JP2603661B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device for lighting a discharge lamp using an inverter circuit whose oscillation frequency is variable.

(Background Art) FIG. 5 is a circuit diagram showing a basic configuration of a discharge lamp lighting device using an inverter circuit. A series circuit of switching elements Q ₁ and Q ₂ is connected to both ends of the DC power supply E. Diodes D ₁ and D ₂ are connected in anti-parallel to switching elements Q ₁ and Q ₂ , respectively. At both ends of the switching element Q _2, the load circuit is connected. The load circuit, inductive capacitor C ₂ for preheating the non-power supply side, the power supply side and the capacitor C ₁ in each series circuit of the parallel-connected discharge lamp l and inductance L are connected to, the load circuit is generally It is designed to exhibit sexual reactance. Capacitor
C ₁ , C ₂ and inductance L are the resonance frequency f ₀ = 1 / 2π ｛L
An LC resonance circuit having (C ₁ + C ₂ )｝ ^{1 ] 2} is formed, and a high voltage is generated at both ends of the discharge lamp 1 using the resonance circuit.
The discharge lamp 1 is started and lit. The oscillation frequency of the inverter circuit is determined by the control circuit 8, and the drive circuits 1 and 2 drive the switching elements Q ₁ and Q ₂ on and off according to the control signal generated by the control circuit 8.

2. Description of the Related Art Conventionally, when a discharge lamp is turned on, a method of applying a high voltage and then turning on the filament after sufficiently heating the bipolar filament has been widely used because the life of the discharge lamp is extended. In the conventional example, as shown in FIG. 6 (a), during the preheating time t ₁ is oscillating the inverter circuit lowered below the lighting voltage across the voltage V _C2 of the capacitor C ₂ at the frequency f ₁ Te sufficiently preheated filament of the lamp l release, after a preheating time t ₁ is to oscillate the inverter circuit at the frequency f _2, and higher than the operating voltage of the voltage across V _C2 of the capacitor C _2, the discharge lamp 1 is started.

Figure 6 (b) shows the current I _C2 flowing through the capacitor C _2, the (c) shows the current Il flowing through the discharge lamp l. FIG (d) shows a current waveform flowing through the switching element in the preheating time t _1, FIG. (E) is flowing through the switching element at the time t ₂ to the discharge lamp l is lit by applying a high voltage 4 shows a current waveform. FIG. 3F shows a current waveform flowing through the switching element after the discharge lamp 1 is turned on. FIG.
The relationship between the voltage V _C2 generated at both ends of the capacitor C ₂ and the oscillation frequency f is shown.

As shown in FIG. 6 (a), and after elapse of the preheating time t _1, changing the lighting frequency f ₂ the oscillation frequency f from the preheating frequency f _1. In this case in order to generate a high voltage to the capacitor C _2, an inductance L and a capacitor, the oscillation frequency f ₂
It is often set lower than the natural vibration frequency f ₀ of C ₁ and C ₂ . In addition, in order to obtain a predetermined discharge lamp current at the time of lighting, f ₂ <f ₀ is almost always satisfied. In this case, during a period from switching the frequency to the discharge lamp l is lit, the shorter the time t ₂ the case, the leading phase current as shown in FIG. (E) flows through the switching element, the simultaneous ON state Surge current flows. In particular, when the power supply voltage E is low, the effective value of the current is large, the surge current is also large, and the ASO region (safe operation region) of the switching element is used.
There is a problem that exceeds.

Also, in this conventional example, in the state where the discharge lamp l is disconnected, the capacitor C ₂ of the non-power supply side is disconnected from the resonance system, the resonance frequency _{f 0 '= 1 / 2π (} LC 1) 1] 2 Changes to In order to obtain a sufficient preheating current, the preheat capacitor C ₂ has a value that can not be neglected as compared with the capacitor C _1, the resonance frequency when the resonance frequency f ₀ of the no-load 'is the discharge lamp l is connected f considerably higher than _0, as shown in FIG. 6 (g), close to the preheat frequency f _1. When the power is turned on in this state, the switching element has the same phase (FIG. 6 (h)), a late phase close to the same phase (FIG. 6 (i)), or
A leading phase current ((j) in the figure) flows. In any case, the peak value of the current is very large, and the stress of the switching element also becomes large. Therefore, as a countermeasure against this, it is conceivable to detect a current flowing through the switching element and control the switching element so that no stress is applied to the switching element when its peak value exceeds a certain level. As the control method, there is a method of forcibly fixing the oscillation frequency to a high frequency to suppress the current flowing through the switching element, or a method of stopping the oscillation. However, even if an overcurrent detection circuit is provided, the peak value I
_As shown in FIG. 6 (k), _Q2 p rapidly increases upon turning on the power. When an overcurrent is detected, a large current has already flowed into the switching element. There is a problem that cannot be reduced.

As another conventional example, there is a control method as shown in FIG. 7 (Japanese Patent Application No. 62-6483). This is because the inverter circuit oscillates at a predetermined frequency for a certain time during the preheating of the discharge lamp,
This is a method in which the oscillation frequency is smoothly changed to the lighting frequency over time. The circuit configuration in this case is the same as the circuit in FIG. FIG. 7 (a) shows the time variation of the oscillation frequency f and the capacitor C ₂ in this conventional example.
_Shows the relationship with the both-ends voltage V _C2 . Also shows the temporal change of the current Il flowing current I _C2 flowing through the capacitor C ₂ in this case the discharge lamp l in FIG. 7 (b), (c).

In the case of this conventional example, since a sufficient preheating current can be obtained,
It does not impair the life of the discharge lamp and the frequency during preheating
Since the resonance point f ₀ is included between f ₁ and the lighting frequency f ₂ , the lighting is performed in the same current waveform as the slow mode current waveform flowing through the switching element at the frequency f _1. No mode current flows, and no large stress is applied to the switching element. However, even in this case, similar to the above-described conventional example, the same problem occurs when the power is turned on when there is no load.

As another conventional example, a lighting method like a soft start as shown in FIG. 8 has also been proposed. The circuit configuration in this case is also the same as the circuit in FIG. Fig. 8 (a)
The oscillation frequency f is indicative of the temporal change of gradually lowering the frequency over time, a control system for changing up to a frequency f ₂ which is obtained a predetermined current during lighting.
In this case, the temporal changes of the current I _C2 flowing through the capacitor C ₂ and the current Il flowing through the discharge lamp 1 are shown in FIG.
(D).

In this prior art example, as can be seen from the resonance characteristic curve shown in FIG. 8 (b), during the oscillation frequency f up to the frequency f ₂ is gradually lowered from the frequency f _1, always a resonance point f ₀ Therefore, the discharge lamp 1 is turned on by applying a sufficiently high voltage in a state where the current of the switching element is in the slow mode, and the discharge lamp 1 is operated in the fast mode as in the control method shown in FIG. It will not light up.

Also, even when the power is turned on without the discharge lamp 1, the current flowing through the switching element takes a small value at first, and then gradually increases as the oscillation frequency decreases, so that the peak value _IQ2p Changes as shown in FIG. 8 (e), and when the detection level is exceeded, the protection circuit can be operated until the current flowing through the switching element reaches a level at which the switching element is destroyed.

However, in this conventional example, since the frequency is gradually decreased from a high frequency, a preheating current cannot be obtained most of the time until the discharge lamp 1 is turned on after the power is turned on, and the discharge lamp A problem arises with the life.

(Objects of the Invention) The present invention has been made in view of the above points, and an object of the present invention is to enable a sufficient preheating current to be obtained during a preheating time, and to provide a non-operating state at the time of starting. An object of the present invention is to provide a discharge lamp lighting device capable of reliably detecting abnormal oscillation of a load so that a large stress is not applied to a switching element.

(Disclosure of the Invention) In the discharge lamp lighting device according to the present invention, in order to achieve the above object, as shown in FIGS. 1 to 4, the oscillation output of the inverter circuit whose oscillation frequency f is variable is changed. In the discharge lamp lighting device for lighting the discharge lamp 1 by turning on the power,
The oscillation frequency f of the inverter circuit is set to a predetermined frequency f ₁ ′, which is farther from the lighting frequency f ₂ than the preheating frequency f ₁ , and is set to a preheating frequency
to f ₁ preheating time (t ₁ -t ₁ ') sufficiently short time compared to the
smooth or to alter over t ₁ ', after during preheat time keeping the preheat frequency f _1, a frequency control unit 4 that changes in either smooth until operating frequency f ₂ with the passage of time, over flowing through the switching element It is characterized by comprising an overcurrent detection section 6 for detecting a current.

FIG. 1A shows the relationship between the temporal change of the oscillation frequency f and the voltage V _C1 across the capacitor C ₁ according to the present invention. The circuit configuration in this case is the same as the circuit in FIG. When the power is turned on, the oscillation frequency f is set to a frequency f ₁ ′ higher than the frequency f ₁ for preheating, and is linearly preheated during a time t ₁ ′ that is negligibly shorter than the preheating time t _1. It is changed to the frequency f _1. Therefore, the peak value I _Q2 p of the current flowing through the switching element Q ₂ is, as shown in FIG. 1 (d), when increased with an inclination, it exceeds the overcurrent detection level, the switching element It can be reliably detected before the destructive stress is applied. Thereby, the stress applied to the switching element can be reduced. Further, after this, the oscillation frequency during the preheating time (t ₁ -t ₁ ') is fixed to the frequency f _1, since the filament of the discharge lamp l at this state is sufficiently preheated,
The life of the discharge lamp is not impaired. Also, in this example, because of an resonance point f ₀ between the frequency f ₂ at the time of lighting the frequency f ₁ during preheating, the same as the slow mode of the current waveform flowing in the frequency f ₁ to the switching element Since the lamp is lit in the state of the current waveform, the current does not flow in the phase advance mode. Incidentally, it is shown Fig. 1 (b), a temporal change of the current Il flowing in the current I _C1 and discharge lamp l flowing through the capacitor C ₁ in (c), respectively.

 Hereinafter, examples of the present invention will be described.

Embodiment 1 FIG. 2 is a circuit diagram of one embodiment of the present invention. In the present embodiment, portions having the same functions as those of the conventional circuit are denoted by the same reference numerals, and redundant description will be omitted. The load circuit, the capacitor C ₂ for preheating the non-power supply side, and a discharge lamp l of a capacitor C ₁ connected in parallel to the power supply side, a series circuit of the inductance L is connected. The natural oscillation frequency of the load circuit is substantially determined by the inductance L and the capacitors C ₁ and C ₂ .

To both ends of the DC power supply E, a control unit power supply circuit composed of a series circuit of a resistor R ₁ and a capacitor C ₃ is connected. The voltage of the capacitor C ₃ is applied to the series circuit of the resistor R ₅ and the Zener diode ZD. The reference voltage generated across the Zener diode ZD is applied to the inverting input terminal of the comparator CP. The voltage of the capacitor C ₆ is applied to the non-inverting input terminal of the comparator CP. Capacitor C ₆ via the transistor Q _4, are charged at the charging voltage of the capacitor C _3. The transistor Q ₄ are, so as to form a current mirror circuit, the transistor Q ₃ is connected. Assuming that the current gain hfe of each of the transistors Q ₃ and Q ₄ is sufficiently large, the current flowing through the transistor Q ₄ becomes the same as the current flowing through the transistor Q ₃ . The transistor Q ₃ is connected to the resistors R ₂ and R
_3, through a series circuit of R ₄ are connected to both ends of the capacitor C _3. The capacitor C ₄ and the transistor Qs are connected to the series circuit of the resistors R ₃ and R ₄ , and the capacitor C ₅ and the transistor are connected to the resistor R _4.
Q ₅ are connected in parallel.

The base of the transistor Q ₅ is connected via a resistor R ₇ output of the timer circuit 3 is connected. The timer circuit 3
Is for setting a preheating time is direct current power supply E is turned on, since the increase in the charging voltage of the capacitor C _3, and outputs a high level signal for a predetermined time. Accordingly, current flowing through the transistor Q ₃ are after the power is turned from a value determined by the resistor R _2, and decreases with increasing charge voltage of the capacitor C _4, after the charging of the capacitor C ₄ is the predetermined time the resistance R _2, R ₃ It is a fixed value that is determined. When the transistor Q ₅ is turned off, and gradually decreases with increasing the charging voltage of the capacitor C _5, in the end, becomes a constant value determined by the series resistance of the resistors _{R 2, R 3, R 4} . The frequency control unit 4 is configured by the CR circuit.

Further, the emitter of the transistor Q ₂ is the resistance Rs for overcurrent detection connected in series, the transistors Q ₂ and the resistor Rs
Is connected to the overcurrent detection circuit 6. Further, the latch circuit 5 is connected to the overcurrent detection circuit 6. The output of the latch circuit 5 is connected to the base of the transistor Qs through the resistance R _8. During normal operation, the transistor Qs is is in the OFF state, an overcurrent flows through the switching element Q _2, an increase in the voltage drop at the resistor Rs is detected by the overcurrent detection circuit 6, the output of the latch circuit 5 transistor Qs is kept in the oN state via a resistor R _8. After the transistor Qs is turned ON, current flowing through the transistor Q ₃ are a constant value determined only by the resistance R _2.

The voltage across the capacitor C ₆ may No.2 timer ICTM, is connected to the sixth and seventh terminals. This timer ICtm
It is a general-purpose timer IC (NEC µPD15555). As is well known, when the trigger terminal (terminal 2) becomes (1/3) Vcc or less, it is triggered and the output terminal (terminal 3 not shown) It becomes high level, and the discharge terminal (7th terminal) becomes high impedance. Also, the threshold terminal (terminal 6) is (2 /
3) At Vcc, the output terminal (terminal 3) goes low, and the discharge terminal (terminal 7) goes low. Therefore, the both ends of the capacitor C ₆ sawtooth wave voltage is generated.
This voltage is compared with the reference voltage by the comparator CP,
A rectangular wave oscillation output is obtained from the comparator CP.

The output of the comparator CP is divided by the D flip-flop FF. D flip-flop FF output Q, NAND
The gates G ₁ and G ₂ are respectively connected to one input.
The output is connected to the data input D. The output of the aforementioned comparator CP is connected to the clock input C. Each time the clock input C rises from a low level to a high level, the output of the D flip-flop FF is inverted and the output
From Q, a rectangular wave having a duty factor of 50% obtained by dividing the output of the comparator CP by half can be obtained. On the other hand, the output of the comparator CP is the inverter gates G ₃ and G ₄ and the resistor R
₆ is connected to the other inputs of the NAND gates G ₁ and G ₂ . Outputs of the NAND gates G ₂ and G ₁ are input to driving circuits 1 and ₂ of the switching elements Q ₁ and Q ₂ , respectively. Therefore, the drive signals of the switching elements Q ₁ and Q ₂ alternate between a first period in which one is at a high level and the other is at a low level, and a second period in which one is at a low level and the other is at a high level. A signal is present, and between the first and second periods there is a third period during which both outputs are low. The third period is a dead-off time for preventing both of the switching elements Q ₁ and Q _{2 from} being turned on, and may be a short time in consideration of the charge accumulation time of the on-state switching element. In the illustrated circuit, the period is determined by the period during which the output of the comparator CP is low.

With the above configuration, frequency control as shown in FIG. 1A can be performed. Sand, when turning on the DC power source E, a certain time the transistor Q ₅ by the output of the timer circuit 3 is turned on. Therefore, the oscillation frequency of the inverter circuit becomes a frequency f ₁ ′ determined by the values of the capacitor C ₆ and the resistor R ₂ at _first , and then smoothly decreases as the charging voltage of the capacitor C ₄ increases. After the charging of the capacitor C ₄ becomes almost definite value and capacitor C ₆ by the values of resistors R _2, R _3, preheating is performed at a frequency f _1. Then, when the timer time t ₁ of the timer circuit 3 has passed, the output goes low, the transistor Q ₅ is turned off. Therefore, the gradually charged capacitor C _5, the charging voltage reaches the divided voltage of the resistors R _2, R ₃ and R _4. At this time, the oscillation frequency of the inverter circuit or the frequency f ₁ during the above-mentioned preheating, resistance
R _2, R _3, gradually changed to a frequency f ₂ which is determined by R ₄ and the capacitor C _6. During the change of the frequency, the discharge lamp 1 is turned on. Above each active, if an overcurrent flows to the switching element Q _2, the transistor Qs is turned on, the oscillation frequency is fixed to the oscillation frequency f ₁ 'determined by the resistor R _2,
It is possible to reduce the current flowing through the switching element Q _2. Incidentally, by setting a relatively small capacitance of the capacitor C _4, transition to a frequency f ₁ from the frequency f ₁ 'can be carried out relatively quickly, in order to ensure a long pre-heating time, the capacitor C ₄ Is desirably set small. However, the capacitance of the capacitor C _4, it is necessary to overcurrent suppressing operation is set so as to ensure the time t ₁ 'to act effectively for the stress-reducing switching element Q _2.

Embodiment 2 FIG. 3 is a circuit diagram of another embodiment of the present invention. In this embodiment, a well-known push-pull circuit is used as an inverter circuit. Oscillation transformer OT for inverter circuit
Consists of a leakage transformer having an intermediate tap in the primary winding, and the switching elements Q ₁ and Q ₂ are turned on alternately, so that an alternating current flows through a load circuit connected to the secondary winding. As the load circuit, the same circuit as that used in the first embodiment is connected, but the leakage inductance of the oscillation transformer OT is used instead of the inductance L.

An oscillation circuit 7 composed of a switching regulator IC (μPC494 manufactured by NEC) is used as a control unit of the inverter circuit. The oscillation frequency of the oscillation circuit 7 and the capacitance of the capacitor C ₈ connected to the fifth terminal, determined from the resistance value connected to the sixth terminal. The fourth terminal receives a potential obtained by dividing the reference voltage of the fourteenth terminal by the resistors R ₉ and R ₁₀ , thereby determining the dead-off time of the switching elements Q ₁ and Q ₂ . The Pin 13 has given high level signal through the resistor R ₁₂ in order to be used for 2 stone. The resistors R ₁₃ and R ₁₄ are used as collector resistors of an open-collector transistor inside the oscillation circuit 7.

The configuration and operation of the frequency control unit 4 used in the present embodiment are the same as those in the first embodiment, and a duplicate description will be omitted.

Embodiment 3 FIG. 4 is a circuit diagram of still another embodiment of the present invention.
This embodiment is an inverter circuit 1 transistor type, are used MOSFET for power as the switching element Q _1. The switching element Q ₁ and the capacitor C ₀ is connected in parallel, through the switching element Q _1, 1 winding of the oscillating transformer OT consisting leakage transformer is connected to a DC power source E. The same load circuit as in the second embodiment is connected to the secondary winding of the oscillation transformer OT. In this case, the reverse current of the switching element Q ₁ is, flows through the MOSFET parasitic diode.

A series circuit of the resistor R ₁ and the capacitor C ₃ is connected to both ends of the DC power supply E, and supplies a power supply voltage Vcc to a drive circuit and a control circuit of the switching element Q ₁ . First, an explanation will be made for a driving circuit of the switching element Q _1. The capacitor C _3, the transistor Q ₆ through the resistor R ₁₅ is connected. The collector of the transistor Q _6, the transistor
It is connected to the base of Q _7, Q _8. The emitter of the transistor Q _7, Q ₈ is connected through a resistor R _16, the transistor Q
_7, the collector of Q ₈ is connected to both ends of the capacitor C _3, respectively. When the transistor Q ₆ is turned on, since the collector potential drops, the transistor Q ₇ is turned state OFF state, the transistor Q ₈ can be turned on and the switching element
The gate of Q ₁ is, resistors R _17, via the transistor Q _8, is pulled down to the ground level. When the transistor Q ₆ is turned off, because the collector potential rises, the transistor Q ₈ is turned off, the transistor Q ₇ is turned on, the resistor R _16, R
_17, the charging voltage of the capacitor C ₃ to the series circuit of the R ₁₈ is applied, the gate potential of the switching element Q ₁ is increased by the divided voltage developed across the resistor R _18. Thus, it is intended to be a gate voltage driven switching element Q _1.

Next, a description will be given of the control circuit of the switching element Q _1. tm ₁ and tm ₂ are general-purpose timer ICs (μPD15555 manufactured by NEC). Resistors R ₁₉ , R constituting the time constant circuit of timer ICtm _1
20, the power supply voltage Vcc is applied to the series circuit of the capacitor C _9. Connection point of the resistors R ₁₉ and R ₂₀ are connected to the discharge terminal of the timer ICTM ₁ (7 Pin), the resistor R ₂₀ and capacitor C ₉
The connection point is connected to a timer ICTM ₁ threshold terminal (6 Pin) and a trigger terminal (pin 2). Thus, the timer ICTM ₁ operates as an astable multivibrator. The oscillation frequency is determined by the time constants of the resistors R ₁₉ and R ₂₀ and the capacitor C ₉ and the voltage of the control terminal (the fifth terminal). Timer ICTM ₁ output terminal (third terminal) is connected to a timer ICTM ₂ trigger terminal (pin 2).

The power supply voltage Vcc is applied to a series circuit of the resistor R ₂₁ and the capacitor C ₁₁ that constitute a time constant circuit of the timer ICtm ₂ . Connection point of the resistors R ₂₁ and capacitor C ₁₁ Timer ICTM ₂
Are connected to the discharge terminal (No. 7 terminal) and the threshold terminal (No. 6 terminal). Control terminal of timer ICtm ₂ (5
Ban terminal) is grounded via a capacitor C _10. Thus, the timer ICTM ₂ operates as a single stable multivibrator. Timer ICTM ₂ output terminal (third terminal) is connected to the base of the transistor Q ₆ in the drive circuit of the switching elements to Q ₁ described above.

The configuration of the frequency control unit 4 is substantially the same as that of the first embodiment. After power since a certain time output of the timer circuit 3 is the transistor Q ₅ is turned on at a high level, minute the operational amplifier OP, firstly a resistor R ₂ and a parallel circuit of a resistor R _0, R _3, R ₄ is voltage is input, is low impedance at the operational amplifier OP, a timer ICTM ₁ control terminal (5
No. 1) to determine the oscillation frequency f ₁ ′ at power-on. The oscillation frequency decreases with increasing charge voltage of the capacitor C _4, after the charging of the capacitor C _4, transistor
During Q ₅ is to be turned off, the resistor R _0, a parallel circuit of R ₄ resistors R
The divided voltage of _2, is determined in the oscillation frequency f _1.
Monostable multivibrator consisting of timer ICtm ₂ is,
It has been used to determine the OFF period of the switching element Q _1.

Then after the lapse of the timer time of the timer circuit 3 t _1, the transistor Q ₅ is turned off and the capacitor C ₅ via the resistor R ₀ is charged, the input voltage to the operational amplifier OP, than that in the preheating gradually increases, the oscillation frequency of the timer ICTM ₁ is gradually lowered thereby. This change, the oscillation frequency f ₂ at the time of lighting the oscillation frequency f ₁ during preheating
The transition is smooth.

Above during each operation, when an overcurrent flows through the switching element Q _1, the increase in the voltage drop at the resistor Rs, the overcurrent detection circuit 6
Is detected, the transistor Qs through the resistance R ₈ by the output of the latch circuit 5 is turned on, by turning off the switching element Q _1, the oscillation of the inverter circuit is stopped, the stress on the switching element Q ₁ It is alleviating.

(Effects of the Invention) As described above, the present invention relates to a discharge lamp lighting device using an inverter circuit having a variable oscillation frequency. Since it changed more smoothly to the preheating frequency and overcurrent detection was performed,
It is possible to reliably detect an overcurrent due to no-load power supply, and to reduce the stress applied to the switching element. In a normal state that is not a no-load condition, the above operation ends promptly after elapse of a sufficiently short time as compared with the preheating time, and thereafter, after oscillating at a preheating frequency for a certain period of time, the oscillation frequency is changed with the elapse of time. By making the change smoothly, a sufficient preheating current can be obtained, and therefore, there is an effect that the life of the discharge lamp is not impaired.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the operation of the present invention, FIG. 2 is a circuit diagram of one embodiment of the present invention, FIG. 3 is a circuit diagram of another embodiment of the present invention, and FIG. FIG. 5 is a circuit diagram of a conventional example, FIG. 6 is an operation explanatory diagram of the above example, FIG. 7 is an operation explanatory diagram of another conventional example, and FIG. 8 is an operation of still another conventional example. FIG. E is a DC power supply, Q ₁ and Q ₂ are switching elements, 1 is a discharge lamp, 3 is a timer circuit, 4 is a frequency control unit, and 6 is an overcurrent detection circuit.

Claims (1)

(57) [Claims] 1. A discharge lamp lighting device for lighting a discharge lamp with an oscillation output of an inverter circuit having a variable oscillation frequency,
After the power is turned on, the oscillation frequency of the inverter circuit is smoothly changed from a predetermined frequency farther from the lighting frequency than the preheating frequency to a preheating frequency with a sufficiently short time compared to the preheating time, and the preheating frequency is changed during the preheating time. After holding
A discharge lamp lighting device comprising: a frequency control unit that smoothly changes to a lighting frequency with the passage of time; and an overcurrent detection unit that detects an overcurrent flowing through a switching element.