JPH0368520B2 - - Google Patents

Description

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

[Background Art] Many proposals have been made regarding instant-start discharge lamp starting devices using normally closed thermal switches. FIG. 2 shows an example of the above-mentioned discharge lamp starting device (Japanese Patent Application No. 139625/1982). 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 chiyoke coil 2, and the filaments 3a and 3b of the discharge lamp 3
is preheated. In addition, in the negative half cycle of the commercial power supply 1, the current-limiting current limiting coil 2 → filament 3b
A current flows through the circuit of → 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. If the thermal switch 7 is set in advance to open after a certain period of time (for example, about 0.5 to 0.8 seconds), the preheating current is cut off by opening the thermal switch 7, and at that time, the current limiting 2, both filaments 3 of the discharge lamp 3
A hard pulse voltage is applied between a and 3b, and the discharge lamp 3 is turned on. Note that the capacitor 5 is for noise prevention.

When the discharge lamp 3 is lit, the voltage between terminals a and b becomes a lamp voltage, and in the positive half cycle, terminal a → positive characteristic thermistor 4 → diode 6 → main heater 9 → diode 10 → resistors 11, 13 and auxiliary heater 12.
→Since the current continues to flow through the circuit of 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. is maintained 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.
By bending b 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.

However, in the above circuit, the voltage across the main heater 9 is prevented from exceeding the Zener voltage _Vz by the Zener diode 8 while the discharge lamp 3 is lit (the amount of heat generated by the main heater 9 is kept constant). However, the lamp voltage during lighting of the discharge lamp 3 is greatly affected by the ambient temperature, fluctuations in the power supply voltage, variations in the impedance of the current limiting coil 2, etc. (For example, in the case of a 30W fluorescent lamp, the lamp voltage is 35V. If the lamp voltage is extremely reduced, the voltage across the main heater 9 will be lower than the Zener voltage _Vz . Therefore, the amount of heat generated by the main heater 9 becomes small, the thermal switch 7 cannot be maintained in the open state, and the discharge lamp 3 cannot be maintained stably lit. In order to improve this problem, it is necessary to keep the amount of heat generated by the main heater 9 constant even when the lamp voltage decreases. Specifically, lower the Zener voltage V _z and lower the resistance value of the main heater 9. .

The resistance values of the resistors 11 and 13 and the auxiliary heater 12 are lowered to substantially increase the voltage applied to the main heater 9.

However, in the case of , the resistance value of the main heater 9 must be lowered, which increases the amount of heat generated by the main heater 9 at startup, so the contact pressure of the thermal switch 7 must be increased. Therefore, even when the light is on, the bimetal 7
The holding gap between a and 7b becomes smaller and there is no substantial improvement. In addition, in the case of , not only does the power consumption of the entire circuit section increase, but also the power consumption of the terminal a-
Since the impedance between b and b becomes small, the kick pulse voltage at the time of starting is absorbed and lowered, causing a problem that starting is difficult.

[Object of the Invention] The present invention has been provided in view of the above-mentioned points, and provides an immediate start-up discharge lamp using a thermal switch that provides a sufficient holding gap between the contacts even when the lamp voltage decreases. The purpose is to provide a device.

[Disclosure of the invention]

Embodiments of the present invention will be described below with reference to the drawings. Note that the parts common to the conventional one will be omitted, and the circuit of the part connected to the non-power supply side terminal of the filament of the discharge lamp 3 will be explained. That is, as in the case of FIG. 2, a commercial power source 1 is connected in series with a chiyoke coil 2, which is an inductive ballast, and a discharge lamp 3.
As shown in FIG. 1, a series circuit consisting of a diode 6 and a normally closed thermal switch 7 is connected between the non-power supply side terminals of both filaments 3a and 3b of the discharge lamp 3. Furthermore, as shown in FIG. 1, a series circuit of a Zener diode 14 as a constant voltage element and a main heater 9 for opening the thermal switch 7 is connected to both ends of the diode 6.

That is, the cathode of the Zener diode 14 is connected to the connection point between the diode 6 and the thermal switch 7, and one end of the main heater 9 is connected to the anode of the diode 6. Further, an impedance circuit section is connected between the connection point between the main heater 9 and the Zener diode 14 and the non-diode side end of the thermal switch 7 via a diode 10 whose anode is connected to the connection point. This impedance circuit section has a resistance of 1
1, 13, an auxiliary heater 12, etc.

At the time of starting, current flows from the diode 6 to the thermal switch 7 during the positive half cycle of the commercial power supply 1, and from the thermal switch 7 to the Zener diode 14 to the main heater 9 during the negative half cycle. Therefore, the voltage applied to the main heater 9 is lowered by the Zener voltage of the Zener diode 14, and even if the amount of heat generated by the main heater 9 is the same as that of the conventional example, the resistance value of the main heater 9 is reduced. be able to.

That is, in the conventional example, the main heater 9 is connected to the Zener diode 8 in a forward direction that does not generate a Zener voltage, so that the resistance value becomes large when the amount of heat generated is the same. However, in the present invention, as shown in FIG. 1, the main heater 9 is connected in the opposite direction to the Zener diode 14 to generate the Zener voltage. As a result, the resistance value of the main heater 9 can be reduced when the amount of heat generated is the same.

Further, while the discharge lamp 3 is lit, the Zener diode 14 is connected in parallel with the main heater 9, and plays the same role as the Zener diode 8 of the conventional example. Therefore, by setting the Zener voltage of the Zener diode 14 to an appropriate value,
The amount of heat generated by the main heater 9 can be adjusted without changing the amount of heat generated at startup, regardless of fluctuations in lamp voltage during lighting.
This means that a sufficient and constant amount of heat generation can be obtained. In other words, even if the lamp voltage decreases during lighting,
Since the resistance value of the main heater 9 is small, sufficient heat can be generated to open the thermal switch 7. As a result, even when the lamp voltage drops significantly, a sufficient contact gap of the thermal switch 7 can be ensured.

〔Effect of the invention〕

As described above, the present invention connects an inductive ballast and a discharge lamp in series to a commercial power source, and connects a first diode and a normally closed thermal switch between the non-power side terminals of both filaments of the discharge lamp. A series circuit consisting of a constant voltage element and a heater for opening the thermal switch is connected across the first diode.
A thermal switch is connected between the connection point of the heater and the constant voltage element and one end of the thermal switch opposite to the first diode, by connecting the cathodes of the diode and the constant voltage element in common and connecting them in parallel. Since the impedance circuit is connected through the second diode that causes current to flow in the direction that turns on the constant voltage element when the discharge lamp is turned on, during the half cycle on one side of the commercial power supply when starting the discharge lamp, the heater Since current flows through the thermal switch, constant voltage element, and heater, the voltage applied to the heater is lowered by the constant voltage of the constant voltage element.If the amount of heat generated by the heater is the same as before, the resistance value of the heater will decrease. In addition, during lighting, the constant voltage element is connected in parallel with the heater during the other half cycle of the commercial power supply, fulfilling the same role as the conventional Zener diode. Moreover, even if the lamp voltage decreases during lighting, the heater's small resistance value can generate enough heat to open the thermal switch, so the constant voltage of the constant voltage element can be adjusted appropriately. By setting the value to a certain value, it is possible to obtain a sufficient and constant amount of heat generation without changing the amount of heat generated by the heater at the time of starting, and regardless of fluctuations in lamp voltage during lighting. . As a result, even when the lamp voltage drops significantly, a sufficient contact gap of the thermal switch can be ensured. In this way, it is possible to obtain sufficient heat generation from the heater against fluctuations in lamp voltage by changing the circuit of one constant voltage element without increasing the number of parts or cost compared to the conventional example, and the thermal switch can be kept in the open state. This has the effect of maintaining stable lighting of the discharge lamp.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a main part of an embodiment of the present invention, and FIG. 2 is a specific circuit diagram of a conventional example. 1 is a commercial power supply, 2 is a choke coil, 3 is a discharge lamp, 3a, 3b are filaments, 6 is a first diode, 7 is a thermal switch, 9 is a main heater,
10 is a second diode, and 14 is a Zener diode.

Claims (1)

[Claims] 1. Connect an inductive ballast and a discharge lamp in series to a commercial power source, and connect a series circuit of a first diode and a normally closed thermal switch between the non-power side terminals of both filaments of the discharge lamp. , a series circuit of a constant voltage element and a heater for opening a thermal switch is connected in parallel to both ends of the first diode, with the cathodes of the first diode and the constant voltage element commonly connected;
A second diode is connected between the connection point of the heater and the constant voltage element and one end of the thermal switch opposite to the first diode, through which a current flows in the direction in which the constant voltage element is turned on when the thermal switch is opened. A discharge lamp starting device consisting of an impedance circuit connected to an impedance circuit.