JPH0154837B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a discharge lamp starting device for starting a discharge lamp such as a fluorescent lamp.

[Background Art] FIG. 5 shows a conventional example of a discharge lamp starting device having a positive temperature coefficient thermistor 4, which is an end-of-life protection circuit that protects the circuit at the end of the discharge lamp's life. The operation of this discharge lamp starting device will be briefly explained as follows. First, when the commercial power supply 1 is turned on, during the positive half cycle of the commercial power supply 1, the filament 3a of the discharge lamp 3 → the positive temperature coefficient thermistor 4 → the diode 6 → the normally closed thermal switch 7 → the filament 3b → the inductive ballast. A preheating current flows through the circuit of a certain current limiting current limiting coil 2, and the filaments 3a and 3b of the discharge lamp 3 are preheated. Also, in the negative half cycle of the commercial power supply 1, the current limiting coil 2
A current flows through the circuit of → filament 3b → thermal switch 7 → main heater 9 → Zener diode 8 → positive temperature coefficient thermistor 4 → filament 3a, and main heater 9 generates heat. Then, this main heater 9 is thermally coupled to one bimetal 7a of the thermal switch 7, and heats this bimetal 7a, so that the bimetal 7a gradually curves in the direction of the arrow. Then, after a certain period of time (for example, 0.5
If the thermal switch 7 is set in advance to open at a time of about 0.8 sec), the preheating current is cut off when the thermal switch 7 opens, and at that time, the discharge lamp 3 is A sharp pulse voltage is applied between both filaments 3a and 3b, and the discharge lamp 3 is turned on.

When the discharge lamp 3 is lit, the voltage between terminals a and b becomes lamp voltage, and in the positive half cycle, terminal a → positive characteristic thermistor 4 → diode 6 → main heater 9 → diode 10 → auxiliary thermal switch 18, resistor 1
1, auxiliary heater 12 and resistor 13, protective heater 1
Since the current continues to flow through the circuit of 9→terminal b, the main heater 9 continues to generate heat due to this current, and the heat generated by the main heater 9 continues to heat the bimetal 7a. 7 is kept in an open state, and the discharge lamp 3 is maintained stably lit. Here, for example, if the discharge lamp 3 is turned off and the commercial power supply 1 is turned on again before the thermal switch 7 is closed, the voltage between terminals a and b becomes the power supply voltage, and the circuit is the same as when the discharge lamp 3 is turned on. A current flows through the
The auxiliary heater 12 generates about five times as much heat as when it is lit. This auxiliary heater 12 is connected to the thermal switch 7
It is thermally coupled to the other bimetal 7b, and the bimetal 7 receives heat from the auxiliary heater 12.
As b bends toward the other bimetal 7a, the thermal switch 7 closes again, enters the preheating state again, and the discharge lamp 3 restarts. When restarting, the voltage between terminals a and b becomes the power supply voltage, but since the voltage across the main heater 9 is kept constant by the Zener diode 8, the main heater 9 does not generate heat both during lighting and when restarting. The amount of heat is almost the same, and at the time of restart, the amount of heat generated by the main heater 9 is less than the amount of heat generated by the auxiliary heater 12, and the thermal switch 7 is closed again.

Next, when the discharge lamp 3 reaches the end of its life in a so-called emissionless state, the discharge lamp 3 cannot be lit and enters the above-mentioned restart mode, and the thermal switch 7 is turned off by the action of the auxiliary heater 12. At the same time as the protection heater 19 repeatedly turns on and off, the protection heater 19 also generates heat. This protective heater 19 is thermally coupled to one bimetal of the auxiliary thermal switch 18, and if the thermal switch 7 repeats on and off for about 10 seconds, it is determined that the discharge lamp 3 has reached the end of its life, and the auxiliary thermal switch 18 is opened. state, stop the heat generation of the auxiliary heater 12, and turn on the thermal switch 7.
The device is kept open and enters protective operation.

In addition, in the case of circuit component failure, contact welding, etc., the thermal switch 7 remains closed and the preheating current continues to flow, and the positive temperature coefficient thermistor 4 is activated to prevent abnormal temperature rise of the ballast coil 2. The Zener diode 8 is inserted and connected between the non-power supply side terminal of the filament 3a and the Zener diode 8. However, the end-of-life protection circuit of such a starter device has the following problems. That is, in the case of a normal end-of-life protection operation at the end of the life of the discharge lamp 3, as shown in FIG.
9 is intermittently applied with a high voltage (the voltage generated when the thermal switch 7 is opened), which generates enough heat to heat the bimetal. Therefore, due to the curvature of the bimetal, the auxiliary thermal The switch 18 is opened, and the thermal switch 7 stops opening and closing and remains open. In FIG. 6, the shaded area indicates when the thermal switch 7 is open, and the other areas indicate when the circuit is closed, indicating that the auxiliary thermal switch 18 is open at time _t1 . However, when the ambient temperature of the starter is very high, the positive temperature coefficient thermistor 4 operates and the resistance value increases before the end-of-life protection is activated by opening and closing the thermal switch 7. As shown in Figure 7, the protective heater As the voltage applied to the auxiliary thermal switch 18 gradually decreases, sufficient heat generation cannot be obtained, and as a result, the auxiliary thermal switch 18
remains closed regardless of the lifespan of the discharge lamp 3, and the thermal switch 7 repeats opening and closing, resulting in a state in which it is not protected. In addition, in Figure 7,
This shows a state in which the positive temperature coefficient thermistor 4 starts operating at time _t1 .

[Effects of the Invention] The present invention has been provided in view of the above-mentioned points, and provides a discharge lamp whose purpose is to reliably operate the protective operation at the end of the life of the discharge lamp, regardless of the operation of the positive temperature coefficient thermistor. It provides a starting device.

[Disclosure of the Invention] Examples of the present invention will be described below with reference to the drawings.
FIG. 1 shows a specific circuit diagram of the present invention,
FIG. 2 shows a block diagram, in which the positive temperature coefficient thermistor 4 is located toward terminal b, and the protective heater 1
One end of the resistor 13 connected in series with the resistor 9 is connected to the connection between the positive temperature coefficient thermistor 4 and the non-power supply side terminal of the filament 3b of the discharge lamp 3. Here, the end-of-life protection circuit A is an auxiliary thermal switch 18,
The lighting determination circuit B is comprised of the auxiliary heater 12, the bimetal 7b of the thermal switch 7, and the like. The thermal switch 7 constitutes a starting switch element, and the driving source C is bimetallic elements 7a and 7b of the thermal switch 7.
Consists of.

For normal starting, lighting maintenance, and restart, the resistance value of the PTC thermistor 4 is much smaller than that of other heaters and resistances, so the operation is exactly the same as in the conventional example regardless of the position of the PTC thermistor 4. .
Further, since the protection operation at the end of the normal discharge lamp life is also the same, the explanation of this operation will be omitted. Here, if the ambient temperature is high and the thermal switch 7
In the case of a malfunction due to opening/closing of the protective heater 19, in the present invention, since the energization path of the protective heater 19 is closer to the discharge lamp 3 than the positive temperature coefficient thermistor 4, the protection heater 19 is affected by the resistance value of the positive coefficient thermistor 4 as shown in FIG. Never. That is, the series circuit of the protective heater 19 and the resistor 13 is connected to the filament 3 of the discharge lamp 3.
Since it is connected between the terminals on the non-power supply side of a and 3b, the voltage applied to the protective heater 19 does not drop when the thermal switch 7 is open. Furthermore, even when the thermal switch 7 is closed, the partial voltage generated in the positive temperature coefficient thermistor 4 is applied to the protective heater 19.
The effective value of the voltage applied to the discharge lamp increases further than during normal protection operation at the end of the discharge lamp's life. As a result, in the present invention, even if the PTC thermistor 4 operates, the end-of-life protection is ensured. Here, in FIG. 3, time t ₁ is the time when the positive temperature coefficient thermistor 4 is activated, and time t ₂ is the time when the auxiliary thermal switch 18 is opened.

FIG. 4 shows another embodiment, in which a CR timer is used to protect the discharge lamp 3 at the end of its life. That is, a capacitor C ₁ , resistors R ₁ to R ₄ , transistors Tr ₁ , Tr ₂ , Zener diodes ZD ₁ , ZD _{2 ,} etc. form an end-of-life protection circuit A, and a transistor Tr ₂ is arranged in series with the auxiliary heater 12 . The collector of the transistor Tr ₁ whose base is connected to the connection point between the resistors R ₁ and R ₂ connected between the terminals a and b is connected to the base of the transistor Tr 2, and the Zener diode ZD ₂ is connected to the base of the transistor Tr ₂ .
is connected through. In addition, the time constant circuit with resistor R ₂ and capacitor C ₁ is connected to Zener diode ZD ₁
It is connected to the base of transistor _Tr1 through. Therefore, during normal lighting, the voltage between terminals a and b becomes the lamp voltage, which is lower than the power supply voltage. Therefore, the voltage charged to capacitor _C1 does not exceed the Zener voltage of Zener diode _ZD1 , and transistor Tr ₂ is turned on, and current flows through the auxiliary heater 12. Here, when the restart mode is entered in the same way as above, the voltage between terminals a and b increases,
After the time constant, the charging voltage of capacitor C ₁ turns on transistor Tr ₁ and
Since Tr ₂ is turned off, no current flows through the auxiliary heater 12 and the thermal switch 7 is maintained in an open state.

[Effects of the Invention] As described above, the present invention includes a discharge lamp connected to a commercial power supply via an inductive ballast, a lighting determination circuit for determining the lighting state of the discharge lamp, and a lighting determination circuit for determining the lighting state of the discharge lamp. A starting switch element is connected between the terminals on the non-power supply side and is driven by the output from the lighting discrimination circuit so that it remains open when the discharge lamp is lit, and repeats opening and closing when the discharge lamp is not lit, and the life of the discharge lamp. There is an end-of-life protection circuit that detects when the discharge lamp cannot be started based on the effective value of the voltage across the discharge lamp, and after a certain period of time, stops the opening/closing of the starting switch element to keep it in an open state. In order to prevent an abnormal temperature rise in the ballast due to the starting switch element being closed when the starting switch element is closed and the preheating current continuing to flow, a positive temperature coefficient thermistor is inserted and connected between the discharge lamp and the starting switch element. In the equipped discharge lamp starting device, the end-of-life protection circuit is inserted and connected to the discharge lamp side from the positive temperature coefficient thermistor, so even if the positive temperature coefficient thermistor operates due to high ambient temperature, the end-of-life protection circuit is not activated. By inserting it closer to the discharge lamp than the positive temperature coefficient thermistor, the end-of-life protection circuit operates reliably without the voltage drop caused by the conventional positive coefficient thermistor, and the starting switch element is maintained in an open state. , has the effect of protecting the discharge lamp at the end of its life,
Furthermore, since the starting switch element does not repeat opening and closing, it is possible to prolong the life of the contacts.

[Brief explanation of drawings]

1 is a specific circuit diagram of an embodiment of the present invention, FIG. 2 is a block diagram of the same as the above, FIG. 3 is an explanatory diagram of the same as the above, FIG. 4 is a specific circuit diagram of another embodiment of the same as the above, and The figure is a specific circuit diagram of a conventional example, and FIGS. 6 and 7 are explanatory diagrams of the same operation. 1 is a commercial power supply, 2 is a choke coil, 3 is a discharge lamp, 3a and 3b are filaments, 4 is a positive temperature coefficient thermistor, 6 is a diode, 7 is a thermal switch, 9 is a main heater, A is an end-of-life protection circuit, and B is lighting The discrimination circuit is shown.

Claims (1)

[Claims] 1 A discharge lamp connected to a commercial power supply via an inductive ballast, a lighting determination circuit that determines the lighting state of the discharge lamp, and a lighting determination circuit that is connected between the non-power supply side terminals of both filaments of the discharge lamp, and a lighting determination circuit that determines the lighting state of the discharge lamp. The starting switch element is driven by the output from the lighting determination circuit so that it remains open when the discharge lamp is out of operation, and repeats opening and closing when the discharge lamp fails. Detected by the effective value of the voltage at both ends,
The end-of-life protection circuit stops opening and closing of the starting switch element after a certain period of time and keeps it in an open state, and when it is impossible to start and light the discharge lamp, the starting switch element becomes closed and the preheating current continues to flow. In a discharge lamp starting device equipped with a positive temperature coefficient thermistor inserted and connected between the discharge lamp and the starting switch element to prevent abnormal temperature rises in the ballast, the end-of-life protection circuit is connected closer to the discharge lamp than the positive temperature coefficient thermistor. A discharge lamp starting device characterized by being inserted into and connected to.