JPH0739199Y2 - Discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a discharge lamp lighting device for lighting a discharge lamp at a high frequency.

[Prior Art] Conventionally, as a discharge lamp lighting device of this type, Figs.
The one shown in the figure is known.

Fig. 8 shows the case where a one-stone type inverter is used. The DC power source 1 has a capacitor 2 and a primary winding 3 _{1 of a} leakage transformer 3.
The switch element 4 is connected through a parallel resonance circuit composed of and, and the diode 5 is connected in parallel to the switch element 4 with the polarity shown in the drawing to form an inverter circuit. In addition,
The switch element 4 is composed of, for example, a transistor or a thyristor and performs high frequency switching operation.

Leakage transformer 3 which is the output terminal of the inverter circuit
The secondary winding 3 ₂ is connected one end of each filament electrode of the discharge lamp 7 via the capacitor 6 is connected a capacitor 8 between the other end of each filament electrodes of the discharge lamp 7.

The circuit switching element 4 when operating the high-frequency switching, the resonant current flows in the resonant circuit of a capacitor 2 and the primary winding 3 _1, the resonance current is transmitted to the secondary winding 32 side.
The startup series resonance circuit is formed by the capacitor 6 and 8 and the secondary winding 3 ₂ and in, between the electrodes of the discharge lamp 7 by slightly higher than the resonance frequency of the overall circuit the resonance frequency of the series resonant circuit A high voltage is applied to. Further, a preheating current flows to each electrode of the discharge lamp 7 via the capacitor 8.

Then, the discharge lamp 7 will start high frequency lighting.

Further, FIG. 9 shows a case where a half-bridge type inverter is used, in which a series circuit of a pair of switch elements 9 and 10 is connected in parallel to a DC power source 1 and a series circuit of a pair of capacitors 11 and 12 is connected, The discharge lamp 7 is connected via a choke coil 13 between the connection points of the switch elements 9 and 10 and the connection points of the capacitors 11 and 12. Note that diodes 14 and 15 are connected in parallel to the switch elements 9 and 10 with the polarities shown in the drawing.

In this circuit, when the switching elements 9 and 10 alternately perform high frequency switching operation, a high frequency alternating current flows through the choke coil 13. At startup, a high voltage is applied between the electrodes of the discharge lamp 7 by the resonance circuit composed of the choke coil 13 and the capacitors 8, 11 and 12. Further, a preheating current flows to each electrode of the discharge lamp 7 via the capacitor 8.

Then, the discharge lamp 7 will start high frequency lighting.

[Problems to be Solved by the Invention] In the discharge lamp lighting device of FIGS. 8 and 9 described above, since the resonance frequency applied to the discharge lamp as the load and the on / off frequency of the switch element are the same, In order to turn on the discharge lamp at a high frequency, a switch element that can withstand a high-speed switching operation is required, and a circuit for switching and driving the switch element is also required to have a high speed, so that there is a problem that the cost is high as a whole.

Therefore, the present invention intends to provide a discharge lamp lighting device capable of lowering the on / off frequency of the switch element with respect to the lighting frequency of the discharge lamp, and therefore not requiring high speed as a switch element and reducing the cost. It is what

[Means for Solving the Problems] The present invention provides a DC power supply, a series circuit of a pair of inductors and a switching element connected in parallel to the DC power supply, and an inductor and a switching element of each series circuit. It consists of a pair of resonance capacitors connected in series between the connection points and a discharge lamp connected via a choke coil between the connection point of each resonance capacitor and the positive or negative terminal of the DC power supply. The switching elements are alternately switched.

[Operation] In the present invention having such a configuration, the three inductors and the two capacitors resonate, but by selecting an appropriate value, the second resonance is generated around the first resonance frequency and a frequency twice that frequency. Determine the circuit constants so that the frequency comes. By alternately opening and closing the switch element, the inductor connected in series with the switch element resonates at the first resonance frequency, and the inductor connected in series with the discharge lamp as the load has the second resonance frequency. Resonates with.

At this time, if the second resonance frequency is near twice the first resonance frequency, the second resonance frequency oscillates as the second harmonic of the first resonance frequency.

Therefore, the frequency applied to the discharge lamp is twice the frequency of the switching element frequency.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a series circuit of a first inductor 22 and a first switch element 23 is connected to a DC power source 21 to form a first inductor.
22 is connected in parallel with the positive side of the power supply, and a series circuit of the second inductor 24 and the second switch element 25 is connected in parallel with the second inductor 24 being the positive side of the power supply.

Diodes 26 and 27 are connected in parallel to the switch elements 23 and 25, respectively, with their anodes on the positive electrode side of the power supply.

A connection point between the first inductor 22 and the first switch element 23, the second inductor 24 and the second switch element 25.
The first and second resonance capacitors 2 are connected between the connection point and
8,29 are connected in series.

Then, one end of one filament electrode 30a of the discharge lamp 30 is connected to each of the resonance capacitors 28, 2 via the choke coil 31.
The discharge lamp 30 is connected to the connection point 9, and the other end of the filament electrode 30b of the discharge lamp 30 is connected to the negative terminal of the DC power supply 21.

A preheating capacitor 32 is connected between the other ends of the filament electrodes 30a and 30b of the discharge lamp 30.

Each of the switch elements 23 and 25 is composed of, for example, a transistor or a thyristor, and is alternately switched by a drive circuit.

In this embodiment having such a configuration, when the first switch element 23 is turned on and off, the voltage across the switch element 23 changes as shown in FIG. When the switch element 25 is turned on and off, the voltage across the switch element 25 changes as shown in FIG. 2 (b).

Now, assuming that the first switch element 23 is turned on at the timing t _1, at this time, as shown in (c) of FIG. Current is flowing through. And the first resonance capacitor
28 supplies a current to the first inductor 22 and
Current is also supplied to the negative electrode side of the DC power supply 21 via the switch element 23. At this time, a sinusoidal current flows through the first switch element 23. After that, the current is inverted and the current flows through the diode 26.

Therefore, the current shown in FIG. 2E flows through the parallel circuit of the first switch element 23 and the diode 26.

During this time, the current flowing through the first inductor 22 increases with a constant slope.

Thus, the current flowing through the first resonance capacitor 28 is the same as the current flowing through the first inductor 22 and the first switching element 23.
It is determined by the current flowing in the parallel circuit of the diode 26 and the diode 26, as shown in FIG.

Further, when the second switch element 25 is turned on at the timing t _2, at this time, the current flows in the second inductor 24 in the direction in which the current flows to the positive electrode side of the DC power source 21 as shown in (d) of FIG. Is flowing. And the second resonance capacitor
29 supplies a current to the second inductor 24 and
A current is also supplied to the negative electrode side of the DC power supply 21 via the switching element 25. At this time, a sinusoidal current flows through the second switch element 25. After that, the current is inverted and the current flows through the diode 27.

Therefore, the current shown in (f) of FIG. 2 flows in the parallel circuit of the second switch element 25 and the diode 27.

During this time, the current flowing through the second inductor 24 increases with a constant slope.

Thus, the current flowing through the second resonance capacitor 29 is the same as the current flowing through the second inductor 24 and the second switching element 25.
It is determined by the current flowing in the parallel circuit of the diode 27 and the diode 27, as shown in (h) of FIG.

The currents flowing through the first resonance capacitor 28 and the second resonance capacitor 29 are 180 degrees out of phase with each other.

At this time, the current flowing in the choke coil 31 is equal to the current flowing in the first resonance capacitor 28 and the second resonance capacitor 29.
The difference is the current flowing in the switch element 28, and the frequency becomes twice the switching frequency of each switch element 28, 29, as shown in FIG.

Thus, the discharge lamp 30 is AC-discharged and lit by the sinusoidal high-frequency current flowing through the choke coil 31.

In the initial state when the discharge lamp 30 does not light up when starting, the choke coil
Each filament electrode from 31 through preheating capacitor 32
Preheating current flows through 30a and 30b. At this time, choke coil 3
1 and the capacitance of the preheating capacitor 32 are appropriately selected so that the resonance frequency of the preheating capacitor 32 is slightly higher than the resonance frequency of the entire circuit.

As a result, in the initial state where the discharge lamp 30 is not started and lit, the entire circuit oscillates near the resonance frequency of the choke coil 31 and the preheating capacitor 32, and a high voltage is applied across the discharge lamp 30.

In this way, the supply of the preheating current and the application of the high voltage to the filament electrodes 30a and 30b cause the discharge lamp 30 to start and light.

In this way, the lighting frequency of the discharge lamp 30 is set to the switching elements 23, 25.
The switching frequency can be doubled, so if the discharge lamp 30 is lit at the same frequency as the conventional switch elements 23,25
As for, it suffices to perform switching operation at half the frequency,
It is possible to sufficiently cope with the switching elements 23 and 25 without using such high-speed switching operation.
Therefore, a relatively inexpensive switch element and its drive circuit can be used. Therefore, the cost can be reduced as a whole.

In the above embodiment, the choke coil 31 and the discharge lamp 30 are used.
The connection position of may be reversed, and the choke coil may be replaced by 2
The discharge lamp 30 may be divided into two parts and connected to both sides.

Next, another embodiment of the present invention will be described with reference to the drawings. The same parts as those in the above embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 3, a series circuit of a choke coil 31 and a discharge lamp 30 is connected to a connection point between the positive terminal of the DC power source 21 and the first and second resonance capacitors 28 and 29.

Even with such a structure, the same high price as that of the above embodiment can be obtained.

As shown in FIG. 4, the series circuit of the choke coil 31 and the discharge lamp 30 is connected to the connection point between the positive terminal of the DC power supply 21 and the first and second resonance capacitors 28 and 29, and
Inductor 22, first switching element 23, diode 26
Connection position with the parallel circuit of the second inductor 24 and the second
The connection position of the switch element 25 and the diode 27 with respect to the parallel circuit is reversed.

Even with such a configuration, the same effect as that of the above-described embodiment can be obtained.

FIG. 5 shows the first and second resonance capacitors 2
Another capacitor 33 is connected in parallel to a series circuit of 8,29.

By adding the capacitor 33 in this way, the discharge lamp 30
The influence of the discharge state on the oscillation frequency can be reduced, and the oscillation state can be stabilized.

It should be noted that the same effects as those of the above-described embodiment can be obtained in this configuration as well.

What is shown in FIG. 6 is each filament electrode 30 of the discharge lamp 30.
Another capacitor 34 is connected between one ends of a and 30b.

By adding the capacitor 34 in this way, it is possible to adjust the current flowing through each filament electrode 30a, 30b and reduce the instability of the resonance state due to the discharge state of the discharge lamp 30.

It should be noted that the same effects as those of the above-described embodiment can be obtained in this configuration as well.

In FIG. 7, the first and second inductors 22 and 24 are magnetically coupled.

By magnetically coupling the inductors 22 and 24 in this manner, the number of windings of each inductor 22 and 24 can be reduced, and the coil components can be integrated into one, and the size and weight can be reduced.

It should be noted that the same effects as those of the above-described embodiment can be obtained in this configuration as well.

[Advantages of the Invention] As described in detail above, according to the present invention, the on / off frequency of the switch element can be lowered with respect to the lighting frequency of the discharge lamp, and therefore, high speed is not required as a switch element, and the cost is reduced. It is possible to provide a discharge lamp lighting device capable of achieving the above.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 is a circuit diagram, FIG. 2 is a diagram showing voltage and current waveforms of respective parts, and FIG. 7 to 7 are circuit diagrams showing another embodiment of the present invention, and FIGS. 8 and 9 are circuit diagrams showing a conventional example. 21 …… DC power supply, 22,24 …… Inductor, 23,25 …… Switch element, 28,29 …… Resonance capacitor, 30 …… Discharge lamp, 31 …… Choke coil.

Claims (1)

[Scope of utility model registration request] 1. A DC power supply, and a series circuit of a pair of inductors and a switching element connected in parallel to the DC power supply,
A pair of resonance capacitors connected in series between the connection points of the inductor and the switch element of each series circuit, and between the connection point of each resonance capacitor and the positive terminal or the negative terminal of the DC power supply. A discharge lamp lighting device comprising a discharge lamp connected via a choke coil, wherein each of the switch elements alternately performs a switching operation.