JPH05234685A - Lighting device for electric discharge lamp - Google Patents

Abstract

PURPOSE:To enhance durability by providing the series circuit of an electric discharge lamp with inductance decreasing peak rush current, making a smoothing capacitor small in capacitance, concurrently transforming a connecting timer switch into a switch-over type one, and using a booster capacitor together with the smoothing capacitor after a boosting period has been over. CONSTITUTION:A lighting device for an electric discharge lamp is made up of a gas-filled electric discharge lamp 7, a booster capacitor 11, a resistor 12, a pulse transformer 14, inductance 15, a smoothing capacitor 81, and of a switching type timer switch TS21. By this constitution, spike current at the time of starting discharge, that is, rush current is made to be delayed in time by inductance 15, so that excess momentary current is thereby restrained. In addition, after a boosting period has been over since electric discharge was started, the boost resistor 12 is shortcircuited by the switch TS21, the capacitor 81 whose capacitance is kept to the minimum as required though, is used together with the capacitor 11, so that pulsation in light is thereby lessened by making current flowing the lamp 7 smooth.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a high-intensity gas discharge lamp containing a gas such as a xenon lamp, a metal halide lamp, a sodium lamp, a mercury lamp, or a composite of these.

[0002]

2. Description of the Related Art Generally, the following three types of power sources (voltage sources) are required for lighting a gas-filled discharge lamp, that is, for starting a discharge and then for a stable discharge. 1. A high voltage of several tens of KV to several KV is required to start the discharge of a discharge lamp in which a gas body is usually enclosed. The high voltage is applied in a pulsed manner to start breakdown and start discharge. (Breakdown power supply) 2. The discharge arc is then maintained, boosting the electrode to a required temperature and boosting the electron emission for several times the steady discharge voltage to continue the discharge. (Boost voltage) 3. After the boost time ends, disconnect the boost power supply,
Discharge is constantly maintained with only the main power supply. (Main power source for maintaining lighting)

FIG. 3 is a general circuit according to the prior art of a discharge lamp lighting device for obtaining the above-mentioned three types of power sources. In the figure, 1 is a commercial AC power supply, 2 is a power supply transformer, and the three types of power supplies (voltage sources) described above are created from the commercial AC power supply 1 by this transformer. When the commercial AC power supply 1 is turned on and then the timer switches TS1 and TS2 are closed, the power supply for generating the start pulse voltage is transferred to the charge-up capacitor 5 through the diode 3, the current limiting resistor 4 and the timer switch TS1 by the terminals H1 and H0. Charges up. The steady discharge voltage of the discharge lamp 7 is supplied to the capacitor 8 from the terminals T ₁ and T ₀ through the diode 6. Further, from the terminals T ₂ and T ₀ , the boost voltage is still the capacitor 8 via the diode 9, the current limiting resistor 10 and the timer switch TS _2.
Boost capacitor 1
1 is also charged with the boost voltage via the current limiting resistor 12. In the above state, when the voltage of the charge-up capacitor 5 rises and reaches the breakover voltage of the discharge gap 13, the charge of the capacitor 5 is instantaneously supplied to the primary coil of the pulse transformer 14, The high-voltage pulse voltage necessary for starting the discharge is applied to the discharge lamp 7 through the secondary coil, and breaks down to start the discharge. At this time, the capacitors 8 and 11 are charged with the boost voltage, and the discharge of the discharge lamp that has started to be discharged by the high-voltage pulse voltage is taken over by the boost voltage to continue the discharge.
The boost voltage is released by the timer switch TS ₂ after a while, but since the electrode temperature of the discharge lamp 7 also rises and the electronic discharge becomes good at that time, the discharge lamp 7 serves as the main power source and the terminal T. ₂ , the steady discharge, that is, lighting is continued by the electric power supplied from T ₀ through the diode 6 and the capacitor 8.

[0004]

In the above description, the capacitor 8 is provided in order to smooth the pulsating current rectified from the commercial AC power source. Made by condenser 8
If only smoothing is performed, the discharge cannot be continued because it is too short, and it becomes impossible to shift to steady discharge. As a measure to prevent this, the boosting capacitor 11 and the current limiting resistor 12 are provided to obtain the time constant τ. If the capacitor capacity is C and the resistance value is R, then τ = CR. The discharge maintaining time can be extended. Further, the discharge current flowing out of the capacitor is the instantaneous maximum discharge current I _p , when the charge-up voltage at that time is V,
Becomes I _p = V / R, and the maximum current can be suppressed.

However, the electric charge of the capacitor 8 flows out as Is = V / R _d current value at the start of discharge. here,
Rd is a resistance value due to the wiring from the condenser 8 to the discharge lamp 7 and is generally a very small value, so I
s has an extremely large value, and sometimes shows a value of several hundred amperes. Further, the total value of Is + Ip will flow into the lamp at the instant when the lighting is started.

In a discharge lamp, it is no exaggeration to say that the excessive instantaneous inrush current at the start of lighting determines the life of the lamp. That is, it is necessary to suppress the start current at the start of lighting as much as possible, and at the same time solve the light ripple reduction due to the pulsating current included in the discharge current.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been proposed in order to reduce the discharge starting current of these discharge lamps, to stably start the discharge, and to reduce the optical ripple after the discharge is started. The circuit is shown in FIG. In Figure 1,
The same parts as those in the conventional example (FIG. 3) are designated by the same reference numerals and the description thereof is omitted. In FIG. 1, TS ₂₁ is a changeover switch type timer switch, and the switch contact is closed to the side a to connect the boost power supply during the boost period at the start of lighting, that is, during the timer operation, and after the boost period ends, the switch is switched. The contact closes on the side b and shorts the power supply control resistor 12 of the capacitor 11. Reference numeral 15 is an inductance that reduces the peak inrush current at the start of discharge. Reference numeral 81 is a capacitor for smoothing the pulsating discharge current, which reduces the peak value of the discharge current by the above-mentioned inductance 15 and is used together with the boost capacitor 11 after the boost period ends so as to use the conventional example (FIG. 3). ) Condenser 8
The capacity may be as small as 1/100, for example.

[0008]

[Embodiment and Its Action] The action will be described based on the circuit diagram of the embodiment of FIG. As mentioned above, the condenser 81
Even if a small capacity of about 1/100 of the conventional example is adopted, if the inductance 15 is not provided, the discharge time becomes shorter in proportion to the capacity, but the discharge peak value does not change. This value can be reduced by inserting the inductance 15 in the discharge circuit. Immediately It is sufficiently possible to suppress the discharge peak value from the L value of the inductance 15 so that the discharge current becomes about the steady discharge current of the lamp. Therefore, the current I _L1 = I _o + I _p flowing through the discharge lamp at the start of discharge becomes much smaller than that of the conventional I _s + I _p , and a very smooth discharge start characteristic can be obtained. However, this discharge start current flows for a very short time, and it is difficult to shift to the steady discharge as it is. So, like the conventional one, the condenser 1
1 and resistor 12 create a boost current duration with a time constant of τ = CR. That is, boost current ICR = V / R
(E− ^{(t / CR)} ), the electric charge of the voltage V stored in the capacitor 11 before the discharge of the lamp starts is generated by the resistance 12
It is the current value when discharging through and decreases with the passage of time.

After the lapse of boost time, steady discharge occurs, but the capacity of the capacitor 81 is much smaller than before, and
Even if the capacitor 11 has the same large capacity as the conventional one, if the resistor 12 is present, the current pulsation rate of steady discharge cannot be improved. Therefore, the timer switch TS ₂₁
If the contacts are switched so that the side b is closed after the boost time has elapsed, the boost capacitor 11 is used together with the capacitor 81 during steady discharge, and the capacity of the capacitor 81 is the same as that of the conventional example. / 100
Since the capacity of the capacitor 11 can be fully utilized even with a small value, the current ripple at the time of steady discharge can be improved. FIG. 2 shows the relationship of the current flowing through the discharge lamp 7 from the start of discharge to the steady discharge described above. In FIG. 2, I _L = Io + I _CR + I _L2 is a current flowing through the discharge lamp 7 from the start of discharge, and I _L2 is a steady discharge current. It should be noted that t ₀ is the power-on time, t ₁ is the discharge start time, and T ₂ is the boost time end time.

[0010]

According to the discharge lamp lighting device (circuit) of the present invention, the inductance 15 limits the current value while making a time delay in the spike current (rush current) at the start of discharge, so that an excessive instantaneous current is generated. It can be suppressed and the influence on the life of the lamp can be eliminated. Further, since the boost resistor 12 is short-circuited by the change-over type timer switch TS ₂₁ after the end of the boost time after the start of discharge, the boost congener 11 and the boost congener 11 are connected even though the capacity of the smoothing capacitor 81 is reduced to the necessary minimum. Since they can be used in combination, the pulsation rate of the steady discharge current is reduced, and the current flowing through the discharge lamp 7 is made into a flatter DC current. Therefore, the pulsation (ripple) of the light emitted from the lamp can be reduced. Although the current can be limited by an inexpensive resistor in place of the inductance 15, it is not preferable to use the resistor even during steady discharge because the resistor generates heat. Also, the inductance is 1
Even if 5 is not used, an appropriate inductance can be obtained by designing the number of turns of the secondary winding of the pulse transformer 14.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to the present invention.

FIG. 2 is a waveform diagram of a discharge current flowing through the discharge lamp in the circuit diagram of the discharge lamp lighting device according to the present invention.

FIG. 3 is a circuit diagram of a conventional discharge lamp lighting device.

[Explanation of symbols]

81 smoothing capacitor 11 boosting capacitor 12 resistance 14 pulse transformer 15 inductance 7 gas discharge lamp TS ₂₁ switchable timer switch

Claims (3)

[Claims] 1. A discharge lamp lighting device, such as a gas-filled discharge lamp, which is provided with an inductance for reducing a peak rush current immediately after the start of discharge, which greatly affects the lamp life. 2. The discharge lamp lighting device according to claim 1, wherein at the start of lighting, the timer switch connected to the boost power supply for a certain period of time is a changeover switch for short-circuiting the boost resistor after the end of the boost time. Discharge lamp lighting device. 3. The discharge lamp lighting device according to claim 2, wherein the capacity of the steady discharge maintaining capacitor is reduced, and the steady discharge maintaining capacitor is used together with the boost discharge maintaining capacitor after the boost time has ended. ..