JPH09260083A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lighting device by which a device and a discharge lamp can be reliably protected by reliably detecting the last stage of the service life of the discharge lamp, by detecting a DC voltage component generated on both ends of the discharge lamp, judging a result by comparing this detecting output and time necessary to start the discharge lamp with each other, and controlling a high frequency inverter circuit. SOLUTION: In a discharge lamp lighting device where a discharge lamp 36 is connected in series to an output terminal of a high frequency inverter circuit 22 through a capacitor 34 and a choke coil 35, the following means is used. A DC voltage detecting circuit 38 to detect a DC voltage component not less than a prescribed level generated on both ends of the discharge lamp 36, is connected between electrodes 36a and 36b of the discharge lamp 36. The fact that detecting output of this DC voltage detecting circuit 38 continues longer than time necessary to start the discharge lamp 36 is judged by a judging circuit 52. Oscillation of the high frequency inverter circuit 22 is stopped or its output in weakened by an inverter circuit control means 56 on the basis of judging output of this judging circuit 52.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting a discharge lamp such as a fluorescent lamp at a high frequency.
The present invention relates to a discharge lamp lighting device that determines the end of life of a discharge lamp.

[0002]

2. Description of the Related Art In a discharge lamp lighting device of this type, as shown in FIG. 13, a DC power source 1 is connected to an input terminal of a high frequency inverter circuit 2, and an output terminal of the inverter circuit 2 is connected to a capacitor 3 and a choke coil 4. Through a discharge lamp,
For example, a fluorescent lamp 5 is connected, and a preheating capacitor 6 is connected between the filament electrodes 5a and 5b of the fluorescent lamp 5. The DC power supply 1 may be a battery or a commercial power supply that is full-wave rectified and smoothed. The high-frequency inverter circuit 2 outputs a generally rectangular high-frequency voltage, and the direct-current component is cut by passing this high-frequency voltage through the capacitor 3 so that only the alternating current flows through the fluorescent lamp 5. The choke coil 4 acts to keep the lamp current uniform with respect to a rapid impedance change due to the discharge of the fluorescent lamp 5 due to the current limiting reactor component. When the inverter circuit 2 oscillates, the preheating capacitor 6 causes a resonance current to flow through the filament electrodes 5a and 5b, heats the filament electrode, and facilitates discharge.

Capacitors 7, 8 are provided between both ends of the fluorescent lamp 5.
Is connected in series, and the AC voltage generated at the midpoint of this voltage dividing circuit is double-voltage rectified by the half-wave voltage doubler rectifier circuit including the diodes 9 and 10 and supplied to the determination circuit 11. There is. In this circuit, a voltage corresponding to the peak voltage of the AC voltage is supplied to the determination circuit 11. The determination circuit 11 compares the input DC voltage with a preset voltage, and when the input voltage exceeds the predetermined voltage, determines the end of the lamp life and supplies an oscillation stop signal to the frequency control circuit 12. The frequency control circuit 12 receives the oscillation stop signal and controls the oscillation frequency of the inverter circuit 2 to zero to stop the oscillation.

If the oscillating operation of the inverter circuit 2 is continued while the lamp 5 is at the end of its life, an overload condition may occur, causing damage to circuit elements and the like, or damage to the lamp. Therefore, it is important to detect the end of the lamp life and stop the oscillation operation of the inverter circuit 2 in order to protect the device and the lamp. In general, when the fluorescent lamp 5 reaches the end of its life, the impedance of the lamp rises, whereby the inverter circuit 2 approaches the resonance Q point and resonance becomes stronger, and the tube voltage (AC component) rises. Therefore, the impedance of the lamp can be indirectly known by looking at the DC voltage obtained by voltage-doubler rectifying this AC component by the half-wave voltage doubler rectifier circuit, and the lamp impedance corresponds to the end of the lamp life. Then, as a result, the end of life of the lamp can be determined. In this conventional device, the oscillation of the inverter circuit 2 is stopped by thus judging the end of life of the lamp.

[0005]

However, the impedance of the lamp increases not only when the lamp reaches the end of its life, but when the lamp is dimmed, the ambient temperature of the lamp becomes low, and If the type is changed, the cost will increase even if there are variations in manufacturing even for the same type of lamp. Therefore, when such a case occurs individually or in combination, there is a problem that the lamp is erroneously determined to be at the end of its life even though the lamp is normal. On the contrary, there is a problem that the end of the lamp life cannot be determined because the tube voltage does not rise due to factors such as the ambient temperature even though the lamp is at the end of its life.

Therefore, the invention according to claim 1 provides a discharge lamp lighting device capable of surely detecting the end of life of the discharge lamp and thereby reliably protecting the device and the discharge lamp.

According to the second aspect of the present invention, in the case of lighting a plurality of discharge lamps at the same time, it is possible to reliably detect the end of life of each discharge lamp, thereby ensuring protection of the device and the discharge lamp. A lighting device is provided.

According to the third aspect of the invention, in the case of lighting a plurality of discharge lamps at the same time, the end of life of each discharge lamp can be surely detected, whereby the device and the discharge lamp can be surely protected, and Provided is a discharge lamp lighting device capable of simplifying the circuit configuration.

Further, the invention according to claim 4 provides a discharge lamp lighting device capable of surely detecting the end of life of the discharge lamp, thereby ensuring protection of the device and the discharge lamp, and preventing malfunction at the time of starting. provide.

Further, according to the invention of claim 5, the end of life of the discharge lamp can be surely detected, whereby the device and the discharge lamp can be surely protected, and the discharge lamp can be surely not lit at the time of starting. Provided is a discharge lamp lighting device that can be detected.

[0011]

According to the first aspect of the present invention,
In a discharge lamp lighting device in which a discharge lamp is connected to an output terminal of a high-frequency inverter circuit via a capacitor and a choke coil in series, a DC voltage detection circuit that detects a DC voltage component of a predetermined level or more generated at both ends of the discharge lamp, A determination circuit that determines that the detection output of this DC voltage detection circuit has continued longer than the time required to start the discharge lamp, and stops the oscillation of the high frequency inverter circuit based on the determination output of this determination circuit or Inverter circuit control means for weakening the output is provided.

According to a second aspect of the present invention, in a discharge lamp lighting device in which a plurality of discharge lamps are connected to the output terminals of a high-frequency inverter circuit via a capacitor and a choke coil in series, a predetermined value is generated at both ends of each discharge lamp. It is determined that one of the plurality of DC voltage detection circuits that detect the DC voltage component of the level or higher and the detection output of each DC voltage detection circuit lasts longer than the time required to start the discharge lamp. The determination circuit and the inverter circuit control means for stopping the oscillation of the high frequency inverter circuit or weakening the output of the high frequency inverter circuit based on the determination output of the determination circuit are provided.

According to a third aspect of the present invention, in a discharge lamp lighting device in which a plurality of discharge lamps are connected to the output terminals of a high frequency inverter circuit via a capacitor and a choke coil in series, a predetermined voltage is generated at both ends of each discharge lamp. A DC voltage detection circuit that detects a DC voltage component above the level, a judgment circuit that judges that the detection output of this DC voltage detection circuit lasts longer than the time required to start the discharge lamp, and a judgment output of this judgment circuit Based on the above, the inverter circuit control means for stopping the oscillation of the high frequency inverter circuit or weakening the output of the high frequency inverter circuit is provided.

According to a fourth aspect of the invention, in the discharge lamp lighting device according to the first, second or third aspect, a DC power source for generating a DC voltage to be supplied as a power source to the DC voltage detection circuit at the output terminal of the high frequency inverter circuit. Is connected.

[0015] The invention according to claim 5 is the invention according to claims 1, 2, and 3.
Alternatively, in the discharge lamp lighting device according to 4, the determination circuit determines the life of the discharge lamp when the detection output of the DC voltage detection circuit continues for a first time longer than the time required to start the discharge lamp, and the first The non-lighting at the time of starting the discharge lamp is determined when the second time, which is longer than the time, is continued.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) As shown in FIG.
A half-bridge type high frequency inverter circuit 22 is connected to. The DC power supply 21 is composed of a battery or a circuit that performs full-wave rectification of an AC power supply and smoothes it. The inverter circuit 22 includes a pair of MOS type F
A series circuit of ETs (field effect transistors) 23 and 24 is connected in parallel, and a resistor 2 is connected between the gate and source of the FET 23.
5 and the series circuit of capacitor 26 are connected and FET
A series circuit of a resistor 27 and a capacitor 28 is connected between the gate and source of 24. Then, the FETs 23,
The connection point of 24 is connected to one end of the first current transformer 29, and the first current transformer 29 is connected to the series circuit of the resistor 25 and the capacitor 26 via the resistor 30.
A second current transformer 31 magnetically coupled with the third current transformer 33 magnetically coupled with the first current transformer 29 via a resistor 32 in a series circuit of the resistor 27 and the capacitor 28. They are connected in parallel.

The other end of the first current transformer 29 is connected to one end of one filament electrode 36a of a fluorescent lamp 36, which is a discharge lamp, via a capacitor 34 and a choke coil 35 in series. The fluorescent lamp 36
The other end of the filament electrode 36b is connected to the FET 2
Connected to 4 sources. And the fluorescent lamp 3
A preheating capacitor 37 is connected between the other ends of the filament electrodes 36a and 36b of No. 6 in FIG. An input terminal of a DC voltage detection circuit 38 is connected between the filament electrodes 36a and 36b of the fluorescent lamp 36. The DC voltage detection circuit 38 includes a series voltage dividing circuit of resistors 39 and 40, which are input terminals, for each filament electrode 36a of the fluorescent lamp 36,
Between one end of 36b, the resistor 39 is connected to the electrode 36a side and the resistor 40
Is connected to the electrode 36b side, and a capacitor 41 is connected in parallel to the resistor 40. The connection point between one end of the resistor 39 and one end of the resistor 40 is connected to the base of an NPN type first transistor 44 through a diode 42 in the forward direction and a constant voltage diode 43, and a diode 45. Is connected to the emitter of the NPN-type second transistor 46 in the reverse direction.

The first transistor 44 has an emitter connected to the other end of the resistor 40, a collector connected to the diode 47 in the reverse direction, and a resistor 48 connected to the + VE power supply terminal. The second transistor 46
Connects the collector to the + VE power supply terminal via the diode 49 in the reverse direction and the resistor 48, and connects the base to the resistor 40 via the constant voltage diode 50 in the forward direction.
Is connected to the other end of. The voltage at the connection point between the resistor 48 and the anodes of the diodes 47 and 49 is output from the output terminal via the inverting circuit 51. The determination circuit 52 is connected to the output terminal of the DC voltage detection circuit 38. The determination circuit 52 connects the output terminal of the inverting circuit 51 of the DC voltage detection circuit 38 to one end of the capacitor 54 via the resistor 53 and also connects one input terminal of the comparator 55. The other end of the capacitor 54 is connected to the cathode terminal of the constant voltage diode 50. The resistor 53 and the capacitor 54 form a time constant circuit. The reference voltage ref is input to the other input terminal of the comparator 55.

The comparator 55 supplies a stop signal for stopping the oscillation of the inverter circuit 22 to the frequency control circuit 56 constituting the inverter circuit control means when the input voltage from the time constant circuit becomes equal to or higher than the reference voltage ref. It is like this. When the frequency control circuit 56 receives a stop signal, it controls the self-oscillation by turning off the circuit of the current transformer 31 or 33 of the inverter circuit 22, for example. In such a configuration, when the DC power supply 21 is turned on at time t1 as shown in FIG. 2, the inverter circuit 22 starts an oscillating operation at time t2 which is a slightly delayed timing. The inverter circuit 22 initially operates at a relatively high frequency and oscillates at a position away from the resonance Q. As a result, the high-frequency voltage applied to the fluorescent lamp 36 is suppressed to a low level, and a preheating current flows through the preheating capacitor 37 to each filament electrode 36a, 36b to preheat each filament electrode.

At time t3, the inverter circuit 22 operates at a relatively low frequency and oscillates at a position close to the resonance Q. As a result, the fluorescent lamp 36
The high frequency voltage applied to is increased. In this way, the fluorescent lamp 36 starts to discharge and light at time t4.
After that, the fluorescent lamp 36 keeps lighting until the inverter circuit 22 stops oscillating. By the way, since the lamp is the same as the insulator while the fluorescent lamp 36 is not lit, when a DC voltage is first applied across the fluorescent lamp 36, this DC component is maintained during this period. And
When the fluorescent lamp 36 is turned on, this time the lamp becomes an equivalent resistance, and the direct current component is canceled.

Therefore, the lamp voltage applied to the fluorescent lamp 36 becomes as shown in FIG. 2 (a), and the DC voltage detection circuit 38 is turned on after the power is turned on until the fluorescent lamp 36 starts lighting. The DC component is detected only for the time T1 and as shown in FIG.
It outputs the high-level signal shown in (b). That is,
When the DC voltage detection circuit 38 detects the DC component of the + voltage, it supplies a base current to the base of the first transistor 44 via the constant voltage diode 43, and this transistor 4
4 turns on. As a result, the input to the inverting circuit 51 becomes low level, and the output of the inverting circuit 51 becomes high level. Further, when the DC component of the −voltage is detected, a base current is caused to flow through the constant voltage diode 50 to the base of the second transistor 46, and the transistor 46 is turned on. As a result, the input to the inverting circuit 51 also goes low and the output of the inverting circuit 51 goes high. In this way, the DC voltage detection circuit 38 sets the output from the inversion circuit 51 to the high level during the time when the DC component is detected.

When the fluorescent lamp 36 is turned on and the direct current component is canceled, a direct current voltage is hardly generated across the resistor 40, so that the transistors 44 and 46 are formed.
Keeps the off state, so that the input to the inverting circuit 51 becomes high level and the output level of the inverting circuit 51 becomes low level. The determination circuit 52 charges the capacitor 54 via the resistor 53 when the output of the inverting circuit 51 is at high level. Then, the charge level of the capacitor 54 changes to the reference voltage re
When f or more, the comparator 55 supplies a stop signal to the frequency control circuit 56.

Therefore, the circuit time constant is set so that the charge level of the capacitor 54 does not exceed the reference voltage ref during the time T1 required for starting from the power-on to the start of lighting when the fluorescent lamp 36 is normally started and lit. And reference voltage re
If f is set in advance, even if the output of the DC voltage detection circuit 38 becomes high level for the time T1 at the time of starting, the output of the comparator 55 of the determination circuit 52 is in the low level state as shown in FIG. 2 (c). It does not hold and supply a high-level stop signal to the frequency control circuit 56. That is, in the determination circuit 52, the charge level of the capacitor 54 is the reference voltage re after the capacitor 54 starts charging.
The time T0 until it becomes f or more is set to T0> T1.

When the fluorescent lamp 36 starts lighting, the DC component is canceled and the output level of the inverting circuit 51 becomes low level as shown in FIG. 2B, and thereafter, the output of the comparator 55 becomes low level state. To hold. Further, the fluorescent lamp 36 reaches the end of its life, and when the fluorescent lamp 36 is turned on, the filament electrode 36a is moved from the filament electrode 36b side.
When the lamp impedance increases with respect to the tube current flowing to the side, there is no difference from the normal state from the power-on until the fluorescent lamp 36 starts lighting.

However, when the fluorescent lamp 36 is turned on, the lamp voltage changes according to the degree of the lamp impedance as shown in FIG.
As shown in (a) of Fig. 3, the DC voltage component of the lamp voltage shifts to the minus side as shown in (b) of Fig. 3. When this DC voltage component deviates to the negative side by a value larger than the Zener voltage of the constant voltage diode 50, the DC voltage detection circuit 38 conducts the constant voltage diode 50 to turn on the second transistor 46 and turn on the inverting circuit 51. Set the input level of to low level. As a result, the output level of the inverting circuit 51, that is, the output level of the DC voltage detection circuit 38 becomes high level as shown in FIG.

When the time T2 becomes longer than the time T0, that is, when T2≥T0, the comparator 55 of the decision circuit 52 outputs a high-level stop signal and supplies it to the frequency control circuit 56. As a result, the frequency control circuit 56 stops the oscillation operation of the inverter circuit 22. On the contrary, when the fluorescent lamp 36 reaches the end of its life and the lamp impedance increases with respect to the tube current flowing from the filament electrode 36a side to the filament electrode 36b side at the time of lighting, the fluorescent lamp 36 is turned on after the power is turned on. There is no difference from the normal state until the start.

However, when the fluorescent lamp 36 is turned on, the lamp voltage changes according to the degree of the lamp impedance as shown in FIG.
As shown in FIG. 4 (a), the DC voltage component of the lamp voltage shifts to the plus side as shown in FIG. 4 (b). When this DC voltage component shifts to the plus side by more than the Zener voltage of the constant voltage diode 43, the DC voltage detection circuit 38 conducts the constant voltage diode 43, turns on the first transistor 44, and turns on the inverting circuit 51. Set the input level of to low level. As a result, the output level of the inverting circuit 51, that is, the output level of the DC voltage detection circuit 38 becomes high level as shown in FIG. 4 (c).

When the time T2 becomes longer than the time T0, that is, when T2≥T0, the comparator 55 of the decision circuit 52 outputs a high-level stop signal and supplies it to the frequency control circuit 56. As a result, the frequency control circuit 56 stops the oscillation operation of the inverter circuit 22. In this way, when the fluorescent lamp 36 reaches the end of its life and the lamp impedance is biased, the DC voltage detection circuit 38 detects the DC voltage component generated thereby and outputs a high level output to the determination circuit 52 at time T0.
Since the supply is continued for the above T2 time, a stop signal is generated from the comparator 55 of the determination circuit 52 after the T2 time continues, and the frequency control circuit 56 stops the oscillation operation of the inverter circuit 22. Therefore, the circuit element of the inverter circuit 22 is not damaged or the fluorescent lamp 36 is damaged due to the overload condition, and the device and the lamp can be reliably protected. Also, instead of detecting the lamp voltage, it detects the DC voltage component applied to the lamp,
Moreover, when the direct current component is equal to or higher than a predetermined level and the fluorescent lamp 36 is started and lit in a normal state for a predetermined time T0 or longer, which is longer than the time T1 required for starting from the power-on to the start of lighting, the lamp is not lamped for the first time. Since the end of life of the lamp is detected, even if the lamp is dimmed, the ambient temperature of the lamp is low, the type of lamp is changed, or there are variations in manufacturing even for the same type of lamp, it is irrelevant The end of life of can be reliably detected.

When the fluorescent lamp 36 is not turned on at the time of starting, the lamp voltage applied to the fluorescent lamp 36 is as shown in FIG. 5A, and the DC voltage component applied to the fluorescent lamp 36 is As shown in FIG. 5B, it is maintained longer than the time T1. Therefore, the high level output from the DC voltage detecting circuit 38 is also maintained longer than the time T1 as shown in FIG. 5 (c). Then, when this maintenance time is continued for T0 or more, the comparator 5 of the determination circuit 52
As shown in FIG. 5 (d), a stop signal is generated from 5 to cause the frequency control circuit 56 to operate in the inverter circuit 2
The oscillation operation of 2 is stopped. Thus, the fluorescent lamp 36
This circuit works even if the
The oscillation operation of the inverter circuit 22 can be stopped.

(Second Embodiment) The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and detailed description thereof will be omitted. This is applied to a discharge lamp lighting device for lighting three lights as shown in FIG. That is, the fluorescent lamp 361 is connected to the output terminal of the high frequency inverter circuit 22 through the capacitor 341 and the choke coil 351 in series.
Of the fluorescent lamp 362 by connecting one ends of the filament electrodes 361 a and 361 b of the fluorescent lamp 362 in series with the capacitor 342 and the choke coil 352.
a and 362b are connected to each other, and one ends of filament electrodes 363a and 363b of the fluorescent lamp 363 are connected to each other via a capacitor 343 and a choke coil 353 in series. Preheating capacitors 371, 372, 373 are provided between the other ends of the filament electrodes 361 a, 362 a, 363 a of the fluorescent lamps 361, 362, 363 and the other ends of the filament electrodes 361 b, 362 b, 363 b. Each is connected.

Each fluorescent lamp 361, 362, 363
DC voltage components of the voltage applied to the DC voltage detection circuits 381 and 3 having the same configuration as the DC voltage detection circuit 38, respectively.
It is designed to detect at 82,383. The outputs of the DC voltage detecting circuits 381, 382 and 383 are supplied to the judging circuit 52 via the OR gate circuit 61. In this configuration, each fluorescent lamp 361, 362, 363
At the end of the life of even one of the above, the output of the corresponding DC voltage detection circuit continues to be in the high level state for time T0 or longer, and this output is supplied to the determination circuit 52 via the OR gate circuit 61. As a result, the determination circuit 52 supplies the stop signal to the frequency control circuit 56. In this way, the oscillation operation of the high frequency inverter circuit 22 is stopped, and the device and the lamp are protected from damage. In this way, when the three fluorescent lamps are turned on at the same time, the end of life of each fluorescent lamp can be reliably detected, and thus the device and the fluorescent lamp can be reliably protected.

Further, at the time of starting, each fluorescent lamp 361, 36
If even one of 2, 363 is not lit, the output of the corresponding DC voltage detection circuit continues to be in the high level state for time T0 or longer, and this output is passed through the OR gate circuit 61 to the determination circuit 5
2 is supplied. As a result, the determination circuit 52 supplies the stop signal to the frequency control circuit 56. Thus,
The oscillation operation of the high frequency inverter circuit 22 is stopped. In this way, the non-lighting of the fluorescent lamp at the time of starting can be reliably detected.

(Third Embodiment) The same parts as those in the above-mentioned embodiment are designated by the same reference numerals and detailed description thereof will be omitted. This is applied to a discharge lamp lighting device for lighting three lights as shown in FIG. That is, the fluorescent lamp 361 is connected to the output terminal of the high frequency inverter circuit 22 through the capacitor 341 and the choke coil 351 in series.
Of the fluorescent lamp 362 by connecting one ends of the filament electrodes 361 a and 361 b of the fluorescent lamp 362 in series with the capacitor 342 and the choke coil 352.
a and 362b are connected to each other, and one ends of filament electrodes 363a and 363b of the fluorescent lamp 363 are connected to each other via a capacitor 343 and a choke coil 353 in series. Preheating capacitors 371, 372, 373 are provided between the other ends of the filament electrodes 361 a, 362 a, 363 a of the fluorescent lamps 361, 362, 363 and the other ends of the filament electrodes 361 b, 362 b, 363 b. Each is connected.

Each of the fluorescent lamps 361, 362, 363
One DC voltage detection circuit 62 detects the DC voltage component of the voltage applied to the. The DC voltage detection circuit 62, as shown in FIG.
Between one end of each filament electrode 361a, 361b of
A series voltage dividing circuit of resistors 391 and 401 is connected with the resistor 391 on the electrode 361a side and the resistor 401 on the electrode 361b side, and the capacitor 411 is connected in parallel to the resistor 401. In addition, a resistor 392 is provided between one ends of the filament electrodes 362 a and 362 b of the fluorescent lamp 362.
, 402 in series with a resistor 392 and an electrode 362.
The a side and the resistor 402 are connected to the electrode 362 b side, and the capacitor 41 2 is connected in parallel to the resistor 402. In addition, resistors 393, 40 are provided between one ends of the filament electrodes 363 a, 363 b of the fluorescent lamp 363.
The series voltage dividing circuit 3 is connected with the resistor 393 on the electrode 363a side and the resistor 403 on the electrode 363b side, and the capacitor 413 is connected in parallel to the resistor 403.

Then, one end of the resistor 391 and the resistor 40
The connection point with one end of 1 is the first of the NPN type through the diode 421 in the forward direction and the constant voltage diode 43.
Is connected to the base of the transistor 44 and the diode 451 is connected in the reverse direction to the emitter of the second NPN transistor 46. Also, the resistor 3
The connection point between one end of the resistor 92 and one end of the resistor 402 is connected to the constant voltage diode 4 through the diode 422 in the forward direction.
3 to the base of the first transistor 44 and a diode 45 2 in the reverse direction to the emitter of the second transistor 46. Further, the connection point between one end of the resistor 393 and one end of the resistor 403 is connected to the first transistor 44 via the diode 423 in the forward direction and the constant voltage diode 43.
And the diode 453 is connected in the reverse direction to the emitter of the second transistor 46.

In the first transistor 44, the emitter is connected to the other ends of the resistors 401, 402 and 403, the collector is connected through the diode 47 in the reverse direction, and the resistor 4
It is connected to the + VE power supply terminal via 8. The second transistor 46 has a collector connected to the + VE power supply terminal via the diode 48 in the reverse direction and the resistor 48, and a base connected to the resistors 401, 402 via the constant voltage diode 50 in the forward direction. It is connected to the other end of 403. The resistor 48 and the diodes 47 and 49
The voltage at the connection point with the anode is output from the output terminal to the determination circuit 52 via the inverting circuit 51.

In this configuration, each fluorescent lamp 361
, 362, 363 at the end of the life, the first transistor 44 is turned on via the constant voltage diode 43, or the second transistor 46 is turned on via the constant voltage diode 50, and the DC voltage detection circuit 62 Output continues to be in the high level state for time T0 or longer, and this output is supplied to the determination circuit 52. As a result, the determination circuit 52 supplies the stop signal to the frequency control circuit 56. Thus, the oscillating operation of the high frequency inverter circuit 22 is stopped,
Equipment and lamps are protected from damage. In this way, when the three fluorescent lamps are turned on at the same time, the end of life of each fluorescent lamp can be reliably detected, and thus the device and the fluorescent lamp can be reliably protected. Moreover, since the DC voltage detection circuit 62 is commonly used for each fluorescent lamp,
The configuration of the DC voltage detection circuit becomes simple.

Further, at the time of starting, each fluorescent lamp 361, 36
If even one of 2, 363 is not lit, the output of the DC voltage detection circuit remains in the high level state for the time T0 or longer, and this output is supplied to the determination circuit 52. As a result, the determination circuit 52 supplies the stop signal to the frequency control circuit 56. In this way, the oscillation operation of the high frequency inverter circuit 22 is stopped. In this way, the non-lighting of the fluorescent lamp at the time of starting can be reliably detected.

(Fourth Embodiment) As shown in FIG. 9, this shows a modified example of the DC voltage detection circuit 38 shown in FIG. 1. This DC voltage detection circuit has a cathode of a diode 42 at a constant voltage. It is connected to one end of a series voltage dividing circuit of resistors 63 and 64 via a diode 43. The other end of the series voltage dividing circuit is connected to the other end of the resistor 40. The connection point of the resistors 63 and 64 is connected to the base of the first transistor 44. The constant voltage diode 43, the resistor 6
Connect the capacitor 65 in parallel to the series circuit of 3,64.
A capacitor 66 is connected between the base and emitter of the first transistor 44.

The collector of the first transistor 44 is connected to the base of the PNP type third transistor 67. The third transistor 67 has an emitter connected to the other end of the resistor 40 and a collector connected to the diode 47.
In the reverse direction, and is further connected to the + VE power supply terminal via the resistor 48. The anode of the diode 45 is connected to the emitter of the second transistor 46. The second
In the transistor 46, the collector is connected to the base of the PNP type fourth transistor 68, and the base is connected to the other end of the resistor 40 via the resistor 69 and the constant voltage diode 50. The base of the second transistor 46,
A parallel circuit of a resistor 70 and a capacitor 71 is connected between the emitters.

The fourth transistor 68 has a collector connected to the other end of the resistor 40, an emitter via the diode 49 in the reverse direction, and a resistor +48 via the resistor 48.
E Connected to the power supply terminal. The second transistor 4
A resistor 72 is connected between the collector of 6 and the emitter of the fourth transistor 68. A parallel circuit of the resistor 70 and the capacitor 71, the resistor 69 and the constant voltage diode 5
A capacitor 73 is connected in parallel to the series circuit with 0.

By configuring the DC voltage detection circuit in this way, the transistor circuit (transistors 44 and 67) which is turned on when the DC voltage component applied to the fluorescent lamp 36 is shifted to the plus side and the minus side is shifted. Transistor circuit (transistors 46, 6
The hfe of 8) can be increased and the sensitivity can be increased. As a result, the output current supplied to the determination circuit 52 becomes sufficiently large. Therefore, it is effective when the input impedance to the determination circuit 52 is low.

(Fifth Embodiment) As shown in FIG. 10, this shows a modification of the DC voltage detection circuit 38 shown in FIG. 1, and this DC voltage detection circuit 75 is provided for each filament of the fluorescent lamp 36. A resistor 76 is provided between one ends of the electrodes 36a and 36b.
The capacitor 77 is connected via. Then, a full-wave rectification diode bridge circuit 78 is added to the capacitor 77.
Connect the input terminals of the diode bridge circuit 78
A capacitor 79 is connected to the output terminal of the. A light emitting diode 82D of a photocoupler 82 is connected to the capacitor 79 via a constant voltage diode 80 and a resistor 81.

The photocoupler 82 connects the emitter of the phototransistor 82T to one end of the filament electrode 36b of the fluorescent lamp 36 via the capacitor 83,
The collector of the phototransistor 82T is connected to the + VE power supply terminal via the resistor 84. The output between the collector and the emitter of the phototransistor 82T is supplied to the determination circuit 52 via the inverting circuit 51.

In this circuit, the capacitor 79 connected to the output terminal of the diode bridge circuit 78 is shown in the figure regardless of whether the DC voltage component applied to the fluorescent lamp 36 is shifted to the positive side or the negative side. When the DC voltage of the polarity is charged and the DC voltage exceeds the Zener voltage of the constant voltage diode 80, the constant voltage diode 80 becomes conductive and the light emitting diode 82D emits light. As a result, the phototransistor 82T is turned on and a high level output is generated at the output terminal of the inverting circuit 51. With this configuration, each filament electrode 36a, 36 of the fluorescent lamp 36 is
It is possible to deal with the case where both of b are away from the ground potential.

(Sixth Embodiment) As shown in FIG. 11, a series voltage dividing circuit of capacitors 85 and 86 is connected in parallel to the output terminal of the high frequency inverter circuit 22, and a diode 87 is connected to the capacitor 86 in reverse. A voltage doubler rectifier circuit is formed by connecting in parallel with the polarity and connecting the capacitor 89 in parallel through the diode 88 in the forward direction.
Then, a resistor 90 is connected in parallel to the capacitor 89, and both ends of the parallel circuit of the capacitor 89 and the resistor 90 are +.
The VE power source is taken out, and this + VE power source is supplied to the + VE power source terminal of the DC voltage detection circuit 38.

In such a configuration, as shown in FIG. 12, even if the DC power supply 21 is turned on at time t1, the inverter circuit 22 does not immediately oscillate, but at time t2 after a relatively long time has elapsed. Assuming that the oscillating operation is started, if the output of the DC voltage detection circuit 38 becomes high level immediately after the power is turned on, the determination circuit 52 waits for time T0 or more before starting the lighting of the fluorescent lamp 36. A malfunction occurs in which a stop signal is generated upon detection. In this regard, in this configuration, the + VE power supply is not supplied to the DC voltage detection circuit 38 unless the inverter circuit 22 starts the oscillation operation, so the DC voltage detection circuit 38 does not operate. That is, as shown in FIG. 12 (c), the output of the DC voltage detecting circuit 38 does not become high level until time t2.

Then, at time t3, the fluorescent lamp 36
When the high-frequency voltage applied to the fluorescent lamp 36 rises and the time t4 is reached, the fluorescent lamp 36 starts discharging and the output of the DC voltage detecting circuit 38 becomes low level. In this operation, the time T10 during which the output of the DC voltage detection circuit 38 is at a high level is sufficiently shorter than the time T0 for the determination circuit 52 to determine the end of life of the fluorescent lamp 36 or non-lighting. Does not accidentally supply the stop signal to the frequency control circuit 56.

In this way, by generating the + VE power supply at the output of the inverter circuit 22, even if the start of the oscillating operation of the inverter circuit 22 is significantly delayed at the time of starting, no malfunction occurs. 12A shows the fluorescent lamp 36.
12B shows the waveform of the lamp voltage applied to the DC voltage component, FIG. 12B shows the waveform of the DC voltage component without the lamp voltage, and FIG.
Shows the output waveform of the determination circuit 52.

In each of the above-described embodiments, the determination circuit uses a common time T for determining the end of life of the fluorescent lamp and the time for determining non-lighting at the time of starting the fluorescent lamp.
Although 0 is used for the determination, the present invention is not limited to this. The time for determining the end of the life of the fluorescent lamp is T01, and the time for determining the non-lighting at the time of starting the fluorescent lamp is T02 (> T01). ) Separately, and when the high level state of the output of the DC voltage detection circuit continues for the second time T02 or more at the time of starting, the determination circuit determines non-lighting, and the high level of the output of the DC voltage detection circuit at the time of lighting. The determination circuit may determine the end of life of the fluorescent lamp when the state continues for the first time T01 or longer. To achieve this, for example, the reference voltage input to the comparator is set to Vre
It may be switched to use f1 and Vref2 (> Vref1), and use the reference voltage Vref1 at the time of starting and use the reference voltage Vref2 at the time of lighting. Further, the time constant of the time constant circuit connected to the input terminal of the comparator may be switched between the time of starting and the time of lighting.

Further, in each of the above-described embodiments, the frequency control circuit has been described in which the oscillation operation of the high frequency inverter circuit is stopped by the stop signal from the determination circuit, but the present invention is not necessarily limited to this.
That is, it is known that the high frequency inverter circuit has a characteristic that it deviates from the resonance Q when the oscillation frequency becomes high, and the oscillation output weakens when the oscillation frequency increases. Therefore, the frequency control circuit may be a circuit for increasing the oscillation frequency of the high frequency inverter circuit and weakening the output of the inverter circuit by the output signal from the determination circuit.
Even in this case, the circuit element of the inverter circuit and the fluorescent lamp can be protected from damage.

[0052]

As described above, according to the first aspect of the present invention, the end of life of the discharge lamp can be reliably detected, and thus the device and the discharge lamp can be reliably protected. According to the second aspect of the invention, in the case of lighting a plurality of discharge lamps at the same time, the end of life of each discharge lamp can be reliably detected, and thus the device and the discharge lamp can be reliably protected. Further, according to the invention described in claim 3, in the case of lighting a plurality of discharge lamps at the same time, the end of life of each discharge lamp can be surely detected, whereby the device and the discharge lamp can be surely protected, and the DC The configuration of the voltage detection circuit can be simplified. According to the invention of claim 4, the end of life of the discharge lamp can be reliably detected,
As a result, the device and the discharge lamp can be reliably protected, and further, a malfunction can be prevented when the start of the oscillation operation of the high frequency inverter circuit is significantly delayed at the time of starting. Further, according to the invention of claim 5, the end of life of the discharge lamp can be surely detected, whereby the device and the discharge lamp can be surely protected, and non-lighting of the discharge lamp at the time of starting can be surely detected. it can.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a waveform diagram of each part for explaining the circuit operation at the time of normal starting and lighting of the lamp in the same embodiment.

FIG. 3 is a waveform chart of each part for explaining the circuit operation at the time of starting and lighting the lamp at the end of its life in the same embodiment.

FIG. 4 is a waveform diagram of each part for explaining the circuit operation at the time of starting and lighting the lamp at the end of its life in the same embodiment.

FIG. 5 is a waveform chart of each part for explaining the circuit operation at the time of starting the non-lighting lamp in the same embodiment.

FIG. 6 is a circuit block diagram showing a second embodiment of the present invention.

FIG. 7 is a circuit block diagram showing a third embodiment of the present invention.

FIG. 8 is a circuit configuration diagram of a DC voltage detection circuit according to the same embodiment.

FIG. 9 is a circuit configuration diagram of a DC voltage detection circuit according to a fourth embodiment of the present invention.

FIG. 10 is a partial circuit configuration diagram including a DC voltage detection circuit according to a fifth embodiment of the present invention.

FIG. 11 is a circuit block diagram showing a sixth embodiment of the present invention.

FIG. 12 is a waveform chart of each part for explaining the circuit operation at the time of starting the lamp in the same embodiment.

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

[Explanation of symbols]

 22 ... High frequency inverter circuit 34 ... Capacitor 35 ... Choke coil 36 ... Fluorescent lamp (discharge lamp) 38 ... DC voltage detection circuit 52 ... Judgment circuit 56 ... Frequency control circuit

Claims (5)

[Claims] 1. A discharge lamp lighting device in which a discharge lamp is connected to an output terminal of a high frequency inverter circuit via a capacitor and a choke coil in series, and a DC voltage component of a predetermined level or more generated at both ends of the discharge lamp is detected. DC voltage detection circuit, a determination circuit for determining that the detection output of the DC voltage detection circuit has continued longer than the time required to start the discharge lamp, and the high-frequency inverter circuit of the high-frequency inverter circuit based on the determination output of this determination circuit A discharge lamp lighting device comprising an inverter circuit control means for stopping oscillation or weakening the output of the high frequency inverter circuit. 2. A discharge lamp lighting device in which a plurality of discharge lamps are connected to output terminals of a high-frequency inverter circuit via a capacitor and a choke coil in series, respectively, and a DC voltage of a predetermined level or more generated at both ends of each discharge lamp. A plurality of DC voltage detection circuits for detecting each component,
Any one of the detection outputs of the DC voltage detection circuits
Determination circuit for determining that one has continued longer than the time required to start the discharge lamp, and an inverter circuit that stops oscillation of the high frequency inverter circuit or weakens the output of the high frequency inverter circuit based on the determination output of the determination circuit. A discharge lamp lighting device comprising a control means. 3. A discharge lamp lighting device in which a plurality of discharge lamps are connected to output terminals of a high-frequency inverter circuit via a capacitor and a choke coil in series, respectively, and a DC voltage of a predetermined level or more generated at both ends of each discharge lamp. A DC voltage detection circuit for detecting a component, a determination circuit for determining that the detection output of the DC voltage detection circuit has continued longer than the time required to start the discharge lamp, and the determination output of the determination circuit A discharge lamp lighting device comprising an inverter circuit control means for stopping oscillation of the high frequency inverter circuit or weakening the output of the high frequency inverter circuit. 4. The discharge lamp lighting device according to claim 1, 2 or 3, wherein a direct current power source for generating a direct current voltage supplied as a power source to the direct current voltage detection circuit is connected to an output terminal of the high frequency inverter circuit. . 5. The determination circuit determines the life of the discharge lamp when the detection output of the DC voltage detection circuit continues for a first time longer than the time required for starting the discharge lamp, and determines the life of the discharge lamp longer than the first time. The discharge lamp lighting device according to claim 1, wherein non-lighting at the time of starting the discharge lamp is determined when the discharge lamp has continued for 2 hours.