JP2001093690A - Discharge lamp lighting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp lighting apparatus, capable of surely detecting a failure at the end of the life of a discharge lamp and securely protecting circuits, and capable of being miniaturized, at a low cost. SOLUTION: This discharge lamp lighting apparatus is comprised of a rectifying/smoothing circuit 1 for rectifying/smoothing a DC power supply, a self-exciting inverter circuit 2 including a load circuit consisting of a series circuit of two switching elements Q1 and Q2 connected between the output ends of the rectifying/smoothing circuit 1 and a current transformer CT connected to both ends of the switching element Q2, etc., a service life end detecting circuit 8 having a smoothing capacitor C5 discharged with a current generated in a secondary coil n22 of the current transformer CT and Zener diode Zd3 for monitoring the voltage at both ends of the smoothing capacitor C5, and a service life end holding circuit 7 for holding the output control condition of the inverter circuit 2, when an irregular condition is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a discharge lamp lighting device.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram of a first conventional discharge lamp lighting device according to the present invention.

This circuit comprises a rectifying / smoothing circuit 1 for rectifying / smoothing an AC power supply (AC), and an inverter circuit 2 for converting a DC voltage output of the rectifying / smoothing circuit 1 into an AC high-frequency voltage and supplying it to a discharge lamp La. Be composed.

The rectifying and smoothing circuit 1 includes diodes D1 and D2.
And a series circuit of smoothing capacitors C1 and C2.

[0005] The inverter circuit 2 is a so-called self-excited half-bridge inverter circuit, which is composed of field effect transistors (hereinafter, referred to as switching elements) Q1 and Q2 connected between the output terminals of the rectifying and smoothing circuit 1. It comprises a series circuit, a load circuit connected to both ends of the switching element Q2, and a drive circuit for the switching element Q1 and the switching element Q2. The load circuit includes a primary winding n1 of the current transformer CT, a current limiting choke L1, and a capacitor C
3, a discharge lamp La, and a preheating capacitor C4 connected between the non-power-supply-side terminals of the discharge lamp La, and a current-limiting choke L1 and a capacitor C4 constitute a resonance circuit. The capacitor C3 is a coupling capacitor. The drive circuit of the switching element Q1 includes a series circuit of a resistor R1 connected between the gate and the source of the switching element Q1 and the secondary winding n21 of the current transformer CT, and a Zener connected between the gate and the source of the switching element Q1. And a diode ZD1. Switching element Q
The drive circuit of No. 2 is the same as the drive circuit of the switching element Q1.

A current limiting choke L1 and a capacitor C
3, a temperature fuse TP is connected to the inverter circuit 2. The temperature fuse TP is opened to protect the inverter circuit 2 and the like when the temperature of the current limiting choke L1 rises at the end of the life of the discharge lamp La. .

FIG. 5 is a circuit diagram of a second conventional discharge lamp lighting device according to the present invention. In the first conventional example shown in FIG. 4, the life of the discharge lamp La is detected by the temperature fuse TP. However, in the present conventional example, the end-of-life detection circuit 4 composed of a switching element, a capacitor, and the like is used. Is configured to detect the end of life of the discharge lamp La. Therefore, the same components as those of the first conventional example are denoted by the same reference numerals, and description thereof is omitted. Note that a gate extraction circuit 3 for extracting the gate voltage of the switching element Q2 is connected between the output of the end-of-life detection circuit 4 and the gate of the switching element Q2.

The end-of-life detecting circuit 4 includes a current transformer CT.
Are connected to both ends of the secondary winding n22.
22 → diode D3 → resistor R3 → smoothing capacitor C5
Charge the smoothing capacitor C5 through the path of
It has a configuration in which c5 is monitored by a Zener diode ZD3. That is, when the discharge lamp La is normal, the charging voltage Vc
Since the reference numeral 5 does not reach the on-voltage of the Zener diode ZD3, a bipolar transistor Q3 (hereinafter referred to as a switching element) having a smoothing capacitor C5 connected between its base and emitter via the Zener diode ZD3 and the like, and its base. The bipolar transistor Q4 (hereinafter, referred to as a switching element) in which Q3 and the like are connected between the emitters is turned off. When the switching element Q4 is turned off, a bipolar transistor Q6 (hereinafter, referred to as a switching element) connected between the gate and the source of the switching element Q2 and a bipolar transistor Q5 (hereinafter, referred to as a switching element) connected between the base and the emitter of the switching element Q6. , Switching elements) are turned off, so that switching element Q2 continues its normal operating state. On the other hand, at the end of the life of the discharge lamp La, the current flowing through the current transformer CT increases, so that the voltage Vc5 increases. When the voltage Vc5 exceeds the ON voltage of the Zener diode ZD3, the gate voltage of the switching element Q2 is pulled out by turning on the switching elements Q3 to Q6, and the switching element Q2 is turned off. Therefore, the oscillation frequency of the inverter circuit 2 increases, the output of the inverter circuit 2 is suppressed, and the inverter circuit 2 and the like are protected.

FIG. 6 is a circuit diagram of a third conventional discharge lamp lighting device according to the present invention. In the first conventional example shown in FIG. 4, the life of the discharge lamp La is detected by the temperature fuse TP.
The end of life of the discharge lamp La is detected by the end of life detection circuit 6 constituted by C1 or the like. The same reference numerals are given to the same components as those of the first conventional example, and the description is omitted. I do. Note that a gate extraction circuit 3 is connected between the output of the end-of-life detection circuit 6 and the gate of the switching element Q2 as in the second conventional example. In this conventional example, the voltage generated in the current limiting choke L1 is compared by the comparator IC1, and when an abnormality such as the end of the life of the discharge lamp La occurs, the output of the inverter circuit 2 is suppressed and the inverter circuit 2 and the like are protected. Make up.

[0010]

However, the first to third conventional examples have the following problems.

In the first conventional example, it is necessary to provide the temperature fuse TP so that heat conduction from the object to be detected (here, the current limiting choke L1) can be smoothly performed, and the installation of the temperature fuse TP is complicated. turn into. Further, once the temperature fuse TP operates, it takes time until the temperature fuse TP returns.

A solution to the problem of the first conventional example is shown in the second and third conventional examples. However, in the second conventional example, when the voltage Vc5 reaches the ON voltage of the Zener diode ZD3, the switching element Q
2, the output of the inverter circuit 2 can be suppressed, but if the output is suppressed too much, the voltage Vc5 falls below the on-voltage of the Zener diode ZD3. That is, the output cannot be sufficiently suppressed in order to operate the Zener diode ZD3.
a is required, resulting in an increase in the size of the device.

Further, in the third conventional example, a circuit or a device for supplying a constant DC voltage is required as a power supply for driving the comparator IC1, which leads to an increase in the number of components and an increase in the size of the device. .

SUMMARY OF THE INVENTION The present invention has been made in view of all of the above problems, and an object thereof is to reliably detect an abnormal state such as the end of life of a discharge lamp and to surely protect a circuit. Accordingly, it is an object of the present invention to provide a low-cost discharge lamp lighting device that can be downsized.

[0015]

According to the first aspect of the present invention, there is provided a self-excited inverter circuit comprising at least one switching element, and a high frequency voltage supplied from the inverter circuit. A discharge lamp and an abnormality detection circuit for detecting an abnormal state of a self-excited inverter circuit, a discharge lamp, etc., and an abnormal state is detected in a discharge lamp lighting device that suppresses the output of the inverter circuit when the abnormal state is detected. And a holding circuit for holding a state in which the output of the inverter circuit is suppressed.

According to a second aspect of the present invention, in the discharge lamp lighting device according to the first aspect, the abnormality detection circuit detects an end of life of the discharge lamp.

According to a third aspect of the present invention, in the discharge lamp lighting device according to the first or second aspect, the abnormality detection circuit has at least a zener diode.

According to a fourth aspect of the present invention, in the discharge lamp lighting device according to any one of the first to third aspects, the inverter circuit has a current transformer, and the abnormality detection circuit has a current flowing through the current transformer. Is detected.

According to a fifth aspect of the present invention, in the discharge lamp lighting device according to any one of the first to third aspects, the inverter circuit has an inductor, and the abnormality detection circuit detects a current flowing through the inductor. It is characterized by that.

According to a sixth aspect of the present invention, in the discharge lamp lighting device according to any one of the first to third aspects, the inverter circuit has a resonance circuit including an inductor and a capacitor, and the abnormality detection circuit. Is for detecting a current flowing through the inductor.

According to a seventh aspect of the present invention, in the discharge lamp lighting device according to any one of the first to third aspects, the abnormality detection circuit detects a voltage across the discharge lamp. And

According to an eighth aspect of the present invention, in the discharge lamp lighting device according to any one of the first to third aspects, the abnormality detection circuit detects the potential of the high potential side terminal of the discharge lamp. There is a feature.

According to a ninth aspect of the present invention, in the discharge lamp lighting device according to the first aspect, the holding circuit includes a thyristor.

According to the tenth aspect of the present invention, the first aspect is provided.
In the discharge lamp lighting device described above, the holding circuit has a thyristor formed by an npn transistor and a pnp transistor.

According to the eleventh aspect, a rectifying / smoothing circuit for rectifying / smoothing an AC power supply, a series circuit of two switching elements connected between output terminals of the rectifying / smoothing circuit,
A current transformer connected to both ends of one switching element and a load circuit including a resonance circuit and a discharge lamp,
A self-excited inverter circuit that converts a DC voltage output of a rectifying / smoothing circuit into an AC high frequency voltage and supplies it to a discharge lamp by alternately turning on and off two switching elements according to a current flowing through a primary winding of a current transformer. And a smoothing capacitor charged by the current generated in the secondary winding of the current transformer, and a zener diode for monitoring the voltage across the smoothing capacitor. An abnormality detection circuit for detecting the abnormal state, when the abnormal state is detected, the discharge lamp lighting device that suppresses the output of the inverter circuit,
A discharge lamp lighting device comprising: a thyristor; and a holding circuit for holding a state in which an output of an inverter circuit is suppressed when an abnormal state is detected.

[0026]

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

The difference from the first, second and third conventional examples is that a thyristor constituted by an npn transistor (hereinafter referred to as a switching element) Q3 and a pnp transistor (hereinafter referred to as a switching element) Q4. And an end-of-life detection circuit 8 having a smoothing capacitor C5 and the like. The same components as those of the conventional example are denoted by the same reference numerals and description thereof is omitted.

The operation of the discharge lamp La in an abnormal state such as at the end of its life will be briefly described below. The end-of-life detection circuit 8
The smoothing capacitor C5 is connected to both ends of the secondary winding n22 of the current transformer CT, and charges the smoothing capacitor C5 through a path of the secondary winding n22 → the diode D3 → the resistor R3 → the smoothing capacitor C5. The charging voltage Vc5 is applied to the Zener diode ZD3. Has a configuration for monitoring. When the discharge lamp La is normal, the charging voltage Vc5 does not reach the ON voltage of the Zener diode ZD3, so that the switching elements Q3 to Q6 are turned off via the Zener diode ZD3 and the like, and the switching element Q2 changes to the normal operating state. continue. On the other hand, when the discharge lamp La is abnormal, such as at the end of its life, the current flowing through the current transformer CT increases, so that the voltage Vc5 increases. When the voltage Vc5 exceeds the on-voltage of the Zener diode ZD3, the switching elements Q3 and Q4 are turned on, and the secondary winding n22 →
The capacitor C6 is charged through the path of the switching element Q4 → the resistor R10 → the capacitor C6. The charging voltage Vc6
Exceeds the ON voltage of the switching element Q5, the switching element Q5 and the switching element Q6 are turned on to turn off the switching element Q2 and increase the oscillation frequency of the inverter circuit 2. When the oscillation frequency of the inverter circuit 2 increases, the output of the inverter circuit 2 is suppressed.
The current flowing through the current transformer CT decreases, and the voltage Vc5
Drops. However, since the collector current of the switching element Q4 is also supplied to the base of the switching element Q3 through the path of the switching element Q4 → the diode D4 → the switching element Q3, even if the voltage Vc5 falls below the on-voltage of the zener diode ZD3, the switching element Q3 ,
Q4 can maintain the ON state, and can maintain output suppression of the inverter circuit 2.

On the other hand, by turning off the power or removing the discharge lamp La, the on state of the switching elements Q3 and Q4 can be released. That is, the protection state of the inverter circuit 2 can be released.

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

The difference from the first embodiment is that a load circuit is connected to both ends of the switching element Q1 and the discharge lamp L
a is provided with an end-of-life detection circuit 9 for detecting the voltage at both ends of terminal a (or the terminal potential on the high potential side of the discharge lamp La). The description will be omitted by attaching. That is, when the discharge lamp La enters an abnormal state such as the end of life, the lamp voltage increases, and the smoothing capacitor C5 is charged through the path of the diode D3 → the resistor R3 → the smoothing capacitor C5.

With the configuration as shown in all of the above embodiments, the output of the inverter circuit 2 can be reliably suppressed in an abnormal state such as the end of the life of the discharge lamp. Or the temperature of the filament of the discharge lamp La can be prevented, and the inverter circuit 2 and the like can be reliably protected. Further, since the output of the inverter circuit 2 can be sufficiently suppressed (see FIG. 3), the detection voltage (for example, the voltage across the smoothing capacitor C5) in the end-of-life detection state can be suppressed low, so that the power supply can be restarted. It is possible to suppress erroneous detection of a discharge lamp in a normal state at the time of turning on, and to obtain a highly reliable detection circuit.

The inverter circuit 2 may be of a single type or of another type, and may be any type of self-excited inverter. In addition, the embodiment according to the present invention is not limited to the above-described embodiments, and any one that can provide the operational effects of the present invention is provided.
The above embodiments may be appropriately combined.

[0034]

According to the first to eleventh aspects of the present invention, the output of the inverter circuit can be reliably suppressed in an abnormal state such as the end of the life of the discharge lamp.
An increase in the temperature of the filament of the inverter circuit and the discharge lamp La can be reliably prevented, and the protection of the inverter circuit and the like can be reliably performed, so that a small-sized discharge lamp lighting device can be provided at low cost. In addition, since the output of the inverter circuit can be sufficiently suppressed, the detection voltage in the end-of-life detection state can be kept low, so that erroneous detection of the discharge lamp in the normal state when the power is turned on again is suppressed. And a highly reliable detection circuit can be obtained.

[Brief description of the drawings]

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

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

FIG. 3 is an operation explanatory view of the embodiment according to the present invention.

FIG. 4 shows a circuit diagram of a first conventional example according to the present invention.

FIG. 5 shows a circuit diagram of a second conventional example according to the present invention.

FIG. 6 shows a circuit diagram of a third conventional example according to the present invention.

[Explanation of symbols]

 2 Inverter circuit 7 Holding circuit 8, 9 Abnormality detection circuit La Discharge lamp Q Switching element ZD Zener diode

Claims (11)

[Claims] 1. A self-excited inverter circuit comprising at least one switching element, a discharge lamp supplied with a high-frequency voltage from the inverter circuit, and an abnormality detection for detecting an abnormal state of the self-excited inverter circuit, the discharge lamp, and the like. A discharge lamp lighting device that suppresses the output of the inverter circuit when an abnormal state is detected, and a holding circuit that holds a state in which the output of the inverter circuit is suppressed when an abnormal state is detected. Discharge lamp lighting device characterized by the above-mentioned. 2. The discharge lamp lighting device according to claim 1, wherein the abnormality detection circuit detects an end of life of the discharge lamp. 3. The discharge lamp lighting device according to claim 1, wherein the abnormality detection circuit has at least a zener diode. 4. The inverter circuit according to claim 1, wherein the inverter circuit has a current transformer, and the abnormality detection circuit detects a current flowing through the current transformer. Discharge lamp lighting device. 5. The discharge circuit according to claim 1, wherein the inverter circuit has an inductor, and the abnormality detection circuit detects a current flowing through the inductor. Lighting device. 6. The inverter circuit includes a resonance circuit including an inductor and a capacitor, and the abnormality detection circuit includes:
The discharge lamp lighting device according to any one of claims 1 to 3, wherein a current flowing through the inductor is detected. 7. The discharge lamp lighting device according to claim 1, wherein the abnormality detection circuit detects a voltage between both ends of the discharge lamp. 8. The discharge lamp lighting device according to claim 1, wherein the abnormality detection circuit detects a potential of a high-potential terminal of the discharge lamp. 9. The discharge lamp lighting device according to claim 1, wherein the holding circuit has a thyristor. 10. The discharge lamp lighting device according to claim 1, wherein the holding circuit has a thyristor formed by an npn transistor and a pnp transistor. 11. A rectifying and smoothing circuit for rectifying and smoothing an AC power supply, a series circuit of two switching elements connected between output terminals of the rectifying and smoothing circuit, and a current transformer connected to both ends of one of the switching elements. And a load circuit comprising a resonance circuit and a discharge lamp, and by alternately turning on and off the two switching elements according to the current flowing through the primary winding of the current transformer, the DC voltage output of the rectifying / smoothing circuit is provided. A self-excited inverter circuit that converts the voltage into an AC high-frequency voltage and supplies the voltage to the discharge lamp; a smoothing capacitor charged by a current generated in a secondary winding of the current transformer; and a Zener that monitors the voltage across the smoothing capacitor. And an abnormal state of the inverter circuit or the discharge lamp is detected by turning on / off the Zener diode. A discharge lamp lighting device that includes a thyristor and suppresses the output of the inverter circuit when an abnormal condition is detected. A discharge lamp lighting device comprising a holding circuit for holding.