JP3321997B2 - Discharge lamp lighting device and protection stop circuit thereof - Google Patents

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 to a discharge lamp which is generated when a current flows through the inverter circuit when the discharge lamp reaches the end of its life. The present invention relates to a discharge lamp lighting device including a detection circuit and a protection circuit for avoiding damage to a switching element.

[0002]

BACKGROUND ART FIG. 7 is a connection diagram schematically showing a conventional discharge lamp lighting device, the half-bridge inverter circuit 1 for converting the output DC voltage of the AC-DC conversion circuit 8 to a high frequency AC voltage V ₁ was The half bridge inverter circuit 1 is connected to a pair of filaments of a discharge lamp 9 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
To control the DC voltage to the high-frequency AC voltage V₁Drive times to convert to
The path 10 is connected to the control terminals of the switching elements 2 and 3.
Pulse transformer 12 to which a pair of secondary windings 12S are connected
And a drive I whose output side is connected to the primary winding 12P.
C11. Resistance R_13,Capacitor C_13,You
And constant voltage diode D ₁₃Receiving the stabilized power supply voltage
The driving IC 11 that operates with a high frequency AC voltage V₁Oscillation
For the dimming section that determines the frequency and the oscillation frequency of the dimming section
Drive unit that generates a corresponding drive voltage.
The last stage consists of a pair of transistors that alternately turn on and off.
Are connected to the primary winding of the pulse transformer.
Connected, and the midpoint of the primary winding is connected to the regulated power supply.
The dimming unit is 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 all-light lighting frequency ff is
It is determined.

In general, when the discharge lamp 9 is turned on, control of filament preheating, all-light lighting, and dimming lighting is performed by changing the frequency. The frequency is determined by setting the resonance frequency of the discharge lamp circuit to f. _0, the preheat frequency of filament f _p, an all-optical lighting frequency ff, the dimming frequency f _d
In this case, for example, 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. Control of the oscillation frequency of the driving IC11 determines the full lighting frequency ff of the reference frequency resistor R _21, V
Performed by the frequency switching section 24 provided in parallel with the series circuit of R _21. In the case of the figure, the frequency switching unit 2
4 collector series circuit of the series connected transistors dimming frequency setting resistor and selector switch is constituted by a series circuit (not shown in this other switch T _r24 is provided to the preheat frequency setting resistor R ₂₄ ).

The operation of the transistor switch _Tr 24 is performed by a preheating timer 26 provided on the output side of the AC / DC conversion circuit 8. Capacitor preheating timer 26 is charged by the output DC voltage of the AC-DC conversion circuit 8 through the resistor R ₂₆ C
_26, constant voltage diode D to charge voltage of the capacitor C ₂₆
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 changed for a certain period of time until
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 During the period, the oscillation frequency of the driving IC becomes the preheating frequency f _p
To rise.

The drive signal output from the drive unit based on the preheating frequency of the light control unit of the drive IC 11 is transmitted to the primary winding 12P.
The pulse transformer 12 which has received the AC signal operates in an AC manner, and generates an AC signal having the same phase in its secondary winding. By applying the two AC signals to the switching elements 2 and 3 so as to have opposite phases to each other, Switching elements 2 and 3
There was alternately turned on and off, high frequency AC voltage V ₁ of the preheat frequency f _p is applied to the discharge lamp circuit including the discharge lamp 9.

FIGS. 8A and 8B are equivalent circuit diagrams showing the operation of the discharge lamp circuit. FIG. 8A shows a lighting state, and FIG. 8B shows a non-lighting state. The resistance R is an internal discharge resistance of the discharge lamp when the discharge lamp 9 is turned on and a discharge current flows. When the discharge lamp 9 is not lit, the discharge current becomes almost zero. Circuit (frequency f ₀ ),
In the all-light lighting state, the capacitance C is terminated by the discharge resistor R, so that the resonance frequency becomes lower than f _{0 and} the Q value also decreases. Thus, although the time of the discharge lamp circuit by applying a high frequency alternating voltage of preheating frequency f _p to start preheating of the filaments is the discharge lamp is no lighting, the discharge lamp tends to light up with increasing filament temperature.
End preheating period, the pre-heating switch is turned off, high frequency AC voltages V ₁ because its frequency is switched to the all-optical lighting frequency ff, the impedance of the discharge lamp circuit is decreased discharge current (lamp current) easily flows, Thereafter, the all-light lighting frequency ff is maintained to maintain a stable all-light lighting operation.

However, at the end of the life of the discharge lamp 9 being turned on, the emitter applied to the filament disappears,
Since the discharge current does not easily flow from the emitterless filament side, 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.
From (b) to (b), 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 lagging phase to the leading phase. When the current flows, an overcurrent flows, and sometimes a trouble such as the occurrence of an arm short circuit in the half-bridge inverter 1 occurs. Therefore, in order to avoid such a trouble, a discharge lamp lighting device is provided with a protection circuit for detecting an emitterless phenomenon at the end of discharge lamp life and for preventing the switching elements 2 and 3 from being damaged. Have been.

FIG. 9 is an equivalent circuit diagram showing a method for detecting and protecting the end of discharge lamp life in a conventional discharge lamp lighting device.
An electrical abnormality detection circuit 7 is connected to the discharge lamp circuit, and when the half-wave discharge phenomenon is detected, an operation stop command is issued to the drive circuit 10. In addition, a method of detecting an overcurrent or an imbalance of current generated in an inverter circuit due to a half-wave discharge phenomenon, a method of detecting an overvoltage generated in a discharge lamp, and a method of detecting an abnormal temperature rise of a switching element are also known. ing.

[0010]

SUMMARY OF THE INVENTION 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 are different depending on which of the two filaments is emitterless, so if one half-wave discharge phenomenon is detected, the other emitterless , And there is a problem that the protection accuracy is low. Also,
In the method of detecting overcurrent, imbalance of current, or overvoltage, discrimination from a similar phenomenon that occurs when the equivalent circuit of a discharge lamp circuit changes from a non-discharged state to a lit state in a normal lighting process is distinguished between the two levels. The determination is made based on the difference, so that not only a sufficient determination accuracy cannot be obtained, but also there is a problem that a traffic jam may occur in the lighting operation due to an erroneous determination. Further, in the method of detecting an abnormal rise in the temperature of the switching element, the response speed of the temperature sensor is low, so that there is a problem that the protection operation cannot be performed in time depending on the method of the inverter circuit.

An object of the present invention is to provide a discharge lamp lighting device provided 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.

[0012]

According to the present invention, there is provided an AC / DC conversion circuit, a half-bridge inverter circuit for converting an output DC voltage into a high-frequency AC voltage and outputting the converted AC voltage. A half-bridge inverter circuit includes a pulse transformer having a secondary winding connected to control terminals of a pair of switching elements, and a driving IC having an output side connected to the primary winding, and alternately turns on and off the pair of switching elements. And a dimming control circuit for switching the input frequency of the driving circuit to an oscillation frequency corresponding to the residual heat, all-light lighting, or dimming lighting of a discharge lamp having a pair of filaments . reactor to the output side of the switching element, in which performs lighting control of the discharge lamp connected in series via a capacitor, The secondary winding is added to the serial reactor
Accordingly, the phase of the high-frequency AC current to be detected and the change in phase difference between the high-frequency AC voltage and
A detection circuit that detects at least one end of life and issues a voltage signal proportional to the phase difference; and a protection stop circuit that receives the voltage signal and issues a protection signal to the dimming control circuit. I do.

[0013] The detection circuit has a collector to said secondary winding, wherein, when the transistor switch circuit whose base is connected via a respective resistor to the output side of the half-bridge inverter circuit, the transistor switch is off two a smoothing capacitor charged by the current flowing to the next winding, and said voltage signal a voltage of the flat smooth capacitor
Or a secondary winding, a comparator circuit having a non-inverting input side connected to the secondary winding and an inverting input side connected to the output side of a half-bridge inverter circuit, and charging by an output voltage of the comparator circuit. A smoothing capacitor to be used, and the voltage of the smoothing capacitor is
No.

Further, a transistor switch which turns on when the output voltage signal of the detection circuit exceeds a predetermined level,
A diode connected between the collector and the oscillation reference signal input terminal of the driving IC with the cathode being the collector side, and the cathode being the collector side between the collector and the base of the detection circuit side transistor switch. And a diode connected thereto, and when the transistor switch is turned on, the diode conducts to generate an oscillation reference signal.
Signal to stop the operation of the inverter circuit
It is preferable to provide a protection stop circuit .

[0015] The transistor switch which is turned on when the output voltage signal of the detection circuit exceeds a predetermined level, comprising a series circuit of a connected frequency setting resistor to the collector side, dimming of the series circuit driving IC The resistance value of the frequency setting resistor is connected in parallel to the frequency switching unit of the control circuit, and sets 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. Protection stop circuit
Obtain and good.

The dimming control circuit is turned on in response to an ON signal from a residual heat timer for instructing the oscillation period of the residual heat frequency, and temporarily stops a protection operation including a transistor switch circuit for preventing input of a voltage signal to the protection stop circuit. Preferably, the circuit is provided on the output side of the detection circuit.

[0017]

According to the present invention, when the emitterless phenomenon of the filament 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 delay phase of the lighting state to the leading phase of the non-lighting state. The end-of-life detection circuit focuses on the end-of-life state, and the detection circuit detects the state of change from the lighting state to the non-lighting state due to the emitterless phenomenon at the end of life based on the progress of the current phase. Since the voltage signal is output as a voltage signal proportional to the current, the function of accurately detecting the end of the life of the discharge lamp without delay is obtained without being affected by the magnitude or direction of the current such as a half-wave discharge phenomenon. In addition, the protection stop circuit is configured to receive a voltage signal proportional to the phase difference from the detection circuit and emit a protection signal to the dimming control circuit, thereby stopping the drive circuit or turning off the discharge lamp. The state can be maintained and the protection can be stopped, and a function of avoiding damage to the switching element due to the current flowing through the half-bridge inverter due to the emitterless phenomenon can be obtained.

The detection circuit includes a transistor switch that detects the current of the discharge lamp circuit, which advances in phase due to the emitterless phenomenon by the secondary winding added to the reactor of the discharge lamp circuit, and that is turned on and off by a high-frequency AC voltage. During the period when the high-frequency AC voltage is in the off state of zero, the leading current component in the secondary winding current blocked by the transistor switch can flow as a charging current to the smoothing capacitor, so it is proportional to the progress of the current in the discharge lamp circuit. The function of outputting the applied voltage signal between the terminals of the smoothing capacitor is obtained.
Note that, as a different detection circuit, the same function can be obtained by replacing the transistor switch of the above detection circuit 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 connected between the collector thereof and the oscillation reference signal input terminal of the driving IC are connected to the collector side. When the detection circuit detects the advance of the current phase based on the emitterless phenomenon and outputs a voltage signal, the transistor switch is turned on and the oscillation reference signal input terminal of the driving IC is provided. , A short circuit is formed via a transistor, so that a protection stop function for stopping the operation of the driving IC and the half-bridge inverter can be obtained.

As a different protection stop circuit, a series circuit of a transistor switch that 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 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 preheating frequency, the discharge lamp increases due to an increase in the frequency f. The current of the circuit is reduced, the discharge lamp can be kept in a non-lighting state, and the frequency f
Since the current phase becomes higher than the resonance frequency f ₀ of the discharge lamp circuit, the current phase can be delayed, so that a function of stopping the protection by holding the discharge lamp in a non-lighting state with a small delay current can be obtained.

Further, a protection circuit temporary stop circuit comprising a transistor switch circuit for receiving an ON signal from a residual heat timer for instructing an oscillation period of the residual heat frequency to be in an ON state and preventing a voltage signal from being input to the protection stop circuit is detected. 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 when the filament is preheated in response to the ON signal from the residual heat timer. Even if an electrical abnormality occurs in the transition period from the lighting state to the lighting state, it is possible to prevent the detection circuit and the protection stop circuit from erroneously recognizing the electrical failure phenomenon as an emitterless phenomenon and performing the protection stop. And a function of preventing malfunction of the protection stop circuit can be obtained.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments.
FIG. 1 shows a discharge lamp lighting device according to an embodiment of the present invention.
The members with the same reference numerals as those of the conventional example are those of the conventional example.
Since it has the same function as that of the example, its description is omitted.
In the figure, the discharge lamp lighting device increases the 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 phase difference_CDetection circuit 30 that emits
And this voltage signal V_cTo drive IC 11
And a protection circuit 40 for generating a protection signal. Detection times
Road 30 is a current detection sensor added to reactor 4
Secondary winding 4A and transistor switch T_r33When,
A resistor R₃₆Smoothing condenser connected via
Sensor C₃₃And the transistor switch T_r33of
The output voltage V of the secondary winding 4A is applied to the collector._TwoIs the resistance R₃₂To
Through a half-bridge inverter
Output high frequency AC voltage V of road 1₁Is the resistance R_31,R_34,R₃₅
By applying the voltage as a voltage divided by
Generated by the occurrence of emitterless phenomenon at the end of life
A voltage signal V proportional to the advance of the phase of the shearing current I _cTo
Smoothing capacitor C₃₃Can be detected as the charging voltage of
Wear. The protection circuit 40 includes a resistor R₄₂R₄₃Inspection divided by
Detection voltage V of output circuit 30_cTransients based on
T switch T_r41Whose collector is a reverse blocking diode
Code D_44,D ₄₅One is the oscillation base of the driving IC 11
Connected to the quasi-signal terminal 22 and the other half-bridge
The transistor side of the output side of the inverter circuit 1 and the detection circuit
Itch T_r33Connected to the base side of each
It is.

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. In a state where the discharge lamp 9 is lit, as shown in FIG. 2, the current flowing to the discharge lamp 9 I (so-called lamp current) substantially in phase with the output high-frequency AC voltage V _1, the secondary winding 4A current I A voltage V ₂ having the same phase as that of FIG. 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 which current I goes low because it is substantially in phase with the voltage V _1. On the other hand, when the discharge lamp 9 approaches the end of life and an emitterless phenomenon occurs and the lamp current becomes difficult to flow, the equivalent circuit of the discharge lamp circuit changes from FIG. 8A to FIG. increased progress gradually, since the charging current i _c of the smoothing capacitor C ₃₃ is increased along with this, the voltage signal V _c proportional to the phase difference increases. Therefore, according to the detection circuit 30, when one of the two filaments of the discharge lamp 9 becomes the emitter-less even, as a voltage signal V _c which is proportional to the change in phase of the current I of the discharge lamp circuit caused along with this Since the detection can be performed, the advantage that the end of the life can be accurately detected without delay is obtained.

Furthermore, the voltage signal V _c proportional to the phase difference is the transistor switch T _r41 is on the protective circuit 40 exceeds a predetermined level, to short-circuit the oscillating reference signal input terminal 22 via the reverse-blocking diode D _44. Accordingly, 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. Therefore, the applied voltage V ₁ of the discharge lamp circuit also decreases to zero, and Since the lighting device stops the protection in a state where the operation is stopped, the advantage is obtained that the lead current can be detected early to prevent the damage to the switching elements 2 and 3.

If a DC power supply such as a driving IC is supplied from the secondary winding 4A, a discharge lamp lighting device having a protection circuit with a simple configuration can be constructed without adding new components. . Further, instead of providing the secondary winding 4A in the reactor, a detection resistor is connected to the discharge lamp circuit and the voltage drop is supplied to the collector of the transistor switch _Tr33. 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. The difference from the foregoing embodiment is that the transistor switch _Tr33 shown in FIG. Even if the detection circuit is configured in this way, the same operation as in the above-described embodiment,
The effect is obtained. FIG. 5 is a connection diagram showing a discharge lamp lighting device according to still another embodiment of the present invention, in which the protection stop circuit 60 detects the voltage signal V exceeding a predetermined level of the detection circuit 30.
The _c via the resistor R _62, etc. consists of a series circuit of a transistor switch (protective switch) T _r61 and the frequency setting resistor R ₆₁ which is connected to the collector of which is turned by receiving the base side, the series circuit 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
Is different from the above embodiments in that the resistance value is set to give In the discharge lamp lighting device configured as described above, the impedance of the discharge lamp circuit increases with an increase in the frequency f, and accordingly, the current I decreases and the discharge lamp can be kept in a non-lighting state. Since f becomes higher than the resonance frequency f ₀ of the discharge lamp circuit, the current phase can be delayed, so that the discharge lamp is held in a non-lighting state by a small delay current to stop protection,
It is possible to prevent an electrical abnormal phenomenon from occurring due to the emitterless phenomenon. Therefore, it is possible to avoid the damage of the switching element based on the emitterless phenomenon without stopping the discharge lamp lighting device.If the discharge lamp lighting device is replaced with a new discharge lamp, the discharge lamp lighting device immediately starts the lighting operation. The advantage that the trouble of shutting off and restarting the lighting operation can be eliminated can be obtained.

FIG. 6 is a connection diagram showing a discharge lamp lighting apparatus according to another embodiment of the present invention, the residual heat timer 26 indicating the oscillation period of the residual heat frequency f _p (preheating period) receives an ON signal on that a temporary stop circuit 70 of the protection operation is configured so as to provide for the output side of the detection circuit 30 having a transistor switch T _r71 to prevent input and each of the embodiments described above of the voltage signal V _c to protected stop circuit 40 in a state Is different. In the discharge lamp lighting device configured as described above,
Dimming control circuit 2 receiving ON signal from remaining heat timer 26
0 transistor switch _Tr24 turns on, and the driving IC
During the period in which 11 is performing the preheating of the filament preheat frequency f _p of the high-frequency AC voltages V ₁ output to the discharge lamp 9,
Transistor switch _Tr71 also turns on and protection stop circuit 4
_Since the base and the emitter of the zero transistor switch _Tr41 are short-circuited, the transistor switch _Tr41 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-lighting state to the lighting state at the end of the preheating period and a transient electrical abnormal phenomenon occurs with this, the detection circuit 30 and the protection stop circuit 40
Discharge lamp lighting device equipped with a function that prevents a malfunction of the detection circuit and the protection stop circuit, thereby preventing traffic jams due to malfunctions of the detection circuit and the protection stop circuit. The advantage that can be provided is obtained.

After the preheating period is over, the remaining heat timer 2
When the output signal of No. 6 changes to the OFF signal, T _R24 and T
Since _R71 monitors the generation of the voltage signal V _c which is based on the emitter-less phenomenon returns to the off state, if the voltage signal V _c generated based on emitter-less phenomenon in this state, which the phase progress of the current A protection function of detecting and stopping the driving IC is obtained. _Further , the collector of the transistor switch _Tr71 of the protection operation temporary stop circuit 70 is
Even if the protection stop circuit 60 of the discharge lamp lighting device shown in FIG. 5 is connected to the base side of the transistor switch _Tr61 , the lighting operation is congested due to malfunction of the detection circuit and the protection stop circuit during the preheating period of the discharge lamp. Benefits

[0029]

As described above, the present invention comprises a detection circuit for detecting the end of the life of the discharge lamp based on the progress of the current phase accompanying the emitterless phenomenon of the filament. As a result, voltages 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 that the emitterless phenomenon generated in one of the filaments is overlooked depending on how to set the threshold level and the direction of the detection circuit. In addition, since it is possible to prevent the switching element from being damaged due to the response delay which has been a problem in the conventional technology for detecting the switching element temperature, even if the emitterless state occurs in either of the two filaments, it can be reliably and quickly performed. And a voltage signal proportional to the amount of advance of the current phase can be output. In addition, a protection stop circuit that receives this voltage signal and issues 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 flows through the half-bridge inverter circuit due to the emitterless phenomenon, thereby eliminating the problems of the prior art such as causing an arm short circuit. Thus, a highly reliable discharge lamp lighting device having excellent failure prevention performance can be provided.

Further, if a protection stop circuit that operates by a voltage signal from the detection circuit and switches the oscillation frequency of the driving IC to a frequency higher than the preheating frequency is provided, the current phase can be delayed, so that the half bridge Since the discharge lamp can be kept in the extinguished state without stopping the inverter, the convenience that the lamp can be turned on immediately after replacement with a new discharge lamp can be obtained.

On the other hand, if the protection operation temporary stop circuit is provided on the output side of the detection circuit, the detection circuit outputs the voltage signal during the preheating of the filament in response to the ON signal from the residual heat timer. Since the lamp is stopped, when the discharge lamp shifts from the non-lighting state to the lighting state in the normal lighting operation, the detection circuit mistakes this as an electrical abnormal phenomenon due to the emitterless phenomenon and performs the protection stop, which is a problem of the conventional technology. And a discharge lamp lighting device having excellent stability of lighting operation can be provided.

[Brief description of the 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 in a lighting state of each part of the discharge lamp lighting device according to the embodiment.

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 a different 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 simplified connection diagram showing a conventional discharge lamp lighting device.

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

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

[Explanation of symbols]

REFERENCE SIGNS LIST 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 conversion circuit 9 discharge lamp 10 drive circuit 11 drive IC 12 pulse transformer 20 dimming control circuit 22 Oscillation reference signal input terminal 24 Frequency switching unit 26 Preheating 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 Voltage of reactor secondary winding V _C (voltage proportional to the phase change of the current I) output voltage of the detection circuit f protection frequency f _p preheat frequency f ₀ the resonance frequency of the discharge lamp circuit (no lighting) ff full lighting frequency T _r24 preheating switch R ₂₄ preheat frequency setting resistance T _r61 protection switch R ₆₁ protection frequency setting resistor

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H05B 41/24 H02M 7/48

Claims (6)

(57) [Claims] An AC / DC conversion circuit, a half-bridge inverter circuit for converting an output DC voltage into a high-frequency AC voltage and outputting the same, and a secondary winding connected to control terminals of a pair of switching elements of the half-bridge inverter circuit. And a driving circuit comprising a driving IC having an output connected to its primary winding and a primary winding thereof, for alternately controlling the pair of switching elements to be turned on and off, and a discharge lamp having an input frequency of the driving circuit and a pair of filaments. A dimming control circuit for controlling switching to an oscillation frequency corresponding to residual heat, all-light lighting, or dimming lighting of the discharge lamp, wherein the discharge lamp is connected in series to the output side of the pair of switching elements via a reactor and a capacitor. In the lighting control, the detection is performed by the secondary winding added to the reactor.
At least one of the filaments due to a change in a phase difference between the phase of the high-frequency AC current and the high-frequency AC voltage.
A detection circuit that detects the end of life of the other and issues a voltage signal proportional to the phase difference, and a protection stop circuit that receives the voltage signal and issues a protection signal to the dimming control circuit. Discharge lamp lighting device. Wherein said detection circuit, the collector to the secondary winding, and a transistor switch circuit whose base is connected via a respective resistor to the output side of the half-bridge inverter circuit, when the transistor switch is off A smoothing capacitor charged by a current flowing through the secondary winding , wherein the voltage of the smoothing capacitor is
The discharge lamp lighting device according to claim 1, characterized in that the. Wherein said detection circuit includes a secondary winding, the non-inverting input to the secondary winding, and a comparator circuit inverting input is connected to the output side of the half-bridge inverter circuit, of the comparator circuit a smoothing capacitor charged by the output voltage, before the voltage of the smooth capacitor
2. The discharge lamp lighting device according to claim 1, wherein the voltage signal is a voltage signal . 4. A transistor switch which is turned on when an output voltage signal of said detection circuit exceeds a predetermined level, and a cathode connected between said collector and an oscillation reference signal input terminal of a driving IC with said collector being connected to said transistor switch. A diode connected between the collector and the base of the detection circuit-side transistor switch with the cathode connected to the collector side, and when the transistor switch is turned on, the diode conducts to generate an oscillation reference signal.
Protection circuit of a discharge lamp lighting apparatus of claims 1 to claim 3, wherein by loss stopping the operation of the inverter circuit. 5. A series circuit comprising a transistor switch that is turned on when an output voltage signal of the detection circuit exceeds a predetermined level, and a frequency setting resistor connected to a collector of the transistor switch. The resistance value of the frequency setting resistor is connected in parallel to the frequency switching unit of the dimming control circuit, and changes 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. claim 1 to protect round of claim 3 discharge lamp lighting apparatus wherein the set comprising
Road . 6. A protection operation comprising a transistor switch circuit for receiving a turn-on signal from a residual heat timer for instructing the dimming control circuit to oscillate a residual heat frequency, and for turning on a voltage signal to a protection stop circuit. 2. The discharge lamp lighting device according to claim 1, wherein a temporary stop circuit is provided on an output side of the detection circuit.