JPH118085A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce voltage to ground, detect disconnection of a filament or no-load of a discharge lamp with a simple circuit formation, and prevent the generation of high voltage. SOLUTION: The DC output of a DC power source 1 is converted into high- frequency output by a half-bridge type inverter circuit 2 and supplied to a discharge lamp La. The discharge lamp La is connected in parallel to a switching element Q2 on the lower voltage side of the inverter circuit 2. The first resistor R1 is connected between one end on the non-power source side of a filament f2 on the low potential side, and the positive electrode of the DC power source 1, and the second resistor R2 is connected at both the ends of the filament f2 on the low potential side. By comparing voltage Va which is detected at the connection point of the first and second resistors R1 , R2 by a detection circuit 4 with reference voltage Vref by a comparator CP1 , the output of the comparator CP1 becomes at a level L at the time of disconnection of the filament f2 , and the driving of the switching elements Q1 , Q2 by a control circuit 3 is stopped.

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 lighting a discharge lamp having a filament.

[0002]

2. Description of the Related Art Conventionally, in a discharge lamp lighting device in which a discharge lamp such as a fluorescent lamp is lit at a high frequency by an inverter circuit, a filament of the discharge lamp is disconnected in a no-load state (a state in which the discharge lamp is disconnected) or at the end of life. If the oscillation of the inverter circuit continues, a high voltage may be generated in the output portion or the socket portion, which may cause a danger such as electric shock. Therefore, when the abnormality described above occurs, the oscillation of the inverter circuit is forcibly stopped. This is commonly done.

FIG. 13 is a circuit diagram showing an example of a conventional discharge lamp lighting device in which the oscillation of the inverter circuit is forcibly stopped when the above-described abnormality occurs. This conventional device is constituted by a so-called half-bridge type inverter circuit. A pair of switching elements Q ₁ and Q ₂ are provided at both ends of a DC power supply 1 (generally, a commercial power supply and a circuit for rectifying and smoothing the same). A series circuit is connected, and a DC cut capacitor C ₁ , a choke coil L ₁ , a low potential side filament f _{2 of the} discharge lamp La, a resonance capacitor C ₂ , and a high potential switching element Q ₁ are connected in parallel with the high potential side switching element Q _1. The filament f ₁ on the potential side is connected in series, and the control circuit 3 turns on and off the pair of switching elements Q ₁ and Q ₂ alternately at a high frequency, thereby lighting the discharge lamp La at a high frequency.

Here, a series circuit of _two voltage dividing resistors R ₁ and R ₂ is connected between a connection point between one end of the filament f ₁ on the high potential side and the capacitor C ₂ and a negative electrode of the DC power supply 1. The base is connected to the connection point between the voltage dividing resistors R ₁ and R ₂ , the emitter is connected to the connection point between the voltage dividing resistor R ₂ and the negative electrode of the DC power supply 1, and a constant operation is performed via the resistor R ₃ to the collector. A transistor Q ₃ to which the power supply V _CC is applied is provided, and a collector of the transistor Q ₃ and a resistor R ₃
A signal (oscillation stop signal) obtained from the connection point with the control signal is output to the control circuit 3.

[0005] That is, if the filament f ₂ of the discharge lamp La in the unloaded condition and end of life or the like is broken, since the predetermined voltage to the connection point of the voltage dividing resistors R _1, R ₂ is obtained, the transistor Q ₃ is turned on As a result, an oscillation stop signal (low-level signal) is output to the control circuit 3. As a result, the drive signal is not output from the control circuit 3 to the switching elements Q ₁ and Q _2, and the oscillation of the inverter circuit 2 is stopped to prevent generation of a high voltage.

[0006]

In the case where the above-described discharge lamp lighting device is installed for indoor lighting, "
In Article 221-5 of the ministerial ordinance stipulating the technical standards for electrical equipment, the operating voltage of the connection circuit (so-called tube lamp circuit) for connecting the inverter circuit and the discharge lamp is 15 V to ground.
When the discharge lamp is installed in a dry place under the condition of 0 V or less (voltage between the tube lamp circuit and the ground), it is stipulated that it is not necessary to perform grounding work.

However, depending on the type and the DC power supply voltage of the discharge lamp, when connected to the switching element Q ₁ to the discharge lamp La in the high-potential side of the inverter circuit 2 as described above prior art device, release low rated voltage Electric lamp La (for example, 15
(0 V or less), the working voltage of the lamp circuit may be 150 V or more to the ground, and grounding work may be required. For example, in a discharge lamp (fluorescent lamp) called Twin Triple 32W (product number: FHT32), even if the rated lamp voltage is 100V, the ground voltage is about 300V.
About V.

On the other hand, it is difficult to perform grounding work for a house or the like, so that the ground voltage must be suppressed to 150 V or less. Therefore, by connecting the discharge lamp La to the switching element Q ₂ on the low potential side of the inverter circuit 2 of the half-bridge type, it is possible to suppress the ground voltage to the 150V or less. For example, in the case of the twin triple 32W discharge lamp, the ground voltage is about 130V.

[0009] However, when connected in this way the discharge lamp of the low-potential side switching element Q ₂ is, in the circuit configuration for detecting the disconnection from the DC power source 1 through the filament f ₂ as the conventional apparatus There is a problem that the circuit configuration becomes complicated because the AC lamp current flows through the detection circuit. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems. A discharge lamp capable of lowering a ground voltage and detecting disconnection or no-load of a filament of the discharge lamp with a simple circuit configuration to prevent generation of a high voltage. It is intended to provide a lighting device.

[0010]

According to the first aspect of the present invention, there is provided a DC power supply, and an inverter circuit for converting a DC output of the DC power supply into a high-frequency output and supplying the high-frequency output to a discharge lamp. A first resistor connected between a non-power supply side of the filament of the discharge lamp in which a power supply side of one filament is connected to a negative electrode of the DC power supply and a positive electrode of the DC power supply, and a first resistance connected to both ends of the filament; Oscillating the inverter circuit by detecting an abnormality such as a disconnection state of the discharge lamp or disconnection of the filament based on a detected second resistance and a detection voltage appearing at a connection point between the first and second resistances. And a detection circuit for stopping the
The above-described abnormality can be detected when the detection voltage appearing at the connection point of the first and second resistors changes from the normal state due to the disconnection state of the discharge lamp or the disconnection of the low-potential side filament, As a result, the ground voltage can be reduced, and the disconnection or no-load of the filament of the discharge lamp can be detected with a simple circuit configuration, and the generation of a high voltage can be prevented.

According to a second aspect of the present invention, in order to achieve the above object, a pair of switching elements are connected in series to both ends of a DC power supply obtained by rectifying and smoothing a commercial power supply, and a series circuit of a capacitor, an inductor and a discharge lamp is formed. The power supply side of the low potential side filament of the discharge lamp is connected in parallel with the low potential side switching element of the switching elements so that the negative side of the DC power supply is connected, and the non-power supply side of both filaments of the discharge lamp is used. And a control circuit for alternately turning on and off the pair of switching elements, the discharge lamp lighting device comprising: a non-power-side end of the low-potential-side filament and the DC power supply. A first resistor connected between the positive electrode, a second resistor connected to both ends of the low-potential-side filament, and a first resistor connected to the first and second resistors. A detection circuit for detecting an abnormality such as disconnection of the discharge lamp or disconnection of the filament based on a detection voltage appearing at a connection point, and outputting a stop signal for stopping on / off driving of the switching element to the control circuit; The above-described abnormality is detected when the detection voltage appearing at the connection point of the first and second resistors changes from the normal state due to the disconnection state of the discharge lamp or the disconnection of the filament. As a result, the ground voltage can be reduced, and the breakage of the filament of the discharge lamp or the no-load can be detected with a simple circuit configuration, and the generation of a high voltage can be prevented.

According to a third aspect of the present invention, there is provided a DC power supply, an inverter circuit for converting a DC output of the DC power supply into a high-frequency output and supplying the high-frequency output to a discharge lamp, and a negative electrode of the DC power supply. A first resistor connected between the power supply side of the filament of the discharge lamp and the positive electrode of the DC power supply, and a second resistor connected to both ends of the filament on the high potential side of the discharge lamp; Third and fourth resistors connected in series to the non-power supply side of both filaments of the discharge lamp, a fifth resistor connected to both ends of the low-potential side filament of the discharge lamp, A detection circuit that detects an abnormality such as a disconnection state of the discharge lamp or a disconnection of the filament based on a detection voltage appearing at a connection point of a fourth resistor, and stops oscillation of the inverter circuit. And the third The above-mentioned abnormality can be detected by the detection voltage appearing at the connection point of the fourth resistor and the fourth resistor changing from the normal state due to the disconnection state of the discharge lamp or the disconnection of both filaments. And a simple circuit configuration can detect disconnection or no-load of the filament of the discharge lamp, thereby preventing generation of a high voltage.

[0013] The invention of claim 4 is the invention of claim 1 or 2 or 3.
In the invention, the commercial AC power supply is rectified and smoothed to obtain the DC power supply, a current fuse is provided on one side of a power supply line from the AC power supply, and a rush current prevention resistor is provided on the other power supply line. It is characterized by the fact that, when incorrectly connected to an AC power supply, an excessive current can be prevented from flowing into the circuit by a current fuse and a resistor for preventing inrush current, and at the point where the circuit component is destroyed even if it is destroyed. Can be specified.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) FIGS. 1 and 2 show a circuit block diagram and a concrete circuit diagram of this embodiment, respectively. Note that the DC power supply 1 in FIG. 2 is obtained by rectifying and smoothing in the lighting circuit block B from the commercial AC power supply AC in FIG. Hereinafter, the present embodiment will be described mainly with reference to the specific circuit diagram of FIG.

In the discharge lamp lighting device of this embodiment, a pair of switching elements Q ₁ and Q ₂ are connected in series to both ends of a DC power supply 1, a DC cut capacitor C ₁ , an inductor (ballast choke) L _{1 and} Discharge lamp (fluorescent lamp) La
Connect the series circuit as the power supply side of the filament f ₂ on the low potential side of the discharge lamp La in parallel on the low potential side switching element Q ₂ is a negative electrode side of the DC power source 1 (ground side),
With a capacitor C ₂ for resonance in the non-power supply side of the two filament f _1, f ₂ of the discharge lamp La, the control circuit 3
And a conventional half-bridge type inverter circuit ₂ that alternately turns on and off a pair of switching elements Q ₁ and Q _2, and is connected to one end of the low-potential side filament f _{2 on} the non-power supply side. the first and the resistor R ₁ is connected between the positive electrode of the DC power source 1, a second resistor R ₂ connected to both ends of the filament f ₂ on the low potential side, of the first and second resistors R ₁ , based on the detection voltage Va at the connection point of the R ₂ a, and detects an abnormality such as a non-connection state or the disconnection of the filament f ₂ of the discharge lamp La from the presence or absence of the filament f ₂ on the low potential side, the control circuit 3 A detection circuit 4 for outputting a stop signal for stopping the on / off driving of the switching elements Q ₁ and Q ₂ .

The detection circuit 4 converts the detection signal Va input to the inverting input terminal into the reference voltage Vref input to the non-inverting input terminal.
And it comprises a comparator CP ₁ for comparing the output terminal of the comparator CP ₁ together with pulled-up to the operating power supply voltage V _CC by the resistors R _7, and is connected to the control circuit 3 and. In a state where the normal discharge lamp La is correctly connected, the detection voltage Va appearing at the connection point a between the _first resistor R ₁ and the second resistor R ₂ is represented by the following equation.

[0017]

(Equation 1)

Generally, the filaments f ₁ ,
resistance value Rf of f ₂ is about several Ω is cold, a starting or about 10~20Ω about even when lighting such as preheating, first
And the second resistors R ₁ and R ₂ are both high resistance (several hundred kΩ), so that the relationship of R ₁ , R ₂ ≫Rf is established.
The above equation can be approximately expressed as follows. Va = Rf / R ₁ × V _DC ≒ 0 [V] On the other hand, the detection voltage Va in an abnormal state such as when there is no load or when the filament f ₂ on the low potential side is broken is expressed by the following equation.

Va = {R ₂ / (R ₁ + R ₂ )} × _VDC Then, the reference voltage Vref of the comparator CP ₁ is set in the following range. Rf / R ₁ × V _DC <Vref <{R ₂ / (R ₁ + R ₂ )}
× V _DC Thus, H output of the comparator CP ₁ is during normal
Level and the output of the comparator CP ₁ becomes L level at the time of the filament f ₂ such as disconnection abnormality.

The control circuit 3 outputs the H level signal from the detection circuit 4.
When the signal is input, the switching element is
Child Q₁, Q_TwoAre turned on and off alternately, and the detection circuit 4
When an L level signal (stop signal) is input
Is the switching element Q₁, Q _TwoBy stopping the drive of
The oscillation of the inverter circuit 2 is stopped. This allows no load
Time or filament f_TwoWhen the inverter circuit 2
Accidents such as electric shock caused by high voltage applied to the force end
Can be prevented.

As described above, in this embodiment, the ground voltage can be reduced (150 V or less) by connecting the discharge lamp La to the switching element Q ₂ on the low potential side of the half-bridge type inverter circuit 2. becomes unnecessary, moreover it has the advantage that perform a simple circuit configuration of a discharge lamp breakage and no-load of the filament f ₂ of La detect occurrence of high voltage can be prevented.

(Embodiment 2) FIG. 3 shows a specific example of this embodiment.
It shows a road map. However, the configuration common to the first embodiment is
Therefore, the same reference numerals are given and the description is omitted. This embodiment
, The switching element is controlled by the control circuit 3.
Q₁, Q_TwoIt is not a separately excited type that drives the
Switching element Q₁, Q_TwoConnection point and capacitor C₁With
Each switch is connected to the secondary winding of the current transformer CT inserted between them.
Switching element Q₁, Q_TwoSelf-drive signal
An excitation type inverter circuit 2 is provided. Power supply
Switching element on the low potential side by the starting circuit 5 at the time of turning on
Q _TwoIs output from the inverter circuit 2 when
High-frequency current flows through the current transformer CT so that the secondary winding
Voltage is induced in each switch,
Element Q₁, Q_TwoAre alternately turned on and off to generate oscillation.
Will be maintained.

By the way, at the time of preheating or the like, the discharge lamp La
Since an excessive current may flow through the filaments f ₁ and f ₂ of the second embodiment, the second embodiment is used in this embodiment to prevent the detection circuit 4 from malfunctioning due to such an excessive current.
Of connecting the integrated circuit to both ends of the resistor R ₂ resistor R ₈ and the capacitor C ₃ in parallel, and the integral of the voltage detection voltage Va by the integration circuit so as to input to the inverting input terminal of the comparator CP _1.

Further, connecting the output terminal of the comparator CP ₁ to the base of the switching element Q ₂ on the low potential side.
That is, the normal at the output of the comparator CP ₁ to the switching element Q ₂ from becoming an H level is turned on and off driven by a voltage induced in the secondary winding of the current transformer CT, a discharge lamp La of the filament f ₂ There the output of the comparator CP ₁ becomes L level when disconnected, the oscillation of the inverter circuit 2 is to stop the induced voltage of the secondary winding is no longer applied to the base of the switching element Q _2.

(Embodiment 3) FIG. 4 is a specific circuit diagram of the present embodiment, and the configuration except for a detection circuit 4 'is the same as that of the second embodiment. And the description is omitted. DB is an AC power supply.
Rectifying the rectifier circuit (diode bridge), C ₀ is a smoothing capacitor for smoothing a pulsating flow output of the rectifier circuit DB.

The detection circuit 4 'in the present embodiment has a
Resistor R ₈ connected resistor R ₂ in series with a capacitor C
₃ , and a transistor Q _{4 that} is turned on / off by the output of the integrating circuit. The collector of the transistor Q ₄ is connected to the base of the switching element Q ₂ on the low potential side of the inverter circuit 2. And Thus, the transistor Q ₄ is turned off since the detection voltage Va becomes substantially zero at the time of normal, the switching element Q ₂ is current transformer CT
Driven on and off by the voltage induced in the secondary winding of, but the transistor Q ₄ is turned on appear the detection voltage Va in the case of the filament f ₂ of the discharge lamp La is disconnected,
Oscillation of the inverter circuit 2 is to stop the induced voltage of the secondary winding is no longer applied to the base of the switching element Q _2.

(Embodiment 4) FIG. 5 shows a specific example of this embodiment.
FIG. 4 shows a schematic diagram of a filament f on the high potential side of the discharge lamp La;₁
Connected between the power supply side of the DC power supply 1 and the positive electrode of the DC power supply 1
Resistance R₁And the filament f on the high potential side of the discharge lamp La₁
The second resistor R connected to both ends of the_TwoAnd the discharge lamp
Lament f₁, F_TwoThird and series connected to the non-power supply side of
And the fourth resistor R_Three, R_FourAnd the low-potential side lamp of the discharge lamp La.
Filament f_TwoResistor R connected to both ends of the_FiveWhen,
Third and fourth resistors R_Three, R_FourDetected at connection point a of
Based on the voltage Va, both filaments f of the discharge lamp La₁,
f_TwoOf the inverter circuit 2 and stops the oscillation of the inverter circuit 2.
And a detection circuit 4 ″ for performing the above operation.
In modes 1 to 3, the filament f on the low potential side of the discharge lamp La
_TwoAlthough only the disconnection was detected in this embodiment,
Filament f on both high and low potential side₁, F_Twoof
The disconnection is detected by the detection circuit 4 ″, and at least one of the
Lament f₁, F _TwoWhen the disconnection is detected
The feature is that oscillation of the data circuit 2 is stopped.
You. However, other configurations are common to the first and second embodiments.
Therefore, the same reference numerals are given to the common configurations.
Description is omitted.

The detection circuit 4 ″ in the present embodiment includes a fourth
Resistor R ₆ and a capacitor C which the resistor R ₄ is connected in parallel
₄ and a pair of comparators CP ₁ and CP ₂ for comparing the detection voltage Va input via the integration circuit with different reference voltages Vref 1 and Vref ₂ , respectively.
The output terminals of the comparators CP ₁ and CP ₂ are pulled up to the operating power supply voltage V _CC via the resistor R ₉ and are connected to the control circuit 3.

In a state where both filaments f ₁ and f ₂ are correctly connected in a normal state, the detection voltage Va is expressed by the following equation, as in the first embodiment. However, R _{1 to} R ₅ ≫
Rf is approximated. Va = R ₄ / (R ₁ + R ₃ + R ₄ ) × V _DC On the other hand, the detection voltage Vaf ₁ in a state where the filament f ₁ on the high potential side is disconnected is represented by the following equation.

By Vaf ₁ = R ₄ / (R ₁ + R ₂ + R ₃ + R ₄ ) × _VDC , the detection voltage Vaf ₁ when the filament f ₁ on the higher potential side is disconnected from the normal detection voltage Va is lower. since (Va> Vaf _1), the reference voltage Vref1 of the comparator CP ₁ is set to a slightly higher level than the detection voltage Vaf ₁ (see FIG. 6).

The detection voltage Vaf ₂ when the filament f ₂ on the low potential side is disconnected is represented by the following equation. Vaf ₁ = (R ₄ + R ₅ ) / (R ₁ + R ₃ + R ₄ + R ₅ )
× V _DC Therefore, since the detection voltage Vaf ₂ becomes higher when the filament f ₂ of the lower potential side than the detection voltage Va in the normal is disconnected (Va <Vaf _2), the detection reference voltage Vref2 of the comparator CP ₂ set slightly lower level than the voltage Vaf ₁ (see FIG. 6).

In the normal state, the comparator CP₁,
CP_TwoAre both at H level, and the control circuit 3
H level signal is input from the output circuit
Switching element Q₁, Q_TwoOn and off alternately
You. Then, the filament f on the high potential side₁Is broken
If the comparator CP₁Output drops to L level
Therefore, an L level signal is sent from the detection circuit 4 ″ to the control circuit 3.
(Stop signal) is input and the switching element Q₁, Q_Two
Is stopped, and the oscillation of the inverter circuit 2 is stopped.
Also, the filament f on the low potential side_TwoIs broken
Is the comparator CP _TwoOutput drops to L level
Therefore, an L level signal (stop) is sent from the detection circuit 4 ″ to the control circuit 3.
Stop signal) is input and the switching element Q₁, Q_TwoNo drive
The operation is stopped, and the oscillation of the inverter circuit 2 is stopped. sand
That is, at least one filament of the discharge lamp La
f₁, F_TwoIs the detection circuit 4 "when is disconnected or disconnected?
Output a stop signal and switch by the control circuit 3.
Element Q₁, Q_TwoWhen the drive stops, the inverter
The oscillation of the circuit 2 is stopped.

(Embodiment 5) By the way, the above-described discharge lamp lighting device is configured by mounting various circuit components on a printed circuit board and is installed in the fixture main body of the lighting fixture. Input terminal 6 to which the AC power supply AC is connected
And a pair of output terminals 7 ₁ and 7 ₂ to which the respective filaments f ₁ and f _{2 of} the discharge lamp La are connected are mounted on a printed circuit board. In recent years, as lighting fixtures have become smaller and thinner, there has been a demand for smaller and thinner discharge lamp lighting devices.
In the prior art, for example, as shown in FIG. 9, there are few restrictions on the dimensions of the discharge lamp lighting device.
_1, 7 ₂ and so that disposed near the ends of opposing the printed circuit board 8, the structure, it was possible to separate without close to the input terminal 6 output terminal 7 _1, 7 _2.

However, miniaturization of the discharge lamp lighting device is required.
In the course of the process, as shown in FIG.
The input terminal 6 and the output terminal 7₁, 7_TwoAnd the pudding
It is inevitable to adopt a structure that is juxtaposed to one end of the substrate 8.
Sometimes. In such a structure, the lighting fixture group
The power supply line and the load line are connected to the input terminal 6 and the output terminal 7 when standing up.₁,
7_TwoIf the connection is incorrectly made, the AC power
Source AC to output terminal 7 _Two, Rectifier circuit DB, inrush current prevention
Current through the resistor 9, the current fuse 10, and the input terminal 6.
Current fuse 1 when a short-circuit current flows when a path is formed
When 0 is disconnected to protect circuit parts such as semiconductor parts
However, as shown in FIG.
The input terminal 6 on the side where the current prevention resistor 9 is not provided
(AC line), the AC power supply AC
Force terminal 7_Two, Rectifier circuit DB, formed via input terminal 6
Circuit components are destroyed by short-circuit current flowing through the current path
Or the wiring pattern of the printed circuit board 8 may be destroyed.
There is. If the wiring pattern of the printed circuit board 8 is broken,
It is impossible to reuse the printed circuit board 8
It is. Also, to prevent the above misconnection,
Force terminal 6 and output terminal 7 ₁, 7_TwoOr colored with different colors
It is possible to change the shape, but due to the increase in the number of parts,
Disadvantages such as increased cost.

Therefore, in this embodiment, a current fuse 10 is provided on one side of a power supply line from an AC power supply AC, and a rush current prevention resistor 9 is provided on the other power supply line. Other configurations are described in the first embodiment.
Therefore, common portions are denoted by the same reference numerals, and illustration and description thereof are omitted. As shown in FIG. 7, in the present embodiment, a rush current prevention resistor 9 and a current fuse 10 are inserted in each power supply line between the input terminal 6 and the AC input terminal of the rectifier circuit DB. an input terminal 6 of the inserted and which side of the power source AC end the current fuse 10, in the case which is connected erroneously to one of the output terminals 7 _2, AC power output from the AC terminal 7 _2,
Although there is no current limiting element in the current path formed through the rectifier circuit DB, the current fuse 10, and the input terminal 6, a short-circuit current flows, but the current fuse 10 is disconnected to constitute a discharge lamp lighting device. (Switching element Q
_1, destruction of the wiring pattern of the fracture and the printed circuit board 8 Q ₂ ', etc.) can be prevented.

Further an input terminal 6 of the inserted and which side of the AC power supply AC of end resistance for preventing inrush current 9 as shown in FIG. 8, as long as when it is connected erroneously to one of the output terminals 7 ₂ , AC power source AC from the output terminal 7 _2, rectifier circuit DB, a rush current prevention resistor 9, but the short-circuit current flows through the current path formed through the input terminal 6, the inrush current prevention resistor 9 and a current limiting element As a result, short-circuit current is suppressed, and destruction of circuit components and wiring patterns can be prevented.

According to the present embodiment as described above, the discharge lamp
Input terminal 6 and output terminal 7 of the lighting device ₁, 7_TwoAC power
When the source AC is incorrectly connected, circuit components and wiring patterns
Destruction can be reliably prevented. Moreover, misconnection
Components that need to be replaced when
Since it is specified as a resistor 10 or a resistor 9 for preventing inrush current,
By replacing only these parts, the printed circuit board 8 and other
There is also an advantage that the circuit component can be reused as it is.

[0038]

According to the first aspect of the present invention, there is provided a DC power supply, an inverter circuit for converting a DC output of the DC power supply into a high-frequency output and supplying the output to a discharge lamp, and a power supply side of one filament being connected to a negative electrode of the DC power supply. A first resistor connected between the non-power supply side of the filament of the discharge lamp and the positive electrode of the DC power source, a second resistor connected to both ends of the filament, A detection circuit that detects an abnormality such as a disconnection state of the discharge lamp or a disconnection of the filament based on a detection voltage appearing at a connection point of the second resistor and stops the oscillation of the inverter circuit.
The above-described abnormality can be detected when the detection voltage appearing at the connection point of the first and second resistors changes from the normal state due to the disconnection state of the discharge lamp or the disconnection of the low-potential side filament, As a result, there is an effect that the ground voltage can be reduced, and the disconnection or no-load of the filament of the discharge lamp can be detected with a simple circuit configuration, and the generation of a high voltage can be prevented.

According to a second aspect of the present invention, a pair of switching elements are connected in series to both ends of a DC power supply obtained by rectifying and smoothing a commercial power supply, and a series circuit of a capacitor, an inductor and a discharge lamp is connected to a low potential of the switching elements. Connected in parallel with the switching element on the side such that the power supply side of the filament on the low potential side of the discharge lamp is the negative electrode side of the DC power supply,
In a discharge lamp lighting device comprising a resonance capacitor connected to a non-power supply side of both filaments of the discharge lamp and a pair of switching elements being alternately turned on and off by a control circuit, the low potential side filament is A first resistor connected between one end on the non-power supply side and a positive electrode of the DC power source, a second resistor connected to both ends of the low potential side filament, and a first resistor connected to the first and second resistors; A detection circuit for detecting an abnormality such as disconnection of the discharge lamp or disconnection of the filament based on a detection voltage appearing at a connection point, and outputting a stop signal for stopping on / off driving of the switching element to the control circuit; The first
And the detection voltage appearing at the connection point of the second resistor changes with respect to the normal state due to the disconnection state of the discharge lamp or the disconnection of the filament, so that the above-mentioned abnormality can be detected. It is possible to detect the disconnection of the filament of the discharge lamp and no load with a simple circuit configuration and to prevent the generation of a high voltage.

According to a third aspect of the present invention, there is provided a DC power supply, an inverter circuit for converting a DC output of the DC power supply into a high-frequency output and supplying the output to a discharge lamp, and a filament of the discharge lamp connected to a negative electrode of the DC power supply. A first resistor connected between a power supply side of the discharge lamp and the positive electrode of the DC power supply, a second resistor connected to both ends of a high-potential side filament of the discharge lamp, A third and a fourth resistor connected in series to the non-power supply side, a fifth resistor connected to both ends of a low-potential side filament of the discharge lamp, and a connection point of the third and fourth resistors. A detection circuit for detecting an abnormality such as a disconnection state of the discharge lamp or disconnection of the filament based on the detected detection voltage and stopping the oscillation of the inverter circuit, so that the connection of the third and fourth resistors is provided. Detected power that appears at the point Can be detected when the discharge lamp changes from the normal state due to the disconnection state of the discharge lamp or the disconnection of both filaments.As a result, the ground voltage can be reduced and the discharge lamp can be configured with a simple circuit configuration. There is an effect that disconnection of the filament and no-load can be detected and generation of a high voltage can be prevented.

According to a fourth aspect of the present invention, a commercial AC power supply is rectified and smoothed to obtain the DC power supply, a current fuse is provided on one side of a power supply line from the AC power supply, and an inrush current is prevented on the other power supply line. The current fuse and the rush current prevention resistor can prevent excessive current from flowing into the circuit when the AC power supply is incorrectly connected, and can be destroyed even if circuit components are destroyed. There is an effect that the place where the information is written can be specified.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing a first embodiment.

FIG. 2 is a specific circuit diagram showing the above.

FIG. 3 is a specific circuit diagram showing a second embodiment.

FIG. 4 is a specific circuit diagram showing a third embodiment.

FIG. 5 is a specific circuit diagram showing a fourth embodiment.

FIG. 6 is an explanatory diagram for explaining the operation of the above.

FIG. 7 is a specific circuit diagram showing a fifth embodiment.

FIG. 8 is an explanatory diagram for explaining the operation of the above.

FIG. 9 is an explanatory diagram for explaining the above.

FIG. 10 is an explanatory diagram for explaining the above.

FIG. 11 is an explanatory diagram for explaining the above.

FIG. 12 is an explanatory diagram for explaining the above.

FIG. 13 is a specific circuit diagram showing a conventional example.

[Explanation of symbols]

Reference Signs List 1 DC power supply 2 Inverter circuit 3 Control circuit 4 Detection circuit R ₁ First resistor R ₂ Second resistor La Discharge lamp

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takashi Furukawa 1-55 Yoshida Shimojima, Higashiosaka-shi, Osaka Asahi National Lighting Co., Ltd.

Claims (4)

[Claims] 1. A DC power supply, an inverter circuit for converting a DC output of the DC power supply into a high-frequency output and supplying the output to a discharge lamp, and a power supply of one filament connected to a negative electrode of the DC power supply. A first resistor connected between the non-power supply side of the filament and the positive electrode of the DC power supply;
An abnormality such as disconnection of the discharge lamp or disconnection of the filament is detected based on a second resistor connected to both ends of the filament and a detection voltage appearing at a connection point between the first and second resistors. And a detection circuit for stopping the oscillation of the inverter circuit. 2. A pair of switching elements are connected in series to both ends of a DC power supply obtained by rectifying and smoothing a commercial power supply, and a series circuit of a capacitor, an inductor and a discharge lamp is connected to a low-potential side switching element of the switching elements. In parallel, the power supply side of the filament on the low potential side of the discharge lamp is connected such that the negative side of the DC power supply is connected, and a resonance capacitor is connected to the non-power supply side of both filaments of the discharge lamp, and a control circuit is used. In a discharge lamp lighting device configured to alternately turn on and off the pair of switching elements, a first resistor connected between one end of the non-power supply side of the low potential side filament and a positive electrode of the DC power supply, A second resistor connected to both ends of the low-potential side filament, and a detection voltage of the discharge lamp based on a detection voltage appearing at a connection point between the first and second resistors. A discharge lamp lighting device, comprising: a detection circuit that detects an abnormality such as a connection state or breakage of the filament and outputs a stop signal to stop on / off driving of the switching element to the control circuit. 3. A DC power supply, an inverter circuit that converts a DC output of the DC power supply into a high-frequency output and supplies it to a discharge lamp, and a power supply side of a filament of the discharge lamp connected to a negative electrode of the DC power supply. A first resistor connected between a positive electrode of the DC power supply, a second resistor connected to both ends of a high-potential side filament of the discharge lamp, and a series connected to a non-power supply side of both filaments of the discharge lamp. Based on the third and fourth resistors connected, the fifth resistor connected to both ends of the low-potential filament of the discharge lamp, and the detection voltage appearing at the connection point of the third and fourth resistors. A discharge circuit for detecting an abnormality such as a disconnection state of the discharge lamp or a breakage of the filament and stopping the oscillation of the inverter circuit. 4. A commercial AC power supply is rectified and smoothed to obtain the DC power supply, a current fuse is provided on one side of a power supply line from the AC power supply, and a rush current prevention resistor is provided on the other power supply line. 2. The method according to claim 1, wherein
Or the discharge lamp lighting device according to 2 or 3.