JP2643961B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device for lighting a hot cathode discharge lamp such as a fluorescent lamp.

(Background Art) Fig. 3 shows a conventional discharge lamp lighting device (Japanese Patent Application No. 61-42620).
FIG. The DC power supply E is composed of a constant voltage power supply obtained by rectifying and smoothing an AC power supply. A series circuit of switching elements Q _1, Q ₂ consisting of the series transistors are connected via the switch SW ₁ to the DC power source E. The switching elements Q ₁ and Q ₂ are alternately turned on and off by the drive circuit unit 3. Also, at least a switching element
Q _1, one of the switching elements Q ₂ Q ₁ and the capacitor C in parallel
₁ , a series circuit of a discharge lamp 1 and an inductance element L is connected. The discharge lamp 1 is, for example, a hot cathode discharge lamp such as a fluorescent lamp, and has a pair of filaments f ₁ and f ₂ . The power supply side terminal of the filament f _1, f ₂ of the discharge lamp l, capacitor C ₂ is connected in parallel, the switch SW ₂ is connected to the non-power supply side terminal. The presence or absence of the discharge lamp l (whether the discharge lamp l is connected, or the discharge lamp l is whether or lit) no-load detecting circuit 1 for detecting the the diode D ₁ and the series of resistors R _1, R ₂ It is constituted by such as consisting circuit voltage dividing circuit, the non-power supply side terminal and a power supply E of the capacitor C ₁
Are connected between the negative terminals. The series resistance of the resistors R ₁ and R ₂ is set higher than the impedance of the discharge lamp 1. Discharge lamp l
Is not connected, the output of the no-load detection circuit 1 is at "Low" level, and when the discharge lamp 1 is lit,
The output of the no-load detection circuit 1 becomes "High" level. The oscillation output control unit 2 changes the operation of the drive circuit unit 3 when the output of the no-load detection circuit 1 becomes “Low” to stop the switching of the switching elements Q ₁ and Q ₂ , or The operation of the switching elements Q ₁ and Q ₂ is controlled so as to reduce the voltage applied to 1 (the voltage across the capacitor C ₂ ). Also, the output of the no-load detection circuit 1 is "Low".
When a level, i.e., the discharge lamp l If the area becomes unloaded, the preheating switch SW ₂ through a preheating switch operation circuit 5 is turned on.

Hereinafter, the operation of the conventional example shown in FIG. 3 will be described. Switch SW ₁ is turned on, the switching element Q ₁ and the DC power source E is applied by the drive circuit section 3, Q ₂ is turned on alternately,
Turned off. When the DC power supply E is applied, the switch SW ₂ is turned on by the timer circuit 4 via the preheating switch operation circuit 5 for a predetermined time. Then, a high-frequency current flows through the capacitor C ₁ , the filaments f ₁ and f _{2 of} the discharge lamp 1 and the inductance element L, and the filaments f ₁ and f ₂ are heated for a certain time. After a certain time, when the switch SW ₂ is turned off, the inductance element L, a high voltage of high frequency is applied by a resonant circuit consisting of the capacitor C _2, the discharge lamp l is lighted.

Here, when the discharge lamp 1 is removed and no load is applied, the output of the no-load detection circuit 1 becomes the “Low” level, and the inverter circuit stops via the oscillation output control unit 2 and the drive circuit unit 3, or the voltage across the capacitor C ₂ is controlled to be reduced. At the same time, preheat the switch SW ₂ is turned through a preheating switch operation circuit 5. Thereafter, when connected again discharge lamp l, a capacitor C _1, the switching element Q ₁ and the parallel-connected impedance elements Z, the inductance element L, filaments f _2, the switch SW _2, through the filament f _1, capacitor charge in the capacitor C ₁ via a closed circuit back to C ₁ is released. When the discharge lamp l is not connected, but the capacitor C ₁ is one that has been charged to the voltage of the DC power source E, the lamp l is connected, the charging voltage of the capacitor C ₁ is lowered by the discharge . The voltage drop of the capacitor C _1, the detection voltage of the no-load detecting circuit 1 is increased. This is because the voltage of the DC power source E is because has a voltage obtained by adding the charging voltage and the voltage across the no-load detecting circuit 1 of the capacitor C _1. When the detection voltage of the no-load detection circuit 1 increases, that is, "Hi
When the gh "level is reached, the operation of the oscillation output control unit 2 is released, the inverter circuit performs a normal oscillating operation, a high voltage is applied to the discharge lamp 1, and the discharge lamp 1 is turned on.

FIG. 4 is a circuit diagram of another conventional example. This circuit is omitted preheat switch SW ₂ in FIG. 3, instead, by a preheating winding n _2, n _3, n ₄ is provided to the inductance element L, the discharge lamp l _1, filaments f ₁ of l _2, The preheating of f ₂ , f ₃ and f ₄ is performed. Impedance elements Z ₂ and Z ₃ are connected in parallel to the respective discharge lamps l ₁ and l ₂ .

In this circuit, the output of the no-load detection circuit 1 is "Low"
If it is at the level, the oscillation output control unit 2 operates to reduce the output of the inverter circuit. When the discharge lamp l _1, l ₂ is connected, the capacitor C _1, the switching element Q ₁ connected in parallel with the impedance element Z _1, the inductance element L, filaments f _4, the impedance element Z _3, filaments f _3, f _2, the impedance element Z _2, filaments f _1,
Charge in the capacitor C ₁ via a closed circuit consisting of the capacitor C ₁ is discharged, the charging voltage of the capacitor C ₁ decreases. Like the conventional example of FIG. 3, the voltage drop of the capacitor C _1, the detection voltage of the no-load detecting circuit 1 increases, the operation of the oscillation output control unit 2 is released, the inverter circuit normal oscillation operation Then, the discharge lamp 1 is turned on by applying a high voltage.

However, as shown in FIG. 4, a configuration in which the preheating current is obtained from the secondary windings n ₂ , n ₃ , and n ₄ of the inductance element L, or a configuration in which the preheating current is obtained by using another preheating transformer. In the configuration, regardless of the presence or absence of the discharge lamps l ₁ and l ₂
From the capacitor C _1, the impedance element Z _1, the inductance element L, the winding n ₄ (or filaments f ₄₎ of the inductance element L, the impedance element Z _3, winding n ₃ of the inductance element L (or filaments f _3, f ₂ ), the impedance element Z _2, through the winding n ₂ (or filament f ₁₎ of the inductance element L, via a closed circuit back to the capacitor C _1, the charge of capacitor C ₁ is discharged, the discharge lamp l _1, l ₂
Output of the no-load detection circuit 1 is always “Hi”
gh "level. Therefore, no load detection cannot be performed as in the conventional example shown in FIG.

(Object of the Invention) The present invention has been made in view of the above points, and an object of the present invention is to simply detect the no-load of a discharge lamp supplied with a preheating current of a filament from a preheating winding. An object of the present invention is to provide a discharge lamp lighting device which can be realized by the configuration.

(Disclosure of the Invention) In the discharge lamp lighting device according to the present invention, in order to achieve the above object, as shown in FIG. 1 or FIG. A pair of switching elements Q ₁ and Q ₂ to be turned off are connected in series, and an impedance element Z ₁ capable of DC conduction is connected in parallel with at least one switching element Q ₁ and _one of the DC power supplies E A series circuit of an inductance element L and a hot cathode discharge lamp l ₁ , l ₂ is connected via a capacitor C ₁ having one end connected to the electrode, and a non-power supply terminal of the capacitor C ₁ and a DC power supply E are connected. A no-load detection circuit 1 for detecting a no-load state due to a voltage drop is connected between the other electrode and the filaments f ₁ , f ₂ , f ₃ , f _{4 of the} hot cathode discharge lamps l ₁ , l _2. Is the preheating winding n ₂ , n ₃ , n ₄
And a DC conduction element Z ₂ , Z ₃ connected between the non-power supply side terminals of the filaments f ₁ , f ₂ , f ₃ , f ₄ in a preheating winding n ₂ , n ₃ , n ₄ and filaments f ₁ , f ₂ , f ₃ , f ₄ , a DC blocking element (capacitors C ₃ , C ₄ , C ₅ or a diode) for blocking a DC discharge current from the capacitor C ₁
D ₂ , D ₃ , D ₄ ).

Thus, in the present invention, during the preheating winding n _2, n _3, n ₄ and the filament _{f 1, f 2, f 3} , f 4, the DC discharge current from the capacitor C ₁ because form a direct current blocking element blocking for, at the time of no load increases and the charging voltage of the capacitor C _1, in which the no-load state detection is performed by the voltage drop of the no-load detecting circuit 1.

 Hereinafter, examples of the present invention will be described.

FIG. 1 is a circuit diagram of one embodiment of the present invention. In this embodiment, portions having the same functions as those of the conventional example shown in FIG. 4 are denoted by the same reference numerals, and redundant description is omitted. The difference from the conventional example shown in FIG.
via n _2, n _3, respectively from the n ₄ capacitors _{C 3, C 4, C 5} , a point that is connected to the filament _{f 1, f 2, f 3} , f 4. Discharge lamp
_{When 1} , l ₂ is unloaded, capacitor C ₁ is connected to diode D ₁ ,
The battery is charged to the voltage of the DC power supply E via the resistors R ₁ and R ₂ .
Therefore, the output of the no-load detection circuit 1 becomes “Low” level, and the switching elements Q ₁ and Q ₂ are both turned off via the oscillation output control unit 2 and the drive circuit unit 3, and the output of the inverter circuit becomes zero. Or reduced.

When the discharge lamps l ₁ and l ₂ are not loaded, the capacitors C ₁ and
Impedance element Z ₁ , inductance element L, part 2
Secondary winding n ₄ , capacitor C ₅ , impedance element Z ₃ , secondary winding n ₃ of capacitor L ₃ , capacitor C ₄ , impedance element Z ₂ , capacitor C ₃ , inductance element L
There is a closed circuit that discharges the charge of the capacitor C ₁ through the secondary winding n ₂ and the capacitor C _1.
The _{C 3, C 4, C 5} , DC discharge current from the capacitor C ₁ is cut, the capacitor C ₁ is not discharged. While the charge in the capacitor C ₁ is transferred partially to the capacitor _{C 3, C 4, C 5} ,
It is so small that it is designed so that the output of the no-load detection circuit 1 does not change from "Low" level to "High" level. That is, the capacitors C ₁ and C ₃ , C ₄ , C ₅
Are selected such that C ₁ > C ₃ , C ₄ , C ₅ .

Therefore, when the discharge lamps l ₁ and l ₂ are not loaded, the capacitor C
Since there is no closed circuit to discharge _1, the output of the no-load detecting circuit 1 becomes "Low" level, the output of the inverter circuit remains limited. Here, when the discharge lamps l ₁ and l ₂ are connected again, the capacitor C ₁ , the impedance element Z ₁ , the inductance element L, the filament f ₄ , the impedance element Z ₃ , the filaments f ₃ and f ₂ , and the impedance element Z _2, filaments f _1, via a capacitor C _1, the charge of capacitor C ₁ is discharged, lowers the voltage of the capacitor C _1, the output of the no-load detecting circuit 1 becomes a "High" level, lights normally become.

Further, the filaments f ₂ and f ₃ on the common side of the discharge lamps l ₁ and l ₂ are
By connecting in series, such as impedance element Z ₂ , filament f ₂ , f ₃ , impedance element Z ₃ , only when all filaments f ₁ , f ₂ , f ₃ , f ₄ are connected, closed circuit to discharge the capacitor C ₁ can be configured, becomes effective when a multi-lamp lighting system as shown in Figure 1. For example, the discharge lamp l ₁ is connected, the discharge lamp l ₂ of the filament f ₄ is connected, if the filament f ₃ is not connected, the capacitor C _1, the impedance element Z _1, the inductance element L, filaments f _4, impedance element
Z _3, winding n ₃ of the inductance element L, a capacitor C _4, the impedance element Z _2, filaments f _1, via a capacitor C _1, although the charge of the capacitor C ₁ is to discharge the capacitor in the closed circuit since C ₄ is inserted in series, the charge of capacitor C ₁ is not discharged, the output of the no-load detecting circuit 1 becomes "Low" level, the output of the inverter circuit becomes limited voltage.

As described above, the capacitors C ₃ , C ₄ , and C ₅ prevent discharge of the charge of the capacitor C ₁ when the discharge lamps l ₁ and l ₂ are not connected, and change the output of the no-load detection circuit 1 to “ As shown in the embodiment of FIG. 2, instead of the capacitors C ₃ , C ₄ , C ₅ , the diodes D ₂ , D ₃ , D ₄
May be used. If any _one of the filaments f ₁ and f _{2 of} the discharge lamp l 1 and the filaments f ₃ and f ₄ of the discharge lamp l ₂ is not connected, the diodes D ₂ , D ₃ and D ₄
Closed circuit for charge and discharge of the capacitor C ₁ is not configured,
The output of the no-load detection circuit 1 becomes "Low" level, and the output voltage of the inverter circuit is limited.

In addition, as in the above embodiments, the inductance element L
When the preheating windings n ₂ , n ₃ and n ₄ are provided in the
Are low when the discharge lamp 1 is turned on and high when the discharge lamp 1 is preheated. The ratio, depending on the constant setting of the series resonant circuit of the inductance element L and the capacitor C _2, approximately doubles during preheating. Therefore, a sufficient preheating current flows during preheating, and the preheating current during lighting is reduced, thereby reducing filament loss.

(Effects of the Invention) As described above, the present invention relates to a discharge lamp lighting apparatus in which a hot cathode type discharge lighting is driven by an inverter circuit having a DC cut capacitor and its filament is preheated by a preheating winding. Since a DC blocking element for blocking a DC discharge current from the capacitor is interposed between the preheating winding and the filament, the capacitor is charged via a no-load detection circuit when no load is applied, The voltage of the no-load detection circuit drops, and the no-load state can be detected.With a simple configuration, the no-load state can be reliably detected, and malfunction due to current sneaking into the preheating winding is prevented. This has the effect of disappearing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a circuit diagram of one embodiment of the present invention, FIG. 2 is a circuit diagram of another embodiment of the present invention, FIG. 3 is a circuit diagram of a conventional example, and FIG. FIG. 9 is a circuit diagram of another conventional example. 1 is a no-load detection circuit, E is a DC power supply, Q ₁ and Q ₂ are switching elements, L is an inductance element, l ₁ and l ₂ are discharge lamps, f
₁ , f ₂ , f ₃ , f ₄ are filaments, n ₂ , n ₃ , n ₄ are preheating windings, C ₁ , C
Is _{2, C 3, C 4,} C 5 _{capacitors, D 1, D 2, D} 3, D 4 is a diode.

Claims (1)

(57) [Claims] A pair of switching elements that are alternately turned on and off at a predetermined cycle are connected in series to a DC power supply, and a DC-conducting impedance element is connected in parallel with at least one of the switching elements. A series circuit of an inductance element and a hot cathode type discharge lamp is connected via a capacitor having one end connected to one electrode of a DC power supply, and a non-power supply terminal of the capacitor is connected to the other electrode of the DC power supply. To a no-load detection circuit that detects a no-load condition due to a voltage drop, a hot cathode type discharge lamp filament is connected to a preheating winding, and a DC conduction element is connected between the non-power supply side terminals of the filament. A discharge lamp, wherein a DC blocking element for blocking a DC discharge current from the capacitor is interposed between the preheating winding and the filament. Light equipment.