JP3532710B2 - Discharge lamp lighting device - 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 for starting and lighting a discharge lamp with a high frequency.

[0002]

2. Description of the Related Art FIG. 8 is a circuit configuration diagram of a conventional discharge lamp lighting device disclosed in Japanese Patent Laid-Open No. 5-326177. In the figure, 1 is a DC power supply, 2 is an inverter circuit composed of transistors 7 and 8 and regenerative diodes 9 and 10, 3 is a detection circuit, and 4 is an inverter circuit 2 according to the output level output from the detection circuit 3. Control circuit to control,
La and Lb are ballast chokes, which are inductance elements for limiting the load current, FLa and FLb are discharge lamps, C1a,
C1b is a preheating capacitor connected in parallel to each of the discharge lamps FLa and FLb, and C2a and C2b are DC blocking capacitors.

The DC power supply 1 is provided with a step-up chopper circuit. This step-up chopper circuit is composed of an inductance element L, a MOSFET Q1, a diode D, and an electrolytic capacitor C. The MOSFET Q1 is turned on / off to input voltage. It is designed to boost. That is, when the MOSFET Q1 of this transistor is turned on, energy is stored in the inductance element L, and when the MOSFET Q1 is turned off, this energy is used to charge the electrolytic capacitor C via the diode D, so that the direct current voltage E higher than the input voltage is obtained. A series circuit of the transistors 7 and 8 of the inverter circuit 2 is connected between both ends of the electrolytic capacitor C.

The inverter circuit 2 includes transistors 7,
An ON signal is alternately supplied by the control circuit connected to the base of 8 to alternately turn ON / OFF. Further, diodes 9 and 10 for regeneration are connected in reverse directions between the collectors and emitters of the transistors 7 and 8, respectively. Between the collector and the emitter of the transistor 8, a ballast choke La which is an inductance element for controlling a load current, a series resonance circuit including a parallel circuit of a discharge lamp FLa and a resonance capacitor C1a is connected via a DC blocking capacitor C2a. Similarly, a series resonance circuit including a parallel circuit of a ballast choke Lb which is an inductance element for controlling a load current, a discharge lamp FLb and a resonance capacitor C1b is connected via a DC blocking capacitor C2b.

The detection circuit 3 has a detection circuit corresponding to each of the discharge lamps FLa and FLb. The detection circuit corresponding to the discharge lamp FLa includes a ballast choke La which is an inductance element for limiting a load current and a discharge lamp FLa. A series circuit including a capacitor C3a and a diode D1a is connected from the connection point, and resistors R1a and R2a are connected to both ends of the diode D1a.
Connect a series circuit of and connect diode D across resistor R2a.
A capacitor 11 is connected via 2a.

The detection circuit corresponding to the discharge lamp FLb connects the series circuit of the capacitor C3b and the diode D1b from the connection point of the ballast choke Lb which is the load current limiting inductance element and the discharge lamp FLb, and the diode D1b. A series circuit of resistors R1b and R2b is connected to both ends, and the capacitor 11 is connected to both ends of the resistor R2b via a diode D2b. In addition,
The resistor 12 connected in parallel with the capacitor 11 is a discharge resistor.

Here, as the discharge lamps FLa and FLb of the conventional example, a fluorescent lamp of FLR40S defined by the JIS standard is used, and the DC voltage obtained by the chopper circuit is 400V.

Next, the operation will be described. First, during the lighting operation, since the oscillating operation of the inverter circuit 2 is not stopped when the discharge lamp FLa is removed, the transistors 7 and 8 are turned on by the ON signal supplied from the control circuit 4.
The discharge lamp FLb connected to the discharge lamp FLb is repeatedly turned off normally. At this time, the potential at the point Xa of the detection circuit corresponding to the discharge lamp FLa side in FIG. 8 has a voltage division waveform of the voltage VCE between the collector and the emitter of the transistor 8. That is, the voltage is 400 V of the DC voltage E and 0 V of the rectangular wave.

On the other hand, the potential at the detection circuit Xb corresponding to the normally lit discharge lamp FLb has a voltage division waveform of the voltage V _{FLb (PP)} between the positive and negative peak values of the lamp voltage V _FLb . Here, when the FLR40S is used as the discharge lamp as described above, since the lamp voltage is about 110 V at the rated current, V _{FLb (PP)} = 110 × 2 × 2 ^1/2 ≈311 V.

As a result, the peak voltage at the point Xa is Xb.
Since the voltage is higher than the peak voltage at the point, the output level of the OR output from the detection circuit 3 is higher than that at the normal time. By increasing this, it is possible to detect the removal of one light. When the output level output from the detection circuit 3 becomes higher than that in the normal state, the control circuit 4 receives the signal and turns on the transistors 7 and 8 of the inverter circuit 2.
The output of the inverter circuit 2 is stopped by controlling the off state.

[0011]

Since the conventional discharge lamp lighting device is constructed as described above, the discharge lamp having a DC power supply voltage of the highest lamp voltage among the discharge lamps is 2 times the normal lamp voltage. When the voltage is lower than × 2 ^1/2 times, the detection circuit cannot detect that any one of the discharge lamps FLa and FLb is disconnected, and therefore the output of the inverter circuit is stopped. There was a problem that I could not do it.

The present invention has been made to solve the above problems, and detects that the discharge lamp (filament) is disconnected regardless of the DC power supply voltage or the lamp voltage when the discharge lamp is normal. An object is to provide a discharge lamp lighting device that can be detected by a circuit. Also,
An object of the present invention is to provide a discharge lamp lighting device capable of detecting the end of life of a discharge lamp with this detection circuit.

[0013]

A discharge lamp lighting device according to claim 1 of the present invention comprises a DC power supply, an inverter circuit connected to the DC power supply, and a circuit connected between output terminals of the inverter circuit. And a load circuit formed by connecting in parallel two or more circuits each including a first series resonance circuit including a discharge lamp and a second series resonance circuit including no discharge lamp; A detection circuit that detects a part of the voltage generated in the series resonance circuit, and operates to stop the output of the inverter circuit when the output level output from the detection circuit exceeds a preset threshold value. A control circuit, and the threshold value is set between the output level output from the detection circuit during normal lamp lighting and the output level output from the detection circuit during end-of-life lamp lighting; inside The output level output from the detection circuit due to the series resonance of the second series resonance circuit when the filament is disconnected is set to be higher than the output level output from the detection circuit during the end-of-life lamp lighting. is there. Therefore, with this configuration, the output of the inverter circuit is stopped when the filament is detached at the end of life lamp lighting and during lighting.

A discharge lamp lighting device according to a second aspect of the present invention is the discharge lamp lighting device according to the first aspect, wherein a resistor is added in series to the second series resonance circuit. This suppresses the surge voltage generated in the detection capacitor when the lamp is attached or detached.

Further, a discharge lamp lighting device according to a third aspect is the discharge lamp lighting device according to the first or second aspect,
A common part is provided in the first series resonance circuit connected in parallel,
The common part is provided with a DC blocking capacitor and an oscillation feedback winding, and only the current flowing through the first series resonance circuit
The inverter circuit self-excitedly oscillates by flowing to the primary side of the oscillation feedback winding . As a result, the current flowing through the oscillation feedback winding decreases during the period from the filament being detached during lighting until the output of the inverter circuit is stopped.

A discharge lamp lighting device according to a fourth aspect is the discharge lamp lighting device according to the third aspect, wherein two load circuits are connected in parallel, and the common source of the first discharge lamp from the DC power source. A starting circuit provided via a filament on the side opposite to the partial side to start oscillation of the inverter circuit; a filament on the side opposite to the common portion side of the second discharge lamp from the DC power supply; A DC detection circuit provided via the filament on the common portion side of the discharge lamp and the filament on the common portion side of the first discharge lamp to detect DC from the DC power source, and output from the DC detection circuit. The starting circuit is operated based on the output label. As a result, the oscillation can be started after the mounting state of the filament is detected.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. 1 is a circuit configuration diagram showing a discharge lamp lighting device according to Embodiment 1 of the present invention. In the figure, 1 is a DC power source, 2
Are transistors 7 and 8 and regenerative diodes 9 and 1
0 is an inverter circuit, 3 is a detection capacitor C3
a, C4b and diodes D1a, D2a and D1b,
A detection circuit 4 composed of D2b, a capacitor 11, and a resistor 12, 4 is a control circuit for controlling the inverter circuit 2 according to the output level output from the detection circuit 3, and La and Lb.
Is a ballast choke which is an inductance element for limiting a load current, FLa and FLb are discharge lamps, C1a and C1b are preheating capacitors respectively connected in parallel to the discharge lamps FLa and FLb, and C2a and C2b are DC blocking capacitors.

Here, the ballast choke La, the preheating capacitor C1a, the discharge lamp FLa, the DC blocking capacitor C2a, or the ballast choke Lb, the preheating capacitor C1b, the discharge lamp FLb, the DC blocking capacitor C2.
b corresponds to the first series resonance circuit. Further, the ballast choke La, the detection capacitors C3a and C4a,
Alternatively, the ballast choke Lb and the detecting capacitor C
3b and C4b correspond to the second series resonance circuit.

Next, the operation of the first embodiment will be described with reference to FIGS. In the discharge lamp lighting device as shown in FIG. 2A, the transistors 7 and 8 of the inverter circuit 2 are alternately turned on and off at a high frequency, so that a high frequency voltage is applied to the load circuit including the discharge lamps FLa and FLb. Is applied. As a result, the discharge lamps FLa, FLb
A high-frequency current limited by the ballast chokes La and Lb flows through the.

The discharge lamp lighting device of FIG. 2 (b) is similar to the discharge lamp lighting device of FIG.
4a, C3b, and C4b are added. If viewed as loads of the inverter circuit 2, these include a preheating capacitor C1a, a series circuit of a discharge lamp FLa and a DC blocking capacitor C2a, and a preheating capacitor C1.
It is a capacitor including b and connected in parallel to each of the series circuits of the discharge lamp FLb and the DC blocking capacitor C2b.
Normally, the constant of this detection capacitor is selected so as to have a sufficiently high impedance with respect to the lamp impedance during lighting so as not to affect the lamp current flowing through the discharge lamps FLa and FLb. Therefore, the voltage applied to the detection capacitor changes as the lamp voltage changes.

The detecting capacitor is composed of a series connection of C3a and C4a and a series connection of C3b and C4b, and a voltage divided by a capacitance ratio is applied to each of the series-connected capacitors.

In FIG. 1, the voltage applied to C4a and C4b of the detecting capacitors is determined by the diode D
Rectifier smoothing (detection) is performed by 1a, D2a and D1b, D2b and the capacitor 11, and the control circuit 4 controls the inverter circuit 2 according to the rectified and smoothed (detected) voltage level (detection output).

Next, the operation when the end-of-life lamp is lit will be described. At the end of the life of the discharge lamp, discharge occurs only from one of a pair of electrodes provided at both ends of the discharge lamp, and a discharge phenomenon called half-wave discharge occurs in which there is almost no discharge from the opposite electrode. become. In this case, the lamp current is difficult to flow, and the lamp impedance is equivalently higher than that during normal lighting.

As an example, when the discharge lamp FLa is half-wave discharged, the waveform is shown in FIG. As is apparent from FIG. 6, the Y-point voltage waveform differs depending on the direction of the half-wave discharge during the half-wave discharge, but in any case, when the peak-to-peak voltage of the Y-point voltage is seen, this FIG. As shown by the Y-point voltage waveform, the voltage becomes larger than the peak-to-peak voltage of the Y-point voltage during normal lighting. That is, since the lamp voltage of the discharge lamp FLa that is performing half-wave discharge becomes high, the voltage applied to the detection capacitors C3a and C4a or the rectification smoothing (detection) voltage of the capacitor 11 is higher than the level during normal lighting. Become.

Then, a threshold value: V (threshold) is provided between the voltage: V (normal) generated in the capacitor 11 during normal lighting and the voltage: V (life) generated in the capacitor 11 during half-wave discharge at the end of life. ) Is set and the capacitor 1
If the control circuit 4 stops the oscillation of the inverter circuit, for example, when a voltage exceeding V (threshold) is generated at 1, the inverter circuit can be protected when the end-of-life lamp is lit.

The detection circuit 3 shown in FIG. 1 has a discharge lamp FLa.
Since the OR side is connected to the FLb side, it is possible to detect if either one of the discharge lamps is at the end of its life, and the inverter circuit can be protected.

In the waveform of FIG. 6, V _{CE (8)} is the collector-emitter voltage of the transistor 8, I _{C (7)} is the collector current of the transistor 7, and I _{C (8)} is the collector current of the transistor 8. Are shown respectively.

Next, the operation when the lamp is turned off during lighting will be described. For example, it is assumed that the discharge lamp FLa is disconnected while the lamp is on in the circuit of FIG. 2A in which the detection capacitors C3a and C4a are not connected. In this case, since the load circuit on the side of the discharge lamp FLa is disconnected, the energy of the ballast choke La loses its discharge path and is applied to the ballast choke La itself or the transistors 7 and 8 as an excessive voltage. It may lead to deterioration or destruction of the transistor.

It is assumed that the discharge lamp FLa is removed while the lamp is lit in the circuit of FIG. 2 (b) to which the detecting capacitors C3a and C4a are connected. Then, in the load circuit on the discharge lamp FLa side, since the series circuit of the ballast choke La and the detecting capacitors C3a and C4a remains, the energy of the ballast choke La is equal to the detecting capacitor C3.
It can be released via 3a and C4a. As a result, the voltage applied to the ballast choke La itself or the transistors 7 and 8 is suppressed, and deterioration of the ballast choke and destruction of the transistors can be prevented.

When the discharge lamp FLa is detached (filament detached), the oscillating operation of the inverter circuit 2 is not stopped at this time, so the transistors 7 and 8 are turned on / off by the supply of the on signal from the control circuit 4. Is repeated, and the connected discharge lamp FLb is normally turned on. At this time, the waveform corresponding to the discharge lamp FLa side is as shown in FIG.

That is, a series circuit including a ballast choke Lb and a preheating capacitor C1b and a discharge lamp FLb and a DC blocking capacitor C2b, and a detecting capacitor C3.
a ballast choke La and detection capacitors C3a and C4a in a waveform determined by the resonance frequency of the load circuit corresponding to the discharge lamp FLb side including a series circuit of b and C4b.
The waveform determined by the resonance frequency of the load circuit corresponding to the separated discharge lamp FLa side, which is composed of a series circuit of and, is superimposed.

When the voltage between peak values of the Y point voltage is observed when the filament is detached, as shown by the voltage waveform of the Y point voltage in FIG. Also grows. That is, the series resonance of the ballast choke La and the detection capacitors C3a and C4a causes
The voltage applied to the detection capacitors C3a and C4a or the rectification smoothing (detection) voltage of the capacitor 11 is higher than the level at the time of half-wave discharge.

As described above, the voltage generated in the capacitor 11 when the filament is detached: V (disengagement) is V (disengagement) ≧
If the constant of the detection capacitor is selected so that V (life) is reached, as with the end-of-life lamp lighting described above,
The inverter circuit can be protected when the lamp is removed.

Embodiment 2. FIG. 3 is a circuit configuration diagram of a discharge lamp lighting device according to the second embodiment of the present invention. In this circuit, resistors R1a and R1b are inserted in series with the detection capacitors C3a and C4a and C3b and C4b. As mentioned above, FIG.
In this circuit, for example, when the discharge lamp FLa is disconnected while the lamp is on, the load circuit on the discharge lamp FLa side is a series resonance circuit of the ballast choke La and the detecting capacitors C3a and C4a. A resonance voltage is applied to the capacitors C3a and C4a.

However, since the series resonance circuit has a resistance component of only the winding resistance of the ballast choke La, Q is large, and a very high resonance voltage is applied to the ballast choke La and the detection capacitors C3a and C4a. Will be done. Therefore, the ballast choke La and the detection capacitors C3a and C4a require high voltage components.

Therefore, the resistor R1a is provided in the series resonance circuit of the ballast choke La and the detection capacitors C3a and C4a.
Since the Q of the series resonance circuit is reduced by interposing, the ballast choke La and the detection capacitor C3.
The resonance voltage applied to a and C4a can be suppressed low. Therefore, the ballast choke La and the detecting capacitors C3a and C4a can be selected from components whose withstand voltage is suppressed.

Embodiment 3. FIG. 4 is a circuit configuration diagram of a discharge lamp lighting device according to a third embodiment of the present invention. Compared with the circuit of FIG. 1, in the circuit of FIG. 1, DC blocking capacitors C2a and C2b are connected to the load circuit connected in parallel with the inverter circuit, respectively, whereas in the circuit of FIG. The DC blocking capacitor C2 is shared by one. usually,
Since this DC blocking capacitor is merely connected for the purpose of preventing a DC component from flowing into the load (lamp) circuit, the operation does not change even if one DC blocking capacitor C2 is shared. . Therefore, the number of parts can be reduced.

Fourth Embodiment FIG. 5 is a circuit configuration diagram of a discharge lamp lighting device according to Embodiment 4 of the present invention. In this circuit, a current transformer CUT (primary side), which is an oscillation feedback winding, is provided in the path through which the combined current of the load circuits connected in parallel flows, and the transistors 7, 8 are generated by the voltage generated on the secondary side. Is supplied with a base current, and is alternately turned on and off. That is, the inverter circuit becomes self-oscillating.

In this circuit, as an example of protection of the inverter circuit at the end of life lamp lighting and lamp disconnection as described above, as shown in FIGS. 5 (a) and 5 (b).
A transistor Q2 is connected between the base and the emitter of the transistor 8 and the transistor Q2 is turned on so that the ON signal from the current transformer CUT is not supplied to the transistor 8 and the oscillation of the inverter circuit is stopped.

When the oscillation of the inverter circuit is stopped,
By turning on the transistor Q2, it can be realized by stopping the supply of the ON voltage between the base and the emitter of the transistor 8 and the supply of the base current. The supply of the ON voltage between the base and the emitter can be stopped by turning on the transistor Q2, but the supply of the base current can be stopped by the current transformer CU.
Transistor Q2 must be able to absorb the current returned to the secondary side by receiving the current flowing in the primary side of T. Therefore, in consideration of stopping the oscillation of the inverter circuit, the one having a smaller amount of feedback to the secondary side by the current transformer CUT, that is, the one having the smaller base current supplied to the transistor 8 is the oscillator of the inverter circuit. It can be said that it can be stopped easily.

Therefore, the circuits of FIGS. 5A and 5B will be compared. In both figures, two lamps are connected in parallel, but here consider the case where the discharge lamp FLb side is disconnected. In the circuit of FIG. 5A, when the discharge lamp FLb is detached during normal lighting (shown by a broken line),
At that moment, (1) the first series resonance circuit on the side of the discharge lamp FLa: the ballast choke La, the discharge lamp FLa, and the preheating capacitor C1.
Current flowing in a parallel circuit with a and a series circuit with a DC blocking capacitor C2. (2) Second series resonance circuit on the discharge lamp FLa side: current flowing in the series circuit of the ballast choke La and the detection capacitors C3a and C4a. (3) Second series resonance circuit on the discharge lamp FLb side: current flowing in a series circuit including the ballast choke Lb and the detection capacitors C3b and C4b. The combined current of (1) to (3) above flows to the primary side of the current transformer CUT.

In the circuit of FIG. 5 (b), when the discharge lamp FLb is detached during normal lighting (shown by the broken line), at that moment, (1) the first series resonance circuit on the discharge lamp FLa side is provided. : Ballast choke La, discharge lamp FLa and preheating capacitor C1
Only the current flowing in the parallel circuit with a and the series circuit with the DC blocking capacitor C2 flows to the primary side of the current transformer CUT.

Thus, comparing the circuits of FIGS. 5A and 5B, when the discharge lamp FLb is disconnected during normal lighting (shown by the broken line), the current flowing through the primary side of the current transformer CUT. Is less in the circuit of FIG. That is, the circuit of FIG. 5 (b) uses the current transformer CUT 2
Since the amount of feedback to the next side is small and the base current supplied to the transistor 8 is small, oscillation of the inverter circuit can be stopped more easily than in FIG. 5A.

Embodiment 5. FIG. 7 is a circuit configuration diagram of a discharge lamp lighting device according to a fifth embodiment of the present invention. In this circuit, a path from the DC power source 1 to the starting circuit 5 via the resistor R2, the ballast choke Lb, and the lamp filament b1, and the DC power source 1 to the resistor R2, the ballast choke La, the lamp filament a1, and the resistor R3. Lamp filament a
2, DC detection circuit 6 through the filament b2 of the lamp
It is equipped with a route leading to. Then, when the DC detection circuit 6 detects a DC, the starting circuit 5 supplies a starting trigger to the inverter circuit 2.

In the circuit constructed as shown in FIG. 7,
For example, if the filament a1 of the lamp is not installed,
Since the path connecting the DC power supply 1 to the DC detection circuit 6 is disconnected, the DC detection circuit 6 cannot detect DC. Therefore, the starter circuit 5 causes the inverter circuit 2 to
The startup trigger cannot be supplied to the inverter circuit 2 and the inverter circuit 2 cannot oscillate. This is the same when the filament a2 of the lamp is not attached or when the filament b2 of the lamp is not attached.

If the lamp filament b1 is not attached, the path from the DC power supply 1 to the starter circuit 5 is cut off, so that the starter trigger cannot be supplied to the inverter circuit 2 and the inverter circuit 2 cannot be supplied. Circuit 2 cannot oscillate.

According to the above configuration, when the lamp is not mounted, particularly when the filament is not mounted, it is possible to identify this and prevent the inverter circuit 2 from oscillating. .

[0048]

According to the discharge lamp lighting device of the present invention, the circuit connected between the output terminals of the inverter circuit includes the first series resonance circuit including the discharge lamp and the second series resonance circuit not including the discharge lamp.
A load circuit formed by connecting two or more circuits configured in parallel with each other in series, a detection circuit that detects a part of the voltage generated in the second series resonance circuit, and a detection circuit that outputs the voltage. With a control circuit that operates to stop the output of the inverter circuit when the output level exceeds a preset threshold, the output level output from the detection circuit during normal lamp lighting and the end of life lamp lighting A threshold is set between the output level output from the detection circuit and the output level output from the detection circuit due to the series resonance of the second series resonance circuit when the filament is detached during the lamp lighting. Since it is set to be higher than the output level output from the detection circuit while the end-of-life lamp is lit, the DC power supply voltage is set to the normal level of the discharge lamp as in the conventional discharge lamp lighting device. Without higher than the 2 × 2 ^1/2 times the voltage of the ramp voltage, if the end-of-life during lamp operation and filament are disengaged, the output of the inverter circuit can be stopped, at the time of lamp replacement It is possible to ensure safety.

Further, since the resistor is added in series to the second series resonance circuit, the surge voltage generated in the second series resonance circuit when the lamp is attached / detached is suppressed, and therefore, the components forming the second series resonance circuit. A low withstand voltage can be used.

Further, a common part is provided in the first series resonance circuit connected in parallel, and a DC blocking capacitor and an oscillation feedback winding are provided in this common part, and the first series resonance circuit is connected to the first series resonance circuit.
Only the flowing current flows to the primary side of the oscillation feedback winding.
By doing so, the inverter circuit oscillates self-excitedly, so it is possible to reduce the number of parts, and at the same time, in the oscillation feedback winding during the period from when the filament is detached during lighting to when the output of the inverter circuit is stopped. The flowing current is reduced, and the output of the inverter circuit can be surely stopped.

The load circuit is composed of two circuits connected in parallel, and the starting circuit is provided from the DC power source through the filament on the side opposite to the common portion side of the first discharge lamp and the second discharge lamp. A direct current detection circuit provided through a filament on the side opposite to the common portion side, a filament on the common portion side of the second discharge lamp, and a filament on the common portion side of the first discharge lamp. Since the start circuit is operated based on the output level output from the detection circuit, the oscillation start is performed after detecting the filament mounting state, and it is possible to reliably identify the lamp unmounted state such as filament disconnection. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram for explaining the operation of the discharge lamp lighting device according to the first embodiment of the present invention.

FIG. 3 is a circuit configuration diagram of a discharge lamp lighting device according to a second embodiment of the present invention.

FIG. 4 is a circuit configuration diagram of a discharge lamp lighting device according to a third embodiment of the present invention.

FIG. 5 is a circuit configuration diagram of a discharge lamp lighting device according to a fourth embodiment of the present invention.

FIG. 6 is an operation waveform diagram of each portion during normal lighting, half-wave discharge, and filament detachment in the embodiment of the present invention.

FIG. 7 is a circuit configuration diagram of a discharge lamp lighting device according to a fifth embodiment of the present invention.

FIG. 8 is a circuit configuration diagram of a conventional discharge lamp lighting device.

[Explanation of symbols]

1. DC power supply, 2. Inverter circuit, 3. Detection circuit, 4. Control circuit, 5. Start-up circuit, 6.
DC detection circuit, 7. Transistor, 8. Transistor, 9. Regeneration diode, 10. Regeneration diode, 11. Capacitor, 12. resistance,
a1. Filament, a2. Filament, b
1. Filament, b2. Filament, C.I.
Electrolytic capacitor, C1a. Preheating capacitor,
C1b. Preheating capacitor, C2. DC blocking capacitor, C2a. DC blocking capacitor, C2
b. DC blocking capacitor, C3a. Detection capacitor, C3b. Detection capacitor, C4a. Detection capacitor, C4b. Detection capacitor, C
UT. Oscillation feedback winding, D. Diode, D1
a. A diode, 1b. Diode, D2a.
Diode, D2b. Diode, FLa.
Discharge lamp, FLb. Discharge lamp, L.L. An inductance element, La. Ballast choke, Lb. An inductance element, Q1. MOSFET, Q2. A transistor, R1a. Resistance, R1b. Resistance, R
2. Resistance, R3. resistance.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-5-326177 (JP, A) JP-A-7-99095 (JP, A) JP-A-6-140177 (JP, A) JP-A-7- 99091 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H05B 41/24 H02M 7/48

Claims (4)

(57) [Claims] 1. A DC power supply, an inverter circuit connected to the DC power supply, a circuit connected between output terminals of the inverter circuit, the first series resonance circuit including a discharge lamp, and a discharge lamp. A load circuit formed by connecting in parallel two or more circuits configured by a second series resonance circuit not included,
A detection circuit that detects a part of the voltage generated in the second series resonance circuit, and stops the output of the inverter circuit when the output level output from the detection circuit exceeds a preset threshold value. A control circuit that operates in such a manner that the threshold value is set between the output level output from the detection circuit during normal lamp lighting and the output level output from the detection circuit during end-of-life lamp lighting, and,
The output level output from the detection circuit due to the series resonance of the second series resonance circuit becomes higher than the output level output from the detection circuit during the end of life of the lamp when the filament is detached during the lamp lighting. Discharge lamp lighting device characterized by being set to. 2. The discharge lamp lighting device according to claim 1, wherein a resistance is added in series to the second series resonance circuit. 3. A first serial resonance circuit connected in parallel is provided with a common part, and the common part is provided with a DC blocking capacitor and an oscillation feedback winding, and a current flows to the first series resonance circuit.
Only the current that flows in the primary side of the oscillation feedback winding
The discharge lamp lighting device according to claim 1 or 2 , wherein the inverter circuit is configured to self-oscillate. 4. The load circuit is a two-circuit parallel connection, and starts oscillation of the inverter circuit provided from the DC power supply via the filament on the side opposite to the common portion side of the first discharge lamp. And a filament on the side opposite to the common portion side of the second discharge lamp from the DC power supply, the filament on the common portion side of the second discharge lamp, and the common portion side of the first discharge lamp. A direct current detecting circuit provided via the filament for detecting direct current from the direct current power source, and the starting circuit is operated based on an output level output from the direct current detecting circuit. The discharge lamp lighting device according to claim 3.