JPH06101388B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device for lighting a discharge lamp such as a high pressure discharge lamp.

[Background Art] In a conventional general discharge lamp lighting device, a ballast is composed of a choke coil, a transformer, a capacitor and the like individually or in combination, and therefore, the size and weight are large.

From this point of view, it is desired to reduce the size, weight and efficiency of the discharge lamp lighting device, and for that purpose, it is considered to light the discharge lamp at a high frequency. For example, in a fluorescent lamp lighting device, a high frequency lighting device using a switching transistor, a thyristor or the like has been put into practical use.

When high frequency is used in the lighting device for high pressure discharge lamps,
Although the same effect as a fluorescent lamp can be obtained, it is conventionally known that when a high-pressure discharge lamp is lit at a high frequency, arc instability due to an acoustic resonance phenomenon exists.

By the way, as a method for eliminating the instability of the arc caused by the acoustic resonance phenomenon, there has been a method of setting the frequency of the lighting power source to an ultrahigh frequency (for example, 100 kHz) (Japanese Patent Laid-Open No. 56-11897, etc.). This is noise (especially radiation noise)
In addition, the switching loss is large, which is a practical problem. Further, there is a method of modulating the frequency of the lighting power source, for example, between 30 KHz and 50 KHz (Japanese Patent Laid-Open No. 56-48095, etc.), but it cannot be suppressed and there is still a problem in practical use. There is also one that is lit by direct current (Japanese Patent Laid-Open No. 56-98499), however, there is another problem in terms of lamp life (blackening, etc.). Further, there is also a method of lighting a rectangular wave.
This rectangular wave lighting is based on the literature "Characteristicis of Acoustical Res.
onance In Discharge Lamps) ”Illuminating
Engineering (ILLUMINATING ENGINEERING) 1970
It is shown in December P713-716.

However, in this method, although the arc is stable, the flat part of the rectangular wave is burdened by the resistor as a current-limiting element, so it becomes large and the power loss becomes large, and the waveform rises and rises in the high-frequency rectangular wave. Since the fall is steep, a problem of noise arises, and there is a problem that this measure leads to a significant increase in cost.

Therefore, basically, it is most practical to operate the current limiting element portion under a high frequency while reducing the frequency of the lamp current flowing through the high pressure discharge lamp to prevent the resonance phenomenon. An example of such a method is disclosed in Japanese Utility Model Laid-Open No. 59-16100. In this device, the flat portion of the rectangular wave is placed in a state where high-frequency components are superimposed, and an inductance is used as a current limiting element to reduce the size of the device. However, this method requires an oscillating transformer and a semiconductor element dedicated to the chopper, and the lighting device is still large.

There is also one disclosed in US Pat. No. 4,170,747. FIG. 6 shows a conventional discharge lamp lighting device shown in US Pat. No. 4,170,747. In the figure, a switching circuit in which transistors 3 to 6 are connected in a bridge shape is connected to power supply terminals 1 and 2 to which a capacitor 16 is connected via a current detection resistor 13, and transistors 3 to 6 are respectively connected to transistors 3 to 6
Diodes 7 to 10 are connected in parallel in the direction opposite to the
A series circuit of a choke coil 11 and a high pressure discharge lamp 12 in which a capacitor 14 is connected in parallel is connected between the connection points of the transistors 3 and 6 and the connection points of the transistors 4 and 5. The control circuit 15 is a circuit for controlling the transistors 3 to 6 according to the detected current.

FIGS. 7A to 7D are timing charts showing the operation of the transistors 3 to 6.

Transistors 3 and 4 are controlled by control circuit 15 to 50 / 60Hz or 400H
When the transistor 3 is on, the transistor 5 performs an on / off operation with a variable duty ratio of, for example, 20 KHz (1 / T ₂ ) when the transistor 3 is on, and when the transistor 4 is on, the transistor 6 performs the same on / off operation as the transistor 5. . Further, when the polarity of the high pressure discharge lamp 12 is reversed, the four transistors 3 to 6 are turned off at the same time, and the idle period T _D is provided. The control circuit 15 changes the on / off duty ratio depending on the voltage of the current detection resistor 13. Therefore, a rectangular wave alternating current containing high frequency ripples flows through the high pressure discharge lamp 12.

The operation of the circuit shown in FIG. 6 will be further described with reference to FIGS. 7 (a) to 7 (d). The transistor 3 operating at a low frequency as shown in FIG. 7 (a) between t ₁ and t ₂ in FIG. Indicates an ON operation state, and the transistor 5 is in a state of operating at a high frequency shown in FIG. And in the meantime, the same figure (b)
As shown in (d), the transistors 4 and 6 are off. When the transistor 5 is turned on, the power supply, the power supply terminal 1,
The parallel circuit of the transistor 3, the choke coil 11, the high-pressure discharge lamp 12 and the capacitor 14, the transistor 5, the current detection resistor 13, the power supply terminal 2, the closed circuit of the power supply is formed, and the current I ₁₁ flowing through the choke coil ₁₁ is constant. It rises linearly with a slope, and when the transistor 5 turns off, the current at this time
The direction in which the stored energy determined by the value of I ₁₁ and the inductance of the choke coil 11 tries to keep the current flowing, that is, the direction of the current when the transistor 5 is on, becomes the same as the choke coil 11 at this time. , The parallel circuit of the high-pressure discharge lamp 12 and the capacitor 14, the diode 8, the transistor 3, and the closed circuit of the choke coil 11 release the stored energy, and this operation is repeated until time t ₂ .

A period T 4 one transistor 3-6 are both turned off in _D of the following t ₂ ~t _3, power supply from the connected power supply during this period the power terminals 1 and 2 is not performed.

Furthermore between t ₃ ~t ₄ is transistor operating during this period is a t ₁ ~t ₂ between basically the same as that of the a transistors 4 and 6, in the transistor 3,5 OFF state. That is, when the transistor 6 is turned on, the power supply, the power supply terminal 1, the transistor 4, the parallel circuit of the high-pressure discharge lamp 12 and the capacitor 14, the choke coil 11, the transistor 6, the current detection resistor 13, the power supply terminal 2, the closed circuit of the power supply, When the transistor 6 is turned off, the current I ₁₁ flows in the parallel circuit of the choke coil 11, the diode 7, the transistor 4, the high pressure discharge lamp 12 and the capacitor 14, and the closed circuit of the choke coil 11. The current I ₁₁ and the high pressure discharge lamp 12 shown in FIG.
The direction of the current I ₁₂ flowing through is from t ₁ to t ₂ , and between t ₃ and t ₄ , the directions of the currents I ₁₁ and I ₁₂ are opposite. In this way, a rectangular wave alternating current containing high frequency ripples flows through the high pressure discharge lamp 12.

The diodes 9 and 10 do not flow current in normal operation, but are for passing surge current during transient.

The above period T _D indicates a period (t _{2 to} t ₃ , t _{4 to} t ₅ ) in which all the transistors 3, 6, 4 and 5 are off, which means that the transistor 3, 6, or 4, 5 is at the same time. Turns on and presents a short circuit,
This is the dead time for preventing the destruction of the lighting device. This simultaneous turn-on occurs when the storage time becomes long due to variations in transistor elements and temperature rise, and due to timing shift between transistors.

FIG. 8 is an enlarged timing diagram showing the vicinity of t ₂ to t _{3 in} FIG. 7, showing the operation of the transistors 5 and 6 in (a) and (b), and showing the currents I ₁₁ , I ₁₂ and high voltage. The waveforms of the voltage V ₁₂ across the discharge lamp 12 are shown in FIGS. 7 (c), (d) and (e). t
_{When the} transistor 5 is turned off as shown in (a) of FIG. ₂ at the _second time point, the electric charge of the capacitor 14 is discharged to the high-pressure discharge lamp 12, so that the current I ₁₂ flows with a slight delay as compared with the current I ₁₁ . Finally the current I ₁₂ becomes zero. In other words, the current I _12, which is the lamp current, becomes quiescent. Next, at t ₃ , the polarity of the current I ₁₂ changes, and the transistor 6 operates as shown in FIG. Since the current I ₁₂ is zero until just before time t _{3, the} voltage V ₁₂ across the high-pressure discharge lamp 12 becomes high immediately after time t ₃ . This is a phenomenon peculiar to discharge lamps, in which the current I ₁₂ becomes zero and the ions in the arc tube disappear, and at time t ₃ , the high-pressure discharge lamp is used to maintain lighting.
A high voltage is required across 12. This voltage is the so-called restrike voltage. If the zero period of the current I ₁₂ is too long, even if a voltage is applied at the time point t ₃ , lighting cannot be maintained and the lamp may go out. Further, even if it does not stand up and disappears, the re-ignition voltage becomes high and flicker may occur when it reaches near the voltage to be supplied. In the case of a fluorescent lamp, the above phenomenon is alleviated a little, but in the case of a high-pressure discharge lamp, the re-ignition voltage rises significantly even if some rest occurs.

The period T _D is provided to prevent simultaneous turn-on, but as described above, the current I ₁₂ was paused, the re-ignition voltage was increased and flickering occurred, and in some cases, it disappeared. Further, the rise of the re-ignition voltage has a problem of accelerating the consumption of the electrode and shortening the life of the lamp, and there is also a problem that the lamp is easily extinguished due to a sudden decrease in the power supply. Especially in the high-pressure discharge lamp, the lower the wattage is, the more the re-ignition voltage rises due to the suspension of the current I ₁₂ , which is troublesome.

On the other hand, if the capacitance of the capacitor 14 is increased, it is possible to prevent the current I _{12 from} becoming zero in the period T _D , but it is necessary to increase the capacitance of the capacitor 14 by several tens of times. Is applied, the size increases.

Among high-pressure discharge lamps, metal halide lamps in particular tend to generate a spike voltage immediately after starting, so that if the current I ₁₂ is interrupted during starting, the voltage between the power supply terminals 1 and 2 should be set so that it will not go out immediately. Although the cost can be increased by this method, the cost increase of this portion becomes large, and the consumption of the electrode by the re-ignition voltage still remains.

[Object of the Invention] The present invention has been made in view of the above problems, and an object of the present invention is to provide a period in which all the switching elements are turned off in the vicinity of a time point when the polarity of a low-frequency current is inverted. At the same time, it is another object of the present invention to provide a discharge lamp lighting device that prevents a re-ignition voltage from rising by eliminating a period in which the current flowing through the high pressure discharge lamp is stopped.

DISCLOSURE OF THE INVENTION The present invention forms an oscillating circuit of LCR including a high-pressure discharge lamp during a period T _D provided to prevent simultaneous turning on of switching elements, and oscillates current while releasing electric charge of a capacitor. The present invention is characterized in that the lamp current of the high-pressure discharge lamp is caused to flow so that no rest period is generated in the high-pressure discharge lamp.

The present invention will be described below with reference to examples.

Embodiment 1 FIG. 1 shows a circuit of this embodiment, which has a so-called full bridge structure, in which transistors 17, 18, 19, 20 which are switching elements and diodes 21, 22, 23, 24 are sixth elements.
Transistors 5, 6, 3, 4 and diodes 9, 10, 7, 8 in the circuit shown
And the basic operation is the same. In the circuit shown in FIG. 6, the transistors 5 and 6 that switch at high frequencies are on the negative side of the power source, and the transistors 3 and 4 that switch at low frequencies are on the positive side of the power source. The high-pressure discharge lamp 12 is different in that low-frequency and high-frequency transistors 17 and 18 that switch at high frequencies are provided on the + side of the power supply, and transistors 19 and 20 that switch at low frequencies are provided on the-side of the power supply. Is different in that the capacitor 14 is connected in parallel to the series circuit of the inductance element 25. The control circuit 15 and the current detection resistor 13 are omitted.

Thus, in the circuit of FIG. 1, when the transistor 17 is turned on, the power supply, the power supply terminal 1, the transistor 17, the choke coil 11,
A circuit in which a capacitor 14 is connected in parallel to a series circuit of a high-pressure discharge lamp 12 and an inductance element 25, a transistor
19, the power supply terminal 2, the closed circuit of the power supply is formed, and when the transistor 17 is turned off, the capacitor 14 is connected to the series circuit of the choke coil 11, the high pressure discharge lamp 12 and the inductance element 25.
Circuit connected in parallel, transistor 19, diode
24, a closed circuit of the choke coil 11 is constructed. When the transistor 18 is turned on, the power supply, the power supply terminal 1, the transistor 18, the circuit in which the capacitor 14 is connected in parallel to the series circuit of the high pressure discharge lamp 12 and the inductance element 25, the choke coil 11, the transistor 20, the power supply terminal 2 are connected. When a closed circuit of the power supply is formed and the transistor 18 is turned off, a circuit in which a capacitor 14 is connected in parallel to a series circuit of a choke coil 11, a transistor 20, a diode 23, a high pressure discharge lamp 12 and an inductance element 25, a choke. A closed circuit of the coil 11 is constructed.

As shown in FIG. 2 (a), the capacitor 14 has the polarity shown in FIG. 1 at the time corresponding to t ₂ when the transistor 17 has finished turning on, and during the period T _D , the capacitor 14 and the high pressure discharge lamp 12 , A closed circuit of the inductance element 25 is configured,
The discharge of the electric charge of the capacitor 14 becomes an oscillating current, and the current I ₁₂ flowing through the high-pressure discharge lamp 12 reverses its polarity while maintaining continuity as shown in FIG. As shown, at time t ₃ , transistor 18 turns on and current I
₁₂ completes the inversion with no pause. The second
The voltage V ₁₂ across the high-pressure discharge lamp 12 shown in FIG. 6E also has a waveform substantially similar to the current I _12, and the re-ignition voltage becomes minimal. FIG. 2 (c) shows the waveform of the current I ₁₁ flowing through the choke coil 11. Further, the broken line portion in FIG. 2 shows a conventional corrugated portion.

Here, the inductance value L ₁ of the inductance element 25 is 1 m
Assuming H and the capacitance C 14 of the capacitor ₁₄ is 0.1 μF, the vibration frequency f is Is about 16 KHz, and the cycle is about 63 μsec. Here, since the resistance component of the high pressure discharge lamp 12 actually enters, the vibration frequency f becomes low and the cycle becomes long. Thus, from such an operation, by connecting the inductance element 25 having a small inductance value in series with the high pressure discharge lamp 12, the high pressure discharge lamp 12 can be maintained in the excited state during the period T _D , and the conventional problem Can be resolved.

FIG. 3 shows a specific circuit of this embodiment, in which the inductance element 25 is used as the secondary winding L ₁ of the pulse transformer Tr, and the capacitor C is connected to the series circuit of the inductance element 25 and the high pressure discharge lamp 12. A series circuit of ₁ and a resistor R ₁ is connected, and a series circuit of a primary winding L ₂ of a pulse transformer Tr and a bidirectional two-terminal thyristor Q is connected in parallel with the capacitor C ₁ .

Turned on and off by Thus to the charging voltage of the capacitor C ₁ bidirectional diode thyristor Q is at the time of start-up, high-voltage pulse which is determined by the charge in the capacitor C ₁ by abruptly released turns ratio on the primary side of the pulse transformer Tr Is induced and applied to the high-pressure discharge lamp 12 via the capacitor 14 to start the engine.
After the start-up lighting, the operation is the same as that of the circuit shown in FIG. In the steady state, the capacitor 14 plays the role of a bypass capacitor that allows high-frequency components to pass therethrough, minimizes the flow of high-frequency components into the high-pressure discharge lamp 12, and prevents arc instability due to the acoustic resonance phenomenon. Further, during the period T _D , the capacitor 14 allows the electric charge to flow as an oscillating current through the inductance element 25 and does not cause a rest period in the current I ₁₂ flowing through the high-pressure discharge lamp 14, and at the time of starting the above, the inductance element 25 The high-voltage pulse generated at both ends of is applied to the high-pressure discharge lamp 12 so that the high-voltage pulse is not applied to other elements.

Second Embodiment The circuit configuration of this embodiment is basically the same as that of the circuit shown in FIG. 1, and as shown in FIG. 4, the choke coil 11 which is the main circuit.
This is different from the circuit shown in FIG. 1 in that a series circuit of a capacitor 14 and a resistor 26 is connected in parallel in a series circuit of an inductance element 25 which also serves as the high pressure discharge lamp 12, and the capacitor 26 is connected to the capacitor 14 by the resistor 26. It is characterized by limiting the current during charging. The operation as the oscillating circuit in the period T _D is the same as that of the circuit shown in FIG.

Embodiment 3 In this embodiment, as shown in FIG. 5, a series circuit of a high frequency transistor 35 for turning on and off at a high frequency and a choke coil 11 'is connected to a power supply terminal 1, and transistors 17 and 18 in the circuit of FIG. The operation is performed only by the transistor 35.

The transistors 27 to 30 are for polarity reversal and are all operated at a low frequency. That is, the transistors 27 and 29, 28 and 30 operate as a pair, and in the positive half cycle of the current I ₁₂ flowing through the high pressure discharge lamp 12, the transistors 27 and 29 are in the ON state, and the transistors 28 and 29 are
30 is turned off, and in the negative half cycle, transistors 28,3
0 is on and transistors 27 and 29 are off. The inductance element 25, the capacitor 14, and the high-pressure discharge lamp 12 have the same operations and functions as the inductance element 25, the capacitor 14, and the high-pressure discharge lamp 12 shown in FIG. diode
36 operates when the transistor 35 is off, and corresponds to the diodes 24 and 23 in FIG. Although the diodes 31 to 34 do not normally operate, they are used to pass surge current in the transition period,
It corresponds to the diodes 21 and 22 in the circuit of FIG. Thus, when the transistor 35 is turned on, the transistors 27 and 29 receive the current I ₁₂
Power source, power supply terminal 1, transistor 35, choke coil 11 ', transistor 27,
A circuit in which a capacitor 14 is connected in parallel to a series circuit of a high-pressure discharge lamp 12 and an inductance element 25, a transistor 29, a power supply terminal 2, and a current flows in a closed circuit of the power supply, and when the transistor 35 is turned off, the choke coil 11 'and the transistor 27. , A circuit in which a capacitor 14 is connected in parallel to a series circuit of a high-pressure discharge lamp 12 and an inductance element 25, a current flows in a closed circuit of a transistor 29, a diode 36, and a choke coil 11 ', and the stored energy of the choke coil 11' is released. In the negative half cycle, it is the same except that current flows through the transistors 28 and 30.

The problem in this embodiment is that the transistor 27, 30 or 28,
29 is to turn on at the same time, but if you turn on at the same time,
For example, power supply terminal 1, transistor 35, choke coil
The circuit of 11 ', the transistor 27, the transistor 30, and the power supply terminal 2 acts as a current limit by the choke coil 11, so that the lighting device is rarely destroyed immediately. However, the surge current at this time increases the stress of each element, and if it occurs frequently, there is a risk of element destruction due to abnormal heat generation due to switching loss.Therefore, the period T _D is necessary in this embodiment as well, The effects of the present invention can be sufficiently applied. In addition, it is possible to eliminate the adverse effects on the control circuit due to the generation of noise due to the surge current and the inconvenience such as noise to the outside, and the inclusion of the high frequency component of the current I ₁₂ flowing in the high pressure discharge lamp 12 by the capacitor 14. Since it can be reduced, the instability of the arc due to the acoustic resonance phenomenon is eliminated.

In each of the above embodiments, the vibration of the vibration circuit is 1 during the period T _D.
However, even if it is vibrated several times, the same effect can be obtained from the viewpoint of the excited state of the high pressure discharge lamp.

It is needless to say that the inverter may be a half-bridge type inverter instead of the full-bridge type inverter.

[Effects of the Invention] The present invention connects a series circuit of at least one pair of switching elements to a DC power supply, alternately switches these switching elements at a low frequency cycle, and before switching of both switching elements. Is set to a high-voltage discharge lamp during the switching period of the above-mentioned pair of switching elements by setting the period during which both are turned off, turning on / off the DC power supply voltage with the high-frequency switching element, and outputting the high-frequency output obtained through the current limiting inductance element. In a discharge lamp lighting device that applies a parallel circuit of a capacitor and a capacitor, a vibration circuit is formed by the capacitor and the high pressure discharge lamp so that an oscillating current flows through the high pressure discharge lamp during a period in which both of the pair of switching elements are off. Since the inductance element was inserted in series with the high-pressure discharge lamp, the A capacitor, an inductance element, and a high-pressure discharge lamp form an LCR oscillation circuit between them, allowing the charge of the capacitor to flow to the high-pressure discharge lamp, and the rest period of the lamp current flowing to the high-pressure discharge lamp does not occur. It is possible to suppress the increase in re-ignition voltage, which has been a problem in the past, and it disappears in response to variations in lamp voltage, abrupt decrease in power supply voltage, increase in lamp voltage, etc., and stable lighting is achieved without flickering. Since it can be maintained and the high frequency current can be bypassed by the capacitor, the high frequency component contained in the current flowing through the high pressure discharge lamp can be reduced, the instability of the arc due to the acoustic resonance phenomenon can be eliminated, and all It is not necessary to design the switching element to be turned off before polarity reversal in a narrow range as in the past, and it is possible to turn on simultaneously under various conditions. Enough that you can stop, yet can be little the period there is no rest of the lamp current,
The degree of freedom in circuit design increases, circuit design becomes easier, reliability can be improved, and a vibration circuit that eliminates the lamp current pause period uses a smaller inductance element than the conventional circuit. Therefore, it is possible to realize an apparatus that is substantially small in size, lightweight and inexpensive.

[Brief description of drawings]

FIG. 1 is a waveform diagram for explaining the operation of Embodiment 1 of the present invention, and FIG.
FIG. 3 is a waveform diagram for explaining the operation of the same as above, FIG. 3 is a specific circuit of the same as above, FIG. 4 is a circuit diagram of an essential part of the second embodiment of the present invention, and FIG. 5 is a circuit diagram of the third embodiment of the present invention. FIG. 6 is a circuit diagram of a conventional example, FIG. 7 is a waveform diagram for explaining the operation of the above, FIG. 8 is a detailed waveform diagram of the above, 11, 11 'are choke coils, 12 is a high pressure discharge lamp, 14 is a capacitor, 25 is an inductance element, 17 to 20 are transistors, 27 to 30 and 31 are transistors, Tr is a pulse transformer, L ₁ is a secondary winding, V _DC is a DC power supply voltage, and T _D is a period.

Claims (4)

[Claims] 1. A direct current power supply is connected to a series circuit of at least one pair of switching elements, these switching elements are alternately switched at a low frequency cycle, and both switching elements are turned off before switching. For a high-voltage discharge lamp and a capacitor during the switching period of the pair of switching elements by setting the period for which the DC power supply voltage is turned on / off by the high-frequency switching element and turning on / off the high-frequency output obtained through the current limiting inductance element. In the discharge lamp lighting device applied to the parallel circuit of
An inductance element forming a vibrating circuit with a capacitor and a high pressure discharge lamp is inserted in series with the high pressure discharge lamp so that an oscillating current flows through the high pressure discharge lamp during a period in which both of the pair of switching elements are turned off. Discharge lamp lighting device. 2. The discharge lamp lighting device according to claim 1, wherein one of the pair of switching elements also serves as a high frequency switching element. 3. The discharge lamp lighting device according to claim 1, wherein the inductance element is also used as a current limiting inductance element. 4. The discharge lamp lighting device according to claim 1, wherein the inductance element is also used as a secondary winding of a pulse transformer for generating a high voltage pulse.