JP2002110384A - Discharge lamp lighting device - Google Patents

Abstract

(57) Abstract: Provided is a discharge lamp lighting device capable of performing stable rated lighting by using inverter means capable of changing an oscillation frequency or a duty ratio. SOLUTION: A lamp voltage is detected by a DC voltage detecting circuit 13, and a reference signal obtained by adding output signals of a lamp current calculating circuit 21 and a bias circuit 22 in accordance with the detected signal, and an input current from an inverter circuit to a discharge lamp are obtained. The switching regulator control IC 19 is controlled via the comparison circuit 24 and the constant current circuit 26 to control the oscillation frequency of the inverter circuit so that the output signal of the corresponding DC current detection circuit 23 matches.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for controlling lighting of a discharge lamp such as a metal halide lamp.

[0002]

2. Description of the Related Art A relatively high voltage is applied between a pair of electrodes of a discharge lamp to reduce or substantially eliminate the detrimental electrophoretic and acoustic resonance effects commonly encountered during operation of a discharge lamp, such as a metal halide lamp. To excite the excitable component enclosed in the discharge lamp, and then maintain the excitation, the pair of electrodes have a size within a predetermined range, and have a predetermined repetition rate. It is already known from Japanese Patent Application Laid-Open No. 2-10697 to use a method in which a rectangular wave current is supplied and the direction in which the rectangular wave current is supplied to the electrodes is alternately changed periodically.

[0003]

However, as disclosed in the official gazette, the apparatus for implementing the above method is very complicated and extremely disadvantageous in practical use.

The present invention solves the above-mentioned conventional problems, and provides a discharge lamp lighting device capable of stably performing rated lighting by using inverter means capable of changing an oscillation frequency or a duty ratio.

[0005]

In order to solve the above-mentioned problems, a discharge lamp lighting device according to the present invention comprises a DC power supply, inverter means driven by the DC power supply and oscillating,
A discharge lamp connected to the inverter means, a lamp voltage detecting means for detecting a lamp voltage, and an output voltage of the lamp voltage detecting means in a lamp starting area, and when a lamp voltage is low, a large lamp current flows; When the lamp voltage is high, an oscillation frequency or a duty ratio of the inverter means is varied so that a small lamp current flows, and lighting control means for controlling the discharge lamp to perform rated lighting is provided.

Further, the lighting control means of the present invention outputs a constant signal when the lamp voltage is equal to or lower than the first predetermined lamp voltage, and outputs a signal as the lamp voltage increases when the lamp voltage is equal to or higher than the first predetermined lamp voltage and equal to or lower than the second predetermined lamp voltage. A lamp current calculating means for reducing the signal to make the output signal zero when the voltage is equal to or higher than a second predetermined lamp voltage; and a bias means. The oscillation frequency of the inverter means is determined by the sum output of the lamp current calculating means and the bias means. And controlling the first
The lamp current is regulated so as to be constant by a constant output signal of the lamp current calculation means below the predetermined lamp voltage.

Further, the lighting control means of the present invention includes a DC current detecting means for detecting a lamp current, and a comparing means for comparing the output of the DC current detecting means with the added output of the lamp current calculating means and the bias means. And the oscillation frequency or duty ratio of the inverter means is controlled by the output of the comparison means.

Further, the lighting control means of the present invention has a time constant switching means connected to the lamp current calculating means and operated by a predetermined lamp voltage, and when the lamp voltage exceeds a predetermined voltage, the lamp current calculating means. The time constant is switched so as to increase the time constant of the decrease with respect to the lamp current.

Further, the lighting control means of the present invention has a bias current circuit for defining an oscillation frequency of the inverter means, and when a lamp current suddenly flows, a constant current flowing through the bias current circuit causes the inverter control circuit to control the inverter current. The oscillation frequency of the means is configured not to be lower than a predetermined frequency.

Further, the lighting control means of the present invention has a lamp current instantaneous value detecting means for comparing the instantaneous lamp current value with a reference value and outputting when the lamp current instantaneous value exceeds the reference value. The configuration is such that the oscillation of the inverter means is inverted or temporarily stopped by the output signal of the lamp current instantaneous value detection means.

Further, the lighting control means of the present invention operates when the lamp voltage is smaller than a predetermined value in a starting region of the discharge lamp, and when the lamp voltage does not exceed the predetermined value within a predetermined time, the oscillation of the inverter means is controlled. Starting voltage timer means for stopping the operation.

Further, the lighting control means of the present invention comprises a
Immediately after restarting, a starting initial current setting means for setting an initial lamp current so that a predetermined lamp current larger than at least a lamp current at the time of stable lighting is supplied.

Further, the lighting control means of the present invention includes a lighting-off time detecting means for detecting a lighting-off time of the lamp, and at least a lamp current at the time of stable lighting immediately after starting and restarting according to an output of the lighting-off time detecting means. A starting initial current setting means for setting an initial lamp current so as to flow a large predetermined lamp current, wherein the initial lamp current is set to be larger when the turn-off time is longer than when the turn-off time is shorter. is there.

Further, the lighting control means of the present invention comprises a
The minimum lamp voltage detecting means after the restart and the lamp having the lower minimum lamp voltage after starting and restarting the lamp in accordance with the output of the minimum lamp voltage detecting means, by flowing a larger lamp current or a larger lamp current for a longer time. It is provided with control means for controlling so as to input lamp power.

Further, the lighting control means of the present invention includes means for changing a lamp voltage set value for switching a control time constant of a lamp current in accordance with an output of the minimum lamp voltage detecting means. It is configured to switch to a long control time constant by voltage.

Further, the lighting control means of the present invention includes means for changing the control time constant of the lamp current according to the output of the minimum lamp voltage detection means, so that the control time constant becomes longer as the minimum lamp voltage becomes lower. It is composed.

Further, the lighting control means of the present invention includes means for controlling the time during which the maximum lamp current flows according to the output of the minimum lamp voltage detection means. The lower the minimum lamp voltage, the longer the time during which the maximum lamp current flows. It is configured so as to be controlled.

According to the above configuration, when the lamp voltage detecting means detects a low lamp voltage in the starting region of the discharge lamp, a large lamp current is caused to flow by varying the frequency or duty ratio of the inverter means, and a high lamp voltage is detected. In such a case, a small lamp current is caused to flow by varying the frequency or duty ratio of the inverter means, so that the lamp current can be reliably controlled and the lamp can be lit at the rated lamp power during stable lighting.

When the lamp voltage is equal to or lower than the first predetermined lamp voltage, a constant signal is output. When the lamp voltage is equal to or higher than the first predetermined lamp voltage and equal to or lower than the second predetermined lamp voltage, the output signal decreases as the lamp voltage increases. Output signal is 0 at lamp voltage or higher
The oscillation frequency of the inverter means is controlled by the addition output of the lamp current calculation means and the bias means.
In the starting region of the lamp, when the lamp voltage is lower than the second predetermined lamp voltage, a large lamp current at the time of starting is supplied to quickly increase the luminous flux of the discharge lamp. It prevents the flow of a large lamp current, and when the lamp voltage is equal to or higher than the second predetermined lamp voltage, a constant rated current is supplied to light the lamp at the rated lamp power.

When the lamp voltage becomes equal to or higher than the predetermined voltage, the time constant is switched by the time constant switching means so as to increase the lamp current decrease time constant in the lamp current calculation means. Since the rated lighting is gradually changed, the light output can be shifted to the stable lighting without a large change after the light output is set to the rated output after the start.

Further, by providing a bias current circuit for defining the lowest oscillation frequency in the inverter means, when the lamp current suddenly flows, the oscillation frequency of the inverter means becomes a constant current flowing in the bias current circuit. By ensuring that it does not fall below the predetermined frequency,
Excessive current is prevented from flowing through the discharge lamp, and damage to the discharge lamp and the lighting device due to excessive input / output can be prevented.

Further, when a large current flows instantaneously into the discharge lamp, the lamp current instantaneous value detecting means detects this, and in order to cut off the large current, the oscillation of the inverter means is immediately reversed at that time. Alternatively, the operation is temporarily stopped to protect the discharge lamp and the lighting device.

When it is detected that the lamp current is larger than a predetermined value or that the lamp voltage is smaller than a predetermined value, the starting voltage timer means is operated. Since the operation is stopped, the starting current is prevented from flowing into the discharge lamp for a long time, and the discharge lamp is prevented from being damaged.

Further, the initial lamp current is set so that at least immediately after the start and restart, a predetermined lamp current larger than the lamp current at the time of stable lighting is supplied. Even in such a case, by supplying a large lamp current, a light output close to that at the time of stable lighting can be obtained immediately after restarting even if the enclosed metal adheres to the tube wall of the lamp when the lamp is turned off.

Further, the initial lamp current is set so as to flow at least a predetermined lamp current larger than the lamp current at the time of stable lighting immediately after starting and restarting according to the output of the light-off time detecting means. By setting the initial lamp current to be longer when the lamp is longer than when the lamp is turned off, the luminous efficiency does not decrease because the vapor pressure of the sealed metal does not decrease when the turn-off time is short. In such cases, the lamp current does not flow so much at restart because the extent to which the gas adheres to the tube wall is low. In this case, a large lamp current can be supplied at the time of restart, and a light output close to that of stable lighting can be obtained immediately after restart.

Further, after starting and restarting the lamp in accordance with the output of the minimum lamp voltage detecting means, a larger lamp current or a larger lamp current is supplied to the lamp having a lower minimum lamp voltage for a longer time, so that a larger lamp power is inputted. The lamp power is not consumed in a lamp with a particularly low lamp voltage after starting due to variations in the lamp during cold starting when the lamp is cold, so the lamp is not easily heated and the vapor pressure does not increase Therefore, even if the rise of the light output may be poor, the required lamp power can be input according to the minimum lamp voltage after starting and restarting even in such a lamp, and the light output of almost constant regardless of the variation of the lamp A rise is obtained.

Furthermore, the control time constant of the lamp current is switched in accordance with the output of the minimum lamp voltage detecting means, and the lower the minimum lamp voltage, the lower the lamp voltage and the longer the control time constant. The required lamp power can be input in accordance with the minimum lamp voltage after starting, and a substantially constant rise in light output can be obtained regardless of lamp variations.

Further, the control time constant of the lamp current is changed in accordance with the output of the minimum lamp voltage detecting means, and the control time constant becomes longer as the minimum lamp voltage becomes lower. The required lamp power can be finely controlled and input according to the minimum lamp voltage, and a substantially constant rise of the light output can be obtained regardless of variations in the lamp.

Further, by controlling the time during which the maximum lamp current flows according to the output of the minimum lamp voltage detecting means, and by controlling the time during which the maximum lamp current flows as the minimum lamp voltage decreases, a simple configuration can be realized. The required lamp power can be finely controlled and input according to the minimum lamp voltage after starting and restarting, and a substantially constant rise in light output can be obtained regardless of lamp variations.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a discharge lamp lighting device according to an embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 1 is a block diagram showing a basic configuration of a discharge lamp lighting device according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a DC power supply, and an inverter circuit 2 is driven by the DC power supply 1 and oscillates a clock signal having a predetermined frequency. The inverter circuit 2 includes a resonance circuit including a series circuit of a choke coil 3 and a resonance capacitor 4 as a load circuit, and a discharge lamp 5 such as a metal highland lamp connected to a connection point between the choke coil 3 and the capacitor 4. have. The load circuit further includes a lamp voltage detection circuit 6 connected in series with the resonance circuit to detect the start of the discharge lamp 5 and detect a lamp voltage for controlling the subsequent start and rated lighting. Is provided. The output signals of the lamp voltage detection circuit 6 and the lamp current detection circuit 7 are input to a lighting control circuit 8, and the lighting control circuit 8 changes the oscillation frequency of the inverter circuit 2 or the duty ratio thereof based on the output signals. The lighting operation of is controlled.

Next, the operation of the above configuration will be described. When the DC power supply 1 is turned on, the inverter circuit 2 first oscillates at a low frequency of about 2 KHz, and applies this low frequency voltage to the resonance circuit of the choke coil 3 and the capacitor 4. At this time, the high-frequency resonance voltage generated by the resonance circuit is superimposed on the low-frequency voltage, and the lamp voltage detection circuit 6 connected to the resonance circuit detects the resonance voltage. The oscillation frequency of the circuit 2 is changed to a high frequency, and a high resonance voltage is generated in the capacitor 4 at a high frequency of, for example, about 100 KHz by the resonance circuit. At this time, the discharge lamp 5 is started by the high resonance voltage generated in the capacitor 4, and a large amount of current flows through the discharge lamp 5. When a current flows through the discharge lamp 5, the voltage across the discharge lamp 5 decreases. At this time, the lamp voltage detecting circuit 6 detects that the current flowing through the capacitor 4 has sharply decreased by the voltage drop in the lamp voltage detecting circuit 6, and thereby the discharge lamp 5
Is activated, and the lighting control circuit 8 controls the oscillation frequency of the inverter circuit 2 to be a low frequency of about 10 KHz based on the lowered detection voltage of the lamp voltage detection circuit 6. When the lamp voltage is low, The oscillation frequency of the inverter circuit 2 is lowered to increase the current flowing to the discharge lamp 5 through the choke coil 3. When the lamp voltage is high, the oscillation frequency of the inverter circuit 2 is increased to flow to the discharge lamp 5 through the choke coil 3. The current is reduced so that the discharge lamp 5 is controlled so as to perform rated lighting.

The choke coil 3 has a configuration as shown in FIG. 2 so that when the inductance is saturated, a large current flows and the discharge lamp 5 is damaged, so that the inductance is not saturated. FIG. 2A shows a center gap 10a at the center leg of a pair of cores 9a of the choke coil 3 facing each other.
FIG. 2B shows a configuration having a space gap 10b through the center leg and both end legs of a pair of opposing cores 9b of the choke coil 3. FIG. FIG.
In the case of (a), the leakage flux is small at both end legs, and the change in the inductance value due to the influence of the surroundings is small. FIG.
In the case of (b), the core is easily insulated.

FIG. 3 is a circuit diagram showing a main part of the inverter circuit 2. In FIG. 3, the inverter circuit 2 has a configuration of a bridge inverter including _four switching transistors Q ₁ , Q ₂ , Q ₃ , and Q ₄ for driving an external circuit 11 including a choke coil 3, a capacitor 4, and a discharge lamp 5. 12 is a drive circuit for driving the bridge inverter, across the primary winding of the drive transformer DT is grounded via the drive transistor Q _5, Q _6, the oscillation to the gate of the drive transistor Q _5, Q ₆ Clocks E ₁ and E ₂ having a frequency of about 2 KHz and having phases inverted to each other are input, and a drive voltage VD is applied to a middle point of the primary winding. Four secondary windings are provided on the secondary side of the drive transformer DT. One end of each of the secondary windings is connected to resistors R ₁₃ , R ₁₅ , R ₁₇ , R ₁₉ and diodes D ₃ , D ₄ connected in parallel to the resistors R ₁₃ , R ₁₅ , R ₁₇ , R _19. , D ₅ , D ₆ and the series circuit of resistors R ₁₂ , R ₁₄ , R ₁₆ , R ₁₈ to the gates of _four switching transistors Q ₁ , Q ₂ , Q ₃ , Q ₄ constituting the bridge inverter. Connected.

The switching transistors Q ₁ and Q ₂
The series circuit of the series circuit and the switching transistor Q ₃ and Q ₄ is interposed between the DC power supply voltage VDD and the bridge of the earth line A, the switching transistor Q _1, the connection point and the switching transistor Q ₃ Q ₂ 'and Q ₄
The external circuit 11 is interposed between the connection points. The other end of the secondary winding is connected to the gate of the switching transistor Q ₁ is connected to a connection point of the transistors Q _1, Q _2,
The other end of the secondary winding connected to the gate of the switching transistor Q ₃ are connected to a connection point of the transistors Q _3, Q _4, the secondary windings are connected to respective gates of the switching transistors Q _2, Q ₄ Are connected to the ground line A of the bridge, and are floating above the ground GND. As a result, the pair of switching transistors Q ₁ and Q ₄ and the switching transistors Q ₂ and Q _{3, which} are diagonally opposed to each other, are configured such that when one Q ₁ and Q ₄ are simultaneously turned on, the other Q ₂ and Q ₃ are simultaneously turned off. It is configured.

C_TwoConstitutes the lamp voltage detection circuit 6 of FIG.
The capacitor for voltage detection is a capacitor for resonance.
The capacity is larger than the capacity of
4 and switching transistor Q_Three, Q_FourWith the connection point
Connected between the capacitors C _TwoThe voltage generated across
This is detected as the lamp voltage of the discharge lamp 5. Ie
Voltage detection capacitor C_TwoBetween the input side of the
Capacitor C_Three, Resistance R _Two, R_ThreeSeries circuit is connected,
Capacitor C between output side and ground GND_Four, Resistance R_Four, Possible
Variable resistance R_FiveConnected in series with a resistor R_Two, R_ThreeConnection
Point and resistance R_Four, Variable resistor R_FiveFrom the connection point
Detection terminal VL₁, VL_TwoIs taken out and the difference is detected by voltage
Capacitor C_TwoLighting control of Fig. 1
Input to the circuit 8.

The switching transistors Q ₂ and Q ₄
With the other end is connected to the ground GND via a resistor R _7, resistance through R ₆ are connected to the current detection terminal IDC, the resistor R _6, R ₇ denotes a current detection terminal IDC and ground G
With capacitor C ₅ interposed between the ND constituting the lamp current detection circuit 7 in FIG. 1. IP is a lamp instantaneous current terminal extracted from the input side of the lamp current detection circuit.

Now, clocks E ₁ and E ₂ having an oscillation frequency of about ₂ KHz which invert the phase with each other are applied to the primary winding of the drive transformer DT. For example, when the switching transistors Q ₁ and Q ₄ are simultaneously turned on, the external circuit 11 The current in the direction (a) flows through the resonance circuit of (1), and the switching transistors Q ₂ and Q ₃ are simultaneously turned on when the next clock signal is inverted.
When N, a current in the direction (b) flows through the resonance circuit of the external circuit 11. At this time, a high-frequency resonance voltage is superimposed on a low-frequency voltage of about 2 KHz, and this voltage is detected by the voltage detection capacitor C ₂ , and the oscillation frequency of the inverter circuit 2 changes, for example, at a high frequency of about 100 KHz. A high resonance voltage is generated in the capacitor 4 to start the discharge lamp 5, and a large amount of current flows through the discharge lamp. Therefore, the potential difference between the voltage detection terminals VL ₁ and VL ₂ sharply decreases, and thereby the start of the discharge lamp is detected.

The secondary winding of the drive transformer DT
Diode D provided for each _Three, D_Four, D_Five, D₆You
And resistance R₁₃, R_Fifteen, R₁₇, R₁₉Is a switching diode
Code Q₁And Q_TwoAnd Q_ThreeAnd Q_FourAre turned on at the same time
This is to add a time delay when reversing to avoid
You.

In this embodiment, the configuration of the bridge inverter is shown, but the switching transistors Q ₃ and Q ₄
A half-bridge inverter having a configuration in which is replaced by a capacitor operates in the same manner.

FIG. 4 is a circuit diagram showing a specific configuration example of the lighting control circuit 8. In FIG. 4, reference numeral 13 denotes a DC voltage detection circuit having an input terminal connected to the voltage detection terminals VL ₁ and VL ₂ of the lamp voltage detection circuit 7, which is constituted by a differential amplifier and a rectifier, and has voltage detection terminals VL ₁ and VL _2. Detect the potential difference between
A voltage corresponding to the high-frequency resonance voltage detected by the lamp voltage detection circuit 7 is output to the output terminal.

Reference numeral 14 denotes a lamp lighting detection circuit. A voltage V _C10 generated at a capacitor C ₁₀ at an output terminal of the DC voltage detection circuit 13 is input to a positive input terminal, and resistors R ₂₁ and R ₂₂ are input to a _negative input terminal.
COM to which a reference voltage obtained from the comparator is input
P1 and an inverter IN1 for inverting the output of the comparator COMP1. When the DC power is turned on, the inverter circuit 2 in FIG. 1 oscillates at a low frequency. When the voltage is superimposed and the voltage V _C10 detected by the DC voltage detection circuit 13 becomes higher than the reference voltage of the lamp lighting detection circuit 14, the output of the comparator COMP1 becomes high level, and the output of the inverter IN1 becomes low level. Become. Next, when the oscillation frequency of the inverter circuit 2 changes and a high resonance voltage is generated, and the discharge lamp 5 starts, the detection voltage of the lamp voltage detection circuit 6 decreases as described above, the output of the comparator COMP1 becomes low level, The output of IN1 becomes high level.

[0043] 15 in the sawtooth wave generating circuit, are added the output voltage via a resistor R _23, a first bias voltage and the resistors R ₂₅ of the bias circuit 16 of the variable resistor R _24, R _26, first The signal is input to the + input terminal of the operational amplifier OP2 of the first constant current circuit 18 through the first cutoff circuit 17. The sawtooth wave generating circuit 15 may be a triangular wave generating circuit. The first cutoff circuit 17 comprises a first transistor Q ₁₁ which is interposed between the + input terminal and the grounding of the operational amplifier OP2 of the constant current circuit 18, its gate the output terminal of the inverter IN1 in the lamp lighting detection circuit 14 is connected to the transistor Q ₁₁ output is at a high level of the inverter IN1 is O
N, the output of the sawtooth wave generating circuit 15 is cut off.
The first constant current circuit 18 has a resistor R ₂₈ connected to the RT terminal of the switching regulator control IC 19, a transistor Q ₁₂ connected in parallel to a bias current circuit 20 composed of a series circuit of a variable resistor R ₂₉ , and a resistor R ₃₀ . having a series circuit, the gate of the transistor Q ₁₂ is an operational amplifier OP2
Is connected to the output terminal, a connection point of the transistors Q ₁₂ and the resistor R ₃₀ is the operational amplifier OP2 - is connected to the input terminal.

Therefore, when the DC power is turned on and the output of the inverter IN1 of the lamp lighting detection circuit 14 is at a high level, the first cutoff circuit 17 operates to output the output of the sawtooth wave generation circuit 15. blocked, the transistor Q ₁₂ of the first constant current circuit 18 is OFF, the current flowing through the R _T terminal of the switching regulator control IC19 is only the current ia flowing through the bias current circuit 20, the current ia and the switching regulator control IC19 Capacitor C connected to _CT terminal
Determined by _12, for example, the clock E _1, E ₂ to each other phase of the low frequency of the order of 2KHz is inverted is output from the switching regulator control IC 19, is applied to the drive circuit 12 of FIG. 3. The choke coil 3 and the capacitor 4
Resonance voltage of higher frequency by a resonance circuit of the superposition, detects the voltage at the voltage detection capacitor C _3, the output voltage V _C10 lamp lighting detection circuit 1 of the DC voltage detecting circuit 13
4 is higher than the reference voltage, the lamp lighting detection circuit 14
The output of a low level, the transistor Q ₁₁ of the first cutoff circuit 17 outputs the sawtooth wave generating circuit 15 becomes OFF is inputted to the operational amplifier OP2 of the first constant current circuit 18, transistor Q ₁₂ is rendered conductive to pull current from the R _T terminal of the switching regulator control IC 19, to increase the absorption current ib to a voltage generated in the resistor R ₃₀ is equal to the sawtooth voltage input, balanced.

As a result, a current of ia + ib flows through the _RT terminal, and the frequency of the clocks E ₁ and E ₂ is set to, for example, 100K.
Hz, to generate a high resonance voltage in the resonance circuit,
Thus, the discharge lamp 5 is started. At this time, the sawtooth wave generating means 15 changes the oscillation frequency of the inverter circuit at a frequency within a predetermined range including a resonance frequency determined by the choke coil and the resonance capacitor, so that the inductance of the choke coil and the capacitance of the resonance capacitor vary,
Even if it is deviated, a resonance voltage can always be generated by the sawtooth wave voltage generated from the sawtooth wave generation circuit 15, and the generation of the resonance voltage is short, so that a large current flows continuously for a long time. Therefore, the reliability of components can be improved, and the output voltage of the DC power supply can be prevented from lowering.

Reference numeral 21 denotes a lamp current calculation circuit connected to the output terminal of the DC voltage detection circuit 13. 22 is a resistor R ₃₁ ,
In the bias circuit composed of the variable resistor R _32, it generates a bias voltage as a reference for the rated current. Reference numeral 23 denotes a DC current detection circuit connected to the current detection terminal IDC of the lamp current detection circuit 7. These output voltages are respectively connected to resistors R ₃₃ and R ₃₃ .
₃₄ , R _35, and are input to the negative input terminal of the operational amplifier OP 3 of the comparison circuit 24. The comparison circuit 24 calculates the sum of the lamp current calculation circuit 21, the first bias circuit 22, and the DC current detection circuit 23. 0, that is, control is performed such that the added output voltage of the lamp current calculation circuit 21 and the first bias circuit 22 is used as a reference voltage, and the negative output voltage of the DC current detection circuit 23 is equal to this reference voltage. Done.

The output of the comparison circuit 24 is passed through a second cutoff circuit 25 to an operational amplifier OP4 of a second constant current circuit 26.
Is input to the + input terminal. The second cutoff circuit 25 comprises a first transistor Q ₁₃ which is interposed between the + input terminal and the grounding of the operational amplifier OP4 of the constant current circuit 26, the output terminal of the inverter IN1 in the lamp lighting detection circuit 14 is an inverter IN2 is connected to the gate of the transistor Q ₁₃ via a transistor Q ₁₃ output of the inverter IN1 is at a low level becomes oN, the output of the comparator circuit 24 is cut off. The second constant current circuit 26 includes a transistor Q ₁₄ connected in parallel to the bias current circuit 20 connected to the _RT terminal of the switching regulator control IC 19,
It has a series circuit of a resistor R _37, together with the gate of the transistor Q ₁₄ is connected to the output terminal of the operational amplifier OP4, a connection point of the transistors Q ₁₄ and the resistor R ₃₇ is an operational amplifier OP4
-Is connected to the input terminal.

The lamp current calculation circuit 21 has a circuit configuration as shown in FIG. 5, for example. The voltage V _C10 generated at the capacitor C ₁₀ at the output terminal of the DC voltage detection circuit 13 is supplied from the resistor R ₄₁ and the variable resistor R _42. It is added to the obtained bias voltage and inverted and amplified by the operational amplifier OP5. This allows
The capacitor C ₁₁ at the output end of the lamp current calculation circuit 21
Is generated between the voltage V _C11 generated in the DC voltage detection circuit 13 and the output voltage V _C10 of the DC voltage detection circuit 13 as shown in FIG.

In FIG. 6, a predetermined lamp voltage or less, that is, a predetermined output voltage V _C10 ″ of the DC voltage detection circuit 13 is used.
In the following, the output voltage V _C11 of the lamp current calculation circuit 21 is clipped to be constant by the saturation voltage of the operational amplifier OP5, and the oscillation frequency of the switching regulator control IC 19 is fixed below a predetermined lamp voltage V _C10 ″. In order to prevent an excessive current from flowing into the discharge lamp and to prevent the discharge lamp from being damaged, when the output voltage is higher than a predetermined output voltage V _C10 ″ and lower than V _C10 ′, V _C11 decreases as the lamp voltage increases, and V _C10 ′ or higher. Therefore, the reference voltage of the comparison circuit 24 is only the bias voltage of the first bias circuit 22. Instead of clipping the high portion of the output voltage V _C11 of the lamp current calculation circuit 21 with the saturation voltage of the operational amplifier OP5, a clip may be performed by connecting a zener diode to the output terminal. Further, a circuit for providing a lower limit value so that the output voltage of the DC voltage detection circuit 13 does not become lower than a predetermined voltage may be added.

As described above, the clock E₁, E_TwoFrequency
To generate a high resonance voltage of the resonance circuit,
When the step 5 is started, the output voltage V of the DC voltage detection circuit 13
_C10Decreases, and the output voltage V of the lamp current calculation circuit 21_C11
Gets bigger and starts. At this time, the lamp current reference
Output voltage of the circuit 21 and the first bias circuit 22.
The reference voltage increases and the output voltage of the DC current detection circuit 23 increases.
Is large, and the output of the comparison circuit 24 becomes negative.
At the same time, the output of the lamp lighting detection circuit 14 becomes high level.
As a result, the transistor Q
₁₁Is turned on to cut off the output of the sawtooth wave generation circuit 15,
The transistor Q of the constant current circuit 18 of FIG. ₁₂To OFF
Stopping the suction operation of the flow and a second shutoff circuit
25 transistors Q₁₃Becomes OFF, and the comparison circuit 2
4 is connected to the second constant current circuit 2
6 is input to the operational amplifier OP4, and the operational amplifier OP
The output of transistor Q₁₄Remains OFF
Therefore, the switching regulator control I
Clock E of C19₁, E_TwoFrequency is about 2KHz
Frequency.

Accordingly, the lamp current increases and the output voltage of the DC current detection circuit 23 increases, and at the same time, the output voltage V _C10 of the DC voltage detection circuit increases, and the output voltage V _C11 of the lamp current calculation circuit 21 decreases accordingly. As a result, the output of the operational amplifier OP3 of the comparison circuit 24 changes from negative to 0 and further positive. At this time, the transistor of the second constant current circuit 26 conducts and current is drawn from the _RT end of the switching regulator control IC 19. , The clocks E ₁ and E _{2 of the} switching regulator control IC 19
To increase the oscillation. Therefore, the output voltage V _{C10 of} the lamp voltage DC voltage detection circuit 13 increases and the output voltage V _C11 of the lamp current calculation circuit 21 decreases, and at the same time, the output voltage of the lamp current DC current detection circuit 23 decreases. increasing the current sink by the transistor Q ₁₄ of the second constant current circuit 26, further the output of the operational amplifier OP3 that is input to the + input terminal of the operational amplifier OP4 - equal the feedback voltage by the resistor R ₃₇ is input to the input terminal By adding such operations, the oscillation frequencies of the clocks E ₁ and E ₂ are further increased.

This control is based on the output of the lamp current calculation circuit 21.
Voltage V_C11Is repeated until the value becomes 0, and finally DC
The output voltage of the current detection circuit 23 is
Becomes stable when the output voltage becomes equal to
2 transistor Q of the constant current circuit 26₁₄Suction current
and the sink current ia by the bias current circuit 20.
Determined by ia + ic of the sum of
Clock E at vibration frequency ₁, E_TwoOscillates and is set when stable lighting
Lights with the rated lamp power.

FIG. 7 shows a lamp voltage (V) -lamp current (I) characteristic diagram. In FIG. 7, a large lamp current flows to flow a large DC current at a predetermined lamp voltage V 'or lower which is a starting region of the lamp, and a constant current flows at a predetermined lamp voltage V' or higher which is a stable lighting region of the lamp. Is controlled as follows. Therefore, the lamp current can be reliably controlled, a large lamp current can be supplied at the time of starting, and the lamp can be stably lit quickly. At the time of stable lighting, the lamp power can be made substantially constant and the lamp can be lit at the rated lamp power.

As described above, in the above process, the lighting control circuit 8 receives the detection voltage of the lamp voltage detection circuit 6 and, when the lamp voltage is low, lowers the frequency of the clocks E ₁ and E ₂ to increase the lamp current. When the lamp voltage is high, control is performed such that the frequency of the clocks E ₁ and E ₂ is increased to flow a small lamp current.

Reference numeral 27 denotes a start-up voltage timer circuit connected to the output terminal of the lamp lighting detection circuit 14. When a DC power supply is turned on, the inverter circuit oscillates at a low frequency. The voltage is superimposed, and the resonance voltage is detected by the DC voltage detection circuit 13,
When the detected voltage V _C10 becomes higher than the reference voltage of the lamp lighting detection circuit 14, the output of the inverter IN1 becomes low level and starts to be started. At this time, the starting voltage timer circuit 27 sets the low level of the inverter IN1. If the inverter IN1 does not go to the high level within a predetermined time, for example, one second, that is, if the discharge lamp is started and turned on within the predetermined time and does not start, the switching regulator control IC 19 starts oscillating the inverter circuit. Stopping, preventing a high voltage from being generated for a long time and being applied to the discharge lamp, preventing breakage of the discharge lamp and ensuring safety.

Reference numeral 28 denotes a starting current timer circuit connected to the output terminal of the lamp current calculation circuit 21 for detecting that the lamp current is larger than a predetermined value, that is, the lamp voltage is smaller than the predetermined value. Current calculation circuit 2
1 operates by detecting that the output voltage V _C11 is higher than a predetermined value, and when the output voltage V _C11 does not become lower than the predetermined value within a predetermined time, that is, within 20 seconds, the switching regulator control IC 19 turns on the inverter circuit. Oscillation is stopped to prevent the starting current from flowing to the discharge lamp for a long time, thereby preventing the discharge lamp from being damaged. Note that the starting current timer circuit 28 may be connected so as to operate with the output voltage V _C10 of the DC voltage detection circuit 13. In this case, when the voltage V _C10 does not exceed a predetermined value within a predetermined time, the starting current timer circuit 28 is _activated . Stop oscillation.

FIG. 8 is a circuit diagram showing another example of the lamp current calculation circuit 21. When a lamp voltage becomes equal to or higher than a predetermined voltage by adding a time constant switching circuit, the lamp current calculation circuit 21 is turned off. The time constant is switched so as to increase the constant. In FIG. 8, a lamp current calculation circuit 2
1 of the output end is terminated by a series circuit of a resistor R ₅₁ and capacitor C _11, the time constant switching circuit 36 is interposed between the output terminals of the lamp current calculation circuit 21 of the DC voltage detecting circuit 13 ing. That is, the time constant switching circuit 36 is a comparator COMP2, having a transistor Q _31, the comparator COMP2 - the output end of the input DC voltage detecting circuit 13, + series for input bias resistor R _53, R ₅₄ Connected to the reference point of the circuit
The output terminal of MP2 is connected to the base of the transistor Q _31, and is connected to the resistor R ₅₁ of the output terminal of the transistor Q resistor R ₅₂ connected in series with the ₃₁ lamp current calculation circuit 21. Resistor R ₅₁ and R ₅₂ connection point through the same resistor R ₃₃ and 4 of the operational amplifier OP3 of the comparator circuit 24 - is connected to the input terminal.

When the output voltage V _C10 of the DC voltage detection circuit 13 is equal to or lower than the reference point of the series circuit for biasing the resistors R ₅₃ and R ₅₄ , the output of the comparator COMP 2 goes high, the transistor Q ₃₁ is turned on, and the resistance R ₅₂ is connected to ground. Therefore, after the discharge lamp is started and the output voltage V _C10 of the DC voltage detection circuit 13 decreases, below the reference point of the bias series circuit, the time constant of the decrease of the lamp current shown in FIG. When the voltage changes to a small resistance _R52 with a smaller time constant and the voltage V _C10 exceeds the reference point,
Transistor Q ₃₁ output of the comparator COMP2 is at the low level is OFF, resistor R ₅₂ is opened. Therefore, the time constant is switched by the resistors R ₅₁ and R ₃₃ so as to increase the time constant of the decrease in the lamp current as shown by the broken line in FIG. I do. As described above, when the lamp voltage becomes equal to or higher than the predetermined voltage, by increasing the time constant, the light output after the start is set to the rated output, and then it is possible to shift to stable lighting without a large change.

FIG. 9 shows a case where an excessive lamp current is generated.
An example of a lamp current instantaneous value detection circuit 37 as a protection circuit is shown in FIG.
FIG. 4 is a circuit diagram showing an example in which the instantaneous current exceeds a predetermined voltage,
Invert or temporarily stop the oscillation of the barter circuit, and
This prevents the current from flowing continuously. FIG.
, IP is the lamp instantaneous power to which the lamp current is input.
Flow terminal (corresponding to IP in FIG. 3) and a resistor R₆₁Through
Connected to the + input terminal of comparator COMP3,
The resistor R is connected to the-input terminal of the₆₂, R ₆₃Series
Connected to the bias point of the bias circuit
You. Or a diode at the output of comparator COMP3.
Code D₁₂Are connected in the forward direction, and this diode D₁₂No
Node is resistor R₆₄Is connected to the power supply Vcc through
Mode is switching regulator control IC19
C_TCapacitor C connected to the end₁₂Connected to
You.

Now, when an excessive current flows through the discharge lamp and becomes larger than the bias voltage of the bias circuit, the output of the comparator COMP3 becomes high level and the capacitor C
₁₂ is rapidly charged by the power supply voltage, and the clocks E ₁ and E ₂
Rapidly reverses, and during the period in which an excessive current is generated, the excessive current is rapidly cut off by this inversion. The clock may be temporarily stopped instead of rapidly inverting the clock.

FIG. 10 is a main part circuit diagram showing another embodiment of the discharge lamp lighting device of the present invention. 41 is a lamp current calculation circuit connected to the output terminal of the DC voltage detecting circuit 13, the voltage divided output voltage V _C10 at the resistor R _81, R ₈₂ of the DC voltage detecting circuit 13 to the positive input terminal of the operational amplifier OP8 is input, the operational amplifier OP8 - to the input terminal negative bias voltage obtained by the variable resistor R ₈₃ is input.
The output of the operational amplifier OP8 is input via the resistor R ₈₄ to the positive input terminal of the operational amplifier OP9 of the constant current circuit 42. The transistor Q ₄₁ for current sink of the constant current circuit 42 is connected to the _RT end of the switching regulator control IC 19.
Only a series circuit of a resistor R ₈₆ is connected, an operational amplifier OP
The output of the 9 is input to the gate of the transistor Q _41, the operational amplifier OP9 - to an input terminal voltage generated across the resistor R ₈₆ is input.

[0062] Now, the operational amplifier OP8 the lamp current arithmetic circuit 41 when V _C10 is 0 outputs a voltage corresponding to the bias voltage of the variable resistor R _83, the transistor Q ₄₁ of the constant current circuit 42 is rendered conductive to a predetermined current And the switching regulator control IC 19 oscillates at a low frequency. After the discharge lamp is started, when the lamp voltage increases, the output of the operational amplifier OP8 increases accordingly,
The sink current of the constant current circuit 42 is increased to increase the oscillation frequency and reduce the lamp current. When the lamp voltage decreases, the current drawn by the constant current circuit 42 decreases, the oscillation frequency decreases, and the lamp current increases. As a result, the lamp is controlled so as to have a predetermined frequency that uniquely corresponds to the lamp voltage and thus the lamp current. As a result, the lamp current is set to a predetermined value and the lamp is controlled to be lit at a stable rated lamp power.

As can be seen, the present embodiment is different from the embodiment of FIG.
3. The second bias circuit 22 and the comparison circuit 24 can be omitted. FIG. 11 is a circuit diagram showing another embodiment of the lighting control circuit shown in FIG. 11 differs from FIG. 4 in that the initial lamp current is set so that a predetermined lamp current larger than at least the lamp current at the time of stable lighting is supplied to the output terminal of the lamp current calculation circuit 21 immediately after the start and restart. That is, a voltage setting circuit 43 as an initial current setting means is provided. The voltage setting circuit 43 includes an inverter circuit IN3 whose input is connected to the lamp lighting detection circuit 14,
A transistor Q ₅₀ which is operated by the output of the inverter circuit IN3, a diode D ₁₃ Metropolitan to one end in the forward direction to the collector of the transistor Q ₅₀ is connected, a series circuit of a transistor Q ₅₀ and diode D ₁₃ is the lamp current a capacitor C ₁₁ connected to the output of the arithmetic circuit 21 are connected in parallel.

The operation of voltage setting circuit 43 will be described below. The description of the same circuit portion as the circuit of FIG. 4 is omitted. When the power is turned on and a voltage is applied to the lamp, the voltage is initially low, so the lamp current calculation circuit 2
1 outputs a large output voltage from the characteristic shown in FIG. 7, a voltage is generated in the capacitor C _11. Next, when the voltage applied to the lamp further increases, the lamp lighting detection circuit 14 operates and the output becomes low level, and the lighting control circuit operates to start the lamp. At this time, receiving the output of the lamp lighting detection circuit 14, an inverter circuit IN3 of the voltage setting circuit 43 to turn on the transistor Q _50. Therefore, the charge of the capacitor C ₁₁ is discharged through the diode D _13, transistors Q _50, its voltage diode D
₁₃ and the forward voltage of the transistor Q ₅₀ becomes a value obtained by adding.

[0065] After being clipped to a predetermined voltage when starting this manner, when lit, the output of the lamp lighting detection circuit 14 becomes high level, the transistor Q ₅₀ is turned off. Since the voltage of the capacitor C ₁₁ when the lamp voltage after lighting is low, the higher the output of the lamp current arithmetic circuit 21 becomes its voltage, the capacitor output is at the start of the lamp current calculation circuit 21 when the lamp voltage is high If less than the value of C ₁₁ is maintained at a value at startup. Based on the value at the time of starting, control can be performed so that the lamp current at the time of restart is increased as compared with the lamp current at the time of stable lighting of the lamp. For this reason,
Even if the lamp voltage is high after restarting, increase the lamp current, and when the lamp is turned off, the enclosed metal adheres to the lamp tube wall,
Even if the vapor pressure of the encapsulated metal is low, a light output close to the time of stable lighting can be obtained immediately after restart.

FIG. 12 is a circuit diagram showing another embodiment of the voltage setting circuit shown in FIG. In FIG.
What is different from 1 is that at the output end of the lamp current calculation circuit 21, an extinguishing time detecting circuit 44 which is an extinguishing time detecting means for detecting an extinguishing time of the lamp, and immediately after starting and restarting according to the output of the extinguishing time detection circuit 44 A voltage setting circuit 45, which is a starting initial current setting means for setting an initial lamp current so as to allow a predetermined lamp current larger than a lamp current at the time of stable lighting to flow. The configuration is such that the initial lamp current is set larger. The extinction time detection circuit 44 has a buffer circuit BU1 whose input is connected to the lamp-on detection circuit 14.
When a capacitor C ₅₀ which is connected via a diode D ₁₄ to the output of the buffer circuit BU1, and a resistor R ₉₀ Metropolitan connected in parallel with the capacitor C _50. The voltage setting circuit 45 includes an inverting circuit OP10 connected to the output of the light-off time detecting circuit 44, and a clipping circuit OP11 that receives the output of the inverting circuit OP10 and limits the output terminal to the voltage. It is connected so as to limit the voltage of the capacitor C ₁₁ connected to the output of the lamp current arithmetic circuit 21.

The operation of the light-off time detection circuit 44 and the voltage setting circuit 45 will be described below. The description of the same circuit portion as the circuit of FIG. 11 is omitted. The power supply is turned on and the voltage to the lamp is applied, initially the lamp current calculation circuit 21 because it is low voltage outputs a large output voltage from the characteristic shown in FIG. 7, a voltage is generated in the capacitor C _11. Next, when the voltage applied to the lamp further increases, the lamp lighting detection circuit 14 operates and the output becomes low level, and the lighting control circuit operates to start the lamp. At this time, receiving the output of the lamp lighting detection circuit 14, lamp lighting buffer circuit in BU1, but the capacitor C ₅₀ through the diode D ₁₄ is charged, its voltage by turning off the time for the resistance R ₉₀ It decreases with. The voltage of the capacitor C ₅₀ to the inverting amplifier by the inversion circuit OP10. Here, the output of the inverting circuit OP10 is set to a positive value when the light-off time is 0, and a negative bias voltage −V _{B1 is} applied to the input terminal so as to increase as the light-off time elapses.
Is entered. Thus, the clip circuit OP11 receives the output of the inversion circuit OP10, and a positive value at the time of the extinguishing time 0 the output of the capacitor C _11, clipped to increase with the passage of the extinguishing time.

[0068] Thus, since the direction of time longer than when the extinguishing time is short increases the voltage of the capacitor C _11,
The initial lamp current can be set larger when the turn-off time is longer than when the turn-off time is short, and when the turn-off time is short, the luminous efficiency does not decrease because the vapor pressure of the encapsulated metal does not decrease. In such cases, the lamp current does not flow so much at restart because the extent to which the gas adheres to the tube wall is low. In this case, a large lamp current can be supplied at the time of restart, and a light output close to that of stable lighting can be obtained immediately after restart.

FIG. 13 is a circuit diagram showing another embodiment of the lighting control circuit shown in FIG. Figure 8 differs from the 13, the time constant switching resistance for switching voltage setting in circuit 36 R _53, instead minimum lamp voltage detected to vary the switching voltage in response to the minimum lamp voltage after starting of R ₅₄ The circuit 46 and the switching voltage setting circuit 47 are provided. The minimum lamp voltage detecting circuit 46 includes an inverting circuit OP12 connected to the DC voltage detecting circuit 13 whose input outputs a voltage corresponding to the lamp voltage, and an inverting circuit OP1.
2 connected via a diode to the output of
_{51 The} transistor Q ₅₁ which is connected and operates via the inverter circuit IN 14 upon receiving the output of the lamp lighting detection circuit 14
Consists of a, the transistor Q ₅₁ is connected in parallel to discharge the capacitor C _51. The switching voltage setting circuit 47 is made up inverting circuit OP13 for inverting the voltage of the capacitor C ₅₁ of the minimum lamp voltage detecting circuit 46,
The output is the comparator COMP2 of the time constant switching circuit 36.
Is connected to the non-inverting side.

Hereinafter, the operation of the voltage setting circuit will be described. Note that the description of the same circuit portion as the circuit in FIG. 8 is omitted. The lowest lamp voltage detection circuit 46 inputs a voltage corresponding to the lamp voltage and inverts and amplifies the voltage by the inverting circuit OP12. Here, a negative bias voltage − is applied to the input terminal so that the lower the minimum ramp voltage is, the higher the positive voltage becomes.
V _B2 is being input. Inputting the output of the inversion circuit OP12 to the capacitor C ₅₁ through the diode. Therefore, the voltage of the capacitor C ₅₁ lower the minimum lamp voltage becomes higher. Lamp of the transistor Q ₅₁ is turned on by the inverter circuit IN4 at startup, the capacitor C
_Since the electric charge of the capacitor ₅₁ is discharged, the voltage of the capacitor C51 has a value corresponding to the minimum lamp voltage after the start. This voltage is input to the inverting circuit OP13 and inverted and amplified. Here, the negative bias voltage −V _B3 is input to the input terminal so that the higher the input voltage, the lower the positive voltage. Therefore, the output voltage of the inverting circuit OP13 decreases as the minimum lamp voltage decreases. As a result, the lower the minimum lamp voltage is, the more the time constant can be switched at a lower lamp voltage. By switching to a longer time constant, the speed of decreasing the lamp current can be reduced, and more power can be input. Therefore, the rising of the light output of the lamp having the lowest minimum lamp voltage can be made faster, and a substantially constant rising of the light output can be obtained irrespective of the variation of the lamp.

FIG. 14 is a circuit diagram showing another embodiment of the lighting control circuit shown in FIG. In FIG. 14, FIG.
3 differs from the resistors R _53, R ₅₄ for switching voltage setting at the time constant switching circuit 36 is set to be used in the same manner as FIG. 8, instead of changing the switching voltage in response to the minimum lamp voltage after starting And a time constant control circuit 48 operated by the output of the minimum lamp voltage detection circuit 46 so as to change the control time constant. Time constant control circuit 4
8, an inverting circuit OP13 for inverting the voltage of the capacitor C ₅₁ of the minimum lamp voltage detecting circuit 46, inversion circuit OP13
, A constant current circuit OP14 Metropolitan inhale current corresponding to the voltage in response to an output of the output transistor Q ₅₂
Is connected to the output of the lamp current calculation circuit 21 through

Hereinafter, the operation of the time constant control circuit 48 will be described. The description of the same circuit portions as the circuits in FIGS. 8 and 13 will be omitted. As the voltage of the capacitor C ₅₁ of the minimum lamp voltage detecting circuit 46 is lower the minimum lamp voltage becomes higher. Inverter circuit IN when starting the lamp
Transistor Q ₅₁ is turned on by 4, the capacitor C ₅₁ is turned on, the charge of the capacitor C ₅₁ is discharged, the voltage of the capacitor C ₅₁ becomes a value corresponding to the minimum lamp voltage after starting. This voltage is supplied to the inverting circuit OP1 of the time constant control circuit 48.
3 and inverting amplification. Here, the negative bias voltage −V _B3 is input to the input terminal so that the higher the input voltage, the lower the positive voltage. Therefore, the inverting circuit OP
13, the lower the minimum lamp voltage, the lower the
Lower. Thus, the lower the minimum lamp voltage, sink current of the transistor Q ₅₂ of the constant current circuit OP14 is reduced, the voltage drop of the order capacitor C ₁₁ becomes slow. That is, the control time constant becomes longer.

As described above, the control time constant of the lamp current can be changed. By changing the long time constant, the rate of decrease of the lamp current can be reduced, and more power can be input. Therefore, the rising of the light output of the lamp having the lowest minimum lamp voltage can be made faster, and a substantially constant rising of the light output can be obtained irrespective of the variation of the lamp.

FIG. 15 is a circuit diagram showing another embodiment of the lighting control circuit shown in FIG. In FIG.
4 is different from the maximum lamp current time setting which operates by the output of the minimum lamp voltage detection circuit 46 so as not to change the control time constant according to the minimum lamp voltage after starting but to change the time for flowing the maximum lamp current. The circuit 49 is provided. Maximum lamp current setting circuit 49 includes a resistor R ₉₅ to discharge the voltage of the capacitor C ₅₁ of the minimum lamp voltage detecting circuit 46, and timer operation by comparing the output with a reference voltage of the capacitor C _51, a predetermined time, lamp current Arithmetic circuit 2
The comparator COMP4 operates to set the output of the lamp current 1 to a high level. The output of the comparator COMP4 is connected to the output of the lamp current calculation circuit 21 through a diode.

Hereinafter, the maximum lamp current time setting circuit 49
The operation will be described. 8, 13, and 14.
The description of the same circuit portion as the circuit is omitted. Lowest run
C of the voltage detection circuit 46₅₁Voltage is the lowest run
The lower the step voltage, the higher the voltage. When the lamp starts
The transistor Q by the inverter circuit IN4.₅₁Is on
And capacitor C₅₁Charge is discharged, so the capacitor
C₅₁Voltage is the value corresponding to the minimum lamp voltage after starting.
You. This voltage indicates the minimum lamp voltage and then the resistance R ₅₉Release
It is lowered by electricity. Comparator COMP4 uses this voltage
And the reference voltage, and the capacitor C₅₁Of the reference voltage
Output voltage until it drops to a value equal to
I do. This output voltage is used as the output of the lamp current calculation circuit 21.
Because it is connected, the capacitor C₁₁Voltage is high level
Becomes Therefore, the output of the comparator COMP4 becomes high.
During the level, the lighting control circuit increases the lamp current to the maximum lamp current.
Control to flow. At this time, the minimum lamp voltage is low.
The lower the capacitor C ₅₁Voltage is high,
The output of the comparator COMP4 remains high for a long time.
The maximum lamp current for a long time.

As described above, the time during which the maximum lamp current flows can be changed, and the lower the minimum lamp voltage, the longer the maximum lamp current can flow, and more power can be input. As a result, the rising of the light output of the lamp having the lowest minimum lamp voltage can be made faster, and a substantially constant rising of the light output can be obtained irrespective of the variation of the lamp.

Although the embodiment of the circuit has been described above, it is needless to say that the present invention is not limited to this, and any other circuit having the same function may be used. In the above embodiment, the lamp current was controlled by lowering the frequency when increasing the current and increasing the frequency when decreasing the current, but in series with the choke coil for limiting the current. It is needless to say that the frequency change direction is opposite when a capacitor is added to the phase shifter and used in the fast phase region.

Although the lamp current is controlled by the frequency in the above embodiment, it goes without saying that the duty ratio may be controlled. Although the inverter is a bridge inverter, other inverters such as a series inverter, a half-bridge inverter, a pushable inverter, and a single inverter may be used. Needless to say, the DC power supply includes a rectified AC power supply.

[0079]

As described above, according to the present invention, in the starting region of the discharge lamp, when the lamp voltage is low, the frequency of the inverter means is reduced to allow a large lamp current to flow, and when the lamp voltage is high, the inverter is operated. Since a small lamp current flows by increasing the frequency of the circuit, the lamp can be lit at the rated lamp power during stable lighting.

When the lamp voltage is equal to or lower than the first predetermined lamp voltage, a constant signal is output. When the lamp voltage is equal to or higher than the first predetermined lamp voltage, the output signal decreases as the lamp voltage increases. By providing a lamp current calculating means for setting the output signal to 0 when the voltage is higher than 0 and a bias means, and controlling the oscillation frequency of the inverter means by the added output, a large lamp current flows at the time of starting to quickly start the discharge lamp. It can be turned on, and at the same time, it can be turned on at the rated lamp power by passing a certain rated current.
When the lamp voltage is equal to or lower than the first predetermined lamp voltage, an excessive lamp current can be prevented from flowing due to a constant signal output from the lamp current calculation means.

If the time constant switching means is provided, the lamp current is switched by increasing the time constant of the decrease in the lamp current in the lamp current calculation means when the lamp voltage becomes equal to or higher than a predetermined voltage, thereby changing the lamp current. Since the rated lighting can be gradually changed by the large time constant, the lighting can be performed after the starting light output is set to the rated output, and the effect of shifting to the stable lighting without a large fluctuation can be obtained.

Further, if the initial lamp current is set so that a predetermined lamp current that is at least larger than the lamp current at the time of stable lighting is supplied immediately after the start / restart, the lamp voltage is particularly stable at the time of restart. Even when the lamp voltage is close to the above, a large lamp current can flow, and even if the encapsulating metal adheres to the lamp tube wall when the lamp is turned off, a light output close to the time of stable lighting can be obtained immediately after restart.

Further, if the initial lamp current is set so that at least a predetermined lamp current larger than the lamp current at the time of stable lighting is supplied immediately after starting and restarting according to the output of the light-off time detecting means, Light output close to the time of stable lighting can be obtained immediately after restart regardless of the magnitude of time.

Further, after starting and restarting the lamp according to the output of the minimum lamp voltage detecting means, a large lamp current or a large lamp current is supplied to the lamp having a low minimum lamp voltage for a longer time to input a large lamp power. Because the lamp power is not consumed in a lamp that has a particularly low lamp voltage after starting due to variations in the lamp during cold start when the lamp is cold, the lamp is not easily heated and the vapor pressure does not increase. Even if the light output rises poorly, even with such a lamp, the required lamp power can be input according to the minimum lamp voltage after starting and restarting, and the light output rise is almost constant regardless of lamp variations. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of a discharge lamp lighting device according to an embodiment of the present invention.

FIG. 2 is a front view showing a configuration example of a choke coil used in the discharge lamp lighting device of the present invention.

FIG. 3 is a circuit diagram showing a main part of an inverter circuit in the discharge lamp lighting device of the present invention.

FIG. 4 is a circuit diagram showing a configuration example of a lighting control circuit in the discharge lamp lighting device of the present invention.

FIG. 5 is a circuit diagram showing a specific configuration example of a lamp current calculation circuit in the lighting control circuit.

FIG. 6 is a characteristic diagram of the lamp current calculation circuit.

FIG. 7 is a lamp voltage-lamp current characteristic diagram of the lighting control circuit.

FIG. 8 is a circuit diagram showing another example of the lamp current calculation circuit in the lighting control circuit.

FIG. 9 is a circuit diagram showing a configuration example of a lamp current instantaneous value detection circuit in the lighting control circuit;

FIG. 10 is a main part circuit diagram showing another embodiment of the discharge lamp lighting device of the present invention.

FIG. 11 is a circuit diagram showing another embodiment of the lighting control circuit.

FIG. 12 is a circuit diagram showing another embodiment of the voltage setting circuit in the lighting control circuit.

FIG. 13 is a circuit diagram showing another embodiment of the lamp current calculation circuit in the lighting control circuit.

FIG. 14 is a circuit diagram showing still another embodiment of the lamp current calculation circuit in the lighting control circuit.

FIG. 15 is a circuit diagram showing still another embodiment of the lamp current calculation circuit in the lighting control circuit.

[Explanation of symbols]

 Reference Signs List 1 DC power supply 2 Inverter circuit 3 Choke coil 4 Resonant capacitor 5 Discharge lamp 6 Lamp voltage detection circuit 7 Lamp current detection circuit 8 Lighting control circuit 11 External circuit 12 Drive circuit 13 DC voltage detection circuit 14 Lamp lighting detection circuit 15 Sawtooth wave generation Circuit 16 First bias circuit 17 First cutoff circuit 18 First constant current circuit 19 Switching regulator control IC 20 Bias current circuit 21 Lamp current calculation circuit 22 Second bias circuit 23 DC current detection circuit 24 Comparison circuit 25 2 shut-off circuit 26 second constant current circuit 27 starting voltage timer circuit 28 starting current timer circuit 36 time constant switching circuit 37 lamp current instantaneous value detection circuit 41 lamp current calculation circuit 42 constant current circuit 43, 45 voltage setting circuit 44 light off Time detection circuit 46 Minimum lamp voltage setting circuit 47 Switching voltage setting circuit 48 Time constant control circuit 49 Maximum lamp current time setting circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiko Ito 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Atsushi Wake 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Takuyuki Kamiya 1006 Odoma Kadoma, Kadoma City Osaka Pref. 1006 Kadoma, Kadoma, Kadoma, Matsushita Electric Industrial Co., Ltd. (72) Inventor Masayoshi Kokuten 1006 Kadoma, Kadoma, Kadoma, Osaka Pref. F term in Matsushita Electric Industrial Co., Ltd. (reference) 3K072 AA13 AC01 AC11 BA03 BC01 CA01 CA05 CA16 CB02 DA00 DD04 DE02 DE04 DE06 EA06 EB07 GA01 GB01 GB18 GC04 GC05 HA05 HA06 HA10 HB02 HB03

Claims (13)

[Claims] 1. A DC power supply, inverter means driven and oscillated by the DC power supply, a discharge lamp connected to the inverter means, lamp voltage detection means for detecting a lamp voltage, and the lamp in a lamp starting area. The output voltage of the voltage detecting means is input, and the oscillation frequency or duty ratio of the inverter means is varied so that a large lamp current flows when the lamp voltage is low and a small lamp current flows when the lamp voltage is high. And a lighting control means for controlling the rated lighting of the discharge lamp. 2. The lighting control means outputs a constant signal when the lamp voltage is equal to or lower than a first predetermined lamp voltage, and decreases the output signal as the lamp voltage increases when the lamp voltage is higher than a first predetermined lamp voltage and lower than a second predetermined lamp voltage. And a lamp current calculating means for setting an output signal to 0 when the voltage is equal to or higher than a second predetermined lamp voltage; and a bias means. 2. The discharge lamp lighting device according to claim 1, wherein the lamp current is regulated so as to be constant by a constant output signal of the lamp current calculation means below the first predetermined lamp voltage. 3. The lighting control means has a DC current detecting means for detecting a lamp current, and a comparing means for comparing the output of the DC current detecting means with the added output of the lamp current calculating means and the bias means. 3. The discharge lamp lighting device according to claim 2, wherein the oscillation frequency or the duty ratio of the inverter means is controlled by the output of the comparing means. 4. The lighting control means includes time constant switching means connected to the lamp current calculating means and operating at a predetermined lamp voltage. When the lamp voltage becomes equal to or higher than a predetermined voltage, the lamp current calculating means controls the lamp current. 3. The discharge lamp lighting device according to claim 2, wherein the time constant is switched so as to increase the time constant of decrease with respect to. 5. The lighting control means has a bias current circuit which regulates the oscillation frequency of the inverter means, and when a lamp current suddenly flows, a constant current flowing in the bias current circuit causes the oscillation of the inverter means to oscillate. 2. The discharge lamp lighting device according to claim 1, wherein the frequency is not lower than a predetermined frequency. 6. The lighting control means includes a lamp current instantaneous value detecting means for comparing an instantaneous lamp current value with a reference value and outputting when the lamp current instantaneous value exceeds the reference value. 2. The discharge lamp lighting device according to claim 1, wherein the oscillation of the inverter is inverted or temporarily stopped by an output signal of the value detector. 7. The lighting control means operates when the lamp voltage is smaller than a predetermined value in a starting region of the discharge lamp, and stops the oscillation of the inverter means when the lamp voltage does not exceed the predetermined value within a predetermined time. 2. The discharge lamp lighting device according to claim 1, further comprising a starting voltage timer means. 8. The lighting control means includes a starting initial current setting means for setting an initial lamp current such that a predetermined lamp current which is at least larger than a lamp current at the time of stable lighting immediately flows immediately after starting and restarting. 2. The discharge lamp lighting device according to 1. 9. The lighting control means includes: a light-off time detecting means for detecting a light-off time of a lamp; and a predetermined large power supply at least immediately after starting and restarting, in response to an output of the light-off time detecting means. 2. A starting initial current setting means for setting an initial lamp current so as to allow the lamp current to flow, wherein the initial lamp current is set to be larger when the turn-off time is longer than when the turn-off time is shorter. Discharge lamp lighting device. 10. The lighting control means includes: a minimum lamp voltage detecting means for detecting a voltage when the lamp voltage becomes the lowest after starting and restarting; and a lamp starting and stopping means in response to an output of the minimum lamp voltage detecting means. 2. The discharge lamp lighting device according to claim 1, further comprising control means for controlling a lamp having a lower minimum lamp voltage to input a larger lamp power by inputting a larger lamp current or a larger lamp current for a longer time after the restart. 11. The lighting control means includes means for changing a control time constant of a lamp current in accordance with an output of the minimum lamp voltage detection means to change a lamp voltage set value, and the lower the minimum lamp voltage, the lower the lamp voltage. The discharge lamp lighting device according to claim 10, wherein the discharge lamp lighting device is configured to switch to a long control time constant. 12. The lighting control means includes means for changing a control time constant of a lamp current in accordance with an output of the minimum lamp voltage detection means, and is configured to have a longer control time constant as the minimum lamp voltage is lower. The discharge lamp lighting device according to claim 10. 13. The lighting control means includes means for controlling the time during which the maximum lamp current flows according to the output of the minimum lamp voltage detection means, and controls the time during which the maximum lamp current flows as the minimum lamp voltage decreases. The discharge lamp lighting device according to claim 10, wherein the discharge lamp lighting device is configured to perform the operation.