JPH0521184A - High-frequency discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To eliminate an unpleasant feeling in a preventive operation and to improve the condition only by replacing the lamp with a normal lamp, by carrying out a protective operation of an inverter circuit from an abnormal condition of a lamp at the final phase of the service life only by separating a circuit in which the lamp current to be a load flows from the inverter circuit, instead of stopping the oscillation. CONSTITUTION:When a lamp 22 is in the normal condition, transistors 6 and 7 for oscillation are turned on and off alternatively to start the oscillation, and a voltage is generated from an oscillation transformer 4. And at the same time, when the charging voltage of a capacitor 30 exceeds the threshold value of a Zener diode 28, a transistor 23 is turned on, and the lamp 22 is made in the lighting condition through a relay 24. When the lamp 22 reaches the end of its service life in such a condition, the lamp voltage is increased by a half-wave discharge and it exceeds the threshold value of a Zener diode 19, and thereby, a thyristor 32 is made in the ON condition, a transistor 31 is also in the ON condition, and the potential of the capacitor 30 is lowered to the earthing voltage. As a result, the Zener diode 28 and the transistor 23 are also turned off to open the relay 24, and the voltage of the transformer 4 is cut off from the lamp 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency discharge lamp lighting device.

[0002]

2. Description of the Related Art In a high-frequency discharge lamp, when the lamp reaches the end of its life, the filament goes into the emitterless state on one side, and if oscillation is continued in this state, the output transformer is biased by a half-wave discharge current and lights up. This may adversely affect the circuit and the discharge lamp that is the load. Therefore, conventionally, a measure has been taken to stop the oscillation of the inverter circuit by detecting the end of the lamp life. FIG. 2 shows a conventional example of a high frequency discharge lamp lighting device. As shown in the figure, the AC current 1 is connected to the AC input terminal of the full-wave rectifier 2, and the smoothing capacitor 3 is connected to both ends of the DC output terminal of the full-wave rectifier 2. Is the power supply for the entire lighting device. The (+) side terminal of the full wave rectifier 2 is connected to the center tap of the primary winding a of the oscillation transformer 4 and is connected to the bases of the oscillation (switching) transistors 6 and 7 via the starting resistor 5 respectively. Connected via resistors 8 and 9. Oscillation transistors 6 and 7
Of the resonance transformer 1 is connected to both ends of the primary winding of the oscillation transformer 4, and is connected to both ends of the primary winding a.
0 is connected. Both ends of the base winding b of the oscillating transformer 4 are connected to the bases of the oscillating transistors 6 and 7, respectively, and an oscillating signal is input. Reference numeral 11 is a base drive circuit for driving the oscillating transistors 6 and 7. The base drive winding c for extracting a part of the output induced by the oscillation transformer 4 is connected to both ends of the smoothing capacitor 13 via a rectifying diode 12. It is connected to the. The (+) side terminal of the smoothing capacitor 13 is connected to the connection point of the starting resistor 5 and the base resistors 8 and 9 via the resistor 14, and the (-) side terminal is connected to the emitters of the oscillation transistors 6 and 7. And the (-) of the full-wave rectifier 2 via the inductance 15.
It is connected to the side terminal. Reference numeral 16 is a lamp abnormality detection circuit, in which a winding d for detecting a lamp abnormality from the voltage state of the oscillation transformer 4 is connected to the AC terminal of the full-wave rectifier 17, and a capacitor 18 is provided at both ends of the DC terminal of the full-wave rectifier 17. In addition to the connection, the gate of the thyristor 21 is connected to the (+) side of the DC terminal via the Zener diode 19 and the resistor 20. The anode of the thyristor 21 is connected to the connection point of the starting resistor 5 and the base resistors 8 and 9, and
The cathode of No. 1 is connected to the (-) side terminal of the full-wave rectifier 17 and the (-) side of the smoothing capacitor 13. In such a device, when power is turned on, the two oscillation transistors 6 and 7 are alternately turned on and off repeatedly, the oscillation transformer 4 starts oscillation, and the secondary winding e of the oscillation transformer 4 is started. A high voltage is generated at both ends, and the lamp 22 lights up. When the lamp 22 is normal in this lighting operation, the voltage generated in the lamp abnormality detection winding d is low and does not exceed the Zener voltage of the Zener diode 19, so that a base current cutoff circuit for the oscillation transistors 6 and 7 is formed. The gate current does not flow through the thyristor 21, and the thyristor 21 remains off. Therefore, the current supplied by the base drive winding c of the base drive circuit 11 flows to the bases of the oscillation transistors 6 and 7 through the resistor 14 and the base resistors 8 and 9 to connect stable oscillation, and the lamp 22 is It keeps lighting. When the lamp 22 reaches the end of its life and the filament on one side is in the emitterless state, the lamp 22 becomes a half-wave discharge, and the lamp voltage rises significantly. Therefore,
Since the voltage generated in the lamp abnormality detection winding d also rises and exceeds the Zener voltage of the Zener diode 19, a gate current flows in the thyristor 21, the thyristor 21 is turned on, and the base currents of the oscillation transistors 6 and 7 are cut off. Then, the oscillation operation is stopped and the lamp 22 is turned off. When the thyristor 21 is turned on, the current of the full-wave rectifier 2 flows through the thyristor 21 via the starting resistor 5, and
The charged electric charge is supplied to the smoothing capacitor 13 of the base drive circuit 11. Here, if the current flowing through the starting resistor 5 is set to be equal to or less than the holding current of the thyristor 21, the holding current of the thyristor 21 flows through the resistor 14 using the output of the base driving winding c as a power source, but the base driving is performed by the oscillation stop. The winding c cannot supply power and the thyristor 21
Is held by the electric charge charged in the smoothing capacitor 13, and when the smoothing capacitor 13 is discharged, the thyristor 21 cannot hold the ON state. As a result, the inverter circuit enters the initial state and starts to oscillate again, and the lamp 22 lights up. However, the lamp abnormality detection circuit 16 turns on the thyristor 21 again to stop the oscillation of the inverter, and thereafter, the above operation is repeated. The lamp 22 blinks until the lamp 22 is replaced.

[0003]

The prior art described above detects the end of life of the lamp and protects the inverter circuit from the abnormal state, and resets the protection operation only by replacing the end of life lamp with a normal lamp. However, since the protection operation is intermittent oscillation, the lamp blinks, which is uncomfortable. The present invention has been made in view of the above points, and it is possible to eliminate the discomfort during the protection operation and reset the protection operation only by replacing the end-of-life lamp with a normal lamp. It is an object of the present invention to provide a high-frequency discharge lamp lighting device as described above.

[0004]

The above object is to provide an oscillation transformer of an inverter circuit that supplies the output of a power supply unit to an oscillation transformer through a collector circuit of a switching transistor and generates a high frequency output on the output side of the oscillation transformer. A base drive circuit that takes out the output from a part of the output winding of rectifying and smoothes it to supply the base current to the switching transistor, a relay that connects the output voltage of the oscillation transformer to the lamp of the load, and an abnormal state at the end of the lamp life. The lamp abnormality detection circuit that detects the current, the preheating current detection circuit that detects the presence or absence of the filament preheating current of the lamp, and the output of the lamp abnormality detection circuit shut off the excitation current of the relay and disconnect the output voltage of the oscillation transformer from the lamp. It consists of a circuit that turns off the lamp at the end of its life, and resets the retention of the excitation current interruption of the relay. By performing the output of the heat current sensing circuit is achieved. That is, the protection of the inverter circuit from the abnormal state at the end of the lamp life is not to stop the oscillation but to disconnect the circuit through which the lamp current of the lamp, which is the load, flows from the output of the inverter circuit. Further, the protection operation is reset by detecting the presence or absence of the filament preheating current of the lamp.

[0005]

Since the above means is provided, the lamp can be continuously turned off during the protection operation, and the lamp can be normally turned on by simply replacing the lamp with a normal lamp. That is, when the excitation current of the relay that connects the output voltage of the oscillation transformer of the inverter circuit to the lamp is cut off by the output of the lamp abnormality detection circuit that detects the abnormality of the lamp, the circuit in which the lamp current flows is disconnected from the inverter circuit. The lamp goes off. As a result, it is possible to eliminate the adverse effect that the oscillating transformer is demagnetized due to the DC discharge generated at the end of the lamp life, which adversely affects the inverter circuit and the lamp. At this time, the inverter circuit continues to oscillate, and current continues to flow in the filament preheating circuit connected to the output side of the oscillation transformer.By detecting the filament preheating current, the output of this preheating detection circuit causes the relay It is possible to maintain the interruption of the exciting current of. Here, when the end-of-life lamp is replaced with a normal lamp, the filament of the lamp is removed from the filament preheating circuit, the preheating current is interrupted, the output of the preheating current detection circuit is lost, and interruption of the relay exciting current cannot be maintained. As a result, the relay operates again, the output voltage of the oscillation transformer is connected to the lamp, and the lamp shifts to normal lighting.

[0006]

EXAMPLES Next, the present invention will be specifically described by way of examples. FIG. 1 shows an embodiment of the present invention. In addition,
Since the same parts as those in the past are designated by the same reference numerals, the description thereof will be omitted. In the present embodiment, the output winding of the oscillation transformer 4 of the inverter circuit that supplies the output of the power supply unit to the oscillation transformer 4 via the collector circuits of the switching transistors 6 and 7 and generates a high frequency output on the output side of the oscillation transformer 4. A base drive circuit 11 which takes out an output from a part of the line, rectifies and smoothes it, and supplies a base current to the switching transistors 6 and 7.
A relay 24 for connecting the output voltage of the oscillation transformer 4 to the lamp 22 of the load; a lamp abnormality detection circuit 16 for detecting an abnormal state at the end of life of the lamp 22; and preheating for detecting the presence or absence of filament preheating current of the lamp 22. The output of the current detection circuit 25 and the lamp abnormality detection circuit 16 causes the relay 2
Circuit for shutting off the exciting current of No. 4 and disconnecting the output voltage of the oscillating transformer 4 from the lamp 22 to turn off the lamp 22 at the end of its life. The preheating current detecting circuit 25 resets the holding of the exciting current of the relay 24. Output. By doing so, the lamp 22 is continuously turned off during the protection operation, and the lamp 22 is switched to the normal lighting simply by replacing the lamp 22 with the normal lamp. It is possible to obtain a high-frequency discharge lamp lighting device capable of performing only by replacing the lamp with a normal lamp. In this embodiment, the thyristor for interrupting the base current used in the conventional example is deleted. In addition, the smoothing capacitor 1 of the base drive circuit 11
Connect the collector of the transistor 23 to the (+) side of 3,
The emitter is the capacitor 1 via the excitation winding f of the relay 24.
3 is connected to the (−) side terminal. In addition, the capacitor 13
The resistor 26 connected to the (+) side terminal of is connected to the (−) side terminal of the capacitor 13 via the resistor 27, and
A Zener diode 28 is connected to the base of the transistor 23 via a resistor 29 at the connection point between the resistors 27 and 26. A capacitor 30 is connected to both ends of the resistor 27, and the collector of the transistor 31 is an emitter.
Furthermore, they are connected via the anode and cathode of the thyristor 32. Full wave rectifier 17 of lamp abnormality detection circuit 16
The (+) side terminal of is connected to the gate of the thyristor 32 via the Zener diode 19 and the resistor 20. The preheating current detection circuit 25 is used for the current transformer 3 inserted in the preheating circuit.
Full wave rectifier 34 with AC terminals connected to 3 and its output winding
And a capacitor 35 connected between the DC terminals of the full-wave rectifier 34, the (+) side terminal of the full-wave rectifier 34 is connected to the base of the transistor 31 via a resistor 36,
The (−) side terminal is connected to the cathode of the thyristor 32. Further, the contact of the relay 24 is installed between the secondary winding e of the oscillation transformer 4 and the lamp 22. When the lamp 22 is in a normal state when the power is turned on in the above circuit configuration, the oscillation transistors 6 and 7 are alternately turned on and off repeatedly to start oscillation as in the conventional case, and the oscillation transformer 4 is turned on. When a voltage is generated across the secondary winding e and the charging voltage of the capacitor 30 exceeds the zener voltage of the zener diode 28, the transistor 23 is turned on, a current flows through the exciting winding f of the relay 24, and the contact g is When closed, the lamp 22 lights up. Further, since the lamp 22 is normal, the voltage generated in the lamp abnormality detection winding d is low and does not exceed the Zener voltage of the Zener diode 19, so that the gate current of the thyristor 32 does not flow and the thyristor 32 is in the off state. Therefore, the current supplied by the base drive winding c continues to flow in the exciting winding f of the relay 24, and the base currents of the transistors 6 and 7 are also supplied via the resistor 14 and the base resistors 8 and 9 to achieve stable oscillation. And the lamp 22 continues to light. As described above, when the lamp 22 reaches the end of its life, the voltage generated in the lamp abnormality detection winding d also increases as the lamp voltage increases due to the half-wave discharge, and the thyristor 32 is turned on when the voltage exceeds the Zener voltage of the Zener diode 19. Becomes At this time, the preheating current is flowing in the current transformer 33 of the preheating current detection circuit 25, and the output thereof causes the transistor 31 to pass through the resistor 36.
Is driven by the base, and the transistor 31 is also in the ON state. Therefore, the potential of the capacitor 30 becomes the ground potential, the Zener diode 28 is turned off, and the transistor 23 is also turned off. Therefore, the exciting current of the relay 24 is cut off, the contact g is opened, the secondary voltage of the oscillation transformer 4 is disconnected from the lamp 22, and the lamp 22 is turned off. Since the inverter continues to oscillate and the preheating current continues to flow even after the lamp 22 is turned off, the transistor 31 continues to be in the ON state as described above, and the holding current of the thyristor 32 supplies the base drive circuit with power. As resistance 26
Since the transistor 23 is in the OFF state, the contact g of the relay 24 continues to open and the lamp 22 is continuously turned off. When the lamp 22 is replaced with a normal lamp, the preheating current is temporarily cut off when the lamp is replaced, so that the output of the preheating current detection circuit is lost and the transistor 31 is turned off. Therefore, the holding current of the thyristor 32 stops flowing, the thyristor 32 is turned off, the inverter circuit is in the initial state, the relay 24 operates again, and the lamp 22 lights up. According to this embodiment, when the lamp 22 reaches the end of its life, the inverter circuit and the lamp 22 can be protected by continuously extinguishing the lamp 22 without causing unpleasant blinking.
The protection operation can be reset simply by replacing the lamp 22 with a normal lamp. Further, in this embodiment, a time constant circuit is formed by the resistors 26 and 27 and the capacitor 30, and when the power is turned on, the inverter starts oscillating and the lamp 22 is preheated sufficiently before the contact point g of the relay 24 is reached. Is closed and the lamp 22 is turned on, the flashing life of the lamp 22 can be extended. As described above, according to this embodiment, since the protection operation at the end of the lamp life is performed by continuously turning off the lamp, the discomfort of the lamp blinking is eliminated, and the protection operation can be reset only by replacing the lamp with a normal lamp. You can

[0007]

As described above, according to the present invention, there is no sense of incongruity during the protection operation, and the protection operation can be reset only by replacing the end-of-life lamp with a normal lamp. It is possible to obtain a high-frequency discharge lamp lighting device capable of eliminating the unpleasant sensation and resetting the protection operation by simply replacing the end-of-life lamp with a normal lamp.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a high frequency discharge lamp lighting device of the present invention.

FIG. 2 is a circuit diagram of a conventional high-frequency discharge lamp lighting device.

[Explanation of symbols]

1 ... AC power supply 2 ... Full wave rectifier 4 ... Oscillation transformer 6, 7 ... Oscillation transistor 11 ... Base drive circuit 16 ... Lamp abnormality detection circuit 22 ... Lamp 24 ... Relay 25 ... Preheat current detection circuit

Claims (1)

Claim: What is claimed is: 1. An inverter circuit for supplying an output of a power supply unit to an oscillation transformer via a collector circuit of a switching transistor to generate a high frequency output on the output side of the oscillation transformer. A base drive circuit that takes out an output from a part of the output winding and rectifies and smoothes it to supply a base current to the switching transistor, a relay that connects the output voltage of the oscillation transformer to a lamp of a load, and a life end of the lamp. A lamp abnormality detection circuit that detects an abnormal state, a preheating current detection circuit that detects the presence or absence of filament preheating current of the lamp, and an output of the lamp abnormality detection circuit that shuts off the exciting current of the relay and outputs the output of the oscillation transformer. It consists of a circuit that disconnects the voltage from the lamp and turns off the lamp at the end of its life. High-frequency discharge lamp lighting apparatus, characterized in that resetting of the holding current interruption by the output of the preheating current sensing circuit.