JPH0658833B2 - Discharge lamp lighting device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a discharge lamp lighting device for starting and lighting a discharge lamp at a high frequency.

2. Description of the Related Art A conventional discharge lamp lighting device is disclosed in, for example, JP-A-62-20.
No. 2494 Publication and National Technical Report (National Technical Report)
t) Vol. 33 No. As shown in 3p296, the circuit is as shown in FIG.

That is, in FIG. 3, 4 is a power supply circuit having a constant polarity of the output voltage composed of the commercial power supply 1, the rectifying bridge 2, and the smoothing capacitor 3, 5 is a capacitor connected in series to its output, and 6 is a capacitor. 5 is a transistor connected between the power supply circuit 4 and the capacitor 5, a series circuit of a fluorescent lamp 7 and an inductance 8 is connected in parallel to the capacitor 5, and a starting circuit is connected in parallel to the end of the fluorescent lamp 7 opposite to the power supply. The capacitor 9 and the inductance 10 are connected. 11
Is a self-excited switching circuit including a capacitor 5, a transistor 6, a capacitor 9, an inductance 8 and an inductance 10. Reference numeral 12 is an inductance, which is a driving inductance in which one end is connected to the base of the transistor 6, and a series circuit of a secondary winding 8b of the inductance 8 and a capacitor 13 which is a driving capacitor is connected between the other end and the emitter. To be done. 17 is a power supply circuit 4
A timer circuit composed of voltage dividing resistors 14 and 15 connected to the output terminals of and a capacitor 16 having one end connected to the midpoint thereof,
Reference numeral 18 is a transistor which is a short-circuiting transistor in which the other end of the capacitor 16 is connected to the base and the collector is connected in parallel to the inductance 12, and 19 is a cathode connected to the base of the transistor 6 and the other end of the transistor 6 is connected via the resistor 20. It is a diode connected to the emitter.

The operation of the conventional circuit configured as above will be described.
When the power is turned on, a voltage is generated in the power supply circuit 4, and the resistor 14, the capacitor 16 and the transistor 18 of the timer circuit 17 are generated.
A starting current flows through the base of the transistor 18 to turn on the transistor 18, and at the same time, the base current causes the transistor 6 to pass.
Conducts. Initially, the fluorescent lamp 7 is not turned on, and a current flows from the power supply circuit 4 through the transistor 6 via the inductance 8, the filament electrode of the fluorescent lamp 7, the capacitor 9 and the inductance 10. At this time, a positive voltage is generated in the secondary winding 8b of the inductance 8 and the transistor 6 passes through the capacitor 13 and the inductance 12.
Is supplied to maintain the transistor 6 on. At this time, the current flowing through the primary winding 8 a of the inductance 8 is the resonance current of the capacitor 9 and the inductance 8. Here, the current flowing by the positive voltage generated in the secondary winding 8b of the inductance 8 is a series resonance current at the natural vibration frequency of the inductance 12 and the capacitor 13, but since the transistor 18 is conducting, the transistor 18 is actually conducting. Since the current flows from the emitter to the collector in the reverse direction to a certain extent, the resonance state is weak and the inductance 12 hardly functions, so that the oscillation cycle becomes short as it approaches the charge / discharge time of the capacitor 13.

Therefore, when the capacitor 13 is charged to a voltage near the voltage generated in the secondary winding 8b and the base current of the transistor 6 stops flowing, and the base current of the transistor 6 is slightly pulled in the reverse direction due to the influence of the inductance 12, the transistor 6
Turns off, so the inductance 8b
When the voltage generated in the transistor 6 becomes small, the charge accumulated in the capacitor 13 is applied in the reverse direction between the base and the emitter of the transistor 6, and feedback is applied, so that the transistor 6 is rapidly turned off. When the transistor 6 is turned off, the energy stored in the series resonance circuit of the capacitor 9 and the inductance 8 and the inductance 10 is released to the capacitor 5, the fluorescent lamp 7, the capacitor 9, the inductance 8 and the inductance 10 and vibrates to preheat the fluorescent lamp 7. It becomes an electric current. At this time, the fluorescent lamp 7 is set so as not to be started by the voltage generated in the capacitor 9. The oscillating current flowing through the primary winding 8a of the inductance 8 when the transistor 6 is off causes a negative voltage to be generated in the secondary winding 8b of the inductance 8. At this time, the transistor 18 conducts in the forward direction, and the inductance 12 does not function at all, so this voltage causes the diode 19 and the resistor 20 to pass.
A reverse voltage is applied between the base and emitter of the transistor 6 via the transistor 6 to keep the transistor 6 off. When the oscillating current passes the negative peak, a positive voltage is gradually generated in the secondary winding 8b of the inductance 8, and the voltage charged in the reverse direction in the capacitor 13 during the off period of the transistor 6 is forwarded to the base of the transistor 6. Applied in the direction, transistor 6 turns on. At this time, since the current of the inductance 8 is still flowing in the opposite direction immediately after the turn-on, the current flows from the base to the collector via the diode 19 and the resistor 20. The reverse current of the inductance 8 gradually decreases and a forward current flows through the transistor 6, and the above operation is repeated thereafter. With the above oscillation operation, the temperature of the preheating electrode of the fluorescent lamp 7 rises with the passage of time.

It should be noted that the timer circuit 17 accumulates electric charges in the capacitor 16 via the resistor 14 after the power is turned on, and then the transistor 18
The base current is supplied, and after a predetermined time, when it is charged to the voltage by the resistors 14 and 15, it is not further charged. Therefore, after this time, the power supply is cut off and the charge of the capacitor 16 is discharged through the resistors 14 and 15. Until no current flows through the base of the transistor 18. Therefore, when the transistor 18 is turned off after a predetermined time, the transistor 6
When ON, a positive voltage is generated in the secondary winding 8b of the inductance 8 and the base current of the transistor 6 is supplied via the capacitor 13 and the inductance 12. This base current is a resonance current of the capacitor 13 and the inductance 12. The base current of the transistor 6 changes from positive to negative in the vicinity of its half cycle, and when the accumulated charge of the transistor 6 is discharged, the transistor 6 turns off. Before the fluorescent lamp 7 is started, the inductance 8 and the capacitor 9 are in a series resonance state, and the capacitor 9 is much larger than when it is turned on and larger than when it is preheated before the timer circuit operates.
Each inductance and capacitor are set to generate a voltage sufficient to start the fluorescent lamp 7. Therefore, the fluorescent lamp 7 is started.

After starting, the circuit operation is almost the same as after the timer circuit 17 operates, but since the impedance of the fluorescent lamp 7 is connected in parallel to the impedance of the capacitor 9 and the inductance 10, the current of the capacitor 9 decreases and the fluorescent lamp 7 is turned on. An electric current flows. Therefore, the resonance of the capacitor 9 having the inductance 8 almost disappears, and
Positive and negative voltages are generated in the next winding 8b according to the difference between the output voltage of the power supply circuit 4 and the lamp voltage, and the transistor is generated according to the natural vibration frequency of the inductance 8, the capacitor 5, the fluorescent lamp 7, the inductance 12, and the capacitor 13. 6
Is turned on and off to keep the fluorescent lamp 7 lit. The inductance 10 is for removing the DC component of the current of the fluorescent lamp 7.

When the fluorescent lamp 7 cannot be normally lit, such as at the end of its life, the circuit operation state (resonance state) is the same as when the starting voltage is generated after the operation of the timer circuit 17. Further, when the fluorescent lamp 7 is removed, no current flows in the inductance 8, so that the transistor 6 does not turn on and does not oscillate.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above configuration, the impedance of the fluorescent lamp 7 is large and changes abruptly and irregularly when the fluorescent lamp 7 is started or in an abnormal state such as the end of life. Therefore, the oscillation frequency temporarily coincides with or approaches the resonance frequency, and the resonance generated between the series resonance circuit of the capacitor 9 and the inductance 8 and the inductance 5 increases, so that the current flowing through the transistor 6 increases. At the same time, the storage time of the transistor 6 becomes long, and the loss of the transistor 6 becomes large. If this state continues as in the end of life, the temperature of the transistor 6 may rise rapidly and may be destroyed. It was

Means for Solving the Problems In order to solve the above problems, the present invention includes a power supply having a constant polarity of an output voltage, at least one transistor connected to an output terminal of the power supply, an inductance, and a capacitor. A switching circuit having a self-excited drive circuit for starting and lighting a discharge lap connected to an output end by turning on / off a current in a forward direction with the power supply by the transistor, and a positive power supply on a non-power supply side of the discharge lamp. A series circuit of a positive characteristic thermistor connected so that the characteristic thermistor is on the side opposite to the transistor of the power source and a starting circuit formed of an impedance element by a capacitor, an inductance, a resistance or a combination thereof, and the positive characteristic thermistor and the starting circuit. A voltage response switch element having one end connected to a connection point with the voltage response switch element And a three-terminal control element for stopping the current for driving the transistor from the drive circuit of the switching circuit by the current flowing into the control terminal connected to the other end.

The present invention has the above-described configuration, and when the fluorescent lamp 7 is in a so-called emitterless state in which the emitters of one or both electrodes disappear at the end of the life of the fluorescent lamp 7, the fluorescent lamp 7 is less likely to be discharged and the impedance becomes high. When a large current flows through the characteristic thermistor and the temperature of the positive characteristic thermistor rises and exceeds the Curie temperature, the resistance value suddenly increases. Therefore, the potential at the connection point between the positive temperature coefficient thermistor and the capacitor becomes high, and the three-terminal control element operates due to the current flowing into the control terminal of the three-terminal control element via the voltage response switching element, causing the switching circuit drive circuit to operate. The current that drives the transistor of the switching circuit is stopped, and the oscillation operation of the switching circuit is stopped immediately. Further, when the negative voltage side or both side electrodes of the power supply is emitterless, a larger current flows through the positive temperature coefficient thermistor, the resistance value of the positive temperature coefficient thermistor increases, and there is almost no current flowing directly from the power source through the lamp. Since the base current of the transistor 6 that flows through the secondary winding 8b is eliminated, the oscillation operation of the switching circuit is more surely stopped. In this way, when the fluorescent lamp 7 is in the emitterless state that occurs at the end of its life, the oscillation operation of the switching circuit can be immediately stopped, and the transistor 6 can be prevented from rapidly increasing in temperature and being destroyed. .

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a circuit diagram showing an embodiment of a discharge lamp lighting device of the present invention. In FIG. 1, commercial power source 1 to resistor 2
Up to 0, the configuration and operation are the same as the conventional example. The difference from the conventional example is that the positive temperature coefficient thermistor 21 is connected in series between the non-power source side of the fluorescent lamp 7 which is a discharge lamp and between the anti-transistor side electrode and the capacitor 9 which is the starting circuit. A current for driving the transistor 6 from the drive circuit of the switching circuit 11 by the current flowing into the Zener diode 22 which is a voltage responsive switch element whose one end is connected to the connection point A with 9 and the base which is connected to the other end of the Zener diode 22. And a transistor 23 which is a three-terminal control element for stopping the operation. In this lighting device, the drive circuit is composed of the inductance 8, the inductance 12 and the capacitor 13. The operation of the circuit of the embodiment configured as above will be described. The operation after the power is turned on until the fluorescent lamp 7 is normally turned on is the same as that of the conventional example, and therefore the description thereof is omitted, and the operation different from the conventional example will be described below.
When the electrode 7a of the fluorescent lamp 7 is emitterless and the electrode 7b has an emitter, when the power supply 1 is turned on, the switching circuit 11 starts the oscillation operation as in the conventional example. However, since the electrode 7a of the fluorescent lamp 7 is emitterless, the lamp current flows from the electrode 7a to the electrode 7b.
On the contrary, it does not flow. Therefore, a large current corresponding to the lamp current flows through the positive temperature coefficient thermistor 21 via the capacitor 9, the temperature of the positive temperature coefficient thermistor 21 rises, and the resistance value rapidly increases near the Curie temperature. FIG. 2 shows changes in the voltage at the connection point A between the positive temperature coefficient thermistor 21 and the capacitor 9 when the resistance value of the positive temperature coefficient thermistor 21 changes. In FIG. 2, before the time t _1, the resistance value of the positive temperature coefficient thermistor 21 is low, and the voltage at the connection point A is almost equal to the output voltage of the power supply circuit 4 because there is almost no potential difference with the positive voltage side of the power supply circuit 4. The voltage is close. After t _1, it is when the resistance value of the positive temperature coefficient thermistor 21 increases, and as the resistance value increases, the resonance voltage between the capacitor 9 and the inductance 8 is superimposed and the peak voltage increases. When the peak voltage at the connection point A reaches the operating voltage of the Zener diode 22, a current flows from the connection point A to the base of the transistor 23 via the Zener diode 22, and the transistor 23 operates to operate the capacitor 13 and the inductance 12.
The connection point B to and the negative voltage side of the power source 4 are short-circuited. Therefore, the supply of the base current to the transistor 6 is stopped and the operation of the switching circuit is stopped.

Next, when the electrode 7b of the fluorescent lamp 7 is emitterless and the electrode 7a has an emitter, the electrode 7a, the electrode 7b
Both will be described in the case of emitterless. In these cases, since there is almost no current flowing directly from the power supply circuit 4 through the lamp, the current directly flows from the power supply circuit 4 through the positive temperature coefficient thermistor 21, and the resistance value of the positive temperature coefficient thermistor is rapidly increased to make the switching circuit by the transistor 23. 11 the oscillation operation is stopped and the power supply circuit 4
Since there is almost no current flowing through the fluorescent lamp 7 and the capacitor 9 from the above, the base current of the transistor 6 flowing through the secondary winding 8b to the inductance 8 disappears, so that the oscillation operation of the switching circuit 11 is more surely stopped.

Further, since the timer circuit 17 is provided in this embodiment, once the oscillation operation of the switching circuit 11 is stopped, the oscillation operation of the switching circuit 11 is not started unless the power supply circuit 4 is turned off and then turned on again.

Although the discharge lamp is a fluorescent lamp in the present embodiment, the same effect can be obtained by using a high pressure discharge lamp that does not require preheating. Further, the self-excited switching circuit unit may be the one-stone type or the two-stone type. Further, the voltage responsive switch element may be another one such as a varistor or a diac as long as a current flows when it becomes a certain voltage or more, and the timer circuit 17 may be another one. Further, although the secondary winding 8b having the inductance 8 is used as the driving power source, the same applies to the case where the secondary winding 8b having the inductance 8 is used.

EFFECTS OF THE INVENTION As described above, according to the present invention, it is possible to immediately stop the oscillation operation of the switching circuit when the emitterless state occurs at the end of the life of the fluorescent lamp with a simple and inexpensive circuit configuration. Therefore, it is possible to realize the discharge lamp lighting device capable of preventing the transistor 6 from being rapidly heated and destroyed.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, and FIG. 2 shows a voltage at a connection point A between the positive temperature coefficient thermistor 21 and the capacitor 9 when the resistance value of the positive temperature coefficient thermistor 21 changes. FIG. 3 is a circuit diagram of a conventional discharge lamp lighting device showing the change. 1 ... Commercial power supply, 4 ... Power supply circuit, 8 ... Inductance, 7 ... Fluorescent lamp, 6 ... Main transistor, 12 ...
… Driving inductance, 13… Driving capacitor,
21 ... Positive characteristic thermistor, 22 ... Zener diode, 23 ... Transistor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Ito 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Masakatsu Yoshibayashi 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. 56) References JP-A 64-21895 (JP, A) JP-A 62-208594 (JP, A) JP-A 62-206796 (JP, A) JP-A 62-133698 (JP, A) JP JP-A-62-126596 (JP, A) JP-A-62-190698 (JP, A) JP-A-63-318094 (JP, A) JP-A-63-281396 (JP, A) Actually developed JP-A-61-26898 (JP , U) Actual Kaihei 1-66794 (JP, U)

Claims (1)

[Claims] 1. A power supply having a constant polarity of an output voltage, at least one transistor connected to an output terminal of the power supply, and an inductance, and a current in a forward direction of the power supply is turned on and off by the transistor. A switching circuit having a self-excited drive circuit for starting and lighting a discharge lamp connected to the output terminal, and a positive temperature coefficient thermistor connected to the non-power supply side of the discharge lamp so as to be on the side opposite to the transistor side of the power supply. A series circuit of a characteristic thermistor and a starting circuit composed of a capacitor, an inductance, a resistance or an impedance element formed by a combination of these, a voltage response switch element having one end connected to a connection point between the positive characteristic thermistor and the starting circuit, The switching switch is driven by the current flowing into the control terminal connected to the other end of the voltage response switching device. Discharge lamp lighting device that includes a three-terminal control elements for stopping the current for driving the transistor from a driving circuit of the circuit.