown in FIG. 6 (d) is the current I _L
This is a combined current of _C3 and the current I _C0 , which also becomes an oscillating current, but this current I _L is a very small resonance current. That is, by connecting the capacitor C ₃ to the inductance element L in parallel and shifting the condition of series resonance between the inductance element L and the stray capacitance Co, the series resonance of the inductance element L and the stray capacitance Co causes the inductance element L to become excessive. It suppresses the generation of various resonance voltages. Specifically, the inductance element L has a current I _L
A small voltage that is advanced by π / 2 from the phase is generated, and the combined voltage of this voltage and the AC voltage V _RL (see FIG. 6 (b)) is no load 2
The next voltage becomes V ₀₂ , and the waveform becomes as shown in FIG. 6 (c). The effective value of the no-load secondary voltage V ₀₂ is compared with the conventional example shown in FIG. 7, in which suppresses the increase of the no-load secondary voltage V _02. When C ₃ > C ₂ , the increase of the secondary no-load voltage V ₀₂ can be suppressed well.

【The invention's effect】

The present invention, in the discharge lamp lighting device configured as described above, in the so-called no load when the discharge lamp is separated from the load circuit,
An impedance element that suppresses generation of an excessive resonance voltage in the inductance element due to series resonance between the stray capacitance existing at both ends of the lamp and the inductance element in the load circuit is provided in the resonance circuit including the inductance element. Since the connection is made in the direction closer to the inductance element than the connection end to which the electric lamp is connected, it is possible to suppress an increase in so-called no-load secondary voltage between the terminals connecting the discharge lamp.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIGS. 2 and 3 are waveform diagrams for explaining the same operation as above, FIG. 4 is a circuit diagram for explaining the same operation as above, and FIG. Circuit diagram of another embodiment, sixth
FIG. 7 is a waveform diagram for explaining the operation of the above, FIG. 7 is a circuit diagram of a conventional example, FIG. 8 is a waveform diagram for explaining the operation of the same, FIG. 9 is a circuit diagram for explaining the operation of the same, and FIG. FIG. 9 is a waveform diagram for explaining the operation of the circuit in FIG. 9. Z ₁ is an impedance circuit, L is an inductance element,
C ₂ is a capacitor, RL is a load circuit, and l is a discharge lamp.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 62-200687 (JP, A) JP 63-175386 (JP, A) JP 63-45798 (JP, A) JP 59- 123199 (JP, A) JP 62-53170 (JP, A) JP 55-22920 (JP, B2) JP 54-3583 (JP, Y2)

Claims (1)

[Claims] 1. An inverter circuit including a direct current power source and a pair of switching elements that alternately turn on and off and converting the voltage of the direct current power source into an alternating current power source for output, and is energized by the output of this inverter circuit. In a discharge lamp lighting device comprising a series circuit of an inductance element and a preheating type discharge lamp, a capacitance circuit connected to a non-power supply side of a filament of the discharge lamp, and a load circuit, the discharge lamp is a load circuit. When there is no load,
The resonance element including the inductance element suppresses the generation of an excessive resonance voltage in the inductance element due to the resonance action of the stray capacitance existing between the wirings connecting the both ends of the discharge lamp and the inductance element. A discharge lamp lighting device, characterized in that the discharge lamp lighting device is connected in a circuit in a direction closer to the inductance element from a connection end to which the discharge lamp is connected.