JPH0831586A - Discharge lamp lighting device - Google Patents

Abstract

(57) [Summary] [Object] To provide a discharge lamp lighting device equipped with a protection circuit capable of accurately detecting an emitterless phenomenon occurring at the end of the life of a discharge lamp without delay and preventing element failure. [Structure] An AC / DC converter circuit 8, a half-bridge inverter circuit 1, a drive circuit 10 including a pulse transformer 12 and a driving IC 11, and a dimming control circuit 20, and a reactor 4 on the output side of a pair of switching elements 2 and 3. , A discharge lamp lighting device that controls the lighting of the discharge lamp 9 connected via the capacitors 5 and 6 detects the end of life of the discharge lamp by the change in the phase of the high frequency AC voltage V ₁ and the current I, and Detection circuit 30 which outputs a voltage signal V _c proportional to the amount of advance
And a protection stop circuit 40 that receives the voltage signal and outputs a protection signal to the dimming control circuit.

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 including an inverter circuit for lighting a discharge lamp at a high frequency, and more particularly, when a discharge lamp reaches the end of its life, a current flows to the inverter circuit and a current flows therethrough. The present invention relates to a discharge lamp lighting device including a detection circuit and a protection circuit that prevent damage to a switching element.

[0002]

2. Description of the Related Art FIG. 7 is a connection diagram showing a simplified conventional discharge lamp lighting device. A half-bridge inverter circuit 1 for converting an output DC voltage of an AC / DC converting circuit 8 into a high frequency AC voltage V ₁ and outputting the high frequency AC voltage V 1 is shown. It is composed of a pair of switching elements 2 and 3 composed of MOSFETs, and a pair of filaments of a discharge lamp 9 is connected to the output side of the half-bridge inverter circuit 1 via a capacitor 6 (capacitance C ₀ ) and a reactor 4 (inductance L). Further, a capacitor 5 (capacitance C) is connected between the pair of filaments to form a discharge lamp circuit as a load.

Further, the half bridge inverter circuit 1
ON / OFF control of a pair of switching elements 2 and 3 alternately
Control the DC voltage to the high frequency AC voltage V₁Drive times to convert to
Path 10 is connected to the control terminals of switching elements 2 and 3.
Pulse transformer 12 to which a pair of secondary windings 12S is connected
And a driving I whose output side is connected to the primary winding 12P
And C11. Resistance R_13,Capacitor C_13,Oh
And constant voltage diode D ₁₃Receives a stabilized power supply voltage at
The driving IC 11 that operates in accordance with₁Oscillation
The dimming part that determines the frequency and the oscillation frequency of the dimming part
It consists of a drive unit that generates the corresponding drive voltage.
The final stage consists of a pair of transistors that turn on and off alternately.
And each collector is the primary winding of the pulse transformer
The midpoint of the primary winding is connected to the regulated power supply.
In addition, the light control unit has a resistor R as an external circuit._{twenty one,}Variable resistance V
R_{twenty one,}And capacitor C_{twenty one}Dimming control circuit 20 including
And the reference, for example, the total light lighting frequency ff
It is determined.

When the discharge lamp 9 is turned on, the filament preheating, all-light lighting, and dimming lighting are generally controlled by changing the frequency, and the frequency is the resonance frequency of the discharge lamp circuit. _0, filament preheat frequency f _p, total light lighting frequency ff, dimming lighting frequency f _d
In order to satisfy the condition of f _p > f ₀ > f _d > ff, for example, the center frequency is f _p = 100 kHz _, f ₀ = 8
_{0~90kH Z, f d = 82kH Z} , ff = 56kH Z, is set to. The control of the oscillation frequency of the driving IC 11 is performed by a resistor R _21, V that determines the total lighting frequency ff as a reference frequency.
This is performed by the frequency switching unit 24 provided in parallel with the series circuit of R ₂₁ . In the case of the figure, the frequency switching unit 2
_{Reference numeral 4} is composed of a series circuit of a preheating frequency setting resistor R ₂₄ and a transistor switch T _{r24 whose} collector is connected in series to the preheating frequency setting resistor R ₂₄ (In addition to this, a series circuit of a dimming frequency setting resistor and a changeover switch is provided. ).

The transistor switch T _r24 is operated by a preheat timer 26 provided on the output side of the AC / DC converting circuit 8. The preheat timer 26 is a capacitor C charged by the output DC voltage of the AC / DC conversion circuit 8 via a resistor R _26.
26 and the charging voltage of the capacitor C ₂₆ to the constant voltage diode D
Includes a transistor switch T _r26 which operates by receiving the base side through the _26, the charging voltage of the capacitor C ₂₆ is increased to a voltage corresponding to the sum of the base voltage of the breakdown voltage and T _r26 of D _26, T _r26 is on The voltage corresponding to the output DC voltage of the AC / DC conversion circuit 8 is applied to the frequency switching unit 2 for a certain period of time.
Output to 4. Thus, the transistor switches T _{r2 4} of the fixed time-frequency switching unit 24 is turned on, so connected in parallel to preheat frequency setting resistor R ₂₄ to the series circuit of the resistors R _21, VR _21, preheating the predetermined time The oscillation frequency of the driving IC is the preheating frequency f _p as the period.
Rise to.

Based on the preheating frequency of the light control section of the drive IC 11, the drive signal output from the drive section is supplied to the primary winding 12P.
The pulse transformer 12 that receives the signal operates in an alternating current manner, and an in-phase alternating current signal is generated in the secondary winding thereof. Therefore, by applying two alternating current signals to the switching elements 2 and 3 so as to have mutually opposite phases, Switching elements 2 and 3
Are alternately turned on and off, and the high frequency AC voltage V ₁ having the preheating frequency f _p is applied to the discharge lamp circuit including the discharge lamp 9.

8A and 8B are equivalent circuit diagrams showing the operation of the discharge lamp circuit. FIG. 8A is a diagram showing a lighting state, and FIG. 8B is a diagram showing a non-lighting state. The resistance R is an internal discharge resistance of the discharge lamp in a state where the discharge lamp 9 is lit and a discharge current flows, and the discharge current becomes almost zero in a non-illuminated state. Therefore, the discharge lamp circuit has a series resonance of L and C. In contrast to the circuit (frequency f ₀ ),
In the all-light lighting state, the capacitance C is terminated by the discharge resistance R, so that the resonance frequency becomes lower than f _{0 and} the Q value also decreases. Therefore, although the discharge lamp is not lit at the time when the high frequency AC voltage of the residual heat frequency f _p is applied to the discharge lamp circuit to start the residual heat of the filament, the discharge lamp is easily lit as the filament temperature rises.
When the preheating period ends and the preheating switch is turned off, the frequency of the high frequency AC voltage V ₁ is switched to the all-light lighting frequency ff, so that the impedance of the discharge lamp circuit is lowered and the discharge current (lamp current) easily flows, Thereafter, the all-light lighting frequency ff is maintained to maintain stable all-light lighting operation.

However, at the end of the life of the discharge lamp 9 during lighting, the emitter coated on the filament disappears,
Since it becomes difficult for the discharge current to flow from the filament side that has become emitterless, a so-called half-wave phenomenon of the discharge current occurs. At this time, the equivalent circuit of the discharge lamp circuit is shown in FIG.
The transition from (b) to (b) occurs transiently, an overvoltage surge occurs in the discharge lamp circuit, and the phase of the current I with respect to the voltage V changes from the delayed phase to the advanced phase. When the current flows, an overcurrent flows, and sometimes a trouble such as an arm short circuit occurs in the half bridge inverter 1. Therefore, in order to avoid the occurrence of such a trouble, there is known a discharge lamp lighting device provided with a protection circuit for detecting an emitterless phenomenon at the end of the discharge lamp life and preventing damage to the switching elements 2 and 3. Has been.

FIG. 9 is an equivalent circuit diagram showing a method of detecting and protecting the end of the discharge lamp life in a conventional discharge lamp lighting device.
An electric abnormal phenomenon detecting circuit 7 is connected to the discharge lamp circuit, and when the half-wave discharging phenomenon is detected, a command to stop the operation is issued to the drive circuit 10. Further, a method of detecting an overcurrent or an unbalance of currents generated in an inverter circuit due to a half-wave discharge phenomenon, a method of detecting an overvoltage generated in a discharge lamp, a method of detecting an abnormal temperature rise of a switching element, or the like is also known. ing.

[0010]

Among the conventional protection methods,
In the method of detecting the half-wave discharge phenomenon, the direction and value of the generated half-wave discharge differ depending on which of the two filaments is emitterless. Therefore, if one of the half-wave discharge phenomena is detected, the other emitter-less phenomenon is detected. There is a problem that the accuracy of protection is low. Also,
In the method of detecting overcurrent, current imbalance, or overvoltage, a distinction is made between the same phenomenon that occurs when the equivalent circuit of the discharge lamp circuit changes from the non-discharge state to the lighting state in the normal lighting process. Since the determination is made based on the difference, not only sufficient determination accuracy cannot be obtained, but sometimes there is a problem that the lighting operation becomes congested due to an erroneous determination. Further, in the method of detecting the abnormal temperature rise of the switching element, there is a problem that the protection operation cannot be performed in time depending on the method of the inverter circuit because the response speed of the temperature sensor is slow.

An object of the present invention is to provide a discharge lamp lighting device provided with a protection circuit capable of accurately detecting the emitterless phenomenon occurring at the end of the life of the discharge lamp without delay and preventing element failure.

[0012]

In order to solve the above-mentioned problems, according to the present invention, an AC / DC converter circuit, a half-bridge inverter circuit for converting the output DC voltage to a high frequency AC voltage and outputting the high frequency AC voltage, and The half-bridge inverter circuit comprises a pulse transformer in which a secondary winding is connected to the control terminals of a pair of switching elements and a driving IC whose output side is connected to the primary winding of the pulse transformer, and the pair of switching elements are alternately turned on / off. A drive circuit and a dimming control circuit that controls switching of an input frequency of the drive circuit to an oscillation frequency corresponding to residual heat of a discharge lamp, all-light lighting, or dimming lighting, are provided on the output side of the pair of switching elements. In the case of controlling the lighting of a discharge lamp connected via a reactor or a capacitor, the end of the life of the discharge lamp is controlled by the high-frequency AC. A detection circuit that emits a voltage signal proportional to the phase difference detected by a change in the phase of the pressure and the current; and a protection stop circuit that receives the voltage signal and issues a protection signal to the dimming control circuit. Shall be.

The detection circuit includes a secondary winding added to the reactor, a transistor switch circuit in which a collector is connected to the secondary winding and a base is connected to the output side of the half-bridge inverter circuit via a resistor, and this transistor A smoothing capacitor, which is charged by the current flowing through the secondary winding when the switch is off, may be provided.

The detection circuit includes a secondary winding added to the reactor, a comparator circuit in which the non-inverting input side is connected to the secondary winding and the inverting input side is connected to the output side of the half-bridge inverter circuit, and the output of the comparator circuit. It may be configured to include a smoothing capacitor that is charged by a voltage. The protection stop circuit is a diode switch connected between the collector of the transistor switch, which is turned on when the output voltage signal of the detection circuit exceeds a predetermined level, and the oscillation reference signal input terminal of the driving IC, with the cathode of the collector side. And a diode connected between the collector and the base of the detection circuit side transistor switch with the cathode on the collector side, and when the transistor switch is turned on, the diode becomes conductive and the oscillation reference signal input terminal It is preferable to form a short circuit between and.

The protection stop circuit includes a series circuit of a transistor switch which is turned on when the output voltage signal of the detection circuit exceeds a predetermined level, and a frequency setting resistor connected to the collector side of the transistor switch. This series circuit is a driving IC. Is connected in parallel to the frequency switching unit of the dimming control circuit, and when the transistor switch is turned on, the oscillation frequency of the dimming control circuit is changed to a protection frequency higher than the residual heat frequency of the discharge lamp. You should decide.

The dimming control circuit receives the ON signal from the residual heat timer that indicates the oscillation period of the residual heat frequency, is turned on, and temporarily stops the protection operation including the transistor switch circuit that blocks the input of the voltage signal to the protection stop circuit. The circuit may be provided on the output side of the detection circuit.

[0017]

According to the present invention, when the filament emitterless phenomenon occurs at the end of the life of the discharge tube, the phase of the current with respect to the high frequency voltage applied to the discharge lamp circuit changes from the lag phase of the lighting state to the lead phase of the non-lighting state. By configuring the detection circuit at the end of life by focusing on that, the detection circuit detects the state that changes from the lighting state to the non-lighting state due to the emitterless phenomenon at the end of the life by the advance of the current phase, and this phase difference Since it is output as a voltage signal proportional to, the function of accurately detecting the end of life of the discharge lamp without delay is obtained without being affected by the magnitude and direction of the current such as a half-wave discharge phenomenon. In addition, the protection stop circuit receives the voltage signal proportional to the phase difference from the detection circuit and outputs the protection signal to the dimming control circuit, so that the drive circuit is stopped or the discharge lamp is not lit. It becomes possible to hold the state and stop the protection, and a function of avoiding damage caused to the switching element due to the current flowing to the half-bridge inverter due to the emitterless phenomenon and flowing of current can be obtained.

As the detection circuit, a transistor switch that detects the current of the discharge lamp circuit that changes in phase due to an emitterless phenomenon by a secondary winding added to the reactor of the discharge lamp circuit and is on / off controlled by a high frequency AC voltage is used. Since the leading current component in the secondary winding current blocked by the transistor switch is allowed to flow as a charging current to the smoothing capacitor during the period when the high-frequency AC voltage is off, which is in the off state, it is proportional to the progress of the current in the discharge lamp circuit. The function of outputting the generated voltage signal between the terminals of the smoothing capacitor is obtained.
As a different detection circuit, the same function can be obtained by replacing the transistor switch of the detection circuit described above with a comparator.

On the other hand, as the protection stop circuit, a transistor switch which is turned on when the output voltage signal of the detection circuit exceeds a predetermined level and a cathode between the collector of the transistor switch and the oscillation reference signal input terminal of the driving IC are provided on the collector side. And a diode connected in parallel, the transistor switch turns on and the oscillation reference signal input terminal of the driving IC when the detection circuit detects the advance of the current phase based on the emitterless phenomenon and outputs the voltage signal. Since a short circuit is formed between and by a transistor, a protection stop function for stopping the operation of the driving IC and the half bridge inverter can be obtained.

Further, as a different protection stop circuit, a series circuit of a transistor switch which is turned on when the output voltage signal of the detection circuit exceeds a predetermined level and a frequency setting resistor connected to the collector side thereof is used. By connecting in parallel to the frequency switching unit of the dimming control circuit of the driving IC and setting the resistance value of the frequency setting resistor to a resistance value that gives a protection frequency f higher than the residual heat frequency, the discharge lamp is increased by the increase of the frequency f. The current of the circuit decreases and the discharge lamp can be kept unlit, and the frequency f
Becomes higher than the resonance frequency f ₀ of the discharge lamp circuit, it becomes possible to delay the current phase, so that the function of holding the discharge lamp in the unlit state by a small delay current and stopping the protection can be obtained.

Furthermore, a temporary stop circuit for the protection operation is detected, which is turned on in response to an ON signal from a residual heat timer that indicates the oscillation period of the residual heat frequency and is turned on to prevent the voltage signal from being input to the protective stop circuit. If it is configured to be provided on the output side of the circuit, the detection circuit stops outputting the voltage signal during the period in which the ON signal is received from the residual heat timer to preheat the filament, so the discharge lamp does not operate during normal lighting operation. Even if an electrical abnormality occurs during the transition from the lighting state to the lighting state, it is avoided that the detection circuit and the protection stop circuit mistakenly recognize this as an electrical abnormality phenomenon due to the emitterless phenomenon and stop the protection. This makes it possible to obtain the function of preventing malfunction of the protection stop circuit.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
FIG. 1 is a connection diagram showing a discharge lamp lighting device according to an embodiment of the present invention.
It is a continuation diagram, and members with the same reference numerals as the conventional example are conventional
Since it has the same function as that of the example, its explanation is omitted.
In the figure, the discharge lamp lighting device has a high end of life of the discharge lamp 9.
Frequency AC voltage V₁And the change in the phase of the current I
Voltage signal V proportional to the phase difference_CDetection circuit 30 which emits
And this voltage signal V_cIn response to the drive IC 11
And a protection circuit 40 that outputs a protection signal. Detection times
The path 30 is a current detection sensor added to the reactor 4.
Secondary winding 4A and transistor switch T_r33When,
Resistor R on its collector₃₆A smoothing capacitor connected via
Sensor C₃₃And a transistor switch T_r33of
The output voltage V of the secondary winding 4A is applied to the collector.₂Resistance R₃₂To
Applied through the half bridge inverter times to the base
Output high frequency AC voltage V of path 1₁Resistance R_31,R_34,R₃₅
By applying as a voltage divided by, the discharge lamp 9
It is caused by the emitterless phenomenon at the end of life.
Voltage signal V proportional to the phase advance of the shifting current I _cTo
Smoothing capacitor C₃₃Can be detected as the charging voltage of
Wear. Further, the protection circuit 40 has a resistor R₄₂R₄₃Inspection divided by
Detection voltage V of output circuit 30_cTransis based on
Switch T_r41, Whose collector is a reverse blocking diode.
Code D_44,D ₄₅One side is the oscillation base of the driving IC 11 via
Connected to the quasi-signal terminal 22, the other half bridge
Transistor switches on the output side of the burner circuit 1 and on the detection circuit
Itch T_r33Connected to the base side of each via a resistor.
Be done.

FIG. 2 is a waveform diagram of each part of the discharge lamp lighting device according to the embodiment in a lighting state, and FIG. 3 is a waveform diagram of each part of the discharge lamp lighting device according to the embodiment in an emitterless state.
The operation of the detection circuit will be described with reference to FIG. As shown in FIG. 2, when the discharge lamp 9 is turned on, the current I (so-called lamp current) flowing through the discharge lamp 9 becomes substantially in phase with the output high frequency AC voltage V _1, and the current I flows through the secondary winding 4A. A voltage V _{2 of the} same phase is generated. Since the output frequency AC voltages V ₁ in this state is the off state transistor switch T _{r3 3} becomes zero, the collector of the transistor switch T _r33, the voltage V ₂ is applied between the emitter, in this period the secondary winding 4A some of the current I flowing through the (leading current component i _c) flows as charging current to the smoothing capacitor C _33, the voltage signal V _c proportional to the phase difference smoothing capacitor C ₃₃ is generated,
The magnitude of the magnitude is low because the current I is almost in phase with the voltage V ₁ . On the other hand, when the discharge lamp 9 approaches the end of its life and an emitterless phenomenon occurs and it becomes difficult for the lamp current to flow, the equivalent circuit of the discharge lamp circuit changes from the above-described FIG. Since the progress is gradually increased and the charging current i _c of the smoothing capacitor C ₃₃ is increased accordingly, the voltage signal V _c proportional to the phase difference is increased. Therefore, according to the detection circuit 30, no matter which one of the two filaments of the discharge lamp 9 is emitterless, the voltage signal V _c proportional to the change in the phase of the current I of the discharge lamp circuit caused by this is obtained. Since it can be detected, there is an advantage that the arrival of the end of life can be accurately detected without delay.

Further, when the voltage signal V _c proportional to the phase difference exceeds a predetermined level, the transistor switch T _r41 of the protection circuit 40 is turned on, and the oscillation reference signal input terminal 22 is short-circuited via the reverse blocking diode D ₄₄ . Therefore, the driving IC stops operating due to the loss of the oscillation reference signal, and the half bridge inverter 1 stops its switching operation accordingly, so that the applied voltage V ₁ of the discharge lamp circuit also drops to zero, and the discharge lamp The lighting device is protected and stopped while its operation is stopped, and there is an advantage that the advance current can be detected at an early stage to prevent damage to the switching elements 2 and 3.

If a DC power source such as a driving IC is supplied from the secondary winding 4A, a discharge lamp lighting device having a protection circuit with a simple structure can be constructed without adding new parts. . Further, instead of providing the secondary winding 4A on the reactor, a detecting resistor is connected to the discharge lamp circuit and the voltage drop thereof is supplied to the collector of the transistor switch T _r33 , the same detecting function as in the embodiment is obtained. can get.

FIG. 4 is a block diagram showing a main part of a discharge lamp lighting device according to a different embodiment of the present invention, which is different from the above-mentioned embodiment in that the transistor switch T _r33 shown in FIG. 1 is replaced with a comparator 37. Therefore, even if the detection circuit is configured in this way, the same operation as in the above-mentioned embodiment,
The effect is obtained. FIG. 5 is a connection diagram showing a discharge lamp lighting device according to a further different embodiment of the present invention, in which the protection stop circuit 60 outputs a voltage signal V exceeding a predetermined reher of the detection circuit 30.
_It is composed of a series circuit of a transistor switch (protection switch) T _r61 which is turned on by receiving _c to the base side via a resistor R _{62 and the} like, and a frequency setting resistor R ₆₁ connected to its collector side. together connected in parallel to the frequency switching section 24 of the dimming control circuit 20, the frequency setting resistor preheat frequency resistance values of R ₆₁ f _p higher protection frequency f
The difference from each of the above-described embodiments is that the resistance value is set to give. In the discharge lamp lighting device configured as described above, since the impedance of the discharge lamp circuit rises as the frequency f rises, the current I decreases accordingly and the discharge lamp can be kept in the non-lighting state, and Since it becomes possible to delay the current phase when f becomes higher than the resonance frequency f ₀ of the discharge lamp circuit, the discharge lamp is held in the non-lighting state by a small delay current, and the protection is stopped.
It is possible to prevent the occurrence of an electrical abnormal phenomenon due to the emitterless phenomenon. Therefore, it is possible to avoid damage to the switching element due to the emitterless phenomenon without stopping the discharge lamp lighting device, so that if the discharge lamp is replaced with a new discharge lamp, the discharge lamp lighting device immediately starts the lighting operation, and the power is temporarily turned on. It is possible to obtain the advantage that it is possible to eliminate the trouble of restarting the lighting operation by shutting off.

FIG. 6 is a connection diagram showing a discharge lamp lighting device according to another embodiment of the present invention, which is turned on by receiving an ON signal from a residual heat timer 26 indicating an oscillation period (preheating period) of the residual heat frequency f _p. With respect to the above-described respective embodiments, the temporary stop circuit 70 of the protection operation having the transistor switch T _r71 for preventing the input of the voltage signal V _c to the protection stop circuit 40 is provided at the output side of the detection circuit 30. Is different. In the discharge lamp lighting device configured in this way,
The dimming control circuit 2 receives the ON signal from the residual heat timer 26.
0 transistor switch T _r24 turns on, driving IC
During the period in which 11 is preheating the filament of the discharge lamp 9 by outputting the high frequency AC voltage V ₁ of the preheating frequency f _p ,
Transistor switch T _r71 also turns on and protection stop circuit 4
_Since the base-emitter of the transistor switch T _r41 of 0 is short-circuited, the transistor switch T _r41 is turned off to stop the operation of the protection stop circuit 40, and the driving IC 11 continues its preheating operation. Therefore, even if the discharge lamp 9 shifts from the non-lighted state to the lighted state at the end of the preheating period and a transient electrical abnormality phenomenon occurs with it, this is detected.
The discharge lamp lighting device has a function to prevent the electric power from being mistakenly recognized as an electrical abnormal phenomenon due to the emitterless phenomenon and stop the protection, and prevent the congestion of the lighting operation due to the malfunction of the detection circuit and the protection stop circuit. The advantage that can be provided is obtained.

After the preheating period ends, the residual heat timer 2
When the output signal of 6 changes to the OFF signal, T _R24 and T
_{Since R71} returns to the OFF state and the generation of the voltage signal V _c based on the emitterless phenomenon is monitored, if the voltage signal V _c based on the emitterless phenomenon is generated in this state, this is determined by the phase advance of the current. A protection function of detecting and stopping the driving IC can be obtained. In addition, the collector of the transistor switch T _r71 of the temporary stop circuit 70 of the protection operation is
Even when the discharge switch is connected to the base side of the transistor switch T _r61 of the protection stop circuit 60 of the discharge lamp lighting device shown in FIG. 5, the congestion of the lighting operation due to the malfunction of the detection circuit and the protection stop circuit during the preheating period of the discharge lamp. The advantage of being able to prevent

[0029]

As described above, the present invention is provided with the detection circuit for detecting the end of life of the discharge lamp by the advance of the current phase due to the emitterless phenomenon of the filament. As a result, voltage such as half-wave discharge current and commutation surge,
In the conventional technology for detecting a transient change in current, it is possible to eliminate the problem of missing the emitterless phenomenon that occurs in one of the filaments depending on the threshold level of the detection circuit and the way of setting its directionality. In addition, since it is possible to prevent damage to the switching element due to a delay in response, which has been a problem in the conventional technology for detecting the temperature of the switching element, even if the current state of the emitterless occurs in any of the two filaments, this can be surely and quickly performed. Therefore, there is an advantage that a voltage signal proportional to the amount of advance of the current phase can be output. Further, a protection stop circuit that receives the voltage signal and outputs a protection signal to the dimming control circuit is provided. As a result, the oscillation of the driving IC can be stopped by the voltage signal, and a current flowing through the half-bridge inverter circuit due to the emitterless phenomenon, causing a problem of the prior art such as causing an arm short circuit, is eliminated. It is possible to provide a highly reliable discharge lamp lighting device having excellent failure prevention performance.

Further, if a protection stop circuit is provided which operates by the voltage signal from the detection circuit to switch the oscillation frequency of the driving IC to a frequency higher than the preheating frequency, the current phase can be delayed and the half bridge can be delayed. Since the discharge lamp can be kept in the off state without stopping the inverter, it is possible to immediately turn on the lamp by replacing it with a new discharge lamp.

On the other hand, if the temporary stop circuit of the protection operation is provided on the output side of the detection circuit, the detection circuit outputs the voltage signal during the period in which the ON signal is received from the residual heat timer to preheat the filament. Since it is stopped, when the discharge lamp shifts from the non-lighting state to the lighting state in the normal lighting operation, the detection circuit mistakenly recognizes this as an electrical abnormal phenomenon due to the emitterless phenomenon and stops the protection. Therefore, it is possible to provide a discharge lamp lighting device that is excellent in stability of lighting operation.

[Brief description of drawings]

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

FIG. 2 is a waveform diagram of each part of the discharge lamp lighting device according to the embodiment in a lighting state.

FIG. 3 is a waveform diagram of each part of the discharge lamp lighting device according to the embodiment in an emitterless state.

FIG. 4 is a configuration diagram showing a main part of a discharge lamp lighting device according to another embodiment of the present invention.

FIG. 5 is a connection diagram showing a discharge lamp lighting device according to still another embodiment of the present invention.

FIG. 6 is a connection diagram showing a discharge lamp lighting device according to another embodiment of the present invention.

FIG. 7 is a connection diagram showing a simplified conventional discharge lamp lighting device.

FIG. 8 is an equivalent circuit diagram showing the operation of the discharge lamp circuit,
(A) is a figure showing a lighting state, (b) is a figure showing a non-lighting state

FIG. 9 is an equivalent circuit diagram showing a method of detecting and protecting the end of a discharge lamp life in a conventional discharge lamp lighting device.

[Explanation of symbols]

1 Half Bridge Inverter Circuit 2 Switching Element 3 Switching Element 4 Reactor (Inductance L) 4A Secondary Winding 5 Capacitor (Capacitance C) 8 AC-DC Converter Circuit 9 Discharge Lamp 10 Driving Circuit 11 Driving IC 12 Pulse Transformer 20 Dimming Control Circuit 22 Oscillation reference signal input terminal 24 Frequency switching section 26 Preheat timer 30 Detection circuit 37 Comparator 40 Protection stop circuit 60 Protection stop circuit 70 Temporary stop circuit V ₁ High frequency AC voltage I Current of discharge lamp circuit V ₂ Reactor secondary winding voltage Output voltage of V _C detection circuit (voltage proportional to phase change of current I) f Protection frequency f _p Preheating frequency f ₀ Resonance frequency of discharge lamp circuit (no lighting) ff Full lighting frequency T _r24 Preheating switch R ₂₄ Preheating frequency setting resistance T _r61 protection switch R ₆₁ protection frequency setting resistor

Claims (6)

[Claims] 1. An AC / DC converter circuit, a half-bridge inverter circuit for converting the output DC voltage into a high-frequency AC voltage and outputting the same, and a secondary winding connected to the control terminals of a pair of switching elements of the half-bridge inverter circuit. Drive circuit configured to alternately turn on and off the pair of switching elements, and a pulse transformer and a drive IC whose output side is connected to the primary winding thereof, and the input frequency of the drive circuit is the residual heat of the discharge lamp and total light. And a dimming control circuit for controlling switching to an oscillation frequency corresponding to lighting or dimming lighting, and performing lighting control of a discharge lamp connected in series to the output side of the pair of switching elements via a reactor and a capacitor. In, the end of life of the discharge lamp is detected by a change in the phase of the high-frequency AC voltage and current, and an electric voltage proportional to the phase difference is detected. A detecting circuit which emits a signal, the discharge lamp lighting apparatus characterized by comprising a protection stop circuit that emits protection signal toward the light control circuit receives this voltage signal. 2. A secondary winding in which a detection circuit is added to a reactor, and a transistor switch circuit in which a collector is connected to the secondary winding and a base is connected to the output side of the half-bridge inverter circuit via resistors, respectively. The discharge lamp lighting device according to claim 1, further comprising: a smoothing capacitor that is charged by a current flowing through the secondary winding when the transistor switch is in an off state. 3. A secondary winding in which a detection circuit is added to a reactor, a non-inverting input side is connected to this secondary winding, and an inverting input side is connected to the output side of a half-bridge inverter circuit, and this comparator circuit. The discharge lamp lighting device according to claim 1, further comprising a smoothing capacitor charged by the output voltage of the discharge lamp. 4. A cathode is placed on the collector side between a transistor switch which is turned on when an output voltage signal of a detection circuit exceeds a predetermined level by a protection stop circuit, and its collector and an oscillation reference signal input terminal of a driving IC. And a diode connected between the collector and the base of the detection circuit side transistor switch with the cathode on the collector side, and when the transistor switch is turned on, the diode conducts and The discharge lamp lighting device according to claim 1 or 2, wherein a short circuit is formed between the oscillation reference signal input terminal and the oscillation reference signal input terminal. 5. A protection stop circuit comprises a series circuit of a transistor switch which is turned on when the output voltage signal of the detection circuit exceeds a predetermined level, and a frequency setting resistor connected to the collector side of the transistor switch. Of the frequency setting resistor connected in parallel to the frequency switching unit of the dimming control circuit of the IC for use, and changing the oscillation frequency of the dimming control circuit to a protection frequency higher than the residual heat frequency of the discharge lamp when the transistor switch is turned on. The discharge lamp lighting device according to claim 1, wherein a resistance value is set. 6. A protection operation comprising a transistor switch circuit for turning off the dimming control circuit and receiving an on signal from a residual heat timer for instructing an oscillation period of the residual heat frequency to turn on the voltage signal to the protection stop circuit. The discharge lamp lighting device according to claim 1, wherein a temporary stop circuit is provided on the output side of the detection circuit.