JPH0752679B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device, and more particularly to an electrode preheating method thereof.

[Prior Art] FIG. 4 shows, for example, LS-85-12-18P17
It is a circuit diagram of the conventional discharge lamp lighting device shown in P20.
In FIG. 4, 1 DC power source, 2 are monolithic transistor inverters that convert the DC voltage of the DC power source 1 into high frequency voltage, 3 are discharge lamps having electrodes 3a and 3b, and 4 is the lamp current of the discharge lamp 3. Limiting ballast yokes 5 are starting capacitors connected to both ends of the discharge lamp 3. In addition,
Here, the power source is simply represented by the symbol of DC power source.

Next, the circuit configuration of the transistor inverter 2 will be described.
Reference numeral 6 is a main transistor for switching, the emitter is connected to the negative electrode of the DC power supply 1, and the output transformer 7 and the resonance capacitor 8 are connected in parallel between the positive electrode and the collector of the DC power supply 1. Reference numeral 9 is a current transformer (hereinafter abbreviated as CT) inserted in the load circuit, 10, 11, 12 are oscillation starting resistors, resistors and diodes connected in series, which are the positive electrode of the DC power supply 1 and the base of the main transistor 6. Between oscillation start resistance
A resistor 11 and a diode 12 are connected between the base and the emitter of the main transistor 6.

In the discharge lamp lighting device configured as described above, when the DC power supply 1 is first turned on, the base current is supplied to the main transistor 6 via the oscillation starting resistor 10 and the main transistor 6 is turned on. As a result, the output transformer 7 or the load circuit (the parasitochoke 4 and the electrode 3 are connected via the main transistor 6).
A current flows through a series circuit of a and 3b and the starting capacitor 5, and this load current is positively fed back to the input of the main transistor 6 via CT9, and the main transistor 6 is kept on while the capacitor 13 is being charged. When this oscillatory base current flows in the opposite direction and the accumulated charge in the junction of the main transistor 6 is erased, the main transistor 6 is erased.
Turns off rapidly. After that, the electromagnetic energy stored in the output transformer 7 resonates with the resonance capacitor 8, and this voltage causes a resonance current to flow in the load circuit. This load current flows through the diode 12 via CT9 and the main transistor 6 is kept in the off state. Then, due to the oscillating load current, the positive feedback current to the main transistor 6 again flows through the secondary winding 9b of CT9, the main transistor 6 turns on and the above operation is repeated, for example, 20 to 50 KHz. The main transistor 6 performs a switching operation at a high frequency of the order. At this time, since the capacity of the starting capacitor 5 is set to a value that causes LC resonance with the parastochoke 4, a high-frequency resonant current flows through the electrodes 3a and 3b of the discharge lamp 3 and at the same time a high voltage is applied across the starting capacitor 5. Occurs, and the discharge lamp 3 is turned on by this voltage. After the discharge lamp 3 is lit, the impedance of the discharge lamp 3 is connected in parallel with the starting capacitor 5, and the transistor inverter 2 continues to oscillate in the same manner as described above using this as a load circuit, and the discharge lamp 3 A high-frequency current limited by the parachute yoke 4 flows into the.

[Problems to be solved by the invention]

However, in the conventional discharge lamp lighting device as described above, high voltage due to LC resonance is generated at both ends of the starting capacitor 5 at the same time when the DC power supply 1 is turned on, so that the electrodes 3a and 3b of the discharge lamp 3 are not sufficiently preheated. This causes a so-called cold start, which causes problems such as early blackening of the discharge lamp 3 and a short life.

The present invention has been made to solve such a problem, and an object of the present invention is to obtain a discharge lamp lighting device capable of preventing early blackening and shortening of the life of the discharge lamp.

[Means for solving problems]

The discharge lamp lighting device according to the present invention is a discharge lamp lighting device of a type that starts a discharge lamp by utilizing LC resonance of a starting capacitor that limits the lamp current of the discharge lamp and a starting capacitor connected in parallel with the discharge lamp. At the time of turning on the power,
An LC preheating means is provided to suppress the LC resonance state to such an extent that the electrode can be preheated sufficiently, but the discharge lamp cannot be started, and the resonance state is switched to a resonance state sufficient to light the discharge lamp after a set fixed time.

[Action]

According to the present invention, when the discharge lamp is turned on by the electrode preheating means, the electrode is sufficiently preheated and then is started without cold start, so that the blackening and shortening of the life of the discharge lamp can be prevented.

〔Example〕

FIG. 1 is a diagram showing the configuration of a discharge lamp lighting device according to an embodiment of the present invention. In the figure, reference numerals 1 to 13 are the same as those of the conventional apparatus, and corresponding parts are designated by the same reference numerals and the description thereof is omitted. Further, 14 is another capacitor connected in series with the capacitor 13, 15 is a switch connected in parallel with this capacitor 14, and 16 is a timer circuit for setting the time for operating the switch 15.

Next, the operation of the discharge lamp lighting device having such a configuration will be described. When the DC power supply 1 is turned on, the transistor inverter 2 oscillates by the same operation as the conventional device, current flows through the load circuit, and the electrodes 3a, 3b are preheated. At this time, the switch 15 is open, so that the combined capacitance of the capacitors 13 and 14 is smaller than that of the capacitor 13, and the oscillation frequency of the transistor inverter 2 is lower than that of the conventional device shown in FIG. It's getting a little higher. Then, due to the deviation of the oscillation frequency, the LC resonance state of the parasitic capacitor 4 and the starting capacitor 5 flows a load current that can preheat the electrodes 3a and 3b sufficiently, but the discharge lamp 3 cannot start. The voltage is suppressed.

On the other hand, the timer circuit 16 starts operating at the same time when the DC power supply 1 is turned on, and the switch 15 is closed after a predetermined time set so that the electrodes 3a and 3b are sufficiently preheated. As a result, the terminal voltage of the starting capacitor 5 is increased under the same oscillation condition as that of the conventional device, and the discharge lamp 3 is started. The oscillation operation of the transistor inverter 2 after the discharge lamp 3 is turned on is the same as that of the conventional device.

As described above, in the above-described embodiment, the capacitor 14 and the switch 15 provided as means for suppressing the LC resonance in the base circuit of the main transistor 6 need only have a small rated voltage and current, so that the device can be made compact and inexpensive.

FIG. 2 shows the switch 15 and the diode 17 in the above embodiment.
2 shows a second embodiment in which the timer circuit 16 is composed of resistors 19 and 20, a capacitor 21 and a constant voltage diode 22 as a parallel circuit of a transistor 18 and a transistor 18. In the discharge lamp lighting device configured as described above, when the voltage of the capacitor 21 charged through the resistor 19 exceeds the Zener voltage of the constant voltage diode 22, the transistor 18 is turned on to perform the same operation as the above embodiment. Done. In addition, the second embodiment has an advantage that the cost can be reduced as compared with the case where a magnet relay or the like is used for the switch 15.

In each of the above embodiments, the case where the transistor inverter 2 is a load current positive feedback type one-stone transistor inverter has been described, but this may be, for example, a voltage feedback type of an output transformer or a two-stone type. Good. The DC power supply 1 may be a commercial AC power supply that is rectified and smoothed. Furthermore, although the capacitors of the base circuit in the second embodiment are connected in series, it is needless to say that the capacitors may be connected in parallel and the capacitance may be changed.

〔The invention's effect〕

As described above, according to the discharge lamp lighting device of the present invention, the electrode preheating means for suppressing the resonance state to the extent that the electrode can be sufficiently preheated but the discharge lamp cannot be started until a predetermined time elapses after the power is turned on is provided. Therefore, there is an effect that it is possible to prevent early blackening and shortening of the life of the discharge lamp.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a discharge lamp lighting device according to a second embodiment of the present invention, and FIG. 3 is a conventional discharge lamp. It is a circuit diagram of a lighting device. 1 ... DC power supply, 2 ... Transistor inverter, 3 ...
… Discharge lamps, 3a, 3b …… Electrodes, 4 …… Plastic yoke,
5 ... Starting capacitor, 6 ... Main transistor, 14 ...
Capacitor, 15,24 ... Switch, 16 ... Timer circuit, 1
7 ... Diode, 18 ... Transistor. The same reference numerals in the drawings indicate the same or corresponding parts.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazutaka Shimizu 5-1, 1-1 Ofuna, Kamakura-shi, Kanagawa Mitsubishi Electric Corporation Ofuna Works (56) Reference JP-A-57-194493 (JP, A) JP-A-58-189994 (JP, A) JP-A-54-34569 (JP, A) JP-A-56-79897 (JP, A) Actually-applied 60-26199 (JP, U) JP-B 38-3359 (JP-A) JP, B1) Actual public 39-3659 (JP, Y1) Actual public 39-3658 (JP, Y1)

Claims (3)

[Claims] 1. A self-excited transistor inverter for converting a DC power supply voltage into a high frequency voltage, a discharge lamp lit by a high frequency output of the transistor inverter, a ballast choke for limiting the lamp current of the discharge lamp, and both ends of the discharge lamp. And a discharge lamp lighting device comprising a starting capacitor for performing electrode preheating and starting of the discharge lamp by resonance with the ballast choke, wherein an LC resonance circuit is formed in the input circuit of the main transistor of the transistor inverter, It consists of a switch for changing the capacitance of the capacitor by switching a plurality of capacitors of the input circuit of the transistor, and a timer circuit for operating this switch, and electrode preheating can be sufficiently performed until a predetermined time has elapsed since the DC current was applied. In addition, the discharge lamp is kept in a resonance state where The discharge lamp lighting device, characterized in that the discharge lamp by operating the switch by a timer circuit comprising an electrode preheating means for switching a sufficient resonance state to light up after between. 2. The discharge lamp lighting device according to claim 1, wherein the self-excited transistor inverter is a single-stone transistor inverter that positively feeds back a load current to the input of the main transistor. 3. The discharge lamp lighting device according to claim 1, wherein the switch comprises a diode and a transistor.