JPH02123696A - Discharge lamp lighting apparatus - Google Patents

Abstract

PURPOSE:To prevent unpleasant blinking of a discharge lamp in its termination period and lower power source consumption at starting time of lighting by installing a circuit to detect the termination of a discharge lamp and lowering resonance electric current of an inverter with an output from the circuit. CONSTITUTION:A discharge lamp 20 is operated by high frequency sent from an inverter circuit 8. A detecting coil 28 is rolled on an inductor 19 for a ballast and a termination detecting circuit 55 and a resonance current lowering circuit 56 are successively connected to the inductor 19. The termination detecting circuit 55 is composed of capacitors 57, 58, resistors 59, 60, a Zener diode 61, and a transistor 62. A light-emitting part 65 of photocouplers 63, 64 forming a part of a resonance current lower circuit 56 is connected to a transistor 62. In termination period of a lamp, voltage of the detecting coil 28 rises, the light- emitting part 65 is electrically conducted, serial resonance current of the inductor 19 and the capacitor 23 is decreased, and the inverter circuit 8 is protected. Electric power source for abnormality detection of a discharge lamp is obtained from the detecting coil 28 therefore another safety circuit is not needed, resulting in save of electric power.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a discharge lamp lighting device that lights a discharge lamp at high frequency using an inverter circuit.

Conventional technology Generally, a pair of power switching transistors (main transistors) are used as a lighting device for discharge lamps such as fluorescent lamps.
A half-bridge type series inverter circuit is known.

Also known is a self-commutated type in which the output current of such a series inverter circuit is detected by a transformer and fed back to the base from the secondary winding of the transformer to alternately turn on and off the transistors. In such a lighting device, a discharge lamp as a load is connected to the output terminal of an inverter circuit via a current-limiting inductance.
In addition, a discharge lamp starting capacitor is connected in parallel with the discharge lamp. This example will be explained based on FIG.

First, a rectifier circuit 5 as a DC power source consisting of a diode bridge circuit 3 and a smoothing capacitor 4 (C,) is connected from a commercial power source 1 via a filter circuit 2 for surge absorption and noise prevention.

The rectifier circuit 5 is connected to an inverter circuit 8 including a pair of switching transistors 6.7 (Q, , Q,) connected in a 5EPP manner. This inverter circuit 8
is a so-called saturable current transformer type self-excited series inverter, and transformer 9 (T, ”) is a saturable type current transformer, with one primary winding W l 1 and two counter-wound secondary windings. Winding W, a.

W3b. The primary winding W I 1 is inserted in series with the output terminal of the inverter circuit 8, detects the load current flowing therein, and outputs two windings having opposite phases to each other in response to the load current flowing therein.
A secondary voltage is generated in each secondary winding wAW, a, W, b. Next, the secondary winding W 1 , a is connected to the base of the switching transistor 6 via a resistor 10 (R, a). Furthermore, a transistor 11 (Q,) and a diode 12 (D,), which are part of the safety circuit, are connected to the base of the switching transistor 6.
are connected. Further, the transistor 11 and the diode 12 are connected to the resistor 13 (Rb,) connected to the base of the transistor 11 and the transistor 11.
1 and an emitter resistor 14 (RE,) connected to the feedback circuit which sets the lamp secondary voltage required when lighting the discharge lamp. Furthermore, the other secondary winding Wsb
Similarly to the two large windings taW,a, it is connected to the base of the switching transistor 7 via a resistor 10 (R,b). Furthermore, the base of the switching transistor 7 is connected to a transistor l 5 which is part of the safety circuit.
(Q,) and the diode 16 (D4) are connected. Moreover, this transistor 15 and diode L6 are
A resistor 1 connected to the base of the transistor 15
7 (Rh, ) and an emitter resistor 18 (RE, ) connected to the transistor 15 constitute a feedback circuit that sets the lamp secondary voltage necessary for lighting the discharge lamp.

Next, the negative side DC output terminal of the rectifier circuit 5 is connected to the output terminal of the inverter circuit 8 via the primary winding mW of the current transformer 9 and the ballast inductor 19 (L4.) recognized as an inductance element. A discharge lamp 20 (F) is connected in an alternating current manner between the two. Here, capacitor 21.22 (C4,.

co) is a dividing capacitor, and capacitor 23 (C
4,) is for starting the discharge lamp 20.

Further, a series circuit connected between the positive side DC input terminal and the output terminal of the inverter circuit 8 and reaching the negative side DC terminal via a resistor 24 (R,) and a capacitor 25 (C,) in order; The starting circuit 27 of the inverter circuit 8 is activated by a relaxation oscillation circuit composed of a bidirectional thyristor 26 (SS) connected in series from the contact point of the resistor 24 and the capacitor 25 to the base of one of the switching transistors 7. It is formed.

Next, the ballast inductor 19 has a detection winding!
28 (L44) is wound. This detection winding 28 is connected to the base of a transistor 33 via a diode 29, resistors 30, 31, and a capacitor 32. The collector of this transistor 33 is connected to the anode of the 5CR 34, and is also connected via a resistor 35, 36 to a constant voltage power source 42 consisting of a resistor 37, a capacitor 38, a resistor 39, and a Zener diode 40, 41. Further, the emitter of the transistor 33 is connected to a resistor 43.
, a capacitor 44, and a Zener diode 45 to the gate of the 5CR34. In addition, the 5C
A resistor 46 is connected between the cathode and gate of R34, and the base of a transistor 47 and a resistor 48 are connected to the cathode. The collector of this transistor 47 is connected to the base of the transistor 7 of the inverter circuit 8.

Furthermore, a transistor 49 constituting a reset circuit is connected to the constant voltage 1'li source 42, and this transistor 49 is connected to a constant voltage conduction element 52 via a resistor 50 and a capacitor 51, and this constant voltage conduction element 52 is connected to the constant voltage conduction element 52. The element 52 is
The collector of this transistor 54, which is connected to the base of the transistor 54 via a resistor 53, is connected to the collector of said transistor 33.

In such a configuration, when the commercial power supply 1 is turned on,
This AC output is rectified by a rectifier circuit 5, and the DC is supplied to an inverter circuit 8, and is passed through a resistor 24 to a capacitor 25.
Charge is accumulated in the As a result, the potential at the connection point between the resistor 24 and the capacitor 25 rises, and when this exceeds the breakdown voltage of the bidirectional thyristor 26, the thyristor 26 becomes conductive and supplies base current to the switching transistor 7 on one side. The transistor 7 becomes conductive. The current flowing through this transistor 7 is
The current flows through the primary winding W18, the ballast inductor 19, the filament of the discharge lamp 20, and the starting capacitor 23, and is positively fed back to the base of the transistor 7 through the secondary winding W2b.

While this transistor 7 is in a conductive state, the primary winding #lW
, , increases with time, and the saturable transformer 9 eventually becomes saturated as the magnetic flux density within the core increases. Then, the induced voltage in the secondary windings W and b becomes zero, and the transistor 7 is turned off. Therefore, when the current flowing through the primary winding W i +, that is, the magnetomotive force against the core of the transformer 9 decreases, and becomes less than the level that saturates the core, a positive voltage is induced in the secondary winding WIa. ,
Transistor 6 turns on. This on state continues until the transformer 9 is saturated due to positive feedback via the primary winding W1° and the secondary windings W1, a. After that, transistors 6 and 7 are turned on alternately in the same way, and inverter circuit 8
continues to oscillate.

In the second state, when the discharge lamp 20 reaches the end of its life, the paralast inductor 1 connected to the discharge lamp 20
When the voltage of the detection winding 28 wound around the 5CR34 rises and the potential of the Zener diode 45 exceeds a predetermined value, the 5CR34
turns on, transistor 47 becomes conductive, shorting the base of transistor 7 of inverter circuit 8 and stopping its oscillation.

Also, at this time, since current flows through the resistors 35 and 36, the transistor 49 acting as a reset circuit is turned on, charging the capacitor 51 with a predetermined time constant, and after a predetermined time, the constant voltage conduction element 52 is turned on. , transistor 54
turns on, resets the 5CR 34, activates the startup circuit 27 as described above, and starts oscillation. however,
At this time, if the discharge lamp 20 has not yet been replaced, the Zener diode 45 is turned on again and oscillation is stopped.

Problems to be Solved by the Invention As mentioned above, each part of the circuit is protected by detecting the abnormal state of the discharge lamp 20 and stopping the oscillation of the inverter circuit 8. When the discharge lamp 20 reaches the end of its life, as a result of the safety circuit acting as described above, the discharge lamp 20 may repeatedly blink, causing discomfort to the user.

In addition, the power source of the safety circuit is a resistor 37, a capacitor 38,
Due to the constant voltage power supply 42 consisting of a resistor 39 and a Zener diode 4o141, even during normal lighting,
Another problem is that the constant voltage power supply 42 consumes a large amount of power.

Means for Solving the Problems An inverter circuit that is connected to a DC power supply and a starting circuit and performs high frequency output through semiconductor switching operation, a discharge lamp that is connected to an output terminal of the inverter circuit via an inductance element, and the inductance element. a detection winding wound around the inverter; an end-of-life detection circuit that detects the end of the life of the discharge lamp based on the voltage generated in the detection winding; It is constructed with a resonant current reduction circuit that reduces the resonant current of the circuit.

When an abnormality occurs in the discharge lamp, the resonant current reduction circuit reduces the resonant current in the inverter circuit, so the discharge lamp does not flicker, causing no discomfort to the user, and abnormal conditions in the discharge lamp can be detected. Part 1 from the winding! Since a power source can be obtained, the power consumed by the conventional safety circuit is not required even during normal lighting, and thus the structure is such that there is no power loss.

Embodiment A first embodiment of the present invention will be explained based on FIG. Components that are the same as those described in FIG. 3 are designated by the same reference numerals, and descriptions thereof will be omitted.

In this embodiment, an end-of-life detection circuit 55 for the discharge lamp 20 and a resonant current reduction circuit 56 for reducing the resonant current of the inverter circuit 8 are sequentially connected to the detection winding 28.

The end-of-life detection circuit 55 includes capacitors 57 (C, .
), 58, resistor 59 (R, ), 60, Zener diode 61 (ZD, □) and transistor 62 (Q, ,
). And the transistor 6
A light emitting portion 65 of a photocoupler 63, 64 (PQ, , PQ,), which is a part of the resonance current reduction circuit 56, is connected to 2. Light receiving section 66 of the photo coupler 63, 64
．． 67 is the secondary winding W and a of the transformer 9 along with diodes 68 and 69.

It is connected between W2b and the base of the transistor 11.15.

In such a configuration, when the discharge lamp 20 reaches the end of its life, the voltage level of the detection winding 28 increases compared to the normal state.
When the transistor 62 becomes conductive at the point where the terminal voltage of the capacitor 57 charged via the resistor 59 exceeds the Zener voltage of the Zener diode 61, the photocoupler 63.6
4's light emission 'f! l565 becomes conductive. Then, the light receiving section 6
Since the resistance value of 6.67 decreases, the base current of the switching transistor 6.7 decreases, and as a result, the series resonant current between the ballast inductor 19 and the starting capacitor 23 decreases, and the inverter circuit 8 is protected. Ru.

Note that when the series resonant current decreases, the voltage of the detection winding 28 wound around the ballast inductor 19 decreases;
If this voltage is set higher than the Zener voltage of the Zener diode 61, the transistor 62 can be maintained in a conductive state and a state in which the series resonant current is reduced can be maintained.

Furthermore, when the discharge lamp 20 is normally lit, the terminal voltage of the capacitor 57 is lower than the Zener voltage, so
Transistor 62 is never conductive, and there is no possibility of erroneously performing a detection operation. Furthermore, when the discharge lamp 20 is normal, a preheating current flows during startup, and at this time,
Although the voltage of the detection winding MA28 increases, if the time required for the charging voltage of the capacitor 57 to reach the voltage that turns on the Zener diode 61 is set to about several seconds, the detection operation will not be performed erroneously.

Next, a second embodiment of the present invention will be described based on FIG. In this embodiment, each ballast inductor 19
The three discharge lamps 20 connected in series with the inverter circuit 8
A different detection winding 28 is wound around each ballast inductor 19, and these detection windings 28 are connected in parallel to the end-of-life detection circuit 55 through diodes 70, 71, and 72. It is connected so that it can be input to.

With such a configuration, when one of the discharge lamps 20 reaches the end of its life or is removed, it operates in the same way as in the case described above.

Effects of the Invention As described above, the present invention comprises an inverter circuit that is connected to a DC power source and a starting circuit and performs high-frequency output through a semiconductor switching operation, and a discharge lamp that is connected to the output terminal of the inverter circuit via an inductance element. , a detection winding wound around the inductance element, an end-of-life detection circuit that detects the end of the life of the discharge lamp based on the voltage generated in the detection winding, and a response to the end-of-life detection output of the end-of-life detection circuit. and a resonant current reduction circuit that reduces the resonant current of the inverter circuit, so that when an abnormality occurs in the discharge lamp, the resonant current reduction circuit reduces the resonant current of the inverter circuit, so that the discharge lamp does not flicker. The lamp does not cause any discomfort to the user, and when the lamp is in an abnormal state, the power is obtained from the detection winding, so the power consumed by the conventional safety circuit is not required even when the lamp is lit normally. , This has effects such as no power loss.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a first embodiment of the invention, FIG. 2 is a circuit diagram showing a second embodiment of the invention, and FIG. 3 is a circuit diagram showing a conventional example. 5... DC power supply, 8... Inverter circuit, 19... Inductance element, 20... Discharge lamp, 27... Starting circuit, 28... Detection winding, 55... End of life detection circuit, 56... Resonant current reduction circuit application Person Tokyo Electric Co., Ltd.

Claims (1)

[Claims] An inverter circuit that is connected to a DC power supply and a starting circuit and performs high-frequency output through a semiconductor switching operation, a discharge lamp that is connected to the output terminal of the inverter circuit via an inductance element, and a detection winding that is wound around the inductance element. and an end-of-life detection circuit that detects the end of the life of the discharge lamp based on the voltage generated in the detection winding, and a resonant current of the inverter circuit is reduced in response to the end-of-life detection output of the end of life detection circuit. A discharge lamp lighting device characterized by comprising a resonant current reduction circuit.