JPH01186595A - Lighting device for electric discharge lamp - Google Patents

Abstract

PURPOSE:To surely detect the end of life of an electric discharge lamp and make stop control by conducting the end of life detection with detection coils additionary provided to an inductance element and by the difference of the voltage generated in each coil of these coils, and by making an action stop state corresponding to a detected output. CONSTITUTION:When either of electric discharge lamps 12 and 13 becomes the end of life, the voltage generated in detection coils 16 and 17 differs since the current flowing in choke coils 10 and 11 varies, and the voltage exceeding the given level preset is generated between terminals a and c. This voltage makes the transistor Tr 26 in an end of life detection circuit 23 to make an ON action via a diode 32. By this action, the thyristor 37 in a quenching circuit 24 is conducted, Tr 39 acts, and an inverter circuit 2 stops an oscillation action. And when the given time passes, a constant-voltage conduction element 47 is conducted by the charging voltage of a condenser 45, and Tr 43 makes an ON action. By this action, the quenching state in a circuit 2 is released with the thyristor 37 turned off and Tr 39 made off action.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a discharge lamp lighting device for lighting a discharge lamp at high frequency, and in particular to a discharge lamp lighting device that can detect the end of the life of a discharge lamp and stop high-frequency oscillation. Regarding.

[Prior Art] Generally, when lighting a discharge lamp at a high frequency, an inverter circuit is used to convert the commercial power frequency to a high frequency, and the high frequency is supplied to the discharge lamp via a choke coil.

In such a discharge lamp lighting device, there is a risk that the discharge lamp will be damaged when the discharge lamp reaches the end of its life, and there is also a risk that the semiconductor elements of the inverter circuit will be damaged.

Therefore, it is necessary to promptly detect when the discharge lamp reaches the end of its life and stop the operation of the device.

Conventionally, as a discharge lamp lighting device that performs such an operation, one is known that detects the high voltage at both ends of the discharge lamp or the high voltage at the choke coil to detect the end of the life of the discharge lamp.

However, such a device requires a special circuit for detecting high voltage, which increases the size of the device and increases the cost.

Conventionally, for example, as seen in Japanese Patent Application Laid-open No. 61-39492, a primary winding of a transformer is inserted between a plurality of parallel-connected discharge lamps and the output terminal of an inverter circuit, and the secondary winding is A device is known that detects the end of the life of a discharge lamp by detecting voltage.

However, in this case, for example, if only one of the discharge lamps reaches the end of its lifespan, the voltage changes will be subtle, so even if the discharge lamp reaches the end of its lifespan, it may not be possible to detect it. There was a problem that stable end-of-life detection was not possible.

[Problem to be solved by the invention] As described above, in the conventional device, when a plurality of discharge lamps are connected in parallel, there is a risk that it becomes difficult to detect the end of the life of the discharge lamp, and stable detection is not possible. was there.

Therefore, the present invention provides a detection winding for each inductance element inserted between the output terminal of an inverter circuit and a plurality of discharge lamps, and determines the difference in voltage generated in the detection winding. An object of the present invention is to provide a discharge lamp lighting device that can reliably detect the end of the life of a discharge lamp and control the operation of an inverter circuit to stop.

[Means for Solving the Problems] The present invention includes an inverter circuit that is connected to a DC power source and outputs high frequency oscillation by the switching operation of a semiconductor switching element, and an inverter circuit that is connected in parallel to the output terminal of this inverter circuit through an inductance element. When the difference between the connected discharge lamps, the detection winding attached to each inductance element, and the voltage generated in each detection winding exceeds a preset level, the discharge lamp is at the end of its life. It is composed of an end-of-life detection circuit that performs detection, and an oscillation stop circuit that maintains the oscillation operation of the inverter circuit in a stopped state in response to the end-of-life detection output of the end-of-life detection circuit.

Further, the present invention further includes a reset circuit for canceling the stop holding operation by the oscillation stop circuit at a predetermined cycle to the above configuration.

The present invention also provides a configuration of the end-of-life detection circuit when the difference between the voltages generated in each detection winding exceeds a preset predetermined level, and when the voltage level exceeds a preset reference level and This device is configured to detect the end of the discharge lamp's life when the discharge lamp continues for more than a certain period of time.

[Function] In the present invention having such a configuration, when the discharge lamp reaches the end of its life, it enters an abnormal state such as a half-wave discharge state, a broken filament state, a preheating state, and a short circuit state. However, the voltage generated between the detection winding attached to the inductance element connected to the discharge lamp that has reached the end of its life and the detection winding attached to the inductance element connected to the normal discharge lamp is Become different.

Therefore, when this voltage difference exceeds a predetermined level, it is determined that a voltage change has occurred due to the end of the life of the discharge lamp, and the end of life detection output is supplied to the oscillation stop circuit to stop and maintain the oscillation operation of the inverter circuit. . In this way, the discharge lamp is kept in an extinguished state.

Further, in the present invention, the oscillation-stopped state of the inverter circuit caused by the oscillation stop circuit is periodically released by the reset circuit. However, if the discharge lamp remains at the end of its lifespan, even if the oscillation stop state of the inverter circuit is released, the difference in voltage generated in each detection winding will still exceed a predetermined level, so the oscillation stop circuit will operate and the inverter will be switched off immediately. The oscillation operation of the circuit is stopped and maintained. However, when a discharge lamp at the end of its lifespan is replaced with a new discharge lamp, the difference in voltage generated in each detection winding becomes small, and the oscillation stop circuit no longer stops the oscillation of the inverter circuit. Therefore, simply by replacing the discharge lamp, the new discharge lamp will automatically start lighting.

Furthermore, in the present invention, for example, when the discharge lamps corresponding to each detection winding that detects a voltage difference simultaneously reach the end of their life and enter a preheating state or a short-circuit state, the difference in voltage generated in each detection winding is small. It will remain as it is. Therefore, it is difficult to detect the end of the discharge lamp's life from this difference.

However, in this case, the voltage itself generated in the detection winding becomes higher than that during normal lighting and exceeds a preset reference level. Moreover, this state continues for a long time, unlike when the discharge lamp is normally preheated.

Therefore, when this state continues for more than a set time, the end of the life of the discharge lamp is detected, and the oscillation operation of the inverter circuit is stopped and maintained by the oscillation stop circuit.

In this way, even if a plurality of discharge lamps reach the end of their lifespan at the same time, it can be reliably detected and the oscillation operation of the inverter circuit can be stopped.

[Example] An embodiment of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, an inverter circuit 2 is connected to a DC power source 1. Note that the DC power source 1 is obtained by rectifying and smoothing a commercial AC power source, for example.

The inverter circuit 2 has a series circuit of a pair of NPN transistors 3 and 4 as semiconductor switching elements connected in parallel with a series circuit of a pair of capacitors 5 and 6, and the base and emitter of each of the transistors 3 and 4 are connected in parallel. A pair of secondary windings 7S1 and 782 of the current feedback transformer 7 are connected between them via resistors 8 and 9, respectively. The connection point between the emitter of the transistor 3 and the collector of the transistor 4 is connected to one end of the primary winding 7P of the transformer 7, and the other end of the primary winding 7P is connected to the connection point of the capacitors 5 and 6. is used as the output terminal.

First and second discharge lamps 12.13 are connected to the output terminal of the inverter circuit 2 via choke coils 10.11, which are inductance elements, respectively.

That is, the first discharge lamp 12 has one end of its filament electrode 12a connected to the other end of the primary winding 7P of the current feedback transformer 7 via the choke coil 10, and the other end of the filament electrode 12b. One end is connected to the connection point of the capacitors 5 and 6. A capacitor 1 is connected between the other ends of each of the filament electrodes 12a and 12b.
4 is connected. Further, the second discharge lamp 13 connects one end of the filament electrode 13a to the primary winding 7P of the current feedback transformer 7 via the choke coil 11.
One end of the other filament electrode 13b is connected to the connection point of the capacitor 5.6.

A capacitor 15 is connected between the other ends of each of the filament electrodes 13a and 13t.

A detection winding 16.17 is attached to each of the choke coils 10.11, and one end of the detection winding 16 is connected to one end d of the detection winding 17 so that the polarities are opposite to each other. A voltage difference is generated between the other ends a and C of each of the detection windings 16 and 17.

In addition, a capacitor 19 is connected to the DC power supply 1 via a resistor 18.
and a parallel circuit of 20 resistors are connected.

A pair of Zener diodes 21 are connected to the parallel circuit.
22 series circuits are connected in parallel.

An end-of-life detection circuit 23, an oscillation stop circuit 24, and a reset circuit 25 are connected to the series circuit of each Zener diode 21, 22, respectively.

The end-of-life detection circuit 23 includes an NPN transistor 26.
, whose collector is connected to the positive terminal of the series circuit of each Zener diode 21 , 22 through a resistor 27 , 28 , and whose emitter is connected to the positive terminal of the series circuit of each Zener diode 21 , 22 through a resistor 29 and a capacitor 30 . .22
is connected to the negative terminal of the series circuit. Further, the transistor 26 has its base connected to a resistor 31 and a diode 32.
is connected to the other end a of the detection winding 16 via the polarity shown, and the resistor 31, diode 33, and Zener diode 34 are connected to the other end a of the detection winding 16 via the polarity shown.
6.17, and is connected to the other end C of the detection winding 17 via a parallel circuit of a resistor 35 and a capacitor 36, as well as the Zener diodes 21.
It is connected to the negative terminal of 22 series circuits.

The oscillation stop circuit 24 includes a three-terminal thyristor 37,
The anode of the thyristor 37 is connected to the positive terminal of the series circuit of each of the Zener diodes 21.22 through the resistor 27.28, and the cathode of the thyristor 37 is connected to the positive terminal of the series circuit of each of the Zener diodes 21.22 through the resistor 38. It is connected to the negative terminal and also to the base of the NPN transistor 39. Further, a resistor 40 is connected between the gate and cathode of the thyristor 37.

The transistor 39 has the resistor 38 connected between its base and emitter, and its collector connected to the base of the transistor 4 of the inverter circuit 2.

The emitter of the transistor 26 of the end-of-life detection circuit 23 is connected to the gate of the thyristor 37 via a Zener diode 41.

The reset circuit 25 includes a PNPN upper type resistor 42 and an N
A PN type transistor 43 is provided, and the transistor 42
The emitter of is connected to the positive terminal of the series circuit of each of the Zener diodes 21 and 22, and its base is connected to the resistor 27.
．． 28, and its collector is connected to the negative terminal of the series circuit of the Zener diodes 21 and 22 through a resistor 44 and a capacitor 45 in series.

Further, the collector of the transistor 43 is connected to the resistor 27.
28 to the positive terminal of the series circuit of each of the Zener diodes 21 and 22, and its base is connected to the connection point between the resistor 44 and the capacitor 45 through a resistor 46 and a constant voltage conduction element 47 in series. , and its emitter is connected to the negative terminal of the series circuit of each of the Zener diodes 21 and 22.

In this embodiment having such a configuration, the inverter circuit 2 outputs a high frequency, and the high frequency output is supplied to the first discharge lamp 12 via the choke coil 10 and to the second discharge lamp via the choke coil 11. is supplied to the discharge lamp 13. In this way, both electric lights 12 and 13 are turned on.

If both discharge lamps 12 and 13 are operating normally, the voltages generated in the detection windings 16 and 17 are approximately equal, and the voltages generated at terminals a and C are of opposite polarity, so terminal a , C, almost no voltage is generated between them. Therefore, the transistor 26 is in an off state, and the oscillation stop circuit 24 does not operate.2 Therefore, the reset circuit 2
5 also does not operate because the transistor 42 remains in O7.

In this state, if one of the discharge lamps reaches the end of its life and enters an abnormal state such as a half-wave discharge state, a thermal state, or a short circuit state, the current flowing through the choke coil connected to that discharge lamp changes. The voltages developed in the detection windings 16, 17 will now be different.

As a result, a large difference appears in the voltages generated in each detection winding 16, 17, and a voltage exceeding a predetermined level is generated between terminals a and C. This voltage is applied to diode 32
and is applied between the base and emitter of the transistor 26 of the end-of-life detection circuit 23 via the resistor 31. In this way, the transistor 26 is turned on.

When the transistor 26 turns on, a gate current flows through the Zener diode 41 to the gate of the thyristor 37 of the oscillation stop circuit 24, making the thyristor 37 conductive. Thus, the transistor 39 is turned on, shorting the base and emitter of the transistor 4 of the inverter circuit 2,
The oscillation operation of the inverter circuit 2 is stopped. This state is maintained by keeping the thyristor 37 conductive.

On the other hand, when the thyristor 37 becomes conductive, a current flows through the resistors 28 and 27, so that a base current flows into the transistor 42 of the reset circuit 25, turning the transistor 42 on.

As a result, a charging current flows through the capacitor 45 via the transistors 4.2 and the resistor 44 based on a predetermined time constant. Then, after a predetermined time has elapsed, the capacitor 4
The constant voltage conduction element 47 is made conductive by the charging voltage No. 5, and the transistor 43 is turned on.

By turning on the transistor 43, the thyristor 3
The anode and cathode of the thyristor 37 are short-circuited and the thyristor 37 is turned off.

In this way, the transistor 39 is turned off, and the oscillation stop state of the inverter circuit 2 is released.

However, if the discharge lamp has not yet been replaced at this time, the difference in voltage generated across each detection winding 16 and 17 will still be large, so the transistor 26 will immediately turn on, making the thyristor 37 conductive again and turning the transistor 39 on. Turn on and operate.

Therefore, even if the oscillation stop state of the inverter circuit 2 is released, if the discharge lamp is not replaced, the inverter circuit 2 will immediately go into the oscillation stop state.

In this way, when one of the discharge lamps reaches the end of its life, the oscillation operation of the inverter circuit 2 is reliably stopped, so there is no risk of the discharge lamp being damaged or the semiconductor elements such as the transistors 3 and 4 being damaged. There isn't.

When a discharge lamp at the end of its life is removed and a new one is installed, the thyristor 37 of the oscillation stop circuit 24 is turned off by the reset circuit 25, and when the oscillation stop state of the inverter circuit 2 is released, each detection winding Since the voltages generated by transistors 16 and 17 are approximately equal, transistor 26 will not be turned on this time.

When the discharge lamp is replaced with a new one, the reset circuit 25 releases the oscillation stoppage held by the oscillation stop circuit 24, and the inverter circuit 2 restarts the oscillation operation, thereby automatically starting the lighting operation.

Furthermore, when both discharge lamps 12 and 13 reach the end of their life at the same time and are in a preheated or short-circuited state, the voltages generated in each detection winding 16 and 17 are approximately equal, so the difference in voltage is small as in normal times. The transistor 26 is not turned on by differential voltage detection.

However, at this time, since the current flowing through the choke coils 10, 11 becomes large, the voltage itself generated in each detection winding 16, 17 becomes large. This voltage level then exceeds the Zener voltage of the Zener diode 34, which is the reference level. In this way, a charging current flows through the Zener diode 34, the diode 33, and the resistor 31 to the capacitor 36 based on a predetermined time constant. When the charging voltage of the capacitor 36 reaches a predetermined level, the transistor 26 turns on, thereby causing the thyristor 3
7 becomes conductive, the transistor 39 turns on, and the oscillation operation of the inverter circuit 2 is stopped. This prevents damage to the discharge lamp and damage to the transistor 3.4.

Note that when the discharge lamps 12 and 13 are in normal condition, a preheating current flows during startup, and at this time also the Zener diode 34
becomes conductive, but if you set the time for the charging voltage of the capacitor 36 to reach the voltage that turns on the transistor 26 to about several seconds, the discharge lamp will turn on and preheat in about 0.5 seconds under normal conditions. Since the current is stopped, there is no risk that the end-of-life detection circuit 23 will erroneously perform a detection operation.

In this way, even if one or both of the discharge lamps 12, 13 reach the end of their life, this can be reliably detected and the oscillation operation of the inverter circuit 2 can be stopped. In other words, a stable end-of-life detection operation is possible at all times.

Next, another embodiment of the invention will be described with reference to the drawings.

Note that the same parts as in the above embodiment are given the same reference numerals and detailed explanations will be omitted.

As shown in FIG. 2, a series circuit of a choke coil 51 and a third discharge lamp 52 is further connected between the output terminal of the inverter circuit 2 and the connection point of the capacitors 5 and 6.
Lights are connected in parallel. That is, one end of one filament electrode 52a of the third discharge lamp 52 is connected to one end of the current feedback transformer 7 through the choke coil 51.
It is connected to the other end of the next winding 7P, and one end of the other filament electrode 52b is connected to the connection point of the capacitors 5 and 6. And each filament electrode 52a, 52
A capacitor 53 is connected between the other ends of b.

Then, another detection winding 54 is attached to the choke coil 10 together with the detection winding 16, and the choke coil 5
1 is attached with a detection winding 55.

One end' of the detection winding 54 and one end f of the detection winding 55 are connected to each other, and connected to the transistor 26 through a Zener diode 56, a diode 57, and a resistor 31 in series.
is connected to the base of The other end a' of the detection winding 54
is connected to the base of the transistor 26 via the diode 58 and the resistor 31 in series. The other end e of the detection winding 55 is connected to the other end C of the detection winding 17.

In this embodiment, a comparison of the current flowing through the first discharge lamp 12 and the second discharge lamp 13 is carried out by means of a detection winding 16.17, which flows through the first discharge lamp 12 and the third discharge lamp 52. Since the comparison of currents is performed by the detection windings 54.55, when either of the discharge lamps 12, 13.52 reaches the end of its life, the difference in voltage occurring in the detection windings 16.17 or The difference in voltages occurring across the detection windings 54,55 increases beyond a predetermined level. Therefore, the transistor 26 of the end-of-life detection circuit 23 is turned on, and the oscillation stop circuit 24 stops and maintains the oscillation operation of the inverter circuit 2.

Further, when the first discharge lamp 12 and the second discharge lamp 13 reach the end of their lifespan at the same time and enter a preheating state or a short-circuit state, or when the first discharge lamp 12 and the third discharge lamp 52 reach the end of their lifespan at the same time. When the device becomes preheated or short-circuited,
Voltage generated in detection winding 16.17, detection winding 54.5
5 becomes larger than the reference level. When this state continues for more than a set time, the transistor 26 of the end-of-life detection circuit 23 is turned on, and the oscillation stop circuit 24 stops and maintains the oscillation operation of the inverter circuit 2.

Even when such three discharge lamps are used, the end of life can be reliably detected, and the same effects as in the embodiment described above can be obtained.

In addition, although the case where two discharge lamps were used and the case where three discharge lamps were used were described in the said Example, it is not necessarily limited to this, and four or more may be used.

[Effects of the Invention] Since the present invention is configured as described above, it produces the effects described below.

A detection winding is attached to each inductance element inserted between the output terminal of the inverter circuit and a plurality of discharge lamps, and the end of life is detected by detecting the difference in voltage generated in the detection winding. Therefore, the end of the life of each discharge lamp can be reliably detected and the operation of the inverter circuit can be controlled to stop.

In addition, a reset circuit is provided to periodically release the oscillation stop state of the inverter circuit caused by the oscillation stop circuit, so when a discharge lamp at the end of its life is replaced with a new discharge lamp, the lighting operation of the discharge lamp will be changed. It can be done automatically.

Furthermore, even if multiple discharge lamps reach the end of their lifespan at the same time, the voltage generated in the detection winding increases and continues, detecting the end of their lifespan and reliably stopping the oscillation operation of the inverter circuit. be able to.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the invention, and FIG. 2 is a circuit diagram showing another embodiment of the invention. 1... DC power supply, 2... Inverter circuit, 3.4.
...Transistor (semiconductor switching element), 10,
'll...Choke coil (inductance element),
12.13...discharge lamp, 16.17...detection winding,
23... End of life detection circuit, 24... Oscillation stop circuit, 25... Reset circuit. Applicant's agent Patent attorney Takehiko Suzue

Claims (3)

[Claims] (1) An inverter circuit connected to a DC power source and outputting high-frequency oscillation by the switching operation of a semiconductor switching element; a plurality of discharge lamps each connected in parallel to the output terminal of the inverter circuit via an inductance element; a detection winding attached to each inductance element, and an end-of-life detection circuit that detects the end of the life of the discharge lamp when the difference between the voltages generated in each of the detection windings exceeds a predetermined level; A discharge lamp lighting device comprising: an oscillation stop circuit that maintains the oscillation operation of the inverter circuit in a stopped state in response to the end-of-life detection output of the end-of-life detection circuit. (2) an inverter circuit that is connected to a DC power source and outputs high-frequency oscillation through the switching operation of a semiconductor switching element; a plurality of discharge lamps connected in parallel to the output terminals of the inverter circuit through inductance elements; a detection winding attached to each inductance element, and an end-of-life detection circuit that detects the end of the life of the discharge lamp when the difference between the voltages generated in each of the detection windings exceeds a predetermined level; An oscillation stop circuit that holds the oscillation operation of the inverter circuit in a stopped state in response to the end-of-life detection output of the end-of-life detection circuit, and a reset circuit that releases the stop holding operation by the oscillation stop circuit at a predetermined cycle. A discharge lamp lighting device characterized by comprising: (3) an inverter circuit that is connected to a DC power source and outputs high-frequency oscillation through the switching operation of a semiconductor switching element; a plurality of discharge lamps that are connected in parallel to the output terminals of the inverter circuit through inductance elements; When the difference between the detection winding attached to each inductance element and the voltage generated in each detection winding exceeds a preset predetermined level, and when the voltage level exceeds a preset reference level, and An end-of-life detection circuit that detects the end of the life of the discharge lamp when the discharge lamp continues for a preset time or more, and an end-of-life detection circuit that maintains the oscillation operation of the inverter circuit in a stopped state in response to the end-of-life detection output of the end-of-life detection circuit. A discharge lamp lighting device characterized by comprising an oscillation stop circuit.