JPS59134595A - Preheating start type discharge lamp firing device - 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 the Invention The present invention relates to a discharge lamp lighting device that uses a semiconductor element to apply a high-voltage pulse between the electrodes of a preheat-start discharge lamp to start and light the discharge lamp. It is something.

Structure of a conventional example and its problems FIG. 1 shows an example of the structure of a conventional discharge lamp lighting device. As shown in the figure, an AC power supply 1 includes a ballast (
(hereinafter simply referred to as a ballast) 2 and a preheating start type discharge lamp (hereinafter simply referred to as a discharge lamp) 3 are connected in series, and between the filament electrodes of the discharge lamp 3, a noise prevention capacitor 4 and the filament An electrode preheating circuit 5 and a transistor switch circuit 6 are connected in parallel. The preheating circuit 6 is composed of a diode 7 and a two-terminal thyristor 8 connected in series. The transistor switch circuit 6 is composed of a diode 9, a DC power supply circuit 1o, a control circuit 11, and a transistor 12. The DC power supply circuit 1o and the transistor 12 are connected in parallel, and these parallel bodies are connected in series with the diode 9. In addition to being connected, the control circuit 1
1 is connected to the output terminal of the DC power supply circuit 1Q, detects the output voltage of the diode 9, and switches the transistor 12 accordingly.
The output terminal is a transistor 120 to control on/off.
connected to the base. The DC power supply circuit 10 includes a diode 13, a resistor 14, and a parallel body consisting of a capacitor 16 and a Zener diode 16 connected in series. In addition, the AC power supply 1 of the diodes 9 and 13
The direction of connection to the diode 7 of the preheating circuit 5 is opposite to that of the diode 7 of the preheating circuit 5. The control circuit 11 is composed of a series body made up of a resistor 17 and a transistor 18, and a series body made up of a voltage detection circuit 19 and a timer circuit 20. The voltage detection circuit 19 is composed of resistors 21, 22, a transistor 23, and an inverter 24, and the timer circuit 20 is composed of a resistor 25.26 and a capacitor 27. It is composed of an inverter 28 and an AND gate 29.

The operation of the above conventional example will be explained.

An AC power supply voltage Vs shown by a broken line in FIG. 2(a) is applied from an AC power supply 1 to a discharge lamp 3 via a ballast 2. First, when the terminal is in a positive half cycle with respect to the terminal a, the voltage is blocked by the diode 9 in the transistor switch circuit 6, and the power supply voltage vs is applied to the preheating circuit 5 in the forward direction.

At this time, since the AC voltage Vs1 is lower than the breakover voltage of the thyristor 8 during the period from θ to θ,
Preheating current IH does not flow. When the voltage vs exceeds the breakover voltage of the thyristor 8 at θ1, the thyristor 8 becomes conductive, and the AC power source 1 passes through the filament electrode of the discharge lamp 3, the preheating circuit 6, and the ballast 2 as shown in FIG. 2(b). The preheating current H flows as a slow phase current and heats the filament electrode. When the preheating current H becomes equal to or less than the conduction holding current of the thyristor 8 at 03 as shown in FIG. vs is discharge lamp 3
is applied to In this half cycle, the terminal C is positive and the power supply voltage vS becomes a reverse voltage with respect to the diode 7, so the preheating circuit 5 is in a cutoff state. On the other hand, since the power supply voltage ■s is in the forward direction with respect to the diode 9, it is also applied to other components of the transistor switch circuit 4 through this. As a result, the charging current of the capacitor 15 flows through the ballast 2 and the filament electrode of the discharge lamp 3 to the DC power supply circuit 1o. When the capacitor 15 is charged to the Zener voltage of the Zener diode 16, power is supplied to the control circuit 11, and the control circuit 11 becomes operational. At the same time, in the voltage detection circuit 19, a base current flows to the transistor 23 through the resistor 21, and the transistor 23 is turned on. As a result, the collector voltage of the transistor 23, which was previously at the DC output voltage level of the DC power supply circuit 10 through the resistor 22 connected to the DC power supply circuit 10, becomes the same voltage level as the terminal d. Then, the output voltage of the inverter 24 which receives the collector voltage of this transistor 23 as input becomes a low voltage level (
(hereinafter referred to as L level) to a high voltage level (hereinafter referred to as H level), which is applied to the timer circuit 2o. In one cycle of the AC voltage, the voltage between the collector and emitter of the transistor 23 and the output voltage of the voltage detection circuit 19 are as shown in FIGS. 2(d) and 2(e), respectively.

When the output voltage of the voltage detection circuit 19 reaches H level, the capacitor 27 of the timer circuit 2o is charged via the resistor 26. Then, the output voltage of the inverter 28 is as shown in Fig. 2 (
As shown in q), after a certain period determined by the resistor 26 and capacitor 27, the level changes from H level to L level. As a result, the output voltage of the AND gate 29, which receives the output voltage of the inverter 24, 28, changes from the L level to the H level at θ3, as shown in FIG. Changes from level to L level.

The rectangular wave voltage that changes in this way becomes the output voltage of the control circuit 2o. This output voltage is then amplified by the transistor 26 and becomes the output of the control circuit 11. That is,
The output voltage of the control circuit 11 changes from θ to θ4-! During the period , a base current sufficient to drive the first transistor 12 is supplied from the DC power supply circuit 10. As a result, during this period, a collector current IC limited by the ballast 2 flows from the AC power supply 1 to the transistor 12 through the ballast 2, the filament of the discharge lamp 3, and the diode 9.

When the control circuit 11 is turned off at the time θ4, the transistor 12 is turned off and its collector current is cut off, so that a kick pulse voltage is generated in the ballast 2. This voltage is superimposed on the power supply voltage vs and is applied as a starting voltage between both filament electrodes of the discharge lamp 30.

If the discharge lamp 3 does not start, an AC voltage is applied between the terminals CD in a half cycle after the pulse is generated as shown in FIG. 2(C), and during this period, the capacitor 1 of the DC power supply circuit 10
6 is charged.

The above operation is repeated every cycle of the AC power supply 1, and the discharge lamp 3 is started.

In such a conventional example, the DC power supply circuit 10 can drive the first transistor 12 with a sufficiently large current, allowing a large collector current to flow therein, and by blocking this current flowing through the ballast 2, a large An energetic starting pulse can be generated. This speeds up the startup of the discharge lamp 3, and
You can ensure that the lights turn on.

However, if the discharge lamp 3 stops lighting due to its lifespan or failure, such as when the electron emitting material on the filament electrode of the discharge lamp 3 runs out, the above operation will be repeated every cycle. In that case, the transistor 12 can be sufficiently driven by the DC power supply circuit 1o, the transistor 120 generates almost no heat, and the element is not destroyed due to heat. Since this high-voltage pulse is applied to the discharge lamp 3 and transistor 6, insulation deterioration in various parts is rapidly accelerated by this high-voltage pulse, shortening the life of the entire discharge lamp lighting device and, in the worst case, causing ignition and heat generation due to dielectric breakdown. There is a problem in that it causes Further, noise generated when pulse voltages are applied to various parts also poses a major problem.

Purpose of the Invention The purpose of the present invention is to provide a discharge lamp lighting device that can solve the problems of the conventional examples as described above, prevent shortening of the life of the entire discharge lamp lighting device, and improve safety. shall be.

Structure of the Invention A discharge lamp lighting device according to the present invention includes a preheat-start type discharge lamp connected in parallel between non-power supply side terminals of a filament electrode of a preheating start type discharge lamp connected to an AC power supply via a ballast including an inductive element. It includes a semiconductor switch circuit that conducts in one direction, a first transistor whose conduction direction is opposite to that of the semiconductor switch, and a DC power supply circuit, a DC output end of the DC power supply circuit, and a base of the first transistor. During this period, a voltage is applied in the forward direction between the collector and emitter of the first transistor during a half cycle of the AC power supply, and then the base current of the first transistor is intermittent, and thereafter, at least for the same half cycle. The inside includes a control circuit that maintains the base current cutoff state and a temperature detection switch circuit that detects the temperature of the component elements of the semiconductor switch circuit. According to this device, which is characterized in that it detects the heat generated by the transistor and shuts off the first transistor, the above-mentioned φ problem can be solved.

DESCRIPTION OF THE EMBODIMENTS One embodiment of the apparatus of the present invention is shown in FIG. In the figure,
Components corresponding to those of the conventional example shown in FIG. 1 are given the same reference numerals.

This embodiment is most different from the conventional example in that it includes a temperature detection switch circuit (hereinafter referred to as temperature switch circuit) 30 that is thermally coupled to the two-terminal thyristor 8 of the preheating circuit 5, and that the voltage detection circuit 19 is An AND gate 31 whose input voltages are the output voltage of the temperature switch circuit 30 and the output voltage of the inverter 24 is added. The temperature switch circuit 3o is configured by connecting a series body of resistors 32 and 33 in parallel with a series body consisting of a resistor 34 and a transistor 35, and is supplied with power from the DC power supply circuit 30. Furthermore, the base of the transistor 35 is connected to the connection point of the resistors 32 and 33, and the transistor 35 is further coupled to the two-terminal thyristor 8 by a thermally conductive medium 36 made of a substance with better thermal conductivity than air. .

In the discharge lamp lighting device of this embodiment, after the AC power supply 10 is turned on, a preheating current flows for a while, a starting pulse is generated, and the operation in which the starting pulse is applied to the discharge lamp 3 is the same as in the conventional example. Here, in the temperature switch circuit 3o, the output voltage of the DC type power supply circuit 1o is divided by the resistors 32 and 33, and the resulting voltage is applied to the base of the transistor 35 for temperature detection. The on/off voltage of the transistor 35 changes depending on the temperature change of the thyristor 8, and the timing of generation of the output voltage to the AND gate 31 changes accordingly. In other words, under normal conditions, after the power is turned on,
The preheating circuit 5 becomes conductive, a preheating current IH flows through the filament electrode of the discharge lamp 3, and the discharge lamp 3 is lit. For this reason,
Since the preheating circuit 60 generates less heat and the resulting temperature rise is less, the threshold voltage VT of the transistor 35 is higher than its base voltage. Therefore, the transistor 35 is in an off state, and the output voltage of the temperature switch circuit 35 is at H level. Therefore, the AND gate 31 is controlled by the output of the inverter 24, and the transistor switch circuit 6 performs the same pulse generation operation as in the conventional example.

Next, if the discharge lamp 3 does not light up and the above-mentioned starting pulse generation operation continues, the preheating current H repeatedly flows through the thyristor 8, so the temperature of the thyristor 8 rises, and the heat is transferred to the transistor 35 by the medium 36. Reportedly. As a result, the temperature of the transistor 35 increases, and the threshold voltage for its on/off operation decreases. When the temperature increases as shown in FIG. 4 and the operating voltage at the preset temperature Th becomes lower than the divided output voltage of the resistor 32, 33, the transistor 35 turns on and current flows through the resistor. The output voltage of the temperature switch circuit 30 becomes L level. When one input of the AND gate 31 becomes L level, the input of the timer circuit 20 remains at L level, so the transistor 12 remains non-conductive.
Generation of starting pulses is stopped. That is, if the discharge lamp 3 cannot be lit even after the time T shown in FIG. 4 has elapsed after the power is turned on, the generation of the starting pulse can be stopped. Moreover, since the preheating circuit 5 continues to conduct every cycle and generate heat even after that, the generation of the starting pulse can also continue to be stopped. Therefore, it is possible to prevent the high voltage starting pulse voltage from being applied to the ballast 2, the transistor 12, etc. for a long period of time.
The entire discharge lamp lighting device including these can be prevented from heat generation, ignition, and shortened life due to insulation deterioration. Furthermore, noise can also be reduced by stopping pulse generation itself. Furthermore, in this embodiment, when the starting pulse is stopped, unless the transistor 12 is maintained in the off state, almost no current flows through the ballast 2 in the positive half cycle of the terminal a with respect to the terminal When the preheating current IH flows through the device 2, the magnetic core becomes saturated, so a larger preheating current flows, and the temperature of the temperature switch circuit 5 rises further. That is, from this, the starting pulse can be stopped quickly and reliably, and the unsaturated operation of the transistor 12 can be further reduced to prevent excessive heat generation. Furthermore, in this embodiment, the control circuit is configured with a logic circuit and is configured to perform on/off control, so that the transistor 12 rarely operates in unsaturated state, causing the transistor 12 to generate heat. The above-mentioned operation can be performed without causing any damage, and the life of the transistor 12 can be further extended.

Further, in this embodiment, in the control circuit 11, the output of the AND gate 29 is amplified by the transistor 18, but the gate output may be directly used to drive the transistor 12. In addition, although the control start signal is assumed to be the collector-emitter voltage of the transistor 12, other input signals such as current may also be used. It goes without saying that it could be replaced with something else. Further, in this embodiment, a transistor is used for the temperature switch circuit 30, but by doing so, not only the control circuit but also the temperature switch circuit can be integrated.

The temperature switch circuit 30 is not limited to this, and may use a diode, a thyristor, or the like, or may have a simple configuration using a thermistor. Further, the temperature switch circuit 3o does not need to be provided independently, and may be provided within the control circuit, or may serve as an element. Although the DC power supply circuit 10 is connected between the filament electrodes of the discharge lamp 3, the same effect can be achieved even if the DC power supply circuit 10 is connected to the power supply via a transformer. Furthermore, although this embodiment does not include a circuit that stops the starting pulse after the discharge lamp 3 is lit, a circuit that stops the starting pulse after the discharge lamp 3 is lit using a thyristor or a transistor may be added. However, it goes without saying that similar effects can be obtained.

Effects of the Invention The present invention regularly stops or suppresses the generation of high-voltage starting pulses when a discharge lamp is in a state where it cannot be lit. It is possible to prevent high voltage from being applied to each component for a long period of time, and it is possible to prevent the lifespan from decreasing due to insulation deterioration.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a conventional preheating start type discharge lamp lighting device, and FIG. 2 is an operating waveform diagram thereof. FIG. 3 is a diagram showing an embodiment of the preheating start type discharge lamp lighting device according to the present invention;
FIG. 4 is a diagram for explaining the operation. 1... AC power supply, 2... Ballast, 3.
...Discharge lamp, 5...Preheating circuit, 6...
...Transistor switch circuit, 10...DC power supply circuit, 11...Control circuit, 12...
Transistor, 19... Voltage detection circuit, 2o.
...Timer circuit, 3o...Temperature detection switch circuit.

Claims (1)

[Claims] A semiconductor switch circuit that conducts in one direction and is connected in parallel between the non-power supply side terminals of the filament electrode of a preheat-start discharge lamp that is connected to an AC power source via a ballast that includes an inductive element, and this semiconductor switch. a first transistor whose conduction direction is opposite to that of the circuit; and a DC power supply circuit, and a DC power supply circuit between the DC output terminal of the DC power supply circuit and the base of the first transistor during a half cycle of the AC power supply. After a voltage is applied in the forward direction between the collector and emitter of the first transistor, the base current of the first transistor is interrupted, and the base current is then cut off for at least the same half cycle. and a temperature detection switch circuit that detects the temperature of a component of the semiconductor switch circuit, the temperature detection switch circuit and the control circuit are connected, and the temperature detection switch circuit and the control circuit are connected to each other. A preheating start type discharge lamp lighting device characterized in that the first transistor is cut off by detecting the generated heat.