JPH10106778A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device capable of preventing the deterioration of an inverter circuit in the final stage of the life of a discharge lamp by correctly stopping the operation of the inverter circuit or reducing output current in the final stage of the life of the discharge lamp. SOLUTION: A discharge lamp lighting device has an inverter circuit INV which is operated with a DC power source VDC and lights a discharge lamp La1 with high frequency, a control means 1 for controlling the inverter circuit INV, a detecting circuit 2 for detecting the rise of output voltage in the inverter circuit INV in the final stage of the life of the discharge lamp La1, and a comparing circuit Comp1 for comparing the tube voltage of the discharge lamp La1 detected with the detecting circuit 2 with the oscillation voltage of the inverter circuit detected with resistors R1, R2, and the life final stage of the discharge lamp and a no load state are judged with the comparing circuit Comp1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device, and more particularly to a discharge lamp lighting device for lighting a discharge lamp at a high frequency using a separately excited inverter circuit.

[0002]

2. Description of the Related Art In a discharge lamp lighting apparatus of this type, a detection of an output voltage of an inverter circuit in an end state of the discharge lamp life is performed, and the operation of the inverter circuit is stopped or the output current is reduced. In some cases, the inverter circuit is prevented from being damaged in the last state of the discharge lamp life.

[0003]

However, in such a conventional example, no consideration is given to an increase in the output voltage of the inverter circuit due to high-frequency noise generated in the no-load state, and the inverter in the no-load state is not considered. Since the output voltage of the circuit is close to the output voltage of the inverter circuit at the end of the life of the discharge lamp, there is a problem that a malfunction occurs in a no-load state.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to appropriately stop the operation of the inverter circuit or reduce the output current in the final state of the discharge lamp life, thereby reducing the discharge lamp life. An object of the present invention is to provide a discharge lamp lighting device capable of preventing deterioration of an inverter circuit in a terminal state.

[0005]

According to the first aspect of the present invention, there is provided an inverter circuit for converting a DC voltage to an AC high frequency voltage and supplying the AC high frequency voltage to at least one discharge lamp. And control means for controlling the oscillation of the inverter circuit, by comparing the square-wave oscillation voltage waveform of the inverter circuit with the tube voltage waveform of the discharge lamp,
The discharge lamp is characterized by distinguishing between an end-of-life state and a no-load state.

According to the second aspect of the present invention, when the phase shift occurs between the rectangular oscillation voltage waveform of the inverter circuit and the discharge lamp tube voltage waveform, and when the discharge lamp tube voltage exceeds a certain value, the discharge is started. An end-of-life state of the lamp is detected, and when the phase of the oscillation voltage waveform substantially matches the phase of the tube voltage waveform, a no-load state is detected.

According to a third aspect of the present invention, a detection signal obtained by detecting a tube voltage is synchronized with a drive signal of an inverter.

According to a fourth aspect of the present invention, a tube voltage at the time of rising of the drive signal of the inverter is detected.

According to a fifth aspect of the present invention, the tube voltage at the time of the falling edge of the drive signal of the inverter is detected.

According to a sixth aspect of the present invention, the inverter circuit lights a plurality of discharge lamps in parallel.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but they are merely exemplary embodiments adopted based on the present invention, and the present invention will be described based on matters unique only to the embodiments. It should not be construed as limiting, and the technical scope of the present invention should be determined based on the matters stated in the claims or matters substantially equivalent thereto.

(Embodiment 1) FIG. 1 shows a circuit diagram of a first embodiment according to the present invention.

This circuit includes, for example, a DC power supply VDC obtained by rectifying a commercial AC power supply (not shown), and a DC power supply VDC.
(Hereinafter, referred to as an inverter circuit) IN for operating the discharge lamp La1 at a high frequency by operating the inverter.
V, an Emiless detection circuit 2 for detecting an increase in the output voltage of the inverter circuit INV in an end-of-life state of the discharge lamp La1, and a capacitor C2 connected between the non-power-supply-side terminals of the discharge lamp La1.

The inverter circuit INV is a so-called half-bridge type circuit, and includes a series circuit of switching elements Q1 and Q2 and a series circuit of a capacitor C1 and an inductor L1 connected to both ends of the switching element Q2 via a discharge lamp La1. , And control means 1 for controlling the switching elements Q1 and Q2. The Emiless detection circuit 2 compares the tube voltage of the discharge lamp La1 with the diode D1 and the capacitor C3.
And the voltage is divided by the resistors R1 and R2, and the other end of the resistor R2 is grounded. In addition, the rectangular oscillation voltage of the inverter circuit INV is divided by the resistors R3 and R4. Note that the other end of the resistor R4 is grounded. The connection point between the resistors R1 and R2 is connected to the non-inverting input terminal of the comparison circuit Comp1, and the connection point between the resistors R3 and R4 is connected to the inversion input terminal of the comparison circuit Comp1. The output terminal of the comparison circuit Comp1 is
It is connected to a rectifying and smoothing circuit composed of a diode D2, a capacitor C4, and a resistor R5, and the output of the comparison circuit Comp1 is input to the control means 1 via the diode D2.

Next, the operation of this circuit will be briefly described with reference to FIG. 2 (a) to 2 (c) show voltage waveforms obtained by detecting the tube voltage of the discharge lamp La1 by the Emiless detector 2. FIG. 2A is a voltage waveform of the discharge lamp La1 in a normal lighting state. FIG. 2B shows a voltage waveform in a no-load state, which is a voltage waveform in which an oscillation waveform due to the floating capacitance of the circuit is superimposed on a rectangular oscillation voltage waveform of the inverter circuit INV. FIG. 2C is a voltage waveform in the end-of-life state of the discharge lamp La1, and shows a peak voltage higher than the normal lighting state of the discharge lamp La1. FIG. 2D shows that the rectangular-wave oscillation voltage of the inverter circuit INV is connected to the resistors R3 and R4.
, That is, the voltage VR4 across the resistor R4.
Is shown. FIG. 2E shows that the switching element Q2 is turned on,
This is a drive voltage waveform that is turned off, and FIG. 2F shows ON and OFF of the switching element Q2.

As shown in FIGS. 2A and 2C, the waveforms of the discharge lamp La1 in the normal lighting state and the end of life state are as follows.
Due to the resonance between the inductor L1 and the capacitor C1,
A phase shift occurs as compared with the oscillation voltage waveform of the inverter circuit INV. On the other hand, as shown in FIG. 2B, the voltage waveform in the no-load state has no phase shift. Here, by setting the voltage dividing ratio of the resistors R1 and R2 and the voltage dividing ratio of the resistors R3 and R4 to be substantially equal, the comparison circuit Com is set.
The output of p1 can be extremely low only under no load conditions. Accordingly, assuming that the input voltage in the no-load state is V1, the input voltage in the normal lighting state is V2, and the input voltage in the end state of the discharge lamp is V3, the input voltage to the control means 1 is V1 <V2 <V3.・ ・ (1) Further, the threshold voltage of the control means 1 is set to V4, and V2 <V4 and V3 is set.

As described above, with the above configuration, at the end of the life of the discharge lamp, the input voltage to the control means 1 becomes equal to or higher than the threshold voltage. Therefore, the control means 1 controls the oscillation frequency of the inverter circuit INV. It is possible to prevent the inverter circuit from deteriorating at the end of life of the discharge lamp, for example, by operating the discharge lamp La1 so as to reduce the current flowing therethrough. Further, it is possible to prevent a malfunction in a no-load state.

Embodiment 2 FIG. 3 shows a circuit diagram of a second embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 1 is that instead of the comparator Comp1, the diode D2, the resistor R5 and the capacitor C4, the emitter is connected to the connection point of the resistors R1 and R2. Switching element Q3
A diode D4 having an anode terminal connected to the collector of the switching element Q3, a resistor R6 having one end connected to the cathode terminal of the diode D4 and the other end grounded, and a capacitor C5 connected to both ends of the resistor R6.
And a diode D3 having a cathode terminal connected to a connection point of the resistors R3 and R4 and an anode terminal connected to a base terminal of the switching element Q3, and a voltage dividing ratio of the resistors R1 and R2 and a diode D3 of the resistors R3 and R4. The difference between the first and second embodiments is the same as that of the first embodiment, and the description is omitted by giving the same reference numerals.

(Embodiment 3) FIG. 4 shows a circuit diagram of a third embodiment according to the present invention.

The difference from the second embodiment shown in FIG. 3 is that the Zener diode ZD1 is connected between the connection point of the resistors R3 and R4 and the cathode terminal of the diode D3 to change the operating point. The same reference numerals are given to the same components as those of the second embodiment, and the description will be omitted.

(Embodiment 4) FIG. 5 shows a circuit diagram of a fourth embodiment according to the present invention.

The difference from the first embodiment shown in FIG. 1 is that instead of the resistors R3 and R4, the comparison circuit Comp1, the diode D2, the resistor R5 and the capacitor C4, they are connected in parallel to both ends of the resistor R2. A switch element SW1 that turns on and off in synchronization with the oscillation of the inverter circuit INV;
A resistor R7 and a capacitor C6 connected in parallel to both ends of the switch element SW1 via a diode D5 are provided. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted. I do.

Next, the operation will be briefly described. As described above, the voltage waveforms of the discharge lamp La1 in the normal lighting state and the end-of-life state are out of phase with the oscillation voltage waveform of the inverter circuit INV due to resonance between the inductor L1 and the capacitor C1, On the other hand, the voltage waveform in the no-load state has no phase shift. By utilizing this fact, the switching element SW1 turns off and on in synchronization with the turning on and off of the switching element Q2, so that the detected output voltage can be extremely reduced only in the no-load state. Thus, the voltage relationship shown in Expression (1) can be obtained.

(Embodiment 5) FIG. 6 shows a circuit diagram of a fifth embodiment according to the present invention.

The difference from the fourth embodiment shown in FIG. 5 is that instead of the switching element SW1, a switching element Q4 connected to both ends of a resistor R2 and a base-emitter of the switching element Q4 are connected. A switching element Q5 and a resistor R8 having one end connected to a base terminal of the switching element Q4, so that the switching element Q4 is turned off and on in synchronization with turning on and off of the switching element Q2. The description of the same components as those in the fourth embodiment will be omitted by retaining the same reference numerals. The control power supply voltage Vcc is supplied to the base terminal of the switching element Q4 via the resistor R8.

(Embodiment 6) FIG. 7 shows a circuit diagram of a sixth embodiment according to the present invention.

The difference from the fourth embodiment shown in FIG. 5 is that instead of the switch element SW1, the diode D5, the capacitor C6 and the resistor R7, a drive voltage waveform for turning on and off the switching element Q2 is received. And the instantaneous determination means 3 operable to detect the voltage value at the connection point of the resistors R1 and R2 at the time of rising of the pulse waveform and to output the detected voltage value to the control means 1. The other fourth embodiment The same components as those described above are denoted by the same reference numerals and description thereof will be omitted.

Next, the operation will be briefly described. As described above, the voltage waveforms of the discharge lamp La1 in the normal lighting state and the end-of-life state are out of phase with the oscillation voltage waveform of the inverter circuit INV due to resonance between the inductor L1 and the capacitor C1, On the other hand, the voltage waveform in the no-load state has no phase shift. Here, the instantaneous value determination means 3 turns on the switching element Q2 as described above,
In response to the drive voltage waveform to be turned off, the voltage value at the connection point of the resistors R1 and R2 at the time of rising of the pulse waveform is detected and the operation is performed so as to output to the control means 1. Therefore, the output voltage of the instantaneous value determination means 3 is , Can be made extremely low only in the no-load state, and the voltage relationship shown in equation (1) can be obtained. The drive voltage waveform applied to the instantaneous value determination means 3 may be a rectangular pulse signal synchronized with the on / off of the switching element Q2. In this case, the setting may be used instead of the rise of the rectangular pulse signal. The configuration may be such that a similar effect can be obtained at the time of falling.

As described above, the configuration as shown in all of the above-described embodiments makes it possible to prevent deterioration of the end-of-life state of the discharge lamp and to prevent malfunction in a no-load state. Become.

More specifically, in all of the above embodiments, when a plurality of discharge lamps are lit in parallel, it is possible to accurately distinguish between the end state of the discharge lamp life and the no-load state. Oscillation of the inverter circuit can be accurately stopped or the output can be reduced at the end of the life of the discharge lamp. Further, for example, even if only one lamp is in a no-load state, it is possible to perform normal lighting without affecting other discharge lamps, and it is possible not to impair the usability of the customer. 8 to 11 show circuit configurations for lighting three lamps in parallel.

The circuit shown in FIG. 8 uses the circuit shown in FIG. 1 so that three discharge lamps La1 to La3 are lit in parallel. The circuit shown in FIG. 9 employs the circuit shown in FIG. 3 so that three discharge lamps La1 to La3 are lit in parallel. The circuit shown in FIG. 10 uses the circuit shown in FIG. 5 so that three discharge lamps La1 to La3 are lit in parallel. The circuit shown in FIG. 11 uses the circuit shown in FIG.
To La3 in parallel. The circuit shown in FIG. 12 is configured so that three discharge lamps La1 to La3 are lit in parallel using the circuit shown in FIG.

In the above-described embodiment, the inverter circuit may use another circuit system, for example, a full-bridge system or a single-circuit system. The switching element Q and the switching element SW1 illustrated in FIGS. 1 to 12 may use, for example, a field-effect transistor or a bipolar transistor, or may use another configuration.

[0034]

According to the first and second aspects of the present invention, it is possible to accurately discriminate between the discharge lamp end-of-life state and the no-load state, and to accurately set the inverter in the discharge lamp end-of-life state. It is possible to provide a discharge lamp lighting device capable of stopping the operation of the circuit or reducing the output current and preventing the deterioration of the inverter circuit in the end state of the discharge lamp life.

According to the present invention, the input voltage to the control means can be extremely reduced only in the no-load state, so that the discharge lamp end-of-life state and the no-load state can be more accurately determined. In addition to being able to determine the state of the discharge lamp, it is also possible to stop the operation of the inverter circuit or reduce the output current accurately in the end state of the discharge lamp life, thereby preventing the deterioration of the inverter circuit in the end state of the discharge lamp. Equipment can be provided.

According to the sixth aspect of the invention, in addition to the effects of the first to fifth aspects of the present invention, for example, even if only one lamp is in a no-load state, other discharge lamps are affected. It is possible to provide a discharge lamp lighting device that can be normally lit without any trouble and that does not impair the usability of customers.

[Brief description of the drawings]

FIG. 1 shows a circuit diagram of a first embodiment according to the present invention.

FIG. 2 shows an operation waveform diagram according to the embodiment.

FIG. 3 shows a circuit diagram of a second embodiment according to the present invention.

FIG. 4 shows a circuit diagram of a third embodiment according to the present invention.

FIG. 5 shows a circuit diagram of a fourth embodiment according to the present invention.

FIG. 6 shows a circuit diagram of a fifth embodiment according to the present invention.

FIG. 7 shows a circuit diagram of a sixth embodiment according to the present invention.

8 is a circuit diagram showing a configuration in which three discharge lamps are lit in parallel using the circuit shown in FIG. 1;

FIG. 9 is a circuit diagram showing a configuration in which three discharge lamps are lit in parallel using the circuit shown in FIG. 3;

FIG. 10 is a circuit diagram showing a configuration in which three discharge lamps are lit in parallel using the circuit shown in FIG. 5;

FIG. 11 is a circuit diagram showing a configuration in which three discharge lamps are lit in parallel using the circuit shown in FIG. 6;

FIG. 12 is a circuit diagram showing a configuration in which three discharge lamps are lit in parallel using the circuit shown in FIG. 7;

[Explanation of symbols]

 INV Inverter circuit La Discharge lamp 1 Control means

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Yoshihiro Sakashita 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. (72) Inventor Koji Fujimoto 1048 Kadoma Kadoma, Kadoma City, Osaka Matsushita Electric Works

Claims (6)

[Claims] 1. An inverter circuit for converting a DC voltage to an AC high frequency voltage and supplying the AC voltage to at least one discharge lamp,
A discharge lamp lighting device comprising control means for controlling the oscillation of the inverter circuit, comprising: comparing a square-wave oscillation voltage waveform of the inverter circuit with a tube voltage waveform of the discharge lamp, thereby ending the life of the discharge lamp. A discharge lamp lighting device for distinguishing between a state and a no-load state. 2. The end of life of the discharge lamp when a phase shift occurs between a rectangular oscillation voltage waveform of the inverter circuit and a tube voltage waveform of the discharge lamp and the tube voltage of the discharge lamp becomes a predetermined value or more. 2. The discharge lamp lighting device according to claim 1, wherein a state is detected, and when a phase of the oscillation voltage waveform substantially coincides with a phase of the tube voltage waveform, a no-load state is detected. 3. The discharge lamp lighting device according to claim 1, wherein a detection signal obtained by detecting the tube voltage is synchronized with a drive signal of the inverter. 4. The discharge lamp lighting device according to claim 1, wherein the tube voltage is detected when the drive signal of the inverter rises. 5. The discharge lamp lighting device according to claim 1, wherein the tube voltage is detected when the drive signal of the inverter falls. 6. The discharge lamp lighting device according to claim 1, wherein the inverter circuit lights a plurality of discharge lamps in parallel.