JPH06101389B2 - 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 of 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 ultra high 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.In addition, 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.

On the other hand, a lighting device for a high pressure discharge lamp 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. 4 shows a conventional discharge lamp lighting device shown in U.S. 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. 5A to 5D are timing charts showing the operations 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 ON / OFF duty ratio of the control circuit 15 changes 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. 4 will be further described with reference to FIGS. 5 (a) to 5 (d). The transistor 3 operating at a low frequency as shown in FIG. 5 (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 during this period, (b) and (d) in FIG.
As shown in, the transistors 4 and 6 are in the off state. When the transistor 5 is turned on, the power supply, the power supply terminal 1, the transistor 3, the choke coil 11, the parallel circuit of the high pressure discharge lamp 12 and the capacitor 14, the transistor 5, the current detection resistor 13,
Power supply terminal 2, closed circuit of power supply is formed, choke coil
The current I ₁₁ flowing through ₁₁ rises linearly with a constant slope, and when the transistor 5 is turned off, the accumulated energy determined by the current I ₁₁ at this time and the inductance value of the choke coil 11 tries to keep the current flowing. Direction, that is, the direction of the current when the transistor 5 is on. At this time, the choke coil 11, the high pressure discharge lamp 12 and the capacitor 14 are connected in parallel, the diode 8, the transistor 3 and the choke coil 11 are closed. The stored energy is released at, 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.

Although even between t ₃ ~t ₄ is t ₁ ~t ₂ between basically the same as that of the above transistors operating during this period a transistor 4 and 6, the transistor 3 and 5 is in the 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 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 timing deviation between transistors.

FIG. 6 is an enlarged timing diagram showing the vicinity of t ₂ to t _{3 of} FIG. 5, showing the operation of the transistors 5 and 6 in (a) and (b), and showing the currents I ₁₁ , I ₁₂ and The waveforms of the voltage V ₁₂ across the high-pressure 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 immediately before the t ₃ time points it is zero, the voltage across V ₁₂ of the high pressure discharge lamp 12 is increased immediately after the time point t _3. This is a phenomenon unique to discharge lamps,
When the current I ₁₂ becomes zero, the ions in the arc tube disappear, and at time t ₃ , the discharge lamp 12
A high voltage is required across both ends of. 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. Even if it does not go out, the re-ignition voltage becomes high and flicker may occur when it reaches near the supplied voltage. 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 increased, and flickering occurred, or 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 capacity of the capacitor 14 is increased, it is possible to prevent the current I _{12 from} becoming zero during the period T _D , but it is necessary to increase the capacity of the capacitor 14 by several tens of times, and this Larger size due to application.

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 stopped 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.

As a method for solving the above problems, the present inventors have devised a discharge lamp lighting device as shown in FIG. This circuit has a so-called full bridge structure, and transistors 17, 18, 19, 20 and diodes 21, 22, 23, 24 which are switching elements are transistors 5, 6, 3, 4 and diode 9 in the circuit of FIG. The basic operation is the same as 10,10,7,8. In the circuit of FIG. 4, the transistors 5 and 6 which switch at high frequencies are on the negative side of the power source, and the transistors 3 and 4 which switch at low frequencies are on the positive side of the power source, whereas in the circuit of FIG. The difference is that the transistors 17 and 18 which are switching elements for high frequency are provided on the + side of the power supply, and the transistors 20 and 19 which switch at low frequencies are provided on the-side of the power supply, and the high pressure discharge lamp 12 and the inductance element 25 are provided. The difference is that the capacitor 14 is connected in parallel to the series circuit of. The control circuit 15 and the current detection resistor 13 are omitted. Thus, in the circuit of FIG. 7, when the transistor 17 is turned on, the power supply, the power supply terminal 1, the transistor
17, a circuit in which a capacitor 14 is connected in parallel to a series circuit of a choke coil 11, a high pressure discharge lamp 12 and an inductance element 25, a transistor 19, a power supply terminal 2 and a closed circuit of a power supply are formed, and when the transistor 17 is turned off. A circuit in which a capacitor 14 is connected in parallel to a series circuit of a choke coil 11, a high pressure discharge lamp 12 and an inductance element 25, a closed circuit of a transistor 19, a diode 24 and a choke coil 11 is configured. When the transistor 18 is turned on, the power supply, the power supply terminal 1, the transistor 18, a 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, the closed circuit of the power supply is formed, when the transistor 18 is turned off, the choke coil 11, the transistor 2
0, diode 23, high pressure discharge lamp 12 and inductance element 2
A circuit in which a capacitor 14 is connected in parallel to a series circuit of 5 and a closed circuit of the choke coil 11 are configured.

At the time corresponding to t ₂ in FIG. 5, the capacitor 14 has the polarity shown in FIG. 7, and in the section T _D , the closed circuit of the capacitor 14, the high-pressure discharge lamp 12, and the inductance element 25 is configured, The discharge of the charge of 14 becomes an oscillating current, and the current I ₁₂ flowing through the high-pressure discharge lamp 12 reverses its polarity while maintaining continuity, and at time t ₃ , the transistor 18 is turned on and the current I ₁₂ is stopped. Complete the inversion without. The voltage V ₁₂ across the high-pressure discharge lamp 12 also has a waveform similar to that of the current I _12, and the re-ignition voltage becomes minimal.

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. Since the resistance component of the high pressure discharge lamp 12 actually enters, the vibration frequency f becomes low and the cycle becomes long. From such an operation, the above-mentioned problem can be solved by connecting the inductance element 25 having a small inductance value in series with the high pressure discharge lamp 12.

However, in the circuit of FIG. 7, a steep surge current may flow when the transistor 18 is turned on immediately after the polarity is inverted as shown in FIG.

The waveform of FIG. 8 shows the waveform of the following part. That is, (a) in the figure shows the operation of the transistor 17, (b) shows the operation of the transistor 18, and (c) in the figure shows the input current I ₁ .
This input current I ₁ corresponds to the collector current of the transistors 17 and 18. The figure (d) shows the current flowing through the choke coil 11.
I ₁₁ is shown, and (e) in the figure shows the current I flowing through the capacitor 14.
₁₄ is shown. The figure (f) shows the voltage V ₁₄ across the capacitor 14, and the figure (g) shows the current I ₁₂ flowing through the high-pressure discharge lamp 12. Now, in the section T _{D from} t _{2 to} t ₃ , the operation is almost the closed circuit of the capacitor 14, the high pressure discharge lamp 12, and the inductance element 25,
The electric charge of the capacitor 14 is discharged to the high-pressure discharge lamp 12 via the inductance element 25, and at this time, an oscillating current flows in a cycle corresponding to these circuit constants. t becomes a polarity of the voltage V ₁₄ is a seventh diagram again at _3, the transistor 18 will be turned on in this condition. That is, since the direction of the voltage V ₁₄ has the polarity shown in FIG. 7 at time t ₃ , when the transistor 18 is turned on, the DC power supply voltage V _DC and the voltage V ₁₄ become additive,
Like the current I ₁ shown in FIG. 8 (c), it becomes a steep current in the vicinity of time t ₃ and flows through the circuit of the power supply terminal 1, the transistor 18, the capacitor 14, the transistor 20, and the power supply terminal 2. A similar surge current will flow between t _{4 and} t ₅ .

Therefore, when such a surge current occurs, problems such as an increase in stress (switching loss, withstand voltage against pulse current, etc.) of the transistor element used, noise, noise, etc. occur, resulting in a transistor element There are drawbacks such as an increase in cost and cost due to noise and measures against noise, and an increase in size of the device.

[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 eliminate the surge current at the time of polarity reversal to reduce the stress of the switching element and to reduce the dead time. It is an object of the present invention to provide a discharge lamp lighting device that has a degree of freedom in setting and alleviates a sudden change in operation due to a transient phenomenon at the time of polarity reversal to obtain stable operation.

DISCLOSURE OF THE INVENTION The present invention is a direction of the voltage of the voltage V ₁₄ of the capacitor 14 in FIG. 7 circuit, focusing on the timing of the transistor 18 is turned on and off at t ₃ time, at t ₃ when the transistor 18 is turned on, It is characterized in that the timing is set so that the polarity of the charging voltage of the capacitor 14 is depolarized with respect to the DC power supply voltage V _DC .

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

Embodiment 1 FIG. 1 shows operation waveforms of this embodiment. Since the circuit configuration of this embodiment is basically the same as that of the circuit shown in FIG. 7, the circuit configuration will be omitted and a description will be given along FIG. First of all, as shown in FIG.
At t ₃ , the DC power supply voltage is _VDC + V ₁₄ , so
Although the power supply voltage is substantially increased and the current when the transistor 18 is turned on is steep, the capacitor 14 or the inductance element is used in this embodiment.
By changing the value of 25, high pressure discharge lamp 12, inductance element 2
5, the vibration frequency in the closed circuit of the capacitor 14 is lowered. Therefore, at time t ₃ shown in FIG. 1, the polarity of the voltage V ₁₄ of the capacitor 14 shown in FIG. 7D is the DC power supply voltage V _DC when the transistor 18 is turned on as shown in FIG. On the other hand, since it is depolarized, no surge current is generated in the input current I ₁ as shown in FIG. The oscillating current does not flow in the capacitor 14 except near the period T _D, and almost all the high-frequency component current flows, and the low-frequency current flows through the high-pressure discharge lamp 12. Also, the impedance relationship between the capacitor 14 and the choke coil 11 is that the choke coil 11
Since the impedance of the capacitor 14 is several times to several tens of times that of the capacitor 14, most of the current flowing in the choke coil 11 is dominated by the choke coil 11 and the high-pressure discharge lamp 12, and the inductance element 25 operates at low frequency. There is almost no function as a current limiting element.

Embodiment 2 FIG. 2 shows an operating waveform of the voltage V ₁₄ of the capacitor 14 of the embodiment. Thus the to this embodiment the side shown by oblique lines across the voltage V ₁₄ of the capacitor 14 shown in FIG. 2 (Ta, Tb, Tc interval) either in transistor 18 is current surge as the input current I ₁ be turned on Did not occur. Further, it was found that the current I ₁₂ flowing through the high-pressure discharge lamp 12 did not stop, and the restriking voltage remained low. It should be noted that turning on the transistor 18 in the Ta period of the first cycle has a greater depolarizing effect, so it is preferable to select the vibration frequency for this purpose. In addition, capacitor 14, inductance element
25, the period T _D may be selected from the viewpoint of simultaneous ON prevention in relation to the vibration frequency of the equivalent resistance R ₁₂ of the high-pressure discharge lamp 12, and a constant satisfying the conditions of the present invention may be set. In this way, also in this embodiment, it is possible to prevent the surge current while having a sufficient period T _D for preventing simultaneous ON.

Embodiment 3 In this embodiment, as shown in FIG. 3, 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.

Transistors 26-29 are for polarity reversal and are all operated at low frequencies. That is, the transistors 26 and 28, 27 and 29 operate in pairs, and in the positive half cycle of the current I ₁₂ flowing through the high pressure discharge lamp 12, the transistors 26 and 28 are in the ON state and the transistors 27 and
29 turns off and on negative half cycle, transistors 27,2
9 is on and transistors 26 and 28 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
30 operates when the transistor 35 is off, and corresponds to the diodes 23 and 24 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 transistor 35 is on, transistors 26,2
8 is the positive half cycle of the current I ₁₂ in the ON state, and the capacitor 14 is connected in parallel to the series circuit of the power supply, the power supply terminal 1, the transistor 35, the choke coil 11 ′, the transistor 26, the high pressure discharge lamp 12 and the inductance element 25. When the current flows in the closed circuit of the transistor 28, the power supply terminal 2 and the power supply and the transistor 35 is turned off, the capacitor 14 is connected in parallel to the series circuit of the choke coil 11 ', the transistor 26, the high pressure discharge lamp 12 and the inductance element 25. Connected circuit, transistor
A current flows in the closed circuit of the diode 28, the diode 30, and the choke coil 11 ', and the energy stored in the choke coil 11' is released. In the negative half cycle, it is the same except that current flows through transistors 27 and 29. In addition to such a basic circuit operation, in the present embodiment, an oscillating current flows during the period T _D ,
In the closed circuit of the capacitor 14, high pressure discharge lamp 12 and inductance element 25, the voltage of the capacitor 14 at the time of polarity reversal is V
_The circuit constant is set so that ₁₄ is depolarized with respect to the DC power supply voltage V _DC , and the sudden change operation due to the transient phenomenon at the time of polarity reversal is alleviated. Although the full bridge type inverter is used in the above embodiment, other circuits such as an LCR oscillating circuit including the high pressure discharge lamp 12 during the period T _D can be formed as long as it substantially forms the circuit. It may be a half-bridge type inverter circuit. That is, the choke coil 11 'is operated at a high frequency, the high-pressure discharge lamp 12 may be a circuit which comprises a capacitor 14 to flow a low frequency current I _12.

[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. And a DC power supply voltage is turned on and off by a high frequency switching element, and a high frequency output obtained through a current limiting inductance element is applied to the inductance element during the switching period of the pair of switching elements. In a discharge lamp lighting device in which a capacitor is connected in parallel to a series circuit of a high-pressure discharge lamp and a capacitor is applied to a parallel circuit forming an oscillating circuit, when switching is performed after a period in which the switching of the pair of switching elements is turned off. The direction of the voltage of the capacitor is depolarized with respect to the voltage of the DC power supply. Since the constant of the vibration circuit is set, it is possible to prevent the surge current from flowing at the time of polarity reversal and prevent the applied switching element from being stressed. As a result, it is possible to reduce the withstand voltage of the switching element and suppress the occurrence of surge current. Therefore, it is possible to reduce the generation of noise and noise.
In addition, because a vibrating circuit is used, there is no pause period in the current flowing through the high-pressure discharge lamp, and as a result, the degree of freedom in designing the circuit that determines the period during which all switching elements are turned off before reversing the polarity is increased. This makes it easier to reduce the cost, and the low frequency lighting eliminates the instability of the arc due to the acoustic resonance phenomenon even when the high pressure discharge lamp is lit, and operates the choke coil at a high frequency. Therefore, there is an effect that the size and weight can be reduced.

[Brief description of drawings]

FIG. 1 is a waveform diagram for explaining the operation of Embodiment 1 of the present invention, and FIG.
FIG. 4 is a waveform diagram for explaining the operation of the second embodiment of the present invention, FIG. 3 is a circuit diagram of the third embodiment of the present invention, FIG. 4 is a circuit diagram of a conventional example,
FIG. 5 is a waveform diagram for explaining the above operation, FIG. 6 is a detailed waveform diagram for the same as above, FIG. 7 is a circuit diagram of a conventional example which is the basis of the present invention, and FIG. 8 is a waveform for explaining the above operation. Figure is 11,1
1'is a choke coil, 12 is a high pressure discharge lamp, 14 is a capacitor, 24 is an inductance element, 17 to 20 are transistors, 35, 26 to 34 are transistors, V _DC is a DC power supply voltage,
T _D is the period.

Claims (2)

[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. The DC power supply voltage is turned on and off by the high frequency switching element and the high frequency output obtained via the current limiting inductance element is applied to the inductance element and high voltage during the switching period of the pair of switching elements. In a discharge lamp lighting device in which a capacitor is connected in parallel to a series circuit with an electric lamp and is applied to a parallel circuit forming an oscillating circuit, the capacitor of the capacitor at the time of switching after switching of a pair of the switching elements is turned off. Oscillate so that the direction of voltage is depolarized with respect to the voltage of the DC power supply. The discharge lamp lighting apparatus characterized by setting the constant of the road. 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.