JPH08293388A - Discharge lamp lighting device and discharge lamp lighting method - Google Patents

Abstract

PURPOSE: To sufficiently decrease the current of a discharge lamp by raising the frequency of the high-frequency power of the rectangular voltage up to the stationary frequency when a high luminance discharge lamp is turned on and the terminal voltage of the discharge lamp reaches the specified voltage lower than the stationary voltage. CONSTITUTION: When a discharge lamp LA is turned on, a transistor TRQ6 of a discharge lamp lighting level judging circuit 60a is turned off, and the transistors TRQ7, TRQ27 are turned on, and therefore the oscillation frequency of an oscillator 81 is lowered to the first frequency lower than the stationary frequency. A Zener diode VZ1 is electrified when the voltage of the discharge lamp La is raised, a hot coupler PC1 sends a signal, the TRQ7 is turned off, the Zener diode VZ21 is electrified when the voltage of the discharge lamp La is further raised, the TRQ27 is turned off, the non-reverse input terminal voltage of an amplifier 71 becomes the reference voltage Eref, and the oscillation frequency of an oscillator 81 is raised to the stationary frequency. The change of frequency of the discharge lamp supply voltage is slower than that of a lighting device DS1, and the discharge lamp LA can be prevented from going out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention converts a direct current voltage into a high frequency voltage by high frequency modulation, switches the polarity of this high frequency voltage at a low frequency, converts a high frequency component into a rectangular wave alternating voltage by a low pass filter, and discharges it. The present invention relates to an electronic lighting device for a high-intensity discharge lamp that stably lights an electric lamp, and particularly to starting of the electronic lighting device.

[0002]

2. Description of the Related Art Generally, a magnetic leakage transformer is generally used as a lighting device for a discharge lamp, but in order to reduce the size and weight and to improve the stability of lighting (flicker and brightness uniformity),
Recently, electronic lighting devices have begun to be used.

Since the electronic ballast uses small parts such as an inductor and a filter, the entire ballast is downsized as compared with the case where a magnetic leakage transformer is used, and high frequency modulation widely used for controlling an ordinary inverter. Is used for power control.

As a conventional high frequency modulation type electronic ballast, there is a discharge lamp lighting device disclosed in US Pat. No. 4,170,747.

FIG. 6 is a diagram mainly showing a bridge inverter circuit of the discharge lamp lighting device DS5 which is the above-mentioned conventional example, and FIG. 7 is a diagram showing operation waveforms of main parts in the discharge lamp lighting device DS5. FIG. 8 is a timing chart showing the operation of the discharge lamp lighting device DS5.

The discharge lamp lighting device DS5 includes a transistor 1
16, 118, 128, 130 and the diode 124,
A full bridge circuit is constituted by 126, 132 and 134, and transistors 116 and 118 are switched at a low frequency and transistors 128 and 130 are switched at a high frequency.

Here, from time t1 to t2 in FIG. 8, the transistor 116 is turned on, and the transistor 130 is turned on at a cycle sufficiently shorter than the time from t1 to t2.
Turn off. When the transistors 116 and 130 are on,
When the DC voltage of the capacitor 108 is generated between the terminals a and b in the direction in which the terminal side a is positive and the transistor 130 is turned off, the choke coil 112, the discharge lamp 110, the diode 126, the diode 120, the transistor 11
6. A current flows through the closed loop of the choke coil 112, short-circuiting the terminals a and b. When the transistor 130 is turned on again, the voltage of the capacitor 108 is generated between the terminals a and b.

By repeating the above operation, all the transistors are turned off at time t2, and the transistor 118 is turned off at time t3.
And 128 are turned on, a voltage of the capacitor 108 is generated between the terminals a and b in the direction in which the terminal b becomes positive. When the transistor 118 is turned on and the transistor 128 is turned off, the choke coil 112, the diode 124, Current flows through the closed loop of the diode 122, the transistor 118, the discharge lamp 110, and the choke coil 112, and the terminal a-
Short circuit between b.

By repeating a series of these operations, a voltage in which the high frequency voltage of the switching period of the transistors 128 and 130 is inverted in the switching period of the transistors 116 and 118 is generated between the terminals a and b.

The switching frequency components of the transistors 128 and 130 are supplied to the choke coil 112 and the capacitor 1.
It is removed at 14, and a low frequency rectangular wave AC voltage is supplied to the discharge lamp 110. The current detection resistor 114 detects the input current of the inverter circuit and controls the on-time of the transistor (duty ratio control) to supply the current to the discharge lamp 110.

Next, the starting of the high-intensity discharge lamp in the above conventional example will be described.

When the inter-electrode voltage of the discharge lamp 110 becomes about 270 V, glow discharge occurs and a high voltage of several kV (depending on the type of discharge lamp and electrode structure) is applied between the electrodes during the glow discharge to insulate. Causes breakdown and shifts to arc discharge. With new discharge lamps that are easy to light up, it shifts to arc discharge immediately after a high voltage is applied and lights up, but with discharge lamps that do not, glow discharge continues for a while, then it shifts to arc discharge, glow discharge and arc discharge. There are things such as arc discharge after several transitions to discharge, and in some cases, a discharge lamp at the end of its life or a discharge lamp with poor lighting performance may not shift to arc discharge.

Next, in the above-mentioned conventional example, the operation in the case of shifting from glow discharge to arc discharge will be described.

At the time of starting the discharge lamp, the voltage shown in FIG. 8 (1) is applied between the electrodes, and the current shown in FIG. 8 (2) flows. During the period from time t1 to time t8, arc discharge does not occur between the electrodes of the discharge lamp 110, and a voltage in which the output voltage of the igniter is added to the input voltage of the inverter is generated. When an arc discharge occurs at time t8, a large current flows through the discharge lamp 110, and the terminal voltage becomes a low value of about 10V. When the polarity of the output voltage of the inverter is switched at time t9, no current flows until time t10 when the next starting pulse voltage is applied. When the polarity is switched again at time t11, the current stops flowing, the current does not flow until time t12 when the next starting voltage is applied, and the current flows again at time t14.

By repeating the above-mentioned operation, a continuous arc is established and a steady state is started.
This is an example at the time of starting, and varies depending on the conditions, the type of discharge lamp, the lighting time, and the like, and depending on the conditions, the arc may not be continuous and may not be lit.

On the other hand, a device for surely lighting a discharge lamp is disclosed in Japanese Patent Publication No. 6-065175. This conventional example is a method in which the polarity of the discharge lamp applied voltage is not switched at the time of starting the discharge lamp, that is, the DC voltage is applied and the polarity is switched after the arc discharge is surely performed.

FIG. 9 is a circuit diagram showing the conventional discharge lamp lighting device DS6.

The discharge lamp lighting device DS6 has a high frequency oscillator 251 and a low frequency oscillator 252. The output of the low frequency oscillator 252 is divided by a flip-flop 253 to determine the operation cycle of a transistor operating at a low frequency. . Contact r of relay RY controlled by timer circuit Tm
1 and r2, "H" of the flip-flop 253,
The "L" output signal is switched.

Before the discharge lamp is lit, the transistor 261 is off, and the contacts r1 and r2 of the relay RY are common contacts c1 and c2, respectively, as shown in FIG.
1 and b2, the NOR circuit 254 inverts the output signal of the high frequency oscillator 251, and the output signal of the NOR circuit 255 becomes "L".

The drive circuits 256 and 257 have NO
According to the signals of the R circuits 254 and 255, the transistor of the bridge inverter, for example, the transistor 12 of FIG.
8 and 130 are driven. On the other hand, drive circuits 258 and 259
Are connected to the common connection points c1 and c2 of the relay, respectively, so that they become "L" and "H", respectively, and the transistors of the bridge inverter, for example, the transistors of the bridge inverter shown in FIG.

Therefore, the output voltage of the bridge inverter is unidirectional, that is, the DC voltage is applied to the discharge lamp. When the transistor 261 is turned on after the lapse of the specified time measured by the timer circuit, the relay operates and the common contacts c1 and c2 are respectively a1 and a.
2 and the input terminal of the NOR circuit is connected to the output terminal of the flip-flop circuit 253.
Drive circuits 258, 2 according to the cycle of the signal output by 2
59 drives a transistor of the bridge inverter circuit, and an AC voltage is applied to the discharge lamp.

As described above, by applying a DC voltage at the time of starting the discharge lamp, the arc is stably grown, and then by applying an AC voltage, a DC voltage is applied at the time of starting the discharge lamp. The stable growth of the discharge lamp and the subsequent application of an AC voltage make it possible to reliably start up the discharge lamp.

[0023]

However, in the above-mentioned conventional method, it is necessary to prepare two oscillators, a low-frequency oscillator and a high-frequency oscillator, which causes a problem of cost increase. Since the voltage polarity is always fixed, there is a problem that the electrode is worn out, which shortens the life of the discharge lamp, and there is a risk that the discharge lamp may extinguish because it changes suddenly from DC to a steady frequency. There's a problem.

On the other hand, at the start of lighting of the discharge lamp, arc discharge does not occur unless a voltage of glow discharge voltage (270 to 300 V) or higher is applied between the electrodes of the discharge lamp. Therefore, the inverter output voltage is set to 300 V or higher. However, once the discharge lamp is lit (arc-discharged), both ends of the discharge lamp are almost short-circuited. In this way, when the discharge lamp shifts to arc discharge, the impedance sharply decreases and a large current flows, which requires current limitation. In order to limit this current, a leakage inductance is used in the magnetic leakage transformer method, and a duty ratio control is used in the electronic ballast as in a general inverter.

However, since the voltage between electrodes immediately after lighting of the discharge lamp is extremely low, about several volts to 10 V, the duty ratio must be made extremely small in order to sufficiently limit the current in the electronic ballast. However, there is a limit to the length of on-time that should be shortened due to the operation delay of the switch element, the transmission delay of the control signal, etc.Therefore, the current amount of arc discharge after the discharge lamp shifts to arc discharge is limited. Difficult to limit (if you limit the amount of current too much, you cannot turn on the lamp).

Therefore, in the above-mentioned conventional example, it is necessary to increase the current capacity, the size of the inductor is increased, and there is a problem that the device is upsized and the cost is increased. Further, in the above-mentioned conventional example, since the amount of current immediately after the start of arc discharge cannot be reduced, there is a problem that an excessive current flows in the discharge lamp and the life of the discharge lamp is shortened.

It is an object of the present invention to provide a discharge lamp lighting device capable of limiting the discharge lamp current immediately after lighting the discharge lamp.

[0028]

DISCLOSURE OF THE INVENTION The present invention provides a lighting device for applying low frequency power, which is obtained by superposing rectangular wave high frequency power, to a high brightness discharge lamp.
When the frequency of the high frequency power of the rectangular wave is lower than that in the steady state, and when the high-intensity discharge lamp lights up and the terminal voltage of the high-intensity discharge lamp reaches a predetermined voltage lower than the steady voltage, the high frequency power of the rectangular wave voltage The frequency is raised to the steady frequency.

[0029]

The present invention lowers the modulation frequency of the rectangular wave voltage applied to the high-intensity discharge lamp at the start of lighting of the high-intensity discharge lamp as compared with that in the steady state, so that the field effect transistor may be delayed due to signal transmission delay or switch operation delay. Even if the on-time of can not be reduced, the on-time ratio of the field effect transistor in the bridge inverter circuit becomes small,
The output current of the inverter can be made small, and therefore, the discharge lamp current immediately after lighting of the discharge lamp can be limited.

[0030]

1 is a circuit diagram showing a discharge lamp lighting device DS1 according to a first embodiment of the present invention.

The discharge lamp lighting device DS1 includes a DC power supply 1 as a DC power supply device, a current detection circuit 10, a bridge inverter circuit 20, and a low-pass filter circuit 30.
A discharge lamp voltage detection circuit 40 and an igniter circuit 50
A discharge lamp lighting level determination circuit 60, an oscillation frequency control circuit 70, a control circuit 80, and a logic circuit 90.
It is a device for lighting a high-intensity discharge lamp (metal halide discharge lamp, sodium discharge lamp, etc.) LA.

The current detection circuit 10 uses the bridge inverter circuit 20 based on the current flowing through the secondary side of the current transformer CT.
It is a circuit that detects the value of the current input to the.

The bridge inverter circuit 20 is a circuit for inputting a DC voltage and outputting a low frequency power on which a high frequency power of a rectangular wave is superimposed, and a low frequency arm drive circuit 21 and
High frequency arm drive circuit 22 and transistors Q1 and Q
2, Q3, Q4 and diodes D1, D2, D3, D
It is a circuit having 4, D5, and D6. The low-frequency arm drive circuit 21 and the high-frequency arm drive circuit 22 are controlled by pulses output from output terminals a, b, c, d of a logic circuit 90 described later. The output terminals a, b, c, d of the logic circuit 90 are connected to the high-frequency arm drive circuit 22,
The input terminals a, b, c and d of the low frequency arm drive circuit 21 are respectively connected.

The low-pass filter circuit 30 is a circuit for applying a desired low-frequency rectangular voltage to the discharge lamp LA by removing the high-frequency component of the high-frequency modulated low-frequency voltage output from the bridge inverter circuit 20, and the inductor L1 and And a capacitor C1.

The discharge lamp voltage detection circuit 40 rectifies the output voltage of the low pass filter circuit 30 by the rectification circuit REC,
Smoothing is performed by the resistor R1 and the capacitor C2, and when the smoothed voltage becomes equal to or higher than the Zener voltage of the Zener diode VZ1, the photocoupler PC is connected via the resistor R2.
A current flows through the light emitting diode of No. 1 and light corresponding to the value of this current is output from the light emitting diode of the photocoupler PC1. Further, the igniter circuit 50 has a transformer T and an oscillating circuit 51, and the discharge lamp LA is connected to its output terminal.
Is connected.

The discharge lamp lighting level discriminating circuit 60 is a circuit for discriminating the lighting level of the discharge lamp LA according to the current flowing through the discharge lamp LA and the voltage applied to the discharge lamp LA.
The voltage of the discharge lamp LA is detected in order to distinguish the current when there is no load from the current when there is a short circuit.

The oscillation frequency control circuit 70 is a circuit for controlling the frequency of high frequency modulation performed in the bridge inverter circuit 20.

The control circuit 80 is the oscillation frequency control circuit 70.
Is a circuit that determines the pulse width according to the collector current of the transistor Q8 and determines the operating frequency by the oscillator 81, and includes a reference voltage source Eref, an amplifier 82, and a comparator 83.

The oscillator 81 is a circuit for generating a triangular wave voltage, the amplifier 82 is a circuit for error-amplifying the output voltage of the current detection circuit 10, and the comparator 83 is for the triangular wave voltage generated by the oscillator 81 and the amplifier 82. The error signal output from the bridge inverter circuit 20 is compared and the field effect transistors Q3 and Q in the arm of the bridge inverter circuit 20 operating at high frequency are compared.
4 is a circuit that outputs a signal for driving the drive circuit 4.

When the transistor Q8 is off, the oscillation frequency of the oscillator 81 becomes a frequency determined by the time constant of the resistor R12 and the capacitor C4, but current is supplied from the collector of the transistor Q8 to the resistor R12. Then, the oscillation frequency of the oscillator 81 becomes low. The reason for this will be described later.

The logic circuit 90 has a frequency divider 91, a flip-flop circuit 92, and AND circuits 93 and 94,
High frequency arm drive circuit 2 of bridge inverter circuit 20
2. A circuit for outputting a pulse to be supplied to the low frequency arm drive circuit 21. The frequency divider 91 is a circuit that reduces the frequency of the output signal of the comparator 83, and the flip-flop circuit 92 is a circuit that divides the signal of the frequency reduced by the frequency divider 91 into two. AND circuits 93, 94
Is a circuit for distributing the output signal of the comparator 83 into drive signals for the field effect transistors Q3 and Q4.

Next, the operation of the discharge lamp lighting device DS1 will be described.

FIG. 5 is a diagram showing the voltage and current across the discharge lamp LA in the discharge lamp lighting device DS1.

Before the discharge lamp LA is turned on (time T0 in FIG. 5), the input current of the bridge inverter circuit 20 has a small value, so the output value of the current detection circuit 10 is small and the discharge lamp lighting level determination circuit. The transistor Q5 in 60 turns off and Q6 turns on, and the potential of the non-inverting input terminal of the amplifier 71 in the oscillation frequency control circuit 70 and the emitter potential of the transistor Q8 are equal. That is, the operational amplifier as the amplifier 71 operates so that the non-inverting input terminal and the inverting input terminal have the same potential, and since the input impedance is very large, the current flowing into the input terminal can be regarded as zero, and therefore flows into R9. The current is zero and the voltage on R9 is also zero, which is why the amplifier 71
The potential of the non-inverting input terminal of the transistor Q8 becomes equal to the potential of the emitter of the transistor Q8.

As described above, since the potential of the non-inverting input terminal of the amplifier 71 is equal to the emitter potential of the transistor Q8, the collector of the transistor Q8 has approximately {R7 / (R7 + R8)}  (Eref / R11). Current flows. As a result, the oscillation frequency of the oscillator 81 becomes low. That is, when the transistor Q6 is turned on, the charge stored in the capacitor C3 is discharged, the voltage at the non-inverting terminal of the amplifier 71 becomes minimum, and the potential at the output terminal of the amplifier 71 becomes
Since the operation is performed so that the potential of the inverting input terminal and the potential of the non-inverting input terminal become equal, the collector current of the transistor Q8 increases. Since the current flows from the oscillator 81 so that the voltage across the resistor R12 is always equal, when the collector current of the transistor Q8 flows, the current flowing from the input terminal above the oscillator 81 decreases, and the resistance of the resistor R12 seen from the oscillator 81 is reduced. The value apparently increases, and the oscillation frequency of the oscillator 81 decreases.

As the oscillation frequency of the oscillator 81 is lowered, the operating frequency of the inverter bridge circuit 20 is lowered. When the operating frequency of the inverter bridge circuit 20 is lowered as described above, the off time of the field effect transistor in the bridge inverter circuit 20 is lengthened, so that the on-time ratio of the field effect transistor is decreased and the output current of the inverter can be decreased. Therefore, the discharge lamp current immediately after lighting of the discharge lamp can be limited.

After that, when the discharge lamp LA is turned on (time T1 in FIG. 5), the current detection circuit 10 detects that a current has flowed in the bridge inverter circuit 20, the transistor Q5 is turned on, and the transistor Q6 is turned off. However, the voltage of the discharge lamp LA is almost zero as described above, the output voltage of the rectifier REC of the discharge lamp voltage detection circuit 40 is also zero, no current flows in the light emitting diode of the photocoupler PC1, and the transistor Q7 is turned on. , The state of the amplifier 71 does not change, and the frequency of the oscillator 81 remains lowered. Therefore, even if the discharge lamp LA is turned on and both ends of the discharge lamp LA are short-circuited, the output current can be prevented from becoming excessive. Although it seems that the current is not limited in FIG. 5, in the conventional example, a larger amount of current flows than the current amount shown in FIG. 5, and in comparison with this conventional example, the embodiment shown in FIG. The amount of current is low.
Further, if the current is not supplied to the extent shown in FIG. 5, the discharge lamp LA
Cannot be kept lit.

When the discharge lamp LA continues to be in the lighting state (time T2 in FIG. 5), the voltage of the discharge lamp LA gradually rises, the discharge lamp voltage detection circuit 40 detects this voltage rise, and the rectifier circuit REC. When the output voltage of the voltage rises to the Zener voltage of the constant voltage diode VZ1 (time T3 in FIG. 5), the light emitting diode of the photocoupler PC1 is turned on, and the transistor Q7 of the discharge lamp lighting level determination circuit 60 is turned on.
Turns off.

At this time, since the transistor Q6 is still off, the voltage across the capacitor C3 rises according to the time constant of the capacitor C3 and the resistor R8. Resistance R
The voltage across R8 drops, and the voltage across R11
Since the voltage is set to be equal to the voltage across 8, the potential of the resistor R11 decreases as the potential of the capacitor C3 increases, and the collector current of the transistor Q8 decreases. As a result,
The oscillation frequency of the oscillator 81 increases. When the voltage across the capacitor C4 rises to the reference voltage value Eref, the collector current of the transistor Q8 becomes zero, and the oscillation frequency of the oscillator 81 stabilizes at the steady frequency.

According to the above embodiment, one oscillation circuit 81
Thus, the current when the discharge lamp LA is turned on can be limited. Therefore, it is possible to eliminate the factor of cost increase by preparing two oscillators, a low frequency oscillator and a high frequency oscillator.

Further, according to the above-described embodiment, the frequency of the voltage applied to the discharge lamp LA at the time of starting can be lowered, and since it is an AC voltage from the time of lighting, the electrodes of the discharge lamp LA may be worn down. Therefore, the life of the discharge lamp LA can be extended.

Further, according to the above-mentioned embodiment, since the rise of the frequency can be controlled gently, the possibility that the discharge lamp LA goes out due to the transient change of the frequency can be remarkably improved.
The discharge lamp LA can be reliably turned on.

FIG. 2 is a circuit diagram showing a discharge lamp lighting device DS2 which is a second embodiment of the present invention.

The discharge lamp lighting device DS2 is basically the same as the discharge lamp lighting device DS1 except that a discharge lamp voltage detection circuit 40a is provided instead of the discharge lamp voltage detection circuit 40.
Instead of the discharge lamp lighting level determination circuit 60, a discharge lamp lighting level determination circuit 60a is provided, and the circuits other than these are
It is the same as the discharge lamp lighting device DS1.

The discharge lamp voltage detection circuit 40a has constant voltage diodes VZ1 and VZ21 having different threshold values.
The constant voltage diode VZ1 has a discharge lamp voltage of 1 which is a steady voltage.
It becomes conductive when it reaches / 4 to 1/3, and the discharge lamp lighting level determination circuit 60 is provided via the photocoupler PC1.
The transistor Q7 of a is turned off. Also,
The constant voltage diode VZ21 conducts when the discharge lamp voltage reaches 1/3 to 2/3 of the steady voltage, and turns off the transistor Q27 of the discharge lamp lighting level determination circuit 60a via the photocoupler PC21. It is a thing.

The discharge lamp lighting level discrimination circuit 60a is a circuit in which a phototransistor of the photocoupler 21, its collector resistance R26, a transistor Q27 and this collector resistance R27 are added to the discharge lamp lighting level discrimination circuit 60.

Next, the operation of the discharge lamp lighting device DS2 will be described.

First, when the discharge lamp LA is lit, similarly to the above, the transistor Q6 of the discharge lamp lighting level discrimination circuit 60a is turned off, and both the transistors Q7 and Q27 are turned on. Therefore, the amplifier 7 of the oscillation frequency control circuit 70
The voltage of the non-inverting input terminal of 1 becomes a value obtained by multiplying the voltage division ratio of the resistors R8 and R7 or the voltage division ratio of the resistors R8 and R27 by the reference voltage Eref, and the oscillation frequency of the oscillator 81 becomes
It goes down to the first frequency lower than the regular time.

Next, the voltage of the discharge lamp LA gradually rises,
When it reaches 1/4 to 1/3 of the voltage of the discharge lamp LA in the constant time, the Zener diode VZ1 becomes conductive, the photocoupler PC1 sends a signal, and the transistor Q7 is turned off. As a result, the voltage of the non-inverting input terminal of the amplifier 71 becomes a value obtained by multiplying the voltage division ratio of the resistors R8 and R27 by the reference voltage Eref, the oscillation frequency of the oscillator 81 is higher than the first frequency, and the steady state is maintained. It rises to a second frequency, which is lower than the frequency.

After that, when the voltage of the discharge lamp LA further rises and reaches 1/3 to 2/3 of the steady state, the Zener diode VZ21 becomes conductive, the photocoupler PC21 sends a signal, and the transistor Q27 turns off. by this,
The voltage of the non-inverting input terminal of the amplifier 71 is the reference voltage Eref.
Then, the oscillation frequency of the oscillator 81 rises to the steady frequency.

According to the discharge lamp lighting device DS2, as described above, when the oscillation frequency rises from the first frequency to the second frequency and thereafter rises from the second frequency to the steady value, the capacitor Since the time constant of C3 and the resistor R8 and the time constant of the resistors R7 and R27 are used, the frequency change of the discharge lamp supply voltage is slower than that of the discharge lamp lighting device DS1 and the discharge lamp supply voltage rises. A rapid change in the process is alleviated, and the extinction of the discharge lamp LA can be prevented more effectively.

That is, according to the discharge lamp lighting device DS2,
Since the modulation frequency of the rectangular wave voltage applied to the discharge lamp LA is changed in three steps, abrupt changes in the rising process of the rectangular wave voltage are alleviated, and the extinction of the discharge lamp LA can be further prevented.

FIG. 3 is a circuit diagram showing a discharge lamp lighting device DS3 according to the third embodiment.

The discharge lamp lighting device DS3 is basically the same as the discharge lamp lighting device DS1, but a logic circuit 90a is provided instead of the logic circuit 90, and the other circuits are the same as the discharge lamp lighting device DS1. Is. The logic circuit 90a is
The frequency divider 91 in the logic circuit 90 is replaced with an oscillator 95.

In the discharge lamp lighting devices DS1 and DS2, the frequency of the discharge lamp voltage changes according to the frequency change on the high frequency side. Therefore, if the frequency of the discharge lamp LA during lighting is too low, flicker occurs. However, the user may feel uncomfortable.

In order to prevent the flicker from occurring, the discharge lamp lighting device DS3 does not lower the frequency on the low frequency side,
Only the modulation frequency is lowered, and the current when the discharge lamp LA is lit is suppressed to a specified value.

That is, generally, immediately after the discharge lamp LA is lit, the short-circuited state occurs as described above, and if too much current flows at this time, it is not only necessary to make the switch element and the filter large, but If the electrodes of the electric lamp LA are deteriorated and the current is restricted too much, the discharge lamp voltage does not rise sufficiently, the rise of the discharge lamp voltage stops halfway, and the discharge lamp goes out.

Therefore, the discharge lamp lighting device DS3 is designed to control the current at the time of starting stably by gradually changing the modulation frequency and continuously changing the duty ratio.

Generally, in a switching power supply, skip control (thinning-out control) is performed as a current limit at the time of a short circuit. However, it is a problem to adopt the current limit by the skip control in the discharge lamp lighting device. In other words, the skip control is a control that protects the power supply by increasing the current when the output of the switching power supply is short-circuited.While supplying power to the load in the steady cycle, the power supply is sometimes paused to suppress the average current. Is the way. Since the skip control pauses during power supply in a steady cycle, a current drop occurs during the pause period.In the case of a voltage-type load, a current drop occurs due to an abnormal state during a short circuit. Although there is no problem, the discharge lamp LA is a current type load, and if the current supply is stopped or dropped, the discharge lamp LA
May disappear. Therefore, there is a problem in adopting the current limitation by the skip control in the discharge lamp lighting device.

FIG. 4 is a circuit diagram showing a discharge lamp lighting device DS4 which is a fourth embodiment of the present invention.

The discharge lamp lighting device DS4 is basically the same as the discharge lamp lighting device DS2, but a logic circuit 90a is provided instead of the logic circuit 90, and the other circuits are the same as the discharge lamp lighting device DS2. Is. The logic circuit 90a is
The discharge lamp lighting device DS4, which is obtained by replacing the frequency divider 91 in the logic circuit 90 with the oscillator 95, uses the same frequency divider circuit 91 in the discharge lamp lighting device DS2 as the discharge lamp lighting device DS3. The operation of this embodiment is the same as that of the discharge lamp lighting device DS3, and the increase of the modulation frequency is made in two stages, and the increase is made gentler.

In the above embodiment, the DC power supply 1 is used as an input, but any configuration may be used as the DC power supply 1, such as a battery, a DC power supply rectified with an AC voltage, and a switch. A DC power supply obtained by using a mode rectification circuit may be used.

[0073]

According to the present invention, it is possible to limit the discharge lamp current immediately after the high-intensity discharge lamp is lit.

[Brief description of drawings]

FIG. 1 is a discharge lamp lighting device D according to a first embodiment of the present invention.
It is a circuit diagram which shows S1.

FIG. 2 is a discharge lamp lighting device D according to a second embodiment of the present invention.
It is a circuit diagram which shows S2.

FIG. 3 is a circuit diagram showing a discharge lamp lighting device DS3 according to a third embodiment.

FIG. 4 is a discharge lamp lighting device D according to a fourth embodiment of the present invention.
It is a circuit diagram which shows S4.

FIG. 5 is a diagram showing a voltage across a discharge lamp and a current in the discharge lamp lighting device DS1.

FIG. 6 is a diagram mainly showing a bridge inverter circuit of a discharge lamp lighting device DS5 which is a conventional example.

FIG. 7 is a diagram showing operation waveforms of main parts of the discharge lamp lighting device DS5.

FIG. 8 is a timing chart showing the operation of the discharge lamp lighting device DS5.

FIG. 9 is a circuit diagram showing a discharge lamp lighting device DS5 which is the conventional example.

[Description of Reference Signs] DS1 to DS4 ... Discharge lamp lighting device, 10 ... Current detection circuit, 20 ... Bridge inverter circuit, 30 ... Low-pass filter circuit, 40 ... Discharge lamp voltage detection circuit, 60, 60a ... Discharge lamp lighting level determination circuit , 70 ... Oscillation frequency control circuit, 80 ... Control circuit, 81, 95 ... Oscillator, 90, 90a ... Logic circuit, 91 ... Divider, LA ... High-intensity discharge lamp.

Claims (9)

[Claims] 1. A direct current power supply device and a bridge inverter device for converting direct current power from the direct current power supply device into low frequency power on which high frequency power of a rectangular wave is superimposed and supplying power to a high brightness discharge lamp. A discharge lamp voltage detecting device for detecting a voltage applied to the high-intensity discharge lamp, the discharge lamp voltage detecting device comprising: and a current detecting device for detecting an input current of the bridge inverter circuit; A discharge lamp lighting device, comprising: modulation frequency control means for stepwise changing a modulation frequency of the high frequency power of the rectangular wave applied to the high intensity discharge lamp according to the voltage detected by the detection device. . 2. The modulation frequency control means according to claim 1, when the lighting of the high-intensity discharge lamp is started, the modulation frequency of the high-frequency power of the rectangular wave applied to the high-intensity discharge lamp is lower than that in a steady state. On the other hand, when the high-intensity discharge lamp is turned on and the terminal voltage of the high-intensity discharge lamp reaches a predetermined voltage lower than a steady voltage, the modulation frequency of the high frequency power of the rectangular wave applied to the high-intensity discharge lamp. Discharge lamp lighting device, which is a means for increasing the temperature to a steady frequency. 3. The modulation frequency control means according to claim 1, wherein the modulation frequency of the high frequency power of the rectangular wave applied to the high-intensity discharge lamp at the start of lighting of the high-intensity discharge lamp is lower than that in a steady state. When the high-intensity discharge lamp is lit up and the terminal voltage of the high-intensity discharge lamp reaches a first predetermined voltage lower than the steady voltage, it is applied to the high-intensity discharge lamp. The modulation frequency of the high frequency power of the rectangular wave is increased to a second frequency which is higher than the first frequency and lower than the steady-state frequency, and then the terminal voltage of the high-intensity discharge lamp is higher than the steady-state voltage. A second voltage lower than the first predetermined voltage
The discharge lamp lighting device is a means for increasing the modulation frequency of the high frequency power of the rectangular wave applied to the high intensity discharge lamp to a steady frequency when the predetermined voltage is reached. 4. A direct current power supply device and a bridge inverter device for converting direct current power from the direct current power supply device into low frequency power on which rectangular wave high frequency power is superimposed and supplying power to a high brightness discharge lamp. A discharge lamp voltage detecting device for detecting a voltage applied to the high-intensity discharge lamp, the discharge lamp voltage detecting device comprising: and a current detecting device for detecting an input current of the bridge inverter circuit; A discharge lamp lighting device, comprising: frequency control means for gradually changing the frequency of the high frequency power and the frequency of the low frequency power according to the voltage detected by the detection device. 5. The frequency control means according to claim 4, wherein the frequency of the high-frequency power and the frequency of the low-frequency power applied to the high-intensity discharge lamp are constant when the high-intensity discharge lamp is started to light. Lower than
On the other hand, when the high-intensity discharge lamp is lit and the terminal voltage of the high-intensity discharge lamp reaches a predetermined voltage lower than the steady voltage, the frequency of the high-frequency power applied to the high-intensity discharge lamp and the low-frequency power A discharge lamp lighting device, characterized in that it is a means for increasing the frequency to a steady frequency. 6. The frequency control means according to claim 4, wherein at the start of lighting of the high-intensity discharge lamp, the frequency of the high-frequency power and the frequency of the low-frequency power applied to the high-intensity discharge lamp are respectively set. Lower the first frequency and the third frequency, which are lower than the normal, while
When the high-intensity discharge lamp is turned on and the terminal voltage of the high-intensity discharge lamp reaches the first predetermined voltage lower than the steady voltage, the frequency of the high-frequency power applied to the high-intensity discharge lamp and the low-frequency power are applied. And the second frequency and the fourth frequency, which are higher than the first frequency and the third frequency and lower than the steady-state frequency, respectively, and thereafter,
When the terminal voltage of the high-intensity discharge lamp reaches a second predetermined voltage that is lower than the steady voltage and higher than the first predetermined voltage, the frequency of the high-frequency power applied to the high-intensity discharge lamp and the low frequency. A discharge lamp lighting device, which is a means for increasing the frequency of frequency power to a steady frequency. 7. The frequency according to claim 3 or 6, wherein when the terminal voltage of the high-intensity discharge lamp reaches a first predetermined voltage and a second second predetermined voltage, each frequency is gradually increased. A discharge lamp lighting device characterized by the above. 8. The method according to claim 1, wherein it is confirmed that the high-intensity discharge lamp is turned on based on an input current and an output voltage of the bridge inverter circuit. Discharge lamp lighting device. 9. A discharge lamp lighting method for converting direct-current power from a direct-current power supply device into low-frequency power in which rectangular-wave high-frequency power is superimposed to supply power to a high-intensity discharge lamp. A discharge lamp voltage detection step of detecting a voltage applied to the electric lamp; at the start of lighting of the high-intensity discharge lamp, a modulation frequency of the high frequency power of the rectangular wave applied to the high-intensity discharge lamp is lowered as compared with a steady state When the high-intensity discharge lamp is turned on and the terminal voltage of the high-intensity discharge lamp reaches a predetermined voltage lower than the steady voltage, the modulation frequency of the high frequency power of the rectangular wave applied to the high-intensity discharge lamp is changed. And a step of increasing the frequency to a steady frequency.