JPH0322398A - Electric discharge lamp lighting circuit - Google Patents

Abstract

PURPOSE:To reduce a voltage drop at a lighting time resulting from winding by connecting a first winding where a high voltage pulse occurs to an electric discharge lamp in series and when the electric discharge lamp is lighted up, saturating the core of the first winding to reduce its impedance. CONSTITUTION:A first winding 3 is connected to a voltage generation circuit 1 and an electric discharge lamp 2 in series to generate a high tension pulse voltage necessary for re-lighting of the discharge lamp 2. A driving circuit 4 impresses a specified voltage on a second winding 7 whose core 6 is in common with the winding 3 to make the winding 3 generate a high tension pulse voltage for relighting. A saturation circuit 5 is equipped with a winding 8 whose core 6 is in common with the winding 3, and when the discharge lamp 2 is lighted up, the core 6 is saturated and an impedance of the winding 3 is made to be lowered. Thereby, if is possible to remove an influence at the time of stationary lighting of the winding 3 generating a high voltage for re-lighting, etc., of the discharge lamp 2, and eliminate a voltage drop due to the winding 3.

Description

[Detailed Description of the Invention] [Summary] The present invention connects a first winding that generates a high voltage pulse necessary for starting or relighting the discharge lamp in series with the discharge lamp, and the discharge lamp is turned on. When this occurs, the core of the first winding is saturated and the inductance of the first wire is reduced, making it possible to significantly reduce the voltage drop caused by the winding during lighting.

[Industrial application field]

The present invention relates to a lighting circuit for high-pressure discharge lamps such as high-pressure sodium lamps and metal halide lamps.

[Prior Art] High-pressure discharge lamps such as mercury lamps, high-pressure sodium lamps, and metal halide lamps are used for various purposes because they are small, have high brightness, and are highly efficient. When starting these high-pressure discharge lamps, it is necessary to apply a higher voltage than when the discharge lamp is in the lighting state, and various discharge lamp lighting circuits have been considered.

If +Hm or a momentary voltage drop occurs in the power supply of the above discharge lamp lighting circuit while the discharge lamp is lit,
Discharge cannot be maintained and the discharge lamp goes out. Once a discharge lamp has been extinguished, it cannot be turned on simply by applying the discharge starting pressure necessary for starting, and cannot be turned on again until the discharge lamp is cooled and the flower pressure inside the arc tube is reduced.

In general, the discharge starting pressure of a lightning lamp is expressed as a function of the product of the distance between the electrodes and the vapor pressure in the tube of the lightning lamp, and since the distance between the electrodes is determined to a constant value depending on the structure of the discharge lamp, the pressure inside the tube is The higher the voltage, the higher the firing voltage required. The air pressure in the pipe of the poison lamp that was in the lighting state is much higher than before it was lit, so in order to relight the lamp in that state, it is necessary to start the lightning strike, which is determined by the smoke pressure in the pipe at that time. It is necessary to apply a voltage higher than the voltage to the discharge lamp or wait until the discharge lamp is cooled and the vapor pressure inside the tube decreases.

For example, it takes 5 to 10 minutes for a mercury lamp to cool down and its vapor pressure decreases until it can be lit again, while a metal halide lamp takes more than 10 minutes, and there is the inconvenience that the lamp cannot be lit during that time. there were.

Therefore, it is conceivable to provide a relighting voltage generation circuit on the secondary side that generates a high voltage capable of relighting the discharge lamp under the high vapor pressure to relight the discharge lamp.

[Problem to be solved by the invention]

However, in the above-mentioned re-lighting voltage generation circuit, for example, if a coil or the like is inserted in series with a discharge lamp to generate a high-voltage pulse voltage, the inductance of the coil will change after the discharge lamp is lit. act as a load, causing a voltage drop.

In order to solve this problem, it is conceivable to provide a short circuit that short-circuits the coil of the re-lighting voltage generating circuit when the discharge lamp is turned on. However, for example, in the case of a 70W metal halide lamp, it is necessary to apply a high voltage of 25KV or more as the relighting voltage.
It is difficult to create a short circuit using a relay, etc. due to insufficient voltage resistance between the contacts. Further, for the same reason, it is difficult to realize it using a semiconductor switch element such as a transistor.

An object of the present invention is to provide a discharge lamp lighting circuit that can generate a high voltage necessary for relighting a discharge lamp and facilitates power supply to the discharge lamp.

[Means to solve the problem]

FIG. 1 is a diagram explaining the principle of the present invention.

In the same figure, the voltage generating circuit 1 is configured such that, for example, a DC current '<l
The output voltage of B+ is boosted to generate at least a voltage that maintains the lighting of the discharge lamp 2.

The first winding 3 is connected in series to the voltage generating circuit 1 and the discharge lamp 2, and generates a high pulse voltage necessary for relighting the discharge lamp 2.

The drive circuit 4 applies a predetermined voltage to the second winding 7 that shares the core 6 with the first winding 3, and
A high voltage pulse voltage is generated to restart the light.

The saturation circuit 5 has a winding 8 in which the first winding 3 and the core 6 are common, and when the discharge lamp 2 is turned on, the saturation circuit 5 saturates the core 6 so that the first winding 3 and the core 6 are connected to each other. Reduce inductance.

[Function] In the discharge lamp lighting circuit having the above structure, for example, when a discharge lamp that has been in a lit state goes out due to a momentary power interruption or the like and the discharge lamp is to be lit again, the drive circuit 4 is first operated. ,
A predetermined voltage is applied to both ends of the second winding 7 to generate a high-voltage pulse pressure in the first winding 3. As a result, the high voltage pulse flood pressure from the first winding 3 is superimposed on the output voltage of the voltage generating circuit 1, and the superimposed voltage is applied to the discharge lamp 2, making it possible to relight the discharge lamp 2. Become.

When the discharge lamp 2 is lit again, the load current of the lighting circuit, which had not been flowing until then, starts to flow.

Therefore, for example, a DC load current is reflected in the saturation circuit 5 to saturate the core 6, thereby reducing the inductance of the first winding 3 wound around the core 6.

Therefore, when the discharge lamp is in the lighting state, the first winding 3 no longer acts as a load on the lighting circuit, and the circuit structure can be simplified.

〔Example〕

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

FIG. 2 is a circuit diagram of a lighting circuit for a metal halide lamp according to an embodiment of the present invention.

In the figure, a capacitor C is connected to the positive electrode side of the DC power supply 11. A filter 12 consisting of a coil L6 and a coil L6 is connected to the filter 12, and a winding L6 of a transformer 14 is connected to the output of the filter 12. This filter 12 has a core l7 which will be described later.
This is a filter for removing noise and the like introduced into the winding L6 by the voltage applied to the winding L5 of the transformer 14 that shares the same voltage.

One end of a coil L1 is connected to the other end of the winding L6, and the other end of the coil L1 is connected to a capacitor Cs, a cathode of a diode D1, and a collector of a transistor TRI.

Further, one end of a capacitor C1 is connected to the other end of the coil L1, and the primary winding L2 of the transformer 13 is connected to the other end of the capacitor Cl. The other end of the capacitor Cs, the anode of the diode D1, the emitter of the transistor TRI, and the other end of the winding L2 are connected to the DC power supply 11.
fLI! connected to the ii side.

These coils Ll, } transistor TRI, capacitor 0
The first prize is a circuit that converts the voltage applied to the winding L2 of the transformer 13 into a rectangular wave alternating current.

A drive signal of several tens of KHz is applied to the base of the transistor TRI from a control circuit (not shown), and the transistor TRI is repeatedly turned on and off according to this drive signal. As a result, a voltage generated by converting the voltage of the DC power supply 11 into a rectangular wave alternating current is generated between the winding L2.

Further, the diode DI is a diode that high-busses the reverse voltage applied between the collector of the transistor TR and the transistor ξ. Capacitor C is a capacitor for absorbing the surge voltage generated between the collector and emitter when the transistor TRI is off. A metal halide lamp 15 is connected to one end of a secondary winding L3 having n times the number of turns as the primary winding L2 of the transformer 13.
A secondary winding L4 of a transformer l4 that generates the high-voltage pulse voltage necessary to relight the lamp is connected to the secondary winding L4, and a metal halide lamp 15 is connected to the other end of the winding L4.

The other end of the metal halide lamp 15 is connected to the other end of the winding L3 of the transformer l3.

A winding L5 and a winding L6 are provided on the primary side of the transformer 14. Volume 1'! A pulse generation circuit 16 is connected to both ends of ffAL5. At the time of starting or relighting, a pulse voltage is applied between this pulse generating circuit l6 and the seventh winding L5, and a high voltage pulse voltage is generated between the winding L4, which has m times the number of turns of the winding L5. .

Further, the above-mentioned filter 2 is connected between both ends of the winding L6, and the output terminal of the filter 12 is connected to the power source l1.
is connected in series between the positive electrode of the coil Ll and the coil Ll. As will be described in detail later, when the metal halide lamp 15 is turned on, a direct current is passed between the winding L6 to saturate the core 17 of the transformer l4 and reduce the inductance of the secondary winding 4.

The transformer 14, filter 12 and pulse generation circuit l
6, the relighting circuit 18 that starts and relights the metal halide lamp 15 is controlled.

Next, the operation of the embodiment having the above structure will be explained.

First, when the transistor TRI is turned on from the initial state (state B where the metal halide lamp 15 is not yet lit and the lamp is cold), energy is stored in the coil I7l. The energy stored in the coil L1 is transferred to the capacitor C1 when the transistor TRI is turned off.
is applied between the winding L2 of the transformer 13 through the winding L2.
The voltage between 2 and 1 increases. Then, the voltage vl between the windings L2 is multiplied by n and outputted as a voltage 2 between the secondary windings L3.

At this time, in the transformer l4, the pulse voltage applied from the pulse generation circuit 16 between both ends of the primary winding L5 is multiplied by m and outputted as a voltage 3 between the primary winding L4. As a result, a voltage equal to the sum of the voltage (2) and the voltage (V3) is applied to both ends of the metal halide lamp 15, and the voltage becomes equal to or higher than the discharge start voltage, and the metal halide lamp 15 lights up.

When the light is on, the metal halide lamp 15
can be regarded as a resistive load, so a constant DC current is output from the DC power supply 1L, and this DC current is passed through the transformer 1.
4 flows into winding L6. This DC current saturates the core 17 of the transformer l4, and the inductance of the secondary winding L4 becomes significantly smaller (for example, the inductance of 10 mH at startup changes to 100 μH due to the saturation of the core 17).

As a result, the inductance of the winding L4 becomes negligible compared to the impedance of the metal halide lamp l5, almost no voltage drop occurs in the winding L4, and all of the power given from the primary side of the transformer 13 is transferred to the metal halide lamp 15. The threads are combined.

On the other hand, when the metal halide lamp 15 that was in the lit state goes out due to a momentary power cut, etc., a direct current flows to the winding L6. A
The current becomes almost zero, and the transformer i4 changes from a saturated state to an unsaturated state.

At this time, the pulse generation circuit l6 detects whether the metal halide lamp 15 is turned off using a current detection circuit (not shown) or the like, and outputs a pulse voltage to the winding L5. This pulse voltage is multiplied by m and output as a voltage 3 between the poles of the winding L4. The turns ratio m of the transformer 14 is determined so that when the vapor pressure inside the lamp 15 is at its maximum, the output voltage V is equal to or higher than the discharge starting voltage at that time (for example, 25 kV in the case of a 70 W metal halide lamp). ,
The metal halide lamp 15 can be reliably lit again.

In this way, when the metal halide lamp 15 is lit again, the core 17 of the transformer 14 is saturated by the DC current flowing through the winding L6, and the winding L
4 inductance decreases. As a result, the voltage drop across winding L4 is negligible, and transformer 1
All voltages sent from the primary side of the lamp 3 are supplied to the metal halide lamp 15.

As described above, according to the above embodiment, the inductance of the winding L4 of the relighting circuit 18 for relighting a discharge lamp such as a metal halide lamp or a sodium lamp can be significantly reduced after the discharge lamp is lit. Therefore, the winding L
4 can be reduced. Also,
As a result, the winding t-4 used in the relighting circuit 18 is
Since there is no need to consider the voltage drop due to the inductance of the winding L4, the inductance of the winding L4 can be set to a large value.

In the above embodiment, the DC current on the primary side of the discharge lamp lighting circuit saturates the core 17 of the winding [, 4, but another power source is provided to saturate the core 17.
When the current detection circuit or the t-pressure detection circuit detects that the discharge lamp has been extinguished due to an external factor, a DC current is caused to flow from the power source to another winding that shares the core 17 to saturate the core 17. It's okay.

Furthermore, the windings L4, L5, etc. are not limited to the above-mentioned structure, but may be any structure that saturates the core 17 and reduces the inductance of the winding L4.

Further, in the above embodiment, the relighting circuit 18 is used to start and relight the discharge lamp, but of course a circuit exclusively for relighting may be used.

Furthermore, the discharge lamp lighting circuit of the present invention is not limited to the lighting circuit of the embodiment, but can also be applied to other lighting circuits that perform sine wave lighting, third harmonic superimposed lighting, or the like.

〔Effect of the invention〕

According to the present invention, it is possible to eliminate the influence of the winding that generates high voltage for relighting the discharge lamp during steady lighting, eliminate the voltage drop caused by the winding, and create a more simplified lighting circuit. can be realized.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention, and FIG. 2 is a diagram illustrating the configuration of a discharge lamp lighting circuit according to an embodiment of the present invention. 1...Voltage generation circuit, -Discharge lamp, -First winding, -Drive circuit, -Saturation circuit, -Core, -Second winding.

Claims (1)

[Scope of Claims] A voltage generation circuit that boosts the output voltage of a power supply and generates a predetermined voltage that maintains at least the lighting of the discharge lamp, the voltage generation circuit being connected in series with the output of the voltage generation circuit and the discharge lamp,
A predetermined voltage is applied to a first winding that generates a high-voltage pulse voltage necessary for starting or relighting the discharge lamp, and a second winding that shares a core with the first winding. A drive circuit that generates the high-voltage pulse voltage in a first winding, and a winding that shares a core with the first winding, and saturates the core when the discharge lamp is in a lighting state. A discharge lamp lighting circuit comprising: a saturation circuit that reduces inductance of the first winding.