JP2008159599A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device performing protective operation by detecting disconnection of filaments and a loose contact state as well as the last stage of lifetime of a discharge lamp. <P>SOLUTION: An output transformer T<SB>1</SB>is provided between an inverter circuit 2 and the discharge lamp La, and a lamp lifetime detecting circuit 4 detects the last stage of lifetime of the discharge lamp La by the output of a detecting coil n<SB>3</SB>of the output transformer T<SB>1</SB>. A DC current is allowed to flow to the filaments of the discharge lamp La, and a first filament detecting circuit 5 detects the presence of disconnection of the filaments by the presence of a DC power source. Further, a second filament detecting circuit 6 detects loose contact based on the balance/unbalance of the current flowing to the filaments when the discharge lamp La is lighted. When one of the lamp lifetime detecting circuit 4, first filament detecting circuit 5 and second filament detecting circuit 6 detects abnormality, the inverter circuit 2 is operated at switching frequency in a preheating time. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a discharge lamp lighting device.

In recent years, a discharge lamp having a small diameter and a high output has been developed, and this type of discharge lamp needs to apply a higher voltage than a fluorescent lamp that has been widely used. Therefore, as a discharge lamp lighting device for lighting this type of discharge lamp, as shown in FIG. 10, a pulsating voltage obtained by rectifying an AC power source such as a commercial power source is boosted by using a chopper circuit 1, and the chopper circuit 1 not only converted into a high frequency alternating voltage the DC voltage more output using an inverter circuit 2, it is conceivable that by boosting the output voltage of the inverter circuit 2 by the output transformer T ₁ applied to the discharge lamp La. Further, a preheating transformer T ₂ is provided separately from the output transformer T _{1 in} order to allow a sufficient preheating current to flow through the filament of the discharge lamp La. Filament of the discharge lamp La is connected via a capacitor C _6, C _7, respectively in the preheating transformer T ₂ are a pair of preheating winding n _p which is provided as the secondary winding DC blocking. A discharge lamp lighting device provided with a preheating transformer is described in Patent Document 1, for example.

The inverter circuit 2 is configured to apply a voltage to the primary winding of the output transformer T ₁ through a resonance circuit composed of an inductor L ₂ and a capacitor C _2, and an operating frequency for turning on and off the switching elements Q ₂ and Q _3. Is configured to adjust the voltage between both ends of the discharge lamp La. Therefore, the discharge lamp La across the output transformer T ₁ for applying the voltage to the discharge lamp La filaments separately provided a preheating transformer T ₂ flowing preheating current to the, for pre-heating the operating frequency of the inverter 2, a starting, Desirable conditions can be obtained when changing to steady lighting. Here, the operating frequency of the inverter circuit 2 is set in a region higher than the resonance frequency of the load circuit.

Since the resonant circuit composed of inductor L ₂ and capacitor C ₂ Metropolitan constitutes a kind of low-pass filter, the voltage applied across the discharge lamp higher operating frequency of the inverter circuit 2 La is low. The inverter because the inter-connection end of the circuit 2 and the resonant circuit is connected to the primary winding of the preheating transformer T ₂ via a capacitor C _5, the inverter circuit preheating transformer T ₂ higher operating frequency of 2 The current flowing through the primary winding of the current increases. Therefore, along with the time of preheating to lower the applied voltage is set higher operating frequency to both ends of the discharge lamp La, increases the current supplied to the primary winding of the preheating transformer T _2, the electric power supplied to the preheating transformer T ₂ it is to relatively larger than the electric power supplied to the output transformer T ₁ a.
JP-A-8-17585

By the way, a lamp life detection circuit 3 for detecting an abnormal increase in the voltage across the discharge lamp La is provided between both ends of the discharge lamp La, and when the lamp life detection circuit 3 detects an abnormal increase in the voltage across the discharge lamp La, The inverter control circuit CN ₂ that controls the switching operation of the switching elements Q ₂ and Q ₃ of the inverter circuit ₂ is instructed to stop the switching elements Q ₂ and Q ₃ from being turned on / off. That is, the operation of the inverter circuit 2 is stopped at the end of the life of the discharge lamp La. By this operation, it is possible to prevent stress on the circuit components at the end of the life of the discharge lamp La.

On the other hand, even if the filament breaks while the discharge lamp La is lit, the discharge lamp La remains in the lit state, so the voltage across the discharge lamp La does not rise and the lamp life detection circuit 3 does not operate. Here, if no filament breakage, by across the series circuit of the preheating transformer T ₂ of the preheating winding n _p and the capacitor C _6, C ₇ are connected through the filament, the output transformer T While current is small flowing in the series circuit from the _first secondary side and the preheating winding _{n p} and the capacitor _C 6, _{C 7} of the preheating transformer _{T 2,} when the filament is disconnected, the preheating winding _{n p} and the capacitor _C 6, C ₇ increases, the amount of heat generated by the capacitors C ₆ and C ₇ and the preheating winding n _p increases. In other words, expected heating value of such a case, it is necessary to use a large-sized ones in the preheating transformer T2 and the capacitor C _6, C _7, a discharge lamp lighting device has a problem that large.

Moreover, defective portions for connection to the secondary side of the output transformer T ₁ and the discharge lamp La (e.g., insertion state of the discharge lamp La to the lamp socket is loose part) when there is a secondary winding of the output transformer T ₁ The poorly connected portion in the path from to the discharge lamp La becomes high resistance. Hereinafter, such a state is referred to as a loose contact state. As described above, since this type of discharge lamp La has a high applied voltage, an arc is likely to be generated in a poorly connected portion having a high resistance, and as a result, the switching elements Q ₂ and Q ₃ of the inverter circuit 2 are switched to each other. Excessive stress may cause the switching elements Q ₂ and Q _{3 to} be damaged, and the safety of structural parts such as lamp sockets may be reduced.

Further, when the operation of the inverter circuit 2 operates the lamp life detection circuit 3 as described above is stopped temporarily from blocking to be necessary to reset the control circuit CN ₂ power after replacing the discharge lamp La There is a problem that circuit parts for resetting the power supply are required, and the number of parts of the circuit parts increases, which also leads to an increase in the size of the discharge lamp lighting device.

  The present invention has been made in view of the above reasons, and its purpose is not only to detect the end of the life of the discharge lamp, but also to detect the breakage of the filament and the loose contact state, thereby preventing an increase in size and damage or safety. It is another object of the present invention to provide a discharge lamp lighting device that can prevent further deterioration in performance and further reduce the size by eliminating the need for resetting the power supply when the discharge lamp is replaced.

  According to the first aspect of the present invention, there is provided an inverter circuit that converts a DC power source into high-frequency power, an output transformer that boosts the output of the inverter circuit and applies it to a discharge lamp, and a resonance circuit that is inserted between the inverter circuit and the output transformer. And a preheating transformer that receives the output of the inverter circuit and sends a preheating current to the filament of the discharge lamp, and is inserted into a preheating current path from the inverter circuit to the filament of the discharge lamp, and increases the preheating current as the operating frequency of the inverter circuit increases. A current flows through a filter, a lamp life detection circuit that determines the end of the life of the discharge lamp when the voltage across the detection winding of the output transformer rises, and a series circuit in which an impedance element is inserted between both filaments of the discharge lamp And a first filament detection circuit for detecting the presence or absence of this current, and a point of the discharge lamp Sometimes the second filament detection circuit that detects the balance / unbalance of the current flowing through both filaments, and the lamp life detection circuit detects the end of the life of the discharge lamp, or the first filament detection circuit detects the current through the filament. If the second filament detection circuit detects an unbalance of the currents flowing through both filaments, it is judged abnormal, and the discharge lamp is turned on with the inverter circuit operating frequency set higher than the resonance frequency of the resonance circuit. And a lamp abnormality protection circuit that is set to be higher than the hourly frequency. According to this configuration, the end of life of the discharge lamp can be detected by the lamp life detection circuit, the filament breakage can be detected by the first filament detection circuit, and the loose contact state can be detected by the second filament detection circuit. Can be detected. The lamp life detection circuit can detect the loose contact state, and the second filament detection circuit can detect the disconnection of one filament. Therefore, it is possible to comprehensively detect these abnormalities and suppress the output of the inverter circuit, reduce stress on circuit components of the inverter circuit, and provide a discharge lamp lighting device with high safety and reliability. can do. Furthermore, when it is determined that there is an abnormality, the inverter circuit operating frequency is set to a higher frequency than when the discharge lamp is lit, and the inverter circuit operation is not stopped even in the event of an abnormality. It is possible to automatically return the discharge lamp to the lighting state when it is detected that the power is reset, and a power reset circuit as in the conventional configuration is unnecessary. As a result, the number of component circuit components is reduced, leading to further miniaturization. Here, if it is determined that there is an abnormality, the power supplied to the discharge lamp through the resonance circuit can be reduced by increasing the operating frequency of the inverter circuit, and as a result, the voltage across the discharge lamp can be reduced. it can. Therefore, it is possible to prevent an electric shock when replacing the discharge lamp.

  According to a second aspect of the present invention, there is provided an inverter circuit that converts a DC power source into high-frequency power, an output transformer that boosts the output of the inverter circuit and applies it to a discharge lamp, and a resonant circuit that is inserted between the inverter circuit and the output transformer. And a preheating transformer that receives the output of the inverter circuit and sends a preheating current to the filament of the discharge lamp, and is inserted into a preheating current path from the inverter circuit to the filament of the discharge lamp, and increases the preheating current as the operating frequency of the inverter circuit increases. A current flows through a filter, a lamp life detection circuit that determines the end of the life of the discharge lamp when the voltage across the detection winding of the output transformer rises, and a series circuit in which an impedance element is inserted between both filaments of the discharge lamp And a first filament detection circuit for detecting the presence or absence of this current, and lamp life detection If the end of life of the discharge lamp is detected by the path or if the current passing through the filament is not detected by the first filament detection circuit, it is judged abnormal, and the operating frequency of the inverter circuit is set higher than the resonance frequency of the resonance circuit. And a lamp abnormality protection circuit that is set to be higher than the frequency when the discharge lamp is turned on. In this configuration, the second filament detection circuit is not provided, but it is possible to detect the loose contact state by appropriately making a determination in the lamp life detection circuit, and the function substantially the same as that of the invention of claim 1 is achieved. The circuit configuration is simple while holding it. That is, it leads to further miniaturization, weight reduction, and cost reduction.

  According to a third aspect of the present invention, there is provided an inverter circuit that converts a DC power source into high-frequency power, an output transformer that boosts the output of the inverter circuit and applies the output to the discharge lamp, and a resonance circuit inserted between the inverter circuit and the output transformer. And a preheating transformer that receives the output of the inverter circuit and sends a preheating current to the filament of the discharge lamp, and is inserted into a preheating current path from the inverter circuit to the filament of the discharge lamp, and increases the preheating current as the operating frequency of the inverter circuit increases. A filter, a lamp life detection circuit that determines the end of the life of the discharge lamp when the voltage across the detection winding on the output transformer rises, and detects the balance / unbalance of the current flowing through both filaments when the discharge lamp is lit The end of life of the discharge lamp is detected by the second filament detection circuit and the lamp life detection circuit. When an unbalance of currents flowing through both filaments is detected by the second filament detection circuit, it is determined that an abnormality has occurred, and the discharge lamp whose operating frequency is set higher than the resonance frequency of the resonance circuit is turned on. A lamp abnormality protection circuit which is set to be higher than the above frequency. According to this configuration, the first filament detection circuit is not provided, but the second filament detection circuit can detect the disconnection of one of the filaments, and therefore has substantially the same function as the configuration of the invention of claim 1. The circuit configuration becomes simple while having a small size, leading to further miniaturization, weight reduction, and cost reduction.

  According to a fourth aspect of the present invention, in the first or second aspect of the present invention, when the lamp abnormality protection circuit determines that there is an abnormality, the output is held on the abnormal side and the first filament detection circuit is replaced with a normal discharge lamp. When the current flowing through the filament is detected, the holding on the abnormal side is released. This configuration is a preferred embodiment of the invention of claim 1 or claim 2, and when an abnormality occurs in the discharge lamp, it is held on the abnormal side until it is replaced with a normal lamp. In addition, since the first filament detection circuit detects that the lamp has been replaced with a normal discharge lamp and returns to a normal lighting state, a power reset circuit becomes unnecessary.

  A fifth aspect of the present invention uses the discharge lamp according to any one of the first to fourth aspects of the present invention, wherein a thermal fuse is connected to each filament in series. According to this configuration, since the temperature fuse built in one end of the filament is disconnected due to the abnormality of the discharge lamp, the first filament detection circuit detects the abnormality and protects the inverter circuit. A high discharge lamp lighting device can be provided.

  According to a sixth aspect of the invention, in the invention according to any one of the first to fifth aspects, when the lamp abnormality protection circuit determines that there is an abnormality, the operating frequency of the inverter circuit is set in the vicinity of the frequency at the time of preheating the discharge lamp. Therefore, when the discharge lamp in which an abnormality has occurred is replaced with a normal discharge lamp, it becomes immediately preheated and it becomes easier to return to the lighting state.

  The invention of claim 7 is the invention according to any one of claims 1 to 6, wherein the operating frequency of the inverter circuit is set within a range of 10 to 100 kHz when the discharge lamp is turned on, and the lamp abnormality protection circuit is provided. If it is determined that there is an abnormality, the operating frequency of the inverter circuit is set to 100 kHz or higher. This configuration is the preferred embodiment.

  According to the first aspect of the present invention, there is provided an inverter circuit that converts a DC power source into high-frequency power, an output transformer that boosts the output of the inverter circuit and applies it to a discharge lamp, and a resonance circuit that is inserted between the inverter circuit and the output transformer. And a preheating transformer that receives the output of the inverter circuit and sends a preheating current to the filament of the discharge lamp, and is inserted into a preheating current path from the inverter circuit to the filament of the discharge lamp, and increases the preheating current as the operating frequency of the inverter circuit increases. A current flows through a filter, a lamp life detection circuit that determines the end of the life of the discharge lamp when the voltage across the detection winding of the output transformer rises, and a series circuit in which an impedance element is inserted between both filaments of the discharge lamp And a first filament detection circuit for detecting the presence or absence of this current, and a point of the discharge lamp Sometimes the second filament detection circuit that detects the balance / unbalance of the current flowing through both filaments, and the lamp life detection circuit detects the end of the life of the discharge lamp, or the first filament detection circuit detects the current through the filament. If the second filament detection circuit detects an unbalance of the currents flowing through both filaments, it is judged abnormal, and the discharge lamp is turned on with the inverter circuit operating frequency set higher than the resonance frequency of the resonance circuit. The lamp abnormality protection circuit is set higher than the frequency of the hour, the end of life of the discharge lamp can be detected by the lamp life detection circuit, and the filament breakage is detected by the first filament detection circuit The second filament detection circuit detects the loose contact state Therefore, it is possible to comprehensively detect these abnormalities and suppress the output of the inverter circuit, reduce the stress on the circuit components of the inverter circuit, and turn on the discharge lamp with high safety and reliability. There is an advantage that an apparatus can be provided. Furthermore, when it is determined that there is an abnormality, the inverter circuit operating frequency is set to a higher frequency than when the discharge lamp is lit, and the inverter circuit operation is not stopped even in the event of an abnormality. It is possible to automatically return the discharge lamp to the lighting state when it is detected that the power is reset, and there is an advantage that the power reset circuit as in the conventional configuration is unnecessary. That is, there is an advantage that the number of component circuit parts is reduced, leading to further miniaturization. In addition, when it is determined that there is an abnormality, the power supplied to the discharge lamp through the resonance circuit can be reduced by increasing the operating frequency of the inverter circuit, and as a result, the voltage across the discharge lamp can be reduced. Therefore, there is an advantage that it is possible to prevent electric shock when replacing the discharge lamp.

  According to a second aspect of the present invention, there is provided an inverter circuit that converts a DC power source into high-frequency power, an output transformer that boosts the output of the inverter circuit and applies it to a discharge lamp, and a resonant circuit that is inserted between the inverter circuit and the output transformer. And a preheating transformer that receives the output of the inverter circuit and sends a preheating current to the filament of the discharge lamp, and is inserted into a preheating current path from the inverter circuit to the filament of the discharge lamp, and increases the preheating current as the operating frequency of the inverter circuit increases. A current flows through a filter, a lamp life detection circuit that determines the end of the life of the discharge lamp when the voltage across the detection winding of the output transformer rises, and a series circuit in which an impedance element is inserted between both filaments of the discharge lamp And a first filament detection circuit for detecting the presence or absence of this current, and lamp life detection If the end of life of the discharge lamp is detected by the path or if the current passing through the filament is not detected by the first filament detection circuit, it is judged abnormal, and the operating frequency of the inverter circuit is set higher than the resonance frequency of the resonance circuit. A lamp abnormality protection circuit that is set to be higher than the frequency at which the discharge lamp is lit, and the second filament detection circuit is not provided. Since it is possible to detect the loose contact state, the circuit configuration is simplified while having almost the same function as the invention of claim 1, which leads to further miniaturization, weight reduction, and cost reduction. There are advantages.

  According to a third aspect of the present invention, there is provided an inverter circuit that converts a DC power source into high-frequency power, an output transformer that boosts the output of the inverter circuit and applies the output to the discharge lamp, and a resonance circuit inserted between the inverter circuit and the output transformer. And a preheating transformer that receives the output of the inverter circuit and sends a preheating current to the filament of the discharge lamp, and is inserted into a preheating current path from the inverter circuit to the filament of the discharge lamp, and increases the preheating current as the operating frequency of the inverter circuit increases. A filter, a lamp life detection circuit that determines the end of the life of the discharge lamp when the voltage across the detection winding on the output transformer rises, and detects the balance / unbalance of the current flowing through both filaments when the discharge lamp is lit The end of life of the discharge lamp is detected by the second filament detection circuit and the lamp life detection circuit. When an unbalance of currents flowing through both filaments is detected by the second filament detection circuit, it is determined that an abnormality has occurred, and the discharge lamp whose operating frequency is set higher than the resonance frequency of the resonance circuit is turned on. And a lamp abnormality protection circuit that is set to be higher than the first frequency, and the first filament detection circuit is not provided, but the second filament detection circuit can detect the disconnection of one filament. Accordingly, there is an advantage that the circuit configuration is simplified while having substantially the same function as the configuration of the first aspect of the invention, leading to further miniaturization, weight reduction, and cost reduction.

  When the lamp abnormality protection circuit determines that an abnormality has occurred, the output is held on the abnormal side, and the current flowing through the filament is detected by the first filament detection circuit after replacement with a normal discharge lamp. If the abnormality occurs in the discharge lamp, it will be held on the abnormal side until it is replaced with a normal lamp, so the discharge lamp can be replaced safely. Since the replacement with the discharge lamp is detected by the first filament detection circuit and returned to the normal lighting state, there is an advantage that the power reset circuit becomes unnecessary.

  As in the fifth aspect of the invention, when a discharge lamp having a thermal fuse connected in series to each filament is used, the temperature fuse built in one end of the filament is disconnected due to an abnormality in the discharge lamp, and the first Since the filament detection circuit detects an abnormality and protects the inverter circuit, there is an advantage that it is possible to provide a discharge lamp lighting device that is much safer and more reliable.

  When the lamp abnormality protection circuit determines that the abnormality is present as in the invention of claim 6, the operation frequency of the inverter circuit is set near the frequency at the time of preheating the discharge lamp. There is an advantage that it becomes easier to return to the lighting state immediately after being replaced.

(Embodiment 1)
This embodiment, as shown in FIG. 1, as in the conventional discharge lamp lighting apparatus shown in FIG. 10, comprises a chopper circuit 1 and the inverter circuit 2 and the output transformer T ₁ and the preheating transformer T _2.

Chopper circuit 1 is intended for receiving the pulsating voltage AC power obtained by full-wave rectification, such as a commercial power supply, the input voltage to the series circuit of the switching element Q ₁ consisting of an inductor L ₁ and the MOSFET Apply. Also, the series circuit of the capacitor C ₀ for smoothing the diode D ₁ to the switching element Q ₁ is connected in parallel. The switching element Q ₁ is chopper control circuit CN _1, is switched at a sufficiently higher frequency than the frequency of the AC power source (power supply frequency).

As is well known, the chopper circuit 1 is a step-up type, releasing the energy stored in the inductor L ₁ during the ON switching element Q ₁ in the capacitor C ₀ through the diode D ₁ when the off-switching element Q _1. Therefore, by adding the voltage between the input voltage and the voltage across the inductor L ₁ is applied to the capacitor C _0, it is capable of boosting than the input voltage capacitor C _0. The gate of the switching element Q ₁ - is performed to protect the chopper control circuit CN ₁ for the short circuit between the gate - between the source is a Zener diode ZD ₁ is connected to the drain of the switching element Q _1.

The inverter circuit 2 includes a series circuit of switching elements Q ₂ and Q ₃ connected between both ends of the capacitor C ₀ , and the switching elements Q ₂ and Q ₃ are alternately switched at a high frequency by the inverter control circuit CN _2. . The switching elements Q ₂ and Q ₃ are MOSFETs, and the protective Zener diodes ZD ₂ and ZD ₃ are connected between the gate and the source in the same manner as the switching element Q ₁ . The one switching element Q ₃ load circuit is connected via a capacitor C ₁ for DC blocking.

The inverter circuit 2 of the foregoing is referred to as a half-bridge, the on period of the switching element Q ₂ as well known in the capacitor C ₀ → switching element Q ₂ → capacitor C ₁ → load circuit → the capacitor C ₀ in a current flows, in which current flows through a path of the switching element Q on period of ₃ to the capacitor C ₁ → switching element Q ₃ → load circuit → capacitor C _1. Thus, alternating current flows through the load circuit by turning on and off the switching elements Q ₂ and Q ₃ . The switching elements Q ₂ and Q ₃ are alternately turned on and off, but are controlled by the inverter control circuit CN ₂ so as not to be turned on at the same time.

The load circuit through the resonant circuit composed of inductor L ₂ and capacitor C ₂ is connected to the output transformer T _1, and the discharge lamp La is connected to the portion on the secondary side of the output transformer T _1, capacitor C ₅ as a filter connect the preheating transformer T ₂ via, and a preheating winding n _p the discharge lamp filaments connecting portion of the La is a secondary side of the preheating transformer T _2. The inductor L ₂ output connected in series with the primary winding of the transformer T _1, the capacitor C ₂ are connected in parallel to the primary winding of the output transformer T _1. Accordingly, the resonant circuit composed of inductor L ₂ and capacitor C ₂ Metropolitan constitutes a low-pass filter, the power supplied to the primary side of the output transformer T ₁ higher operating frequency of the inverter circuit 2 is reduced. Conversely, the power supplied to the primary winding of the preheating transformer T ₂ becomes large current operating frequency of the inverter circuit 2 passes through capacitor C ₅ higher increases.

That is, the operating frequency of the inverter circuit 2 than the resonant frequency of the resonant circuit composed of inductor L ₂ and capacitor C ₂ Metropolitan set to a higher region, by setting the higher frequencies the operating frequency of the inverter circuit 2 at the time of preheating, a voltage applied to the primary winding of the output transformer T ₁ through resonant circuit is lowered, increasing the current flowing through the primary winding of the preheating transformer T2. Therefore, it is possible to sufficiently preheat the current supplied from the preheating winding n _p of the secondary side of the preheating transformer T ₂ to the filaments of the discharge lamp La most to.

On the other hand, by pulling than during preheat the operating frequency of the inverter circuit 2 at the time of start-up, the voltage applied to the primary of the output transformer T ₁ through the resonant circuit is increased, also the preheating transformer by increasing the impedance of the capacitor C ₅ current flowing through the primary winding of T ₂ is reduced. Therefore, it is possible to start by applying a high voltage across the discharge lamp La. In addition, after the start-up, the discharge lamp La can be rated-lit or dimmed by appropriately setting the operating frequency. Here, the capacitor C ₄ is connected to the secondary winding of the output transformer T ₁ , and the filament of the discharge lamp is connected to the secondary winding of the preheating transformer T ₂ via the DC cutting capacitors C ₆ and C 7. Is done.

By the way, in this embodiment, the state of the discharge lamp La is detected by three types of information. End of life of the discharge lamp La is detected based on the voltage across the detection winding n ₃ provided on the output transformer T _1. At the end of the lifetime when the electron emission material on the filament surface is scattered (so-called Emires), it is in a half-wave lighting state in which only one polarity of the voltage applied to the discharge lamp La is turned on or in a non-lighting state. ramp voltage across La rises, as a result, the voltage across the detection winding n ₃ of the output transformer T ₁ is also increased. Therefore, the lamp life detection circuit 4, the voltage across the detection winding n ₃ by comparison with appropriate reference voltage, it is possible to detect the end of life of the discharge lamp La. Here, in the lamp life detection circuit 4, when the end of life of the discharge lamp La is detected, the output is set to the H level, and the output is always set to the L level.

The second information for detecting the state of the discharge lamp La is the presence or absence of breakage of the filament obtained by flowing a minute direct current through a path passing through the two filaments of the discharge lamp La. That is, current flows from both ends of the capacitor C ₀ which is the power source of the inverter circuit 2 to a circuit including a series circuit of the resistor R ₄ -filament-resistor R ₅ -filament-resistor R _6. If the current is flowing, the filament is normal, and if the current does not flow, it is determined that the filament is disconnected. The first filament detection circuit 5 sets the output to the L level when the filament is normal, and sets the output to the H level when it is detected that the current path has disappeared due to filament breakage or the like.

Here, there is a filament-resistor R ₅ -filament path as a path through which a direct current flows, and the second filament detection circuit 6 is inserted into this path. The second filament detection circuit 6 will be described later. Thus, the DC current is configured to pass therethrough. The second filament detection circuit 6 is inserted between the secondary winding of the output transformer T ₁ and the discharge lamp La, but the power supply from the secondary side of the output transformer T ₁ to the discharge lamp La It is configured not to interfere.

  The third information for detecting the state of the discharge lamp La is the magnitude relationship between the currents flowing through the two filaments of the discharge lamp La. In other words, the second filament detection circuit 6 detects the balance / unbalance of the current flowing through each filament of the discharge lamp La, and the current flowing through each filament is different when the balance is unbalanced. And) The output is set to H level, and if balanced, the output is maintained at L level. The current flowing through each filament becomes unbalanced when only one filament is disconnected or when the connection with the lamp socket is loose on one end side of the discharge lamp La (that is, in a loose contact state). .

  The output of the lamp life detection circuit 4 and the output of the second filament detection circuit 6 are input to the lamp abnormality protection circuit 8 through the OR circuit 7, and the output of the first filament detection circuit 5 is directly input to the lamp abnormality protection circuit 8. Is done. Therefore, it is possible to make the operation of the lamp abnormality protection circuit 8 the same at the end of the life of the discharge lamp La and at the time of loose contact, and to separate the operation of the lamp abnormality protection circuit 8 when the filament is disconnected.

Lamp fault protection circuit 8, any of the signals to be input becomes H level, and controls the inverter control circuit CN ₂ so as to increase the operating frequency than the time of lighting. Therefore, output transformer supplying power to the T ₁ is reduced by lowering the voltage applied to the discharge lamp La is increased the voltage stress on the switching element Q _2, Q ₃ is prevented. That is, the inverter circuit 2 is protected. Here, the inverter control circuit CN ₂ is controlled to vary the operating frequency in response to an external signal, preheating, starting, operating frequency corresponding to the lighting is instructed by an external signal.

Further, since the filament breakage is detected by the first filament detection circuit 5 or the second filament detection circuit 6 and the output of the inverter circuit 2 is reduced, the capacitors C ₆ and C ₇ and the preheating winding are used when the filament breaks. A large current does not flow through n _p to generate heat, and it is not necessary to use a large-sized preheating transformer T ₂ or capacitors C ₆ and C ₇ .

Furthermore, since the output of the inverter circuit 2 is also reduced when the second filament detection circuit 6 detects the loose contact state, a high voltage may be applied to the power supply path to the discharge lamp La in the loose contact state. In addition, it is possible to prevent the switching elements Q ₂ and Q ₃ from being damaged and the components from being damaged due to the occurrence of arc.

By the way, the lamp life detection circuit 4 is configured as shown in FIG. In the illustrated example, the voltage across the detection winding n ₃ of the output transformer T ₁ is divided by resistors R ₇ and R ₈ through a DC cut capacitor C ₃ , then rectified by a diode D ₂ , and further by a capacitor C _8. It is smooth. Accordingly, the voltage across the capacitor C ₈ is proportional to the average value of the voltage across the detection winding n _3. Therefore, compared with the reference voltage _{V ref1} voltage across capacitor C8 in a comparator CP _1, if voltage across the capacitor _{C 8} and the reference voltage _{V ref1} or more, an abnormality is judged that there is (end of life) Output H Make a level. Zener diode ZD ₄ which are connected across capacitor C ₈ is intended higher than the reference voltage V _ref1 breakover voltage, in which to limit the input voltage to the comparator CP ₁ to protect the comparator CP ₁ .

The first filament detection circuit 5 is configured as shown in FIG. In this configuration example, the DC current flowing from the capacitor C ₀ through the series circuit of the resistor R ₄ -filament-resistor R ₅ → filament-resistor R ₆ is rectified by the diode D ₃ and smoothed by the capacitor C _9. A voltage obtained by dividing the voltage between both terminals ₉ by resistors R ₁₀ and R ₁₁ is compared with a reference voltage V _ref2 by a comparator CP ₂ . Zener diode ZD ₅ has a function of limiting the input voltage to the comparator CP _2, protecting the comparator CP _2. First filament detection circuit 5, the voltage across the capacitor C ₉ to the burnout of the filament when lower than the reference voltage V _ref2, the output of the comparator CP ₂ to the H level. The reference voltage V _ref2 is obtained by _dividing a separately configured DC power source with resistors R ₁₂ and R ₁₃ . Since the resistors R ₄ and R ₆ are connected to the non-power supply side of the discharge lamp La and the resistor R ₅ is connected to the power supply side (step-up transformer side) of the discharge lamp La, the resistors R ₄ and R ₆ each filament between the resistor R ₅ is interposed, the disconnection of the filament by simply passing a minute current in the series circuit can be easily detected. Here, the connection relationship between the power supply side and the non-power supply side to the discharge lamp La of the resistor R ₄ to R ₆ may be reversed.

By the way, in this embodiment, it is comprised so that the operating frequency of the inverter circuit 2 may become the same frequency as the time of preheating at the time of a break of a filament. That is, in the present embodiment, Yes constructed from power to perform preheating of the predetermined time, the preheating time timer configured using a charging being timed by the time (the capacitor C ₁₁ of the capacitor C ₁₁ The circuit is omitted). Moreover, when pulling the voltage across the capacitor C _11, and the timer circuit operates the preheating operation (i.e., operation for setting a high operating frequency) performs. Therefore, the first filament detection circuit 5, the output of the comparator CP ₂ becomes the H level, and is configured to short-circuit the capacitor C ₁₁ of the timer. That is, the three switching elements Q _{10 to} Q ₁₂ made of transistors are turned on / off by the output of the comparator CP ₂ , and the switching element Q _{12 in} which the collector-emitter is connected between both ends of the capacitor C ₁₁ is connected to the comparator CP _12. since the output of the ₂ is turned on becomes H level, the output of the comparator CP ₂ across is short-circuited capacitor C ₁₁ becomes H level. With this configuration, it is possible to share a circuit portion for suppressing power supplied from the inverter circuit 2 to the discharge lamp La and preheating control, and the circuit configuration is simplified.

Second filament detection circuit 6 is, for example, those composed as shown in FIG. 4, two windings being inserted between each end and the filaments of the secondary winding of the output transformer T ₁ constituted by a current transformer T ₃ having a. The secondary winding output of the current transformer T ₃ is input to the lamp abnormality protection circuit 8 through the OR circuit 7. Current transformer T ₃ is connected to a polarity the secondary winding output is canceled by the current flowing during lighting of the discharge lamp La to both filaments. In other words, the power supply side end of each filament of the discharge lamp La is, since is connected in the same direction of winding ends of the two windings of the current transformer T _3, one with respect to winding end as shown in black circles in FIG. 4 When the current flows in the winding, the current flows in the other winding, and when the current flowing in both windings is equal, the output of the secondary winding is completely canceled. On the other hand, one of which or disconnection of the filaments, becomes loose contact state eliminates equal in magnitude of the current flowing in the two windings connected to the filament, the output to the secondary winding of the current transformer T ₃ occurs.

Therefore, the output of the second filament detection circuit 6 is given to the lamp abnormality protection circuit 8 through the OR circuit 7 configured as a wired OR by the diodes D ₄ and D ₅ , and the secondary winding of the current transformer T ₃ as described above. When the output is generated, the output of the lamp abnormality protection circuit 8 is set to the H level. Here, the lamp abnormality protection circuit 8 is shared with a part of the lamp life detection circuit 4 shown in FIG. That is, the resistor R ₈ is connected to the series circuit of the capacitor C ₃ and the resistor R _{7 of} the lamp life detection circuit 4 shown in FIG. 2 via the diode D ₄ , and the diode is connected to the secondary winding output of the current transformer T _3. than is to connect a resistor _{R 8} through D ₅ and the resistor _{R 9.} That is, the voltage across the detection winding n ₃ is divided by the resistors R ₇ and R ₈ , and the secondary output voltage of the current transformer T ₃ is divided by the resistors R ₉ and R ₈ .

With this configuration, when the open or loose contact state of the filaments occurs, as in the case of end of life of the discharge lamp La, the output of the comparator CP ₁ is become H level. As described above, the lamp abnormality detection circuit 8 is shared by the lamp life protection circuit 4 and the second filament detection circuit 6, so that the circuit configuration is simplified.

Incidentally, as described above, the first filament detection circuit 5 has a function of short-circuiting the capacitor C ₁₁ for timed preheating time upon breakage of the filaments, this function lamp life protection circuit 4 and the second to connect the filament detection circuit 6, as shown in FIG. 5, are the base of the transistor Q ₁₀ of the first filament detection circuit 5 connects the output terminal of the comparator CP _1. Further, when the abnormality by the first filament detection circuit 5 (broken filaments) is detected, in order to hold the state, the comparator CP by pulling the reference voltage V _ref1 of the comparator CP ₁ in lamp life detection circuit 4 The output of ₁ is kept at the H level. That is, the resistor _{R 14,} R _15, and applying a DC power source Vcc to the series circuit of the _{R 16,} a reference voltage _{V ref1} from the connection point of the resistors _{R 14, R 15} a of giving to the comparator CP _1, the resistor _{R 16} connects the switching element Q ₁₃ consisting of transistors in parallel connected to the common base of the switching element Q ₁₃ to the switching element Q ₁₀ total over scan. Therefore, the output of one of the comparators CP1, CP ₂ becomes H level, across capacitor C ₁₁ are short-circuited, the operating frequency of the inverter circuit 2 is of the same frequency as when preheating. In FIG. 5, the second filament detection circuit 6 is omitted. The switching element _{Q 13} is across the resistor _{R 16} is turned on is short, the reference voltage _{V ref1} of the comparator CP ₁ is pulled down. That is, when the output of the comparator CP ₁ becomes H level, the switching element Q ₁₃ is turned on, the output of the comparator CP ₁ is to remain at the H level. FIG. 6 shows the operation of each part when an abnormality occurs in the discharge lamp La. 6 (a) shows the relationship between the input voltage to the comparator CP ₁ (solid line) and the reference voltage (a chain _{line) V ref1,} FIG. 6 (b) input voltage (solid line) and the reference voltage (star point to the comparator CP ₂ The chain line shows the relationship with V _ref2 . FIG. 6 shows a case where the end of life of the discharge lamp La is detected as abnormal. First, when the preheating period _t 1 ~t _2, at the start of the period _t 2 ~t _3, time _t 3 the input voltage at the time of steady lighting of ~t ₄ to the comparator CP ₁ is lower than the reference voltage _{V ref1,} the comparator CP _Since the input voltage to ₂ is higher than the reference voltage V _ref2 , the outputs of both comparators CP ₁ and CP ₂ are both at L level, and the capacitor C ₁₁ is not short-circuited.

Then, when it is detected by the lamp life detection circuit 4 during lighting is end of life at the time t _4, after a predetermined time required for the voltage across the capacitor C ₈ is increased has elapsed, at time t ₅ the output of the comparator CP ₁ becomes H level, the reference voltage _{V ref1} is pulled at this time. Therefore, thereafter, the operating frequency becomes the same as that during preheating, the voltage across the discharge lamp La is lowered, and stress is prevented from being applied to the circuit components of the inverter circuit 2.

Discharge lamp Remove the La when from the input voltage to the comparator CP ₂ falls below the reference voltage _{V ref2} at time _{t 6,} the output of the comparator CP ₂ becomes the H level. Since a no-load condition in this case, the output of the comparator CP ₁ keeps the H level.

Next, when installing a normal discharge lamp La at the time t _7, the output of the comparator CP ₂ provided to the first filament detection circuit 5 from being energized filament becomes L level. In this case, by the discharge lamp La is normal, the switching element Q ₁₃ is turned off the output of the comparator CP ₁ also becomes L level, further charging of the switching element Q ₁₂ is the capacitor C ₁₁ is turned off Is started. That is, in the same manner as when the normal discharge lamp La is mounted and the power is turned on, a steady lighting state is reached through the preheating and starting processes. Thus, if there is an abnormality in the discharge lamp La, the operation frequency of the inverter circuit 2 is set to the same frequency as during preheating, and a protective operation is performed to prevent a high voltage from being applied across the discharge lamp La. preheating by simply releasing the short circuit state between both ends of the capacitor C ₁₁ when mounting the discharge lamp La, the starting is the automatically perform steady lighting. That is, it is not necessary to reset the power supply, and the configuration is simple. In the above-described configuration, when the lamp abnormality protection circuit 8 determines that an abnormality has occurred, the operating frequency of the inverter circuit 2 is made equal to the frequency at the time of preheating the discharge lamp La. It is not necessary to set the frequency near the preheating frequency. In general, the operating frequency of the inverter circuit 2 is set within a range of 10 to 100 kHz when the discharge lamp La is steadily lit, and is set to 100 kHz or more when preheating or abnormal (protective operation).

(Embodiment 2)
In the present embodiment, as shown in FIG. 7, the second filament detection circuit 6 is omitted from the configuration of the first embodiment, and the OR circuit 7 is also omitted accordingly. Although but also to detect other loose contact state of disconnection of the second filament in the filament detection circuit 6, because the loose contact state secondary voltage of the output transformer T ₁ is increased, lamp life detection circuit in this embodiment By adjusting the reference voltage V _ref1 of 4, the lamp contact detection circuit 4 can detect the loose contact state. Therefore, there is a possibility that the configuration of the present embodiment can realize a reduction in size, weight, and cost by reducing the number of parts as compared with the configuration of the first embodiment.

(Embodiment 3)
In the present embodiment, as shown in FIG. 8, the first filament detection circuit 5 is omitted from the configuration of the first embodiment, and the resistors R _{4 to} R ₆ are accordingly omitted. The first filament detection circuit 5 is provided for detecting the breakage of the filament, and the second filament detection circuit 6 can detect that any one of the filaments is broken. Even if the first filament detection circuit 5 is omitted, the same protection as in the first embodiment is possible. Therefore, there is a possibility that the configuration of the present embodiment can realize a reduction in size, weight, and cost by reducing the number of parts as compared with the configuration of the first embodiment.

(Embodiment 4)
As shown in FIG. 9, the present embodiment is an example in which the discharge lamp La in which the thermal fuse F is built in the configuration of the first embodiment is used. That is, the thermal fuse F is inserted in the electric path passing through the filament and is arranged in the vicinity of the filament, and there is an abnormality such that the temperature near the filament rises abnormally or the current flowing through the filament becomes excessive. When this occurs, the thermal fuse F is disconnected, and the operation of the first filament detection circuit 5 causes the inverter circuit 2 to be in a protective operation state. In this configuration, by using the discharge lamp La provided with the temperature fuse F, it is possible to provide a safer and more reliable discharge lamp lighting device.

It is a circuit diagram which shows Embodiment 1 of this invention. It is a principal part circuit diagram same as the above. It is a principal part circuit diagram same as the above. It is a principal part circuit diagram same as the above. It is a principal part circuit diagram same as the above. It is operation | movement explanatory drawing same as the above. It is a circuit diagram which shows Embodiment 2 of this invention. It is a circuit diagram which shows Embodiment 3 of this invention. It is a circuit diagram which shows Embodiment 4 of this invention. It is a circuit diagram which shows a prior art example.

Explanation of symbols

2 Inverter circuit 4 Lamp life detection circuit 5 First filament detection circuit 6 Second filament detection circuit 8 Lamp abnormality protection circuit C ₂ capacitor C ₅ capacitor F Thermal fuse L ₂ Inductor La Discharge lamp n ₃ Detection winding T ₁ Preheating transformer T ₁ output transformer

Claims (7)

  An inverter circuit that converts DC power into high-frequency power, an output transformer that boosts the output of the inverter circuit and applies it to the discharge lamp, a resonance circuit that is inserted between the inverter circuit and the output transformer, and an output of the inverter circuit A preheating transformer that receives the preheating current through the filament of the discharge lamp, a filter that is inserted into the preheating current path from the inverter circuit to the filament of the discharge lamp and increases the preheating current as the operating frequency of the inverter circuit increases, and an output transformer In addition, a current is passed through a series circuit in which an impedance element is inserted between both filaments of the discharge lamp and the presence / absence of this current is detected. A first filament detection circuit that operates and both filaments when the discharge lamp is lit The second filament detection circuit for detecting the balance / unbalance of the current flowing through the lamp and the lamp life detection circuit detects the end of the life of the discharge lamp, or the first filament detection circuit detects whether the current through the filament is detected. When the unbalance of the currents flowing through both filaments is detected by the filament detection circuit 2, the operation frequency of the inverter circuit is determined to be higher than the resonance frequency of the resonance circuit. A discharge lamp lighting device comprising: a lamp abnormality protection circuit that is set higher than the above.   An inverter circuit that converts DC power into high-frequency power, an output transformer that boosts the output of the inverter circuit and applies it to the discharge lamp, a resonance circuit that is inserted between the inverter circuit and the output transformer, and an output of the inverter circuit A preheating transformer that receives the preheating current through the filament of the discharge lamp, a filter that is inserted into the preheating current path from the inverter circuit to the filament of the discharge lamp and increases the preheating current as the operating frequency of the inverter circuit increases, and an output transformer In addition, a current is passed through a series circuit in which an impedance element is inserted between both filaments of the discharge lamp and the presence / absence of this current is detected. The first filament detection circuit and the lamp life detection circuit Of the discharge lamp in which the operating frequency of the inverter circuit is set to be higher than the resonance frequency of the resonance circuit. A discharge lamp lighting device comprising: a lamp abnormality protection circuit that is set to be higher than a frequency at the time of lighting.   An inverter circuit that converts DC power into high-frequency power, an output transformer that boosts the output of the inverter circuit and applies it to the discharge lamp, a resonance circuit that is inserted between the inverter circuit and the output transformer, and an output of the inverter circuit A preheating transformer that receives the preheating current through the filament of the discharge lamp, a filter that is inserted into the preheating current path from the inverter circuit to the filament of the discharge lamp and increases the preheating current as the operating frequency of the inverter circuit increases, and an output transformer A lamp life detection circuit for determining the end of the life of the discharge lamp when the voltage at both ends of the detection winding rises, and a second filament detection circuit for detecting the balance / unbalance of the currents flowing in both filaments when the discharge lamp is lit Whether the end of life of the discharge lamp is detected by the lamp life detection circuit or the second filament If the current detection circuit detects an imbalance in the current flowing through both filaments, it is determined that the inverter circuit is operating abnormally, and the operating frequency of the inverter circuit is set higher than the resonant frequency of the resonant circuit. A discharge lamp lighting device comprising a lamp abnormality protection circuit that is set higher.   The lamp abnormality protection circuit holds the output on the abnormal side when it is determined to be abnormal, and releases the abnormal side holding when the first filament detection circuit detects the current flowing through the filament after replacement with a normal discharge lamp. The discharge lamp lighting device according to claim 1 or 2.   The discharge lamp lighting device according to any one of claims 1 to 4, wherein in the discharge lamp, a thermal fuse is connected in series to each filament.   The discharge lamp lighting device according to any one of claims 1 to 5, wherein the lamp abnormality protection circuit sets the operating frequency of the inverter circuit in the vicinity of a frequency at the time of preheating the discharge lamp when it is determined as abnormal.   The operating frequency of the inverter circuit is characterized in that the operating frequency when the discharge lamp is lit is set within a range of 10 to 100 kHz, and that the operating frequency of the inverter circuit is set to 100 kHz or more when the lamp abnormality protection circuit determines that it is abnormal. The discharge lamp lighting device according to any one of claims 1 to 6.

Images