JPS63190298A - Discharge lamp lighter - 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] <Industrial Application Fields> The present invention is a method for manufacturing oscillation circuits and switching elements using DC power obtained by full-wave rectifying and smoothing commercial AC using a full-wave rectifier or DC power from a DC power supply. The present invention also relates to a device for driving a passive inverter consisting of an output transformer and lighting a discharge lamp using the high frequency output of the inverter.

<Prior art and its problems> This type of discharge lamp lighting device is equipped with a preheating circuit consisting of a PNPN switch, a diode, a resistor, etc. connected in series between the reheating electrodes of the discharge lamp, and the power supply By flowing a preheating current through the preheating circuit during the period from when the discharge lamp is turned on until the discharge lamp is lit, the re-preheating electrode of the discharge lamp is sufficiently heated to smoothly light the discharge lamp.

Incidentally, elements such as a PNPN switch and SSS provided in the preheating circuit suffer from a shortage of preheating current because current does not flow unless the breakover voltage is exceeded. Therefore, the cathode of the discharge lamp is significantly worn out, which shortens the life of the discharge lamp.

<Purpose of the Invention> The present invention has been made in view of the above-mentioned problems in the prior art. It is an object of the present invention to provide a lighting device for a discharge lamp that can reduce as much as possible wear and tear on the cathode when starting the lighting of the discharge lamp due to a shortage.

<Means for Solving the Problems> In order to achieve the above-mentioned object, the lighting device for a discharge lamp of the present invention includes a switching element that is controlled on and off by the oscillation output of an oscillation circuit, and a DC An output transformer to which power is supplied intermittently, - a current limiting element connected between the output transformer and the discharge lamp as a load, and a lighting device through which preheating current flows only in the non-lighting state at the time of starting the discharge lamp. comprising a starting circuit and a lighting start detection element that changes the oscillation frequency of the oscillation circuit by switching an oscillation frequency determining element of the oscillation circuit depending on whether or not a preheating current is flowing through the lighting start circuit; The lighting start detection element is characterized in that the oscillation frequency of the oscillation circuit is switched so that the impedance of the current limiting element before lighting the discharge lamp becomes smaller than after lighting.

<Operation> When the discharge lamp starts lighting, when the oscillation circuit is supplied with DC power and starts oscillating, the switching element is turned on and off by this oscillation output, DC power is intermittently supplied to the output transformer, and the output High frequency AC power is supplied from the transformer to the discharge lamp via the current limiting element, and the discharge lamp enters a preheating state. This preheating current flows through the output transformer, the current limiting element, one preheating electrode of the discharge lamp, the lighting starting circuit, and the other preheating electrode of the discharge lamp. The lighting start detection element that detects this preheating current switches the oscillation frequency determining element of the oscillation circuit, and the oscillation frequency of the oscillation circuit is varied so as to reduce the impedance of the current limiting element. Therefore, since the impedance of the current limiting element connected to the preheating circuit is reduced, a sufficiently large preheating current flows, and wear and tear on the cathode of the discharge lamp is extremely reduced. Then, the discharge lamp lights up when its heat electrode is sufficiently heated by the preheating current, and the preheating current no longer flows through the lighting starting circuit. The lighting start detection element detects this and switches the oscillation frequency determining element so that the oscillation frequency of the oscillation circuit becomes a predetermined value, so that the current limiting element thereafter functions at a predetermined impedance.

<Example> Hereinafter, preferred examples of the present invention will be described in detail with reference to the drawings.

In FIG. 1 showing an embodiment of the present invention, a commercial AC power supply 1 is connected to both input terminals of a full-wave rectifier 3 via a power switch 2, and two DC power supplies are connected between both DC output terminals of the full-wave rectifier 3. Capacitors 4 and 5 are connected in series, and a Zener diode 6 for stabilizing the voltage supplied to an oscillation circuit 7, which will be described later, is connected in parallel to the smoothing capacitor 5. A single-turn output transformer 8 whose center tap is connected to the positive DC output end of the full-wave rectifier 3 has one winding end connected to a switching element 9 made of a transistor, and the other winding end connected to a switching element 9 consisting of a transistor. The wire end is connected to one preheating electrode of a discharge lamp La serving as a load via a current limiting element 10 made of a coil.

The oscillation circuit 7 controls the switching element 9 on and off to intermittently supply direct current to the output transformer 8.
It consists of a semiconductor integrated circuit, such as NE555 manufactured by Sidanetics, which has a built-in voltage comparator, SR Frilithoflop circuit, transistor buffer circuit, etc., and the oscillation frequency can be arbitrarily varied by simply changing the constants of the capacitor and resistor. Two timing capacitors IIA and IIB are connected in series to the connection point between trigger terminal TR and threshold terminal TH, and two timing resistors 12 and 13 are connected in series to these capacitors 11A and 11B. is connected to the discharge terminal DC, the timing capacitor 1
1A and 11B perform self-oscillation by repeating charging and discharging, and output from the output terminal OUT.

That is, the oscillation frequency of the oscillation circuit 7 is determined by the timing resistors 12 and 13 and the timing capacitors IIA and IIB. In order to perform this self-oscillation operation,
It is necessary that the reset terminal R3 is not set to "O" level, and in the embodiment, the reset terminal R3 is connected to the power supply capacitor 4 together with the power supply terminal VCC, and the bypass capacitor 14 is connected to the control voltage terminal CV. This bypass capacitor 14 eliminates the influence of power supply noise.

A lighting starting circuit 15 for flowing a preheating current to both preheating electrodes of the discharge lamp La when the power is turned on includes a PNPN switch 15A, a diode 15B, a resistor 15C, and a resistor 15C connected in series between the heat electrodes of the discharge lamp 10. It is composed of resistors 150 connected in parallel. This lighting starting circuit 1
A light emitting diode 16A of the lighting start detection element 16 made of a photocoupler is inserted and connected between the diode 15B and the resistor 15G. On the other hand, the phototransistor 16B of the lighting start detection element 16 is connected in parallel to one timing capacitor IIB. In addition, in the figure, the lighting start detection element 16 is shown divided into two parts for convenience.

b, a', and b' are the same point.

Next, the operation of the above embodiment will be explained. When the power switch 2 is turned on, DC power that has been full-wave rectified by the full-wave rectifier 3 is supplied to the oscillation circuit 7 via the capacitor 4, and the oscillation circuit 7 starts oscillating. The switching element 9 is controlled on/off by the oscillation output of the oscillation circuit 7, and the full-wave rectifier 3 is connected to the output transformer 8.
DC power is supplied intermittently. From this output transformer 8 to the current limiting element 10. One preheating electrode 1 of discharge lamp La
A preheating current flows through the lighting starting circuit 15 and the other preheating electrode of the discharge lamp La.

This preheating current drives the light emitting diode 16A of the lighting start detection element 16 to emit light, and the phototransistor 16B is turned on. The phototransistor 16B in the on state short-circuits the timing capacitor IIB, and only one timing capacitor IIA is turned on. It contributes as an element for determining the oscillation frequency of the oscillation circuit 7. here,
Oscillation frequency f08 of the oscillation circuit 7 consisting of a linear RC. is the resistance value of each timing resistor 12 and 13 as R1
, R2, and both timing capacitors 11A.

When the combined capacity of 11B is C, it is expressed as follows. Therefore, by detecting the preheating current, the phototransistor 16B of the lighting start detection element 16 is turned on, and the two timing capacitors IIA, which are connected in series,
When one of IIB is short-circuited, the combined capacitance C becomes larger than the combined capacitance C, so the oscillation frequency r asc becomes lower. On the other hand, the impedance value Z of the current limiting element 10 made of a coil is expressed as 2πfL as is well known. As a result, the oscillation frequency f08 of the oscillation circuit 7. decreases, the impedance value Z of the current limiting element 10 becomes smaller, and the cathode preheating current flowing through this current limiting element 10 becomes larger. This large preheating current prevents the cathode of the discharge lamp La from being worn out as much as possible. When both preheating electrodes of the discharge lamp La are sufficiently heated by this preheating current, the discharge lamp La is turned on.
When the PNPN switch 15A of the lighting starting circuit 15 becomes lower than the breakover voltage, it becomes non-conductive and no preheating current flows, and the phototransistor 16B of the lighting starting detection element 16 turns off, and the oscillation frequency of the oscillation circuit 7 changes. , the other timing capacitor IIB is included as a frequency determining element to have a predetermined value determined, and the current limiting element 10 functions at a predetermined impedance value.

FIG. 2 shows another embodiment of the present invention, in which the same or equivalent parts as in FIG. 1 are given the same reference numerals. and,
The difference from FIG. 1 is that a capacitor is used as the current limiting element 17, and that the oscillation frequency determining element of the oscillation circuit 7, which is switched by the lighting start detection element 16, has been replaced accordingly. That is, timing capacitor 1
1 as two timing capacitors 11A in FIG.

11B is provided, and in place of the other timing resistor 13 in FIG. 1, two timing resistors 13A each having a resistance value obtained by dividing the resistance value of the timing resistor 13A at a predetermined ratio are provided. , 13B are connected in series, and a photocoupler 16B of the lighting start detection element 16 is connected in parallel to one of the timing resistors 13B.

Here, since the series combined resistance value of both timing resistors 13A and 13B is equal to R2 in the above equation, the photocoupler 16B of the lighting start detection element 16 is turned on by detecting the preheating current, and the timing resistor 13B is turned on. When short-circuited, the oscillation frequency f08. becomes higher. Since the impedance value Z of the current limiting element 17 consisting of a capacitor is expressed as 2=-2πfc as is well known, the oscillation frequency f03. As the current becomes higher, it becomes smaller, the preheating current becomes larger, and the same effect as in the embodiment described above can be obtained.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various embodiments are possible without departing from the scope of the claims. For example, the lighting starting circuit 15 may be
It is also possible to use an SSS instead of the PN switch 15A. In addition, when driving the inverter by supplying DC power from a different DC power source, use an electrolytic capacitor 4.
．． 5, the voltage may be divided by resistors.

<Effects of the Invention> As detailed above, according to the discharge lamp lighting device of the present invention, when a preheating current flows through the lighting starting circuit, the lighting starting detection element detects this and determines the oscillation frequency of the oscillation circuit. The determining element is switched and the oscillation frequency is varied so that the impedance value of the current-limiting element becomes smaller than when the lamp is lit.This makes it possible to reduce the preheating current at the start of lighting the discharge lamp with an extremely simple and rational configuration. This makes it possible to significantly reduce wear and tear on the cathode during startup of the discharge lamp.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram of one embodiment of a lighting device for a discharge lamp according to the present invention, and FIG. 2 is an electric circuit diagram of another embodiment of the present invention. 7...Oscillation circuit 8...Output transformer 9...Switching element 10.17...Current limiting element 11, IIA, IIB, 12.13° 13A, 13B...Oscillation frequency determining element 15.・・・
Lighting start circuit 16...Lighting start detection element La...Discharge lamp

Claims (1)

[Claims] (1) A switching element that is controlled on and off by the oscillation output of the oscillation circuit, an output transformer to which DC power is intermittently supplied by this switching element, and a connection between this output transformer and a discharge lamp as a load. the oscillation frequency of the oscillation circuit is determined based on whether or not the preheating current is flowing through the lighting starting circuit; and a lighting start detection element that changes the oscillation frequency of the oscillation circuit by switching the lighting start detection element, and the lighting start detection element makes the impedance of the current limiting element smaller before lighting the discharge lamp than after lighting. A lighting device for a discharge lamp, characterized in that it is configured to switch the oscillation frequency of an oscillation circuit.