JP2818595B2 - 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.

[Prior Art] FIG. 7 is a circuit diagram showing a conventional inverter circuit used for a discharge lamp lighting device. In the figure, a DC power supply E is constituted by a constant voltage power supply obtained by rectifying a commercial AC power supply. Switching element for DC power supply E via power switch SW
A series circuit of Q ₁ and Q ₂ is connected. Switching element Q
₁ and Q ₂ are composed of transistors and the like, and are alternately turned on and off. These switching elements Q ₁ , Q
Of the _two, in parallel, at least one of the switching elements Q _1, a capacitor C ₁ for coupling a load R, the inductance element L _1, and is a series circuit of the primary winding n ₁ current transformer T ₁ is connected I have. Load R, the capacitor C ₂ for resonance is connected in parallel. Between the negative terminal of the non-power-side terminal and the DC power source E of the capacitor C _1, the voltage detecting circuit 2 is connected. The voltage detection circuit 2 is configured by a voltage dividing circuit using a resistance element having a higher impedance than the load R, and detects the presence or absence of the load R. When the load R is not connected, the capacitor C ₁ is charged to the same voltage level as the DC power source E, an input voltage of the voltage detecting circuit 2 becomes a low level. Further, when the load R is connected, the capacitor C ₁ is charged to a voltage level of about half of the DC power source E, an input voltage of the voltage detection circuit 2 becomes high level. Inverter stop circuit 4, when the detection output from the voltage detecting circuit 2 has disappeared, the transistor Q ₅ is turned off, the transistor Q ₄ is turned on, forcibly turning off the switching element Q _2, the switching element
This is to stop the switching operation of Q ₁ and Q ₂ .

Hereinafter, the operation of this circuit will be described. Power switch SW is turned on, the DC power source E is applied, the switching element Q ₂ is turned on by the activation circuit 6, and thereafter, the switching element Q _1, Q ₂ by the drive circuit 5 consisting of the current transformer T ₁ is alternately On and off. Across the load R becomes than the inductance element L ₁ and the capacitor C ₂
A high frequency high voltage is applied by the LC series resonance circuit,
The load R operates.

Here, when the no-load and remove the load R, only charged in one direction the capacitor C ₁ via the resistor R _4, R _5, since it is charged to the same voltage as the DC power source E, the voltage detection circuit 2 The detection output goes low. At this time, under the control of the inverter stop circuit 4, the oscillation of the inverter circuit 1 stops.

Thereafter, when connected again load R, the switching element Q ₁ and the parallel-connected resistors R _3, diode D _3, 1 winding n ₁ of the current transformer T _1, the inductance element L _1, through the load R , the charge of capacitor C ₁ is discharged, the charging voltage of the capacitor C ₁ decreases. Thereby, the voltage detection circuit 2
Is at a high level. When the input voltage of the voltage detection circuit 2 becomes high level, a voltage detection output is generated.
The operation of the inverter stop circuit 4 is released, the inverter circuit 1 performs a normal operation, a high voltage is applied to the load R, and the load R lights normally.

[Problem to be Solved by the Invention] FIG. 8 shows a circuit diagram in the case where the load R includes a series circuit of the discharge lamps l ₁ and l _{2 in} the above-described conventional example. In this circuit, the non-power supply side terminal of the filament f ₄ of the discharge lamp l _2, the capacitor C ₄ and the discharge lamp l via the parallel circuit and the primary winding N ₁ of the current transformer T ₂ of the preheat resistor R _{8 1} filament
It is connected to the non-power supply side terminal of the f _1. Also, both discharge lamps
The other filaments f ₂ and f ₃ of l ₁ and l ₂ are connected in series,
And it is connected to the secondary winding N ₂ of the current transformer T _2. These resistors R ₈ and the capacitor C ₄ and the current transformer T _2, the preheating circuit 7 of filament _{f 1, f 2, f 3} , f 4 is formed.

Here, when the discharge lamps l ₁ and l ₂ are of a round tube type, since the pair of filament sockets are integrated, both filaments are connected almost simultaneously, but the discharge lamps are of a straight tube type. , The socket for each filament is independent, and therefore, as shown in FIG.
When l ₁ and l ₂ are connected in series, the sockets of the filaments f ₁ , f ₂ , f ₃ and f ₄ are independent of each other. Thus, for example, to connect the discharge lamp l ₂ above, when the next connecting discharge lamp l _1, when it is no problem by connecting the filament f ₂ above, to connect the filament f ₁ above, the filament
through f _1, f ₄ and preheating circuit 7, the charge of capacitor C ₁ is discharged, until the filament f ₂ is connected, starts the inverter circuit 1 is oscillating operation remain abnormal load conditions and will, since the switching elements Q _1, Q ₂ flows a large resonance current, there is a problem that the switching loss of the switching elements Q _1, Q ₂ is increased. Also, when the resonance current increases, the voltage across the capacitor C ₂ also increases,
The output voltage may exceed 300V in effective value. When used as lighting equipment, in circuits where the power supply is not insulated from the discharge lamps l ₁ and l ₂ , if the output voltage exceeds 300 V in effective value, it will be incompatible with the Electrical Appliance and Material Control Law and JIS standards. It is necessary to prevent the generation of such an excessive voltage.

A similar problem occurs when the filament is broken. Of the filaments on the non-common side of the discharge lamps l ₁ and l ₂ , when the filament f ₁ or f ₄ is disconnected, a complete no-load state occurs, so that the voltage detection circuit 2 operates normally,
The oscillation of the inverter circuit 1 stops. However, when the filament f ₂ or f ₃ is disconnected, the same reason the voltage detecting circuit 2 does not operate normally due to the above, the oscillation of the inverter circuit 1 is not stopped. The latter problem occurs not only when a straight tube-type discharge lamp is used but also when a round tube-type discharge lamp is used.

The present invention has been made in view of such a point,
The purpose is to provide a discharge lamp lighting device with a simple circuit configuration in which the oscillation of the inverter circuit is started only when all the filaments of the discharge lamps connected in series are completely mounted. is there.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, as shown in FIG. 1 and FIG.
And the second switching elements Q ₁ and Q ₂ are connected to a DC power supply E, one end of the DC power supply E is connected to one end of a capacitor C ₁ ,
A discharge lamp l ₁ , connected in series between the other end of the capacitor C ₁ and a connection point of the first and second switching elements Q ₁ , Q ₂
l ₂ is connected via an inductance element L ₁ , and the first and second switching elements Q ₁ and Q ₂ are alternately turned on and off to supply AC power to the discharge lamps l ₁ and l _2. an inverter circuit 1 supplies, between the other ends of the DC power supply E of the capacitor C _1, the discharge lamp lighting apparatus is connected with a voltage detecting circuit 2, the first resistor from one end of the DC power source E
R ₁₁ , the DC power supply E via the commonly connected filaments f ₂ , f _{3 of} the series-connected discharge lamps l ₁ , l ₂ and the second resistor R _10.
Of the second resistor R ₁₀
A filament detecting circuit 3 for detecting the commonly connected filaments f ₂ , f ₃ of the discharge lamps l ₁ , l ₂ connected in series by the voltage between both ends. An inverter stop circuit 4 for stopping the oscillation of the inverter circuit 1 when at least one of them disappears is provided.

[Operation] In the present invention, as described above, the first resistor R ₁₁ , the commonly connected filaments f ₂ and f _{3 of} the discharge lamps l ₁ and l ₂ connected in series are connected from one end of the DC power supply E. and has a direct current energization path to the other end of the DC power source E through a second resistor R _10, the discharge lamp l ₁ which are connected in series by the voltage across the second resistor R _10,
Since the filament detecting circuit 3 for detecting the commonly connected filaments f ₂ and f ₃ of l ₂ is provided, the filament f ₂ or
When f ₃ is not connected, the detection output of the filament detection circuit 3 disappears. The voltage detecting circuit 2 connected between the other end of the capacitor C ₁ and the other end of the DC power source E
Detects the filaments f ₁ and f ₄ and the filament f
_{When 1} or f ₄ is not connected, the voltage detecting circuit 2
Detection output disappears. In the present invention, the oscillation of the inverter circuit 1 is stopped by the inverter stop circuit 4 when at least one of the detection outputs of the voltage detection circuit 2 and the filament detection circuit 3 disappears.
When any filament is not connected,
By stopping oscillation of the inverter circuit 1, useless power consumption can be prevented and generation of excessive voltage can be prevented.

Embodiment 1 FIG. 2 is a circuit diagram of a first embodiment of the present invention. Less than,
The circuit configuration will be described. The inverter circuit 1 is connected to the DC power supply E via a power switch SW.
The inverter circuit 1 includes switching elements Q ₁ and Q ₂ composed of transistors, and an input DC voltage is applied to a series circuit of the switching elements Q ₁ and Q ₂ . One parallel to the switching element Q _1, a capacitor C ₁ for coupling,
Discharge lamp l ₁ and l _2, the inductance element L _1, a series circuit of the primary winding n ₁ current transformer T ₁ of the current feedback is connected. Between the first of each power supply terminal of the discharge lamp l ₁ of filaments f ₁ and second discharge lamps l ₂ of the filament f _4, the capacitor C ₂ for resonance is connected in parallel. This capacitor C ₂ may be a stray capacitance. Non-power side terminal of the filament f ₄ of the discharge lamp l ₂ through the primary winding of the current transformer T ₂ of the second parallel circuit and the preheating of the capacitor C ₄ and a resistor R ₈ of the discharge lamp l ₁ of filaments f ₁ Connected to non-power supply terminal. Also, the other filaments f ₂ , f _{3 of} both discharge lamps l ₁ , l ₂
Constitute a series circuit, in the series circuit, are a secondary winding of the current transformer T ₂ is connected via a capacitor C _5.
By this current transformer T ₂ and a resistor R ₈ and the capacitor C _4, the filament _{f 1, f 2, f 3} , the preheating circuit 7 f ₄ is formed.

Next, the configuration of the voltage detection circuit 2 will be described. One end of the coupling capacitor C ₁ is connected to the positive input terminal of the inverter circuit 1, and a discharge lamp is provided between the other end of the coupling capacitor C ₁ and the negative input terminal of the inverter circuit 1. The resistance R ₄ , which has higher impedance than l ₁ and l ₂ ,
A series circuit of R ₅ is connected. The voltage obtained at the connection point between the resistors R ₄ and R ₅ is used as a detection output of the voltage detection circuit 2.

Next, the configuration of the filament detection circuit 3 will be described. In the present embodiment, as described above, connect one end of the secondary winding of the current transformer T ₂ in the preheating circuit 7 to one end of the filament f ₂ in the first discharge lamp l ₁ through the capacitor C ₅ and connects the other end of the secondary winding to one end of the filament f ₃ in the second discharge lamp l _2, filaments
The other ends of f ₂ and f ₃ are connected. Connection point of the capacitor C ₅ and the filament f ₂ is connected to the positive input terminal b of the inverter circuit 1 through the resistor R _11, 2 of the current transformer T ₂
Connection point of the primary winding and the filament f ₃ is connected to the negative input terminal c of the inverter circuit 1 through the resistor R _10. The filament C ₃ and the resistors R ₁₀ and R ₁₁ constitute a filament detection circuit 3. The voltage at one end (point a) of the resistance R ₁₀ is a detection output of the filament detection circuit 3.

Next, the configuration of the inverter stop circuit 4 will be described. The detection output of the voltage detection circuit 2 is input to the base of the transistor Q ₅ through a resistor R _7. The detection output of the filament detection circuit 3 is inputted to the base of the transistor Q ₆ through the resistor R _9. Each transistor Q ₅ , Q
The emitter ₆ is connected to the negative input terminal c of the inverter circuit 1. The collectors of the transistors Q ₅ and Q ₆ are connected to the positive input terminal b of the inverter circuit 1 via resistors R ₁₂ and R ₁₃ , respectively, and between the anode and cathode of the diodes D ₄ and D ₅ , respectively. It is connected to the base of the transistor Q _4. The collector of the transistor Q ₄ are connected to the base of the switching element Q _2, the emitter is connected to the negative input terminal c of the inverter circuit 1. The inverter stop circuit 4 is provided with a detection output of the voltage detection circuit 2,
When at least one of the detection output of the filament detection circuit 3 becomes "Low" level, the transistor Q ₄ is turned on, but is forcibly turns off the switching element Q _2. In the case of both detection outputs are both "High" level, the transistor Q ₄ is turned off, the switching element
Q ₂ is intended to operate on and off successfully according to the output of the secondary winding n ₂ of the current transformer T _1.

Current transformer T ₁ for current feedback has two secondary windings
n ₂ and n ₃ , one secondary winding n ₂ is connected between the base and the emitter of the switching element Q ₁ via a bias resistor R ₁ , and the other secondary winding n ₃ It is connected between the base and emitter of the switching element Q ₂ via a resistor R _2. Thus, the drive circuit 5 is configured.

Further, the input terminal b of the inverter circuit 1, between c, resistance series circuit of R ₃ and the capacitor C ₃ is connected, the connection point of the resistors R ₃ and capacitor C ₃ via a diac Q _3, the switching elements Q Connected to the base of diode ₂ and diode D ₃
The switching element Q ₂
Connected to the collector. The resistance R ₃ , the capacitor C ₃ , the diac Q ₃ and the diode D ₃ constitute a starting circuit 6 of the inverter circuit 1. Although diodes D ₁ and D ₂ are connected in anti-parallel to switching elements Q ₁ and Q ₂ , these diodes D ₁ and D ₂ are not necessarily required.

Hereinafter, the operation of the present embodiment will be described. When the power switch SW is turned on, the DC power source E is connected to the inverter circuit 1, the capacitor C ₃ is charged through the resistor R _3.
When the voltage of the capacitor C ₃ reaches the breakover voltage of the diac Q _3, then conducts diac Q _3, charges of the capacitor C ₃ is discharged through the base-emitter of the switching element Q _2. Thereby the switching element Q ₂ is turned on. After that, the current transformer T ₁
The switching elements Q ₁ and Q ₂ are turned on and off alternately by the feedback current obtained from the next windings n ₂ and n ₃ . At this time, the capacitor C ₁ for coupling, approximately half of the voltage E / 2 of the DC power source E is charged. Therefore, the voltage divided by the resistors R ₄ and R ₅ becomes “High” level, and the detection output of the voltage detection circuit 2 becomes “High” level. Thus, the transistor Q ₅ is turned on, the base current to the transistor Q ₄ through a bias resistor R ₁₂ and diode D ₄ is interrupted.

Here, when at least one of the filaments f ₁ , f ₄ of the discharge lamps l ₁ , l ₂ is removed to be in a no-load state, the coupling capacitor C ₁ is connected only in one direction via the resistors R ₄ , R _5. Since the battery is charged and charged to the same voltage level as the DC power supply E, the input voltage to the voltage detection circuit 2 becomes low, and the detection output of the voltage detection circuit 2 becomes “Low” level. Therefore, the transistor Q ₅ is turned off, base current flows through the transistor Q ₄ through a bias resistor R _12, the transistor Q ₄ is turned on. When the transistor Q ₄ is turned on, since one switching element Q ₂ is forcibly turned off, the feedback current is obtained from the secondary winding n _2, n ₃ of the current transformer T ₁ of the current feedback And the switching elements Q ₁ and Q ₂ are both turned off. Therefore, the oscillation of the inverter circuit 1 stops.

Next, when at least one of the filaments f ₂ and f ₃ of the discharge lamps l ₁ and l ₂ has come off, the detection output of the filament detection circuit 3 becomes “Low” level. Now, illustrated in FIG. 3 the state of the filament detection circuit 3 in the case where only the filament f ₃ is out. In the drawing, the portions denoted by reference numerals a to e correspond to the portions denoted by the same reference numerals in FIG. In the state shown in FIG. 3, the filament f ₃ is off, the current path A through the filament f _2, f ₃ is not formed. The current path B through the secondary winding of the current transformer T ₂
In the direct current capacitor C ₅ from the DC power source E
Therefore, this current path is not formed.
Therefore, no current flows to the resistor R _10, the resistor R ₁₀
Is at a "Low" level. Therefore, the detection output of the filament detection circuit 3 becomes "Low" level, and the transistor Q ₆ is turned off in the inverter stop circuit 4, the base current flows through the transistor Q ₄ through a bias resistor R ₁₃ and diode D _5, transistor Q ₄ is turned on, since the forcibly turns off the switching element Q _2, so that the oscillation of the inverter circuit 1 is stopped. Discharge lamp l ₁
If only the filament f ₂ has come off, for the same reason as described above, the oscillation of the inverter circuit 1 is stopped.

On the other hand, when the filaments f ₂ and f _{3 of} the discharge lamps l ₁ and l ₂ are connected together, a current flows through the current path A in FIG. 3, so that a voltage is generated across the resistor R ₁₀ , The detection output of the filament detection circuit 3 becomes “High” level. Therefore, the transistor Q ₆ is turned on, the bias resistor R
The base current of the transistor Q ₄ through ₁₃ is intended to be cut off.

When all the filaments f ₁ , f ₂ , f ₃ , f _{4 of the} discharge lamps l ₁ , l ₂ are connected, both the detection output of the voltage detection circuit 2 and the detection output of the filament detection circuit 3 are at “High” level. As a result, both the transistors Q ₅ and Q ₆ are turned on. Therefore, the base current of the transistor Q ₄ through a bias resistor R _12, R ₁₃ is blocked together, the transistor Q ₄ are turned off. At this time, since the drive current from the current transformer T ₁ is given to the switching element Q _2, the inverter circuit 1 performs normal oscillation operation. In the steady state, composed of the inductance element L ₁ and the capacitor C ₂ and C ₄ LC
A high frequency high voltage is applied to both ends of the discharge lamps l ₁ and l ₂ by the resonance circuit, and the discharge lamps l ₁ and l ₂ are turned on.

Embodiment 2 FIG. 4 is a circuit diagram of a second embodiment of the present invention. In the present embodiment, one end of the secondary winding of the current transformer T ₂ of the preheat each end of the common side of the filament f _2, f ₃ in the discharge lamp l _1, l ₂ via a capacitor C ₅ And the other end of the secondary winding is connected to the other end of each of the filaments f ₂ and f ₃ . That is, in the present embodiment, the filaments f ₂ , f
₃ are connected in parallel. One end of each filament f _2, f _3, the positive input terminal b of the inverter circuit 1 through the resistor R ₁₁
It is connected to the inverter circuit 1 and the other end through a resistor R ₁₀
Is connected to the negative input terminal c. One end of the resistor R ₁₀ (a
The voltage at point (dot) is applied to one input terminal of the comparator CP. The other input terminal of the comparator CP, the reference voltage V _R is applied. The filament detection circuit 3 is constituted by the comparator CP and the reference voltage V _R , the capacitor C ₅ and the resistors R ₁₀ and R ₁₁ , and the output of the comparator CP is the detection output of the filament detection circuit 3. Other configurations are the same as those of the first embodiment, and thus, portions having the same functions are denoted by the same reference numerals, and redundant description will be omitted.

Hereinafter, the operation of the present embodiment will be described. In this embodiment, since the filaments f ₂ and f ₃ on the common side of the discharge lamps l ₁ and l ₂ are connected in parallel, when both filaments f ₂ and f ₃ are normally connected, a resistance R ₁₁ and filament resistance Rf ₂ of the R ₁₀ both filaments f _2, f _3, Rf ₃ is that they are connected in parallel. One end of this time, the resistance R ₁₀ (a point)
The voltage generated in the e _1, the comparator than the voltage e ₁
The reference voltage V _R is set so that the reference voltage V _R of CP becomes small. One end of the comparator CP, the resistance R ₁₀ (a point)
Is higher than the reference voltage V _R , the output goes to “High” level. Therefore, the filament f
_2, when the f ₃ is normally connected, the output of the filament detection circuit 3 becomes "High" level.

Next, when one of the filaments f ₂ and f ₃ comes off,
Since the filament resistance is reduced by one, the current flowing through the filament detection circuit 3 is reduced. Now, the state of the filament detection circuit 3 in the case where only the filament f ₂ is out fifth
Shown in the figure. In the figure, the parts denoted by reference numerals a to c and f and g correspond to the parts denoted by the same reference numerals in FIG. Fifth
In the state shown in FIG., The filament f ₂ is disconnected,
There is no current path through the resistor Rf _2, is only the current path through the resistor Rf _3. Therefore, the current flowing through the resistor R ₁₀ decreases, voltage drops occurring in one end of the resistor R ₁₀ (a point). This voltage is e _2, so that the reference voltage V _R of the comparator CP than the voltage e ₂ is high, the reference voltage V _R
Is set. The comparator CP is the voltage generated at one end of the resistor R ₁₀ (a point) and smaller than the reference voltage V _R, the output becomes "Low" level. Therefore, when the filament f ₂ is not connected, the output of the filament detection circuit 3 becomes "Low" level. Filament f ₃
Is not connected, for the same reason as above,
The output of the filament detection circuit 3 becomes "Low" level.

When both filaments f ₂ and f ₃ come off,
Current path through the filament f _2, f ₃ is longer, the current path through the secondary winding of the current transformer T ₂ are blocked DC-by capacitor C _5, no current flows to the resistor R _10, the The voltage at one end (point a) becomes “Low” level. Therefore, the output of the comparator CP is also at the “Low” level, and the output of the filament detection circuit 3 is at the “Low” level.

 Other operations are the same as in the first embodiment.

Third Embodiment FIG. 6 is a main part circuit diagram of a third embodiment of the present invention. This embodiment, in the circuit shown in FIG. 2, is obtained by replacing the capacitor C ₅ to the diode D _6. In this case, when the filaments f ₂ and f _{3 of} the discharge lamps l ₁ and l ₂ are connected together, the resistance R ₁₁ , the filaments f ₂ and f ₃ ,
Current flows through the resistor R _10, the voltage level of one end of resistor R ₁₀ (a point) rises, the detection output of the filament detection circuit 3 becomes "High" level. At this time, the filaments f ₂ and f ₃ are connected to the current transformer T ₂ via the diode D _6.
Is preheated by the output of Next, the filaments f ₂ and f
_When at least one of ₃ is removed, the filament f ₂ ,
The current path through the f ₃ is cut off, also, the current path through the secondary winding of the current transformer T ₂ are due to being blocked DC-by diode D _6, no current flows to the resistor R _10, the The voltage level at one end (point a) decreases. Therefore, the detection output of the filament detection circuit 3 becomes "Low" level. Other operations are the same as in the first embodiment.

As a modified example of the present invention, instead of completely stopping the oscillation of the inverter circuit 1, the switching operation of the switching elements Q ₁ and Q ₂ is controlled so that the oscillation output of the inverter circuit 1 decreases. It can also be configured.

[Effects of the Invention] As described above, the present invention provides a discharge lamp lighting device including an inverter circuit for lighting a discharge lamp in series and a voltage detection circuit for detecting a no-load state of the inverter circuit. A first resistor, a commonly connected filament of a discharge lamp connected in series, and a DC current supply path from the other end to the other end of the DC power supply via the second resistor. An inverter for providing a filament detection circuit for detecting a commonly connected filament of the discharge lamps connected in series by a voltage, and stopping oscillation of the inverter circuit when at least one of the filament detection circuit and the detection output of the voltage detection circuit is lost; Since the stop circuit is provided, when the filament on the non-common side of the discharge lamp is not connected, the no-load state of the inverter circuit is detected. When the detection output of the voltage detection circuit for disappears, the oscillation of the inverter circuit is stopped, and when the filament on the common side of the discharge lamp is not connected,
The disappearance of the detection output of the filament detection circuit stops the oscillation of the inverter circuit. Therefore, even with a simple configuration, any one of the filaments of the discharge lamps connected in series is disconnected. In this case, the oscillation of the inverter circuit can be stopped, and there is an effect that wasteful power consumption can be prevented and excessive generation of voltage can be prevented.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a basic configuration of the present invention, and FIG.
FIG. 3 is a circuit diagram of the first embodiment of the present invention, FIG. 3 is a main part circuit diagram of the same, FIG. 4 is a circuit diagram of the second embodiment of the present invention, FIG. FIG. 6 is a main part circuit diagram of a third embodiment of the present invention, FIG. 7 is a circuit diagram of a conventional example, and FIG. 8 is a circuit diagram of another conventional example. 1 is an inverter circuit, 2 is a voltage detection circuit, 3 is a filament detection circuit, 4 is an inverter stop circuit, l ₁ and l ₂ are discharge lamps, and f ₁ , f ₂ , f ₃ and f ₄ are filaments.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-200688 (JP, A) JP-A-62-163293 (JP, A) JP-A-1-157099 (JP, A) JP-A-1-157099 186788 (JP, A) JP-A-62-200687 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H05B 41/24

Claims (1)

(57) [Claims] A first and a second switching element connected in series are connected to a DC power supply, one end of the DC power supply is connected to one end of a capacitor, and the other end of the capacitor is connected to the first and second switching elements. A load circuit including a discharge lamp connected in series is connected via an inductance element between the connection points of the switching elements, and the first and second switching elements are turned on and off alternately, so that an alternating current is applied to the discharge lamp. A discharge lamp lighting device including an inverter circuit for supplying power, and a voltage detection circuit connected between the other end of the capacitor and the other end of the DC power supply, wherein a first resistor is connected in series from one end of the DC power supply; And a common path of a discharge lamp connected in series to the other end of the DC power supply through the second resistor through the filament connected to the common discharge lamp and the voltage across the second resistor. Was done A filament detection circuit for detecting the filament; and an inverter stop circuit for stopping oscillation of the inverter circuit when at least one of the detection outputs of the filament detection circuit and the voltage detection circuit is lost. apparatus.