JPS60246597A - Device for firing discharge lamp - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a lighting device equipped with a preheating circuit using a time constant circuit. Apparatus 1/[Related to.

[Background of the invention]

An example of a conventional every-cycle lighting circuit is shown in FIG.

In operation, when the commercial AC power supply 1 is turned on, the thyristor 12 is gate triggered, the thyristor 12 becomes conductive, and preheating starts. Then gradually capacitor 9 becomes resistor 16.18
(and 14 and 15), but after about 1 second, the sensitive voltage of the voltage sensitive element 11 is reached, and the voltage sensitive element 11 becomes conductive.

As a result, the gate signal of the thyristor 12 is cut off, and the thyristor 12 becomes non-conductive. This period is the preheating operation,
After that, the lamp is turned on by the switch circuit BK.

Here, when combined with the switch 25 with an extinguishing indicator light, the following phenomenon occurs.

That is, when the switch 25 with an off indicator light (hereinafter simply referred to as the switch) 25 is off, the resistance 251. Through the neon light 252, the capacitor 9
is constantly photoelectrically charged, and this charging voltage then switches switch 2
When turning on 5, the preheating time becomes extremely short and the lamp can no longer be lit.

This means that the impedance of the switch 25 is 251°252
- Choke coil 2 - Diode 8 - Resistor 18 (and 15-14) - A closed circuit of capacitor 9 is formed, and the potential of v1 in the figure becomes V (Z, +, Z1 - / (Z51W + Z, +z, -
...-(, j), and the capacitor 9 is charged by this voltage V.

z: Impedance across resistor 18 z2: Impedance across capacitor 9 Note that the impedance of choke coil 2 is 2sw, Z
I ignored it because it was very small compared to IK.

The capacitor 9 is also charged via the resistor 13, but the impedance of the resistor 13 is much higher than the impedance of the choke coil 2, and it hardly affects the charging and discharging of the capacitor 9 while the lamp 3 is turned off.

In fact, when considering that the voltage applied to the capacitor 9 reaches about 7V and the voltage sensed by the voltage sensitive element 11 is about 8V, there is a possibility that there will be no preheating time.

As a countermeasure for this, as shown in FIG. 2, a Zener diode 31 having a voltage determined by the above formula (1) is connected,
The present inventors also found a method of setting Kj so that the capacitor 9 would not be charged, but if the impedance of the switch 25 differs, the voltage of the Zener diode would be difficult to set because (2) changes. It was also found that if a general switch was used, the preheating time would be longer.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a discharge lamp lighting device that reliably turns on preheating without being affected by a switch with an extinguishing indicator light even when used in combination with the switch.

[Summary of the invention]

When the switch is off, it was found that if the voltage applied to the capacitor 9VC in the conventional circuit is set to 2V or less, there is almost no difference in preheating time compared to when using a general switch, so the charging voltage of the capacitor 90 is reduced. Invented a circuit system.

That is, the present invention includes a lighting pulse generation circuit that generates a lighting pulse for a discharge lamp every cycle, a preheating circuit that supplies a preheating current for the discharge lamp at the initial stage of lighting the discharge lamp, and a preheating operation of the preheating circuit that is controlled. The lamp is equipped with a dead time constant circuit and a limiting circuit that limits the voltage applied to the time constant circuit when the discharge lamp is turned off.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. The circuit configuration is as shown in Figure 1 by removing diode 8 and adding resistor 15.
The other end is connected to the output side of a diode 4.5 that constitutes a full-wave rectifier circuit, and the capacitor 10 is connected to a diode 28.
30, and a diode 27 is connected so as to be substantially parallel to these diodes 28 to 3o.

Here, the resistance value of resistor 13 is sufficiently larger than the resistance value of resistors 14 and 15.

To further explain this, B is a switch circuit that is connected to the choke transformer 2, conducts at the beginning of each cycle, and then turns off, thereby generating a lighting pulse and lighting the lamp 3. It is. That is, this switch circuit B and the choke transformer 2 basically constitute a lighting pulse generation circuit. C is a preheating circuit for supplying preheating current to the lamp, and the preheating current continues to flow through the lamp 3 while the thyristor 12 constituting this circuit is conductive. E is a time constant circuit for controlling the preheating circuit C, and the resistor 15 supplies a gate signal for making the thyristor 12 of the preheating circuit C conductive at the beginning of each cycle. Also, a resistor 1! with one end connected to the switch 25 side! When the charging voltage of the capacitor 9 charged by the divided current of I and 16 exceeds the sensing voltage of the normal pressure sensing element 11, this voltage sensing element 11 becomes short-circuited. Therefore, after the normal pressure sensing element 11 is short-circuited, the signal for making the thyristor 12 conductive via the resistor 15 is no longer applied to the gate of the thyristor 12, and the preheating of the lamp 6 is completed. Note that the capacitor 26 is for preventing the capacitor 9 from discharging. Now, when the switch 25 is off, the capacitor 9 is charged by the choke coil 2 - resistor 15 - diode 27 - resistor. 14 and diode 26-resistor 16
There are 02 circuits. However, in the latter case, since the charging of the capacitor 9 is a half wave and the resistance value of the resistor 15 is sufficiently larger than that of the resistor 15.degree. 14, it can be ignored. Therefore, the charging voltage of the capacitor 9 is determined by the former, but the potential of V does not exceed the voltage expressed by the following equation.

(Diode 28-290 on voltage) + (thyristor 1
2 gate-cathode voltage)... group (2) Therefore,
When the capacitor is 90 charged, the voltage VC is Vc≦V, -(diode 270 on voltage) (5).

In fact, Vc determined by equation (3) is about 2V, and the first
This can be significantly lower than the voltage of about 7V of the capacitor 9 having the configuration shown in the figure.

The present inventors have confirmed that there are no practical problems such as adversely affecting the preheating operation of the switch and the preheating time when using a general switch.

In the embodiments described above, a limiting circuit was configured that limits the charging of the capacitor 9 of the time constant circuit E by using the forward voltage drop of the diode and the voltage between the gate and cathode of the thyristor. Alternatively, it is also possible to configure a similar limiting circuit using transistors or the like.

〔Effect of the invention〕

As is clear from the above description, the discharge lamp lighting device of the present invention includes a lighting pulse generation circuit that generates a discharge and lamp lighting pulse every cycle, and a preheating current for preheating the discharge lamp at the initial stage of lighting. The present invention includes a preheating circuit that supplies a preheating circuit, a time constant circuit that controls the preheating operation of the preheating circuit, and a limiting circuit that limits the voltage applied to the time constant circuit when the light is turned off. The operation is stable and the discharge lamp can be lit reliably.

[Brief explanation of drawings]

Fig. 1 is a diagram for explaining the circuit configuration of a conventional discharge lamp lighting device, Fig. 2 is a diagram showing an improvement plan for the conventional example, and Fig. 6 is a diagram for explaining one embodiment of the present invention. It is. DESCRIPTION OF SYMBOLS 1... Commercial AC power supply, 2... Choke, 5... Lamp, 8... Diode, 9, 10... Capacitor, 11... Voltage sensing element, 12... Thyristor, 2
5. Firefly lamp, 2. B...Lighting pulse generation circuit, 3...Discharge lamp, C...Preheating circuit, D...Limiting circuit, E...Time constant circuit Day 1

Claims (1)

[Claims] A lighting pulse generation circuit that generates a lighting pulse for the discharge lamp every cycle, a preheating circuit that supplies a preheating current for the discharge lamp, a time constant circuit for controlling the preheating operation of this preheating circuit, and a circuit that turns off the discharge lamp. A discharge lamp lighting device characterized in that a limiting circuit is provided to sometimes limit the applied voltage tIf of the time constant circuit.