KR19980024273A - Discharge lamp lighting device - Google Patents

Abstract

Disclosed is a discharge lamp lighting device which converts a DC power source into a high frequency voltage by a transistor inverter circuit and turns on the discharge lamp at the high frequency voltage. In order to provide a discharge lamp lighting device composed of a circuit and a control circuit, a direct current power source, a transistor inverter circuit for converting the direct current voltage thereof to a high frequency voltage, a plurality of discharge lamps connected in series, and the lamp current thereof connected in series When both ends of the ballasts and the discharge lamps are connected to each other by the electrodes and the starter capacitors start the discharge lamps by the ballast and the series resonance, and at least one of the discharge lamps is at the end of its service life. Detection circuit for detecting the end of life state and output from this detection circuit Normal discharge lamp by the output signal to maintain the discharge, but the end of life discharge lamp can not maintain the discharge electrode so that the warm-up condition was a configuration in a control circuit for reducing the output of the transistor inverter circuit.

With such a configuration, even when the end-of-life discharge lamp and the normal discharge lamp are mixed, it can be easily distinguished from the outside, protect the transistor inverter circuit, stabilize the discharge of the discharge lamp, and at the same time configure the circuit. The effect that can be made simple and inexpensive is obtained.

Description

Discharge lamp lighting device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting apparatus for converting a direct current power source into a high frequency power source by a transistor inverter circuit and lighting a discharge lamp at this high frequency voltage.

Fig. 3 is a diagram showing a conventional example of Fig. 1, for example, a circuit diagram in which two discharge lamps of the conventional discharge lamp lighting apparatus disclosed in Japanese Patent Laid-Open No. 62-264600 are connected in series. In the same drawing, reference numeral 1 denotes a DC power supply, and 2 denotes a transistor inverter circuit for converting a DC voltage of the DC power supply 1 into a high frequency voltage, and FLa and FLb each have electrodes FLa1, FLa2 and FLb1 and FLb2, respectively. The lamp 3 denotes a ballast choke for limiting the lamp currents of the discharge lamps FLa and FLb, and Ca and Cb are starter capacitors connected to both ends of the discharge lamps FLa and FLb via filaments.

Next, the circuit configuration of the transistor inverter circuit 2 will be described. (4) is a main transistor for switching, (5) is a return type thermal protector operating by detecting abnormal heat generation of the main transistor (4), (6) is a positive electrode and heat of the DC power source (1) An output transformer connected to the collector of the main transistor 4 via a protector 5, 7 a resonant capacitor connected in parallel to the output transformer 6, 8 a current transformer inserted into the load circuit, 9 ), (10) and (11) are oscillation starting resistors, diodes and resistors connected in series, respectively, and oscillation starting resistance (9) and main between the positive electrode of DC power supply 1 and the base of main transistor (4). The diode 10 and the resistor 11 are connected to the base and the emitter of the transistor 4.

In the discharge lamp lighting device configured as described above, when the DC power source 1 is first supplied, the base current is supplied to the main transistor 4 via the oscillation starting resistance 9, and the main transistor 4 transitions to on. As a result, current flows through the main transistor 4 to the output transformer 6 or the load circuit (stabilizer 3, electrodes FLa1 and FLa2, start capacitor Ca, FLb1 and FLb2, and start capacitor Cb). The current is positively fed back to the input of the main transistor 4 via the current transformer 8, and the main transistor 4 remains on while the capacitor 12 is charged. When the vibrating base current flows in the reverse direction and the accumulated charge force at the junction of the main transistor 4 is canceled, the main transistor 4 turns off rapidly.

After that, the electric energy accumulated in the tank circuit composed of the output transformer 6 and the resonant capacitor 7 resonates, and a resonant current flows in the load circuit. This load current flows through the diode 10 through the current transformer 8 and the main transistor 4 is kept off. Then, the positive feedback current to the main transistor 4 mainly flows again through the secondary winding 8b of the current transformer 8 by vibrating load current, and the main transistor 4 is turned on to repeat the above operation at high frequency. The main transistor 4 performs the switching.

At this time, the capacitances of the starting capacitors Ca and Cb are set to the values of LC resonance with the ballast 3, so that a high frequency resonant current flows to the electrodes FLa1, FLa2 and FLb1 and FLb2 of the discharge lamps FLa and FLb and simultaneously starts the capacitor. High voltage is generated at both ends of Ca and Cb, and the discharge lamps FLa and FLb are turned on by this voltage.

After the discharge lamps FLa and FLb are turned on, the impedances of the discharge lamps FLa and FLb are connected in parallel with the starter capacitors Ca and Cb, and the transistor inverter circuit 2 starts the oscillation operation as described above as the load circuit. Then, a high frequency current limited by the ballast 3 flows through the discharge lamps FLa and FLb.

In the first conventional example as described above, when the rectification or preheating is continued at the end of the life of the discharge lamp FLa, for example, a load current larger than the normal lighting continues to flow and the main transistor 4 supplies power. The temperature rises ideally by increasing the loss. In this abnormality, the contact of the thermal protector 5 is opened due to the temperature rise, so that the load current does not flow through the main transistor 4, and the oscillation of the transistor inverter circuit 2 is stopped and protected.

In addition, as a second conventional example, a detection circuit for detecting an abnormality and a control circuit for controlling the inverter circuit by the detection circuit, instead of the protection by the return type thermal protector method of the prior art example 1, are used. There is one disclosed in Japanese Patent Application Laid-Open No. Hei 1-251593 which controls reduction without stopping, and a circuit diagram thereof is shown in FIG. The same figure is comprised of the power supply circuit a, the inverter circuit b, the lamp circuit c, the self hold detection circuit d, and the inverter output control circuit e. The power supply circuit a converts a commercial power supply into a DC voltage. Inverter circuit b is an inverter circuit of one-pass power mode.

The lamp circuit c has a configuration in which discharge lamps are connected in series.

The self-holding detection circuit d detects an abnormality of the discharge lamp and maintains a protection state, and the inverter output control circuit e controls the output of the inverter circuit b in accordance with the self-holding detection circuit d.

In this conventional apparatus, one of the discharge lamps La and Lb of the current lamp circuit is at the end of its lifetime, and at the end of this lifetime, the voltage at both ends of the capacitor C1 of the lamp circuit c is higher than at normal lighting. A phenomenon occurs, whereby in the self-holding detection circuit d, the voltage is divided by the resistors R1 and R2 and the voltage of the capacitor C2 is detected as a change. As a result, since the bidirectional trigger element SBS can be turned on to trigger the thyrister SCR, a current flows through the resistor R3 to the photodiode PD to emit light. By receiving the light emitted by the phototransistor PT of the inverter output control circuit e and turning it on, the transistor Q2 is turned off, the combined capacitance of the capacitors C3 and C4 is reduced, and the on-duty of the main transistor Q1 in the inverter circuit is small. The output of the inverter circuit b is reduced.

In the second conventional example as described above, an expensive semiconductor such as a bidirectional trigger element, a thyristor, a photodiode, and the like has an increased component score.

Since the discharge lamp lighting device of the first conventional example is constituted as described above, when the normal discharge lamp and the end-of-life discharge lamp are mixed, the oscillation of the transistor inverter circuit 2 is stopped to discharge the normal discharge lamp and the end-of-life discharge. There is a problem in that it is difficult to distinguish the discharge lamps at the end of the life since the lamps cannot be distinguished. In the second conventional example, the number of parts is large and expensive.

An object of the present invention is to solve the above problems, and to provide a discharge lamp lighting device comprising a detection circuit and a control circuit which can distinguish between the normal discharge lamp and the end-life discharge lamp, and inexpensive and low component score. .

1 is a circuit diagram of a discharge lamp lighting apparatus showing a first embodiment of the present invention;

2 is a circuit configuration diagram of a discharge lamp lighting apparatus showing a second embodiment of the present invention;

3 is a circuit configuration diagram of a conventional discharge lamp lighting apparatus,

4 is a circuit diagram of a conventional discharge lamp lighting apparatus.

* Description of the symbols for the main parts of the drawings *

1: DC power supply, 2: transistor inverter circuit,

3: ballast, FLa: discharge lamp

FLb: discharge lamp, FLn: multiple discharge lamp,

Ca: start capacitor, Cb: start capacitor,

Cn: several start capacitors, 13: control circuit,

16: DC blocking capacitor, 17: detection circuit,

19: Bidirectional trigger element.

The discharge lamp lighting apparatus according to the present invention includes a transistor inverter circuit for converting a current power source and a direct current voltage of the current power source into a high frequency voltage, a plurality of discharge lamps connected in series lit by the transistor inverter circuit, and a plurality of discharge lamps. A discharge lamp lighting device having a ballast for limiting lamp current and a starter capacitor connected to both ends of the plurality of discharge lamps via electrodes, respectively, and starting a discharge lamp by series revolution with the ballast. Although the normal discharge lamp can maintain the discharge by the detection circuit for detecting the end of life state and the output signal outputted from the detection circuit when at least one of the lamps has reached the end of life, the discharge lamp in the end of life is discharged. Output of the transistor inverter circuit so that the And a control circuit for reducing.

In addition, a capacitor for direct current blocking is connected between the ballast and the discharge lamp to support the flow of direct current.

In addition, the transistor inverter circuit includes one transistor for switching, a feedback power source connected to the base of the transistor, an inductance element connected in series and self-resonant between the base and the emitter of the transistor.

In addition, the control circuit includes electrode preheating means for preheating the electrodes of the discharge lamp with the same circuit, dimming means for dimming the discharge lamp, and control means for reducing the output of the transistor inverter circuit at the end of the lifetime of the discharge lamp. Will serve as each.

The detection circuit includes a secondary winding on the secondary side of the ballast, a diode that half-wave rectifies the output voltage output from the secondary winding, a capacitor that smoothes the voltage half-wave rectified by the diode, and a smoothing voltage smoothed by the capacitor. On is provided with a bidirectional trigger element, a resistor for limiting a holding current for maintaining the on state of the bidirectional trigger element, and a transistor for controlling the control circuit by turning on the bidirectional trigger element.

EXAMPLE

Example 1

1 is a circuit configuration diagram showing a discharge lamp lighting apparatus according to Embodiment 1 of the present invention. The same components as those of the conventional apparatus of FIG. 3 are denoted by the same reference numerals and description thereof will be omitted. Denoted at 13 is a control circuit for reducing and controlling the output of the transistor inverter circuit 2, and at 17 is a detection circuit for detecting the end-of-life state of the discharge lamp and holding the control circuit. Reference numeral 16 denotes a capacitor for direct current blocking, which is connected in series with the ballast 3 and supports the flow of a direct current. In addition, reference numeral 13 denotes a condenser 14 connected in parallel with the condenser 12 and a switch 15 connected in series with the condenser 14.

Next, the operation will be described.

In the configuration of FIG. 1, the control circuit 13 starts the transistor inverter circuit 2 by the same operation as the conventional apparatus shown in FIG. 3, and current flows in the load circuit to preheat the electrodes FLa1, FLa2, FLb1, and FLb2. . At this time, the switch 15 is open, and therefore the capacitance of only the capacitor 12 is increased, and the oscillation frequency of the transistor inverter circuit 2 is slightly increased.

In the LC resonant state of the ballast 3 and the starting capacitors Ca and Cb due to the shift of the oscillation frequency, a load current capable of sufficiently preheating the electrodes FLa1, FLa2, and FLb1, FLb2 flows, but the discharge lamp FLa , FLb determines the capacitor capacities of the start capacitors Ca and Cb so as not to start, and suppresses the voltage. After this preheating is sufficient, the switch 15 is closed by, for example, a control of a timer circuit (not shown), and starts at a voltage necessary for turning on the discharge lamps FLa and FLb which are the oscillation conditions of the conventional apparatus of FIG. The terminal voltages of the capacitors Ca and Cb increase, the discharge lamps FLa and FLb start up, and the entire light is turned on. In the preheating of the electrodes FLa1, FLa2, and FLb1, FLb2, the constants of the parts are determined so that the preheating is sufficient within the prescribed time.

The oscillation state of the transistor inverter circuit 2 after the discharge lamps FLa and FLb is turned on is the same as in the conventional apparatus of FIG.

In addition, when the switch 15 is turned off while all the lights are turned on, the capacitor 14 is disconnected from the circuit, so that the combined capacitance connected in series with the secondary winding 8b of the current transformer is reduced and the LC resonance described above is reduced. Since the frequency of is increased, the on time of the main transistor 4 is shortened, and at the same time the oscillation frequency of the transistor inverter circuit 2 is increased, the discharge lamps FLa and FLb decrease the lamp current and the brightness of the lamp is reduced.

In addition, the discharge lamp FLa or FLb can not be discharged when the discharge lamp FLa, for example, the discharge lamp FLa becomes at the time of rectification lighting at the end of its life or when the electrode preheating is continued, therefore, the starting capacitor Ca, the discharge lamp FLb and A larger load current continues to flow to the ballast 3 than when the discharge lamps FLa and FLb are normally turned on, and the oscillation of the transistor inverter circuit 2 becomes abnormal. In this case, since the voltages at both ends of the discharge lamps FLa and FLb increase in the end-of-life states of the discharge lamps FLa and FLb, the detection circuit 17 detects the voltages at both ends of the discharge lamps FLa and FLb. In accordance with the output from the control circuit 13, the output of the transistor inverter circuit 2 is reduced so that the normal discharge lamp is turned on and the discharge lamp at the end of life cannot be turned on.

That is, when the switch 15 is turned off, the capacitor 14 is disconnected from the circuit, so that the combined capacitance connected in series with the secondary winding 8b of the current transformer is reduced, and the frequency of the above-described LC resonance is increased. Since the on period of 4) is shortened and the oscillation frequency of the transistor inverter circuit 2 is increased, the current flowing through the discharge lamps FLa and FLb is reduced.

As a result, since the current and voltage necessary to light the normal discharge lamps FLa and FLb are provided, discharge of the discharge lamp can be maintained. However, the discharge lamps FLa and FLb at the end of the lifetime are applied to the discharge lamp. The heat dissipation is prevented and radiation (normal lighting) cannot be maintained without the thermal transfer caused by the heating of the filament, and the electrode preheating continues.

Further, as described above, the control circuit includes electrode preheating means for preheating the electrodes of the discharge lamp with the same circuit, dimming means for dimming the discharge lamp, and control means for reducing the output of the transistor inverter circuit at the end of the life of the discharge lamp. It's both of them.

As described above, it is possible to easily distinguish the discharge lamp from the discharge lamp in the end of life state from the normal discharge lamp in appearance and protect the transistor inverter circuit.

In addition, since the transistor inverter circuit is self-explanatory, the circuit configuration is simple and the component number is small and inexpensive without requiring a special oscillation device.

Moreover, since the capacitor | condenser for DC blocking was provided, lighting of a discharge lamp can be stabilized.

In addition, since the control circuit serves as the electrode preheating means, the dimming means, and the control means, respectively, without sharing the respective means independently, the circuit configuration can be made simple and inexpensive.

In addition, in the above embodiment, the case where the discharge lamp lamp is composed of two is described, but the same effect is obtained even if three or more lamps are used.

In addition, although there was one discharge lamp in the end of life, one or more discharge lamps may be used.

Example 2

Fig. 2 is a circuit arrangement showing the discharge lamp lighting apparatus according to the first embodiment of the present invention. In this arrangement, in the first embodiment, the detection circuit 17 uses the secondary side auxiliary winding 3b of the ballast 3, the diode 21 for half-wave rectifying the output voltage output by the auxiliary winding 3b, and this diode. A condenser 22 for smoothing the half-wave rectified voltage by (21), a bidirectional trigger device 19 turned on by the smoothed voltage smoothed by the capacitor 22, and an on state of the bidirectional trigger device 19. It consists of a transistor element 18 which controls the control circuit by turning on the resistor 20 and the bidirectional trigger element 19 which limit the holding current to be held, and the rest of the configuration is the same as that in the first embodiment and the first embodiment. The same reference numerals are given to the same components as those of, and description thereof is omitted.

Next, the operation will be described.

In the configuration of FIG. 2, as in the first embodiment, when one of the discharge lamps FLa and FLb is discharged, for example, when the discharge lamp FLa is at the time of rectification or end of electrode preheating at the end of its life, the starting capacitor Ca, In the discharge lamp FLb and the ballast 3, a load current which is larger than the normal lighting of the discharge lamps FLa and FLb continues to flow.

As a result, a voltage higher than normal lighting occurs in the auxiliary winding 3b of the ballast 3, the voltage of the capacitor 22 changes, and the bidirectional trigger element 19 is turned on to operate the transistor 18. do. By the operation of the transistor 18, the switch 15 of the control circuit 13 is turned off, which is the same as that of the first embodiment.

The detection circuit detected as described above can be made simple and inexpensive.

Since this invention is comprised as mentioned above, the effect as described below is acquired.

DC power supply, transistor inverter circuit for converting DC voltage of this DC power source into high frequency voltage, several discharge lamps connected in series lit by this transistor inverter circuit, ballasts for limiting lamp currents of several discharge lamps, and the like A discharge lamp lighting device having a starter capacitor connected to both ends of a discharge lamp via an electrode and starting the discharge lamp by series resonance with the ballast, wherein at least one of the plurality of discharge lamps is in a state of end of life. When the end of the lifetime of the discharge lamp can maintain the discharge by the detection circuit for detecting the end of life and the output signal output from the detection circuit, the discharge lamp in the end of the life can not maintain the discharge to come to the electrode preheating state Since a control circuit for reducing the output of the transistor inverter circuit is provided, Even when the discharge lamp at the end of its life and the normal discharge lamp are mixed, it can be easily distinguished in appearance and can protect the transistor inverter circuit.

Moreover, since the capacitor | condenser for DC blocking which is connected between a ballast and a discharge lamp, and prevents a direct current flows, the discharge of a discharge lamp can be stabilized.

In addition, the transistor inverter circuit includes one transistor for switching, a feedback power source connected to the base of the transistor, an inductance element and a capacitor connected in series and self-resonating between the base and the emitter of the transistor. It can be simple and inexpensive.

The control circuit also serves as electrode preheating means for preheating the electrodes of the discharge lamp, dimming means for dimming the discharge lamp, and control means for reducing the output of the transistor inverter circuit at the end of the life of the discharge lamp. Therefore, the circuit configuration can be made simple and inexpensive.

The detection circuit includes a secondary winding on the secondary side of the ballast, a diode that half-wave rectifies the output voltage output from the secondary winding, a capacitor that smoothes the voltage half-wave rectified by the diode, and a smoothing voltage smoothed by the capacitor. The on-off is provided with a bidirectional trigger element, a resistor for limiting a holding current for holding the bidirectional trigger element on, and a transistor for controlling the control circuit by turning on the bidirectional trigger element, which is simple and inexpensive.

Claims (3)

DC power supply, transistor inverter circuit for converting DC voltage of this DC power source into high frequency voltage, several discharge lamps connected in series lit by this transistor inverter circuit, ballasts for limiting lamp currents of several discharge lamps, and the like A discharge lamp lighting device having a starter capacitor connected to both ends of a discharge lamp via an electrode and starting the discharge lamp by series resonant with the ballast, A detection circuit for detecting an end of life state when at least one of the plurality of discharge lamps is in an end of life state; The control signal outputs from the detection circuit reduces the output of the transistor inverter circuit so that the normal discharge lamp can maintain the discharge, but the discharge lamp in the end of life cannot maintain the discharge and becomes the electrode preheated state. Discharge lamp lighting device characterized in that it comprises a. The method of claim 1, A discharge lamp lighting device comprising a DC blocking capacitor connected between a ballast and a discharge lamp to prevent a DC current from flowing. The method of claim 1, The transistor inverter circuit includes one transistor for switching, a feedback power source connected to the base of the transistor, an inductance element connected in series and self-resonant between the base and the emitter of the transistor, and a discharge lamp. Lighting device.