JPH033358B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a discharge lamp starting device.

A thermal switch made of bimetal, a heater, etc. are built into the circuit, and when a preheating current flows through the circuit, the heater heats the bimetal of the thermal switch, and when the contact of the thermal switch is opened, it is heated via the induction switch from the ballast. Conventionally, a starting device for lighting a discharge lamp has already been provided.

However, unlike glow discharge tube lighting devices, this type of device does not control the timing of opening of the contacts, so its operation is unstable, and the contacts open when no current is flowing. In this case, there was a drawback that a pulse voltage was not generated and lighting could not be achieved.

The present invention was proposed in view of the above points, and by making the contact always open near the peak of the preheating current, a pulse voltage is always generated based on the inductance L of the ballast, and the discharge lamp is reliably started. It is an object of the present invention to provide a discharge lamp starting device.

The present invention will be described below with reference to the drawings.

Figure 1 shows an embodiment of the present invention, where the power supply Vs
When the current is turned on, in a positive cycle, a current flows through the path of ballast 1 → filament F 1 of discharge lamp ₂ → diode 4 → normally closed thermal switch 3 → filament F ₂ , preheating filaments F ₁ and F ₂ .
On the other hand, in the negative cycle of current, conversely, filament F ₂ → thermal switch 3 → main heater H ₁ →
The main heater H ₁ through which current flows in the path from the filament F ₁ to the ballast 1 generates heat, and this main heater H ₁ is thermally coupled to the operating bimetal 3a of the thermal switch 3 and heats the bimetal 3a. Then, after a certain period of time, thermal switch 3 opens,
At the same time, the discharge lamp 2 is turned on by the induction switch from the ballast 1.

When the light is on, the voltage between terminals a and b becomes a discharge voltage, and in its negative cycle, the voltage regulator diode 5 → resistor 6 → resistor 7 → resistor 8 → resistor 9 → main heater
Current flows through the circuit of _H1 , and the main heater _H1 continues to generate heat, keeping the thermal switch 3 open and keeping the discharge lamp 2 lit.

In addition, when discharge lamp 2 fails to light or restarts (when the discharge lamp is lit and the power supply Vs is turned off and then immediately turned on again), the voltage between terminals a and b will rise to the power supply voltage Vs. As a result, the voltage across the voltage dividing resistor 10 rises, the constant voltage diode 11 becomes conductive, the transistor 12 also becomes conductive, and the follow-up heater
_H2 generates heat. The follow-up heater _H2 is thermally coupled to the compensation bimetal 3b of the thermal switch 3, and upon receiving the heat from the follow-up heater _H2 , the compensation bimetal 3b quickly moves in the direction of the operating bimetal 3a. The contact point closes again and the transition to the initial preheating state occurs. Further, 13 is a negative characteristic thermistor, and when the discharge lamp 2 stops discharging at the end of its life, its resistance value decreases due to the heat generated by the resistor 14, turning off the transistor 12 and opening the contact of the thermal switch 3. It functions to maintain the condition.

Next, the opening/closing operation of the contacts described above will be explained with reference to FIG. The thermal switch 3 is a parallel bimetal switch 3 with a contact point at the tip.
It consists of tongues a and 3b, and the bimetal bends in the direction in which the contacts open when heated by the main heater _H1 .

On the other hand, when currents in opposite directions flow through two parallel conductors made of bimetal tongues, an electromagnetic repulsion force F acts in a direction that separates the conductors from each other. As shown in FIG. 3, the current (preheating current) is a half-wave pulsating current, and an electromagnetic repulsive force proportional to this current is generated.

By the way, as shown in Figure 4, the contact contact pressure approaches zero (contact open) state over time due to the overlap of the decrease a due to heater heating and the decrease b due to electromagnetic repulsion. .

In this case, if the contact opening (the point at which the contact pressure becomes 0) occurs at (i) the pulsating part of the electromagnetic repulsion, the preheating current is flowing, so the discharge lamp 2 where the pulse is generated is Light. (ii) On the other hand, if the electromagnetic repulsion occurs in a part other than the part where the pulsation is generated, that is, in the part where the linear contact pressure of the bimetal is reduced by heating the heater, the preheating current is not flowing, so no pulse is generated and the lamp does not turn on.

Therefore, in order to reliably obtain the above condition (i), it is preferable that the contact pressure before heating with the heater is 0.1 to 2 g or less. That is, the electromagnetic repulsion force mainly depends on the value of the preheating current, which is determined by the lamp ballast characteristics. In addition, the time from heater heating to contact opening is the time until the temperature of the lamp filament has risen to a state where it is easy to discharge, so this also depends on the value of the preheating current and is fixed at a constant value (approximately 1 second). It is worshiped.

As described above, according to the present invention, since the contact pressure of the contact part of the thermal switch, which is made up of parallel opposed bimetal tongues having a contact part at the tip, is set to 0.1 to 2 g in the state before heating by the heater, the preheating current always peaks. Since the contacts open nearby, a pulse voltage is always generated based on the inductance L of the ballast, which has the effect of reliably starting the discharge lamp.

[Brief explanation of the drawing]

FIG. 1 is an embodiment of the present invention, and FIGS. 2 to 4 are explanatory views of the same operation. V _s ...power supply, 1...ballast, 2...discharge lamp,
3...Thermal switch, 4...Diode,
5, 11... Constant voltage diode, 6, 7, 8,
9, 10, 14...Resistor, 12...Transistor, 13...Negative characteristic thermistor.

Claims (1)

[Claims] 1 Connect a power supply to the power supply side terminals of both filaments of the discharge lamp via a ballast, connect a series circuit of a diode and a normally closed thermal switch to the non-power supply side terminals of both filaments, and connect the above in parallel to the diode. In a discharge lamp starting device configured to connect a main heater for heating a thermal switch and open a contact point of the thermal switch as the temperature rises, the thermal switch is connected to a main heater for heating the thermal switch, and the thermal switch is connected to a main heater for heating the thermal switch. A discharge lamp starting device characterized in that the contact pressure of the contact portion is 0.1 to 2 g in a state before heating by the heater.