JPH0542637Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improvement of a DC discharge lamp lighting device.

[Prior Art] Generally, a DC discharge lamp lighting device, commonly called a ballast, is used to light a DC discharge lamp, such as an ultra-high pressure mercury lamp. In the past, this ballast had a major drawback of being heavy, but recently, ultra-compact and lightweight ballasts that employ a semiconductor element opening/closing control system have been developed.

FIG. 2 is a conventional circuit diagram showing a design example of the ballast that employs a semiconductor element opening/closing control method;
To explain this with reference to FIG. 2, the AC power supply 1 is connected to the semiconductor switching elements TR 1 and ₁ through a rectifying and smoothing circuit 11 consisting of a rectifying element D ₅ and a smoothing element C ₄ .
TR ₂ and an inverter 10 constituted by a transformer T ₁ , and one 2A of the two secondary side output parts of the transformer T ₁ is connected to a rectifier D ₁ ;
A smoothing circuit 4 consisting of a high frequency choke coil L ₁ and a capacitor C ₁ is connected to the rectifier D 1 via a current detection element 3 connected to the negative side of the rectifier D ₁ .
The positive output terminal of the smoothing circuit 4 is connected to one side of a discharge lamp (hereinafter referred to as a lamp) _{6 via a diode D 6} to prevent current from flowing to the capacitor C ₁ when the starter 5 is activated. , the negative output terminal of the smoothing circuit 4 is connected to the other end of the lamp 6. Here, from inverter 10, 20 to 100KHz
Since a high frequency alternating current is outputted, a chiyoke coil suitable for high frequencies is used as the smoothing circuit 4. Further, 5 is a starter, which has a power supply 13, and one terminal of this power supply 13 is connected to a switch SW for starting (starting lamp lighting) and a resistor _R2.
and diode _D4 are connected to the positive terminal of capacitor _C3 , and the other terminal of power supply 13 is connected to the capacitor C3.
Connected to the negative terminal of C ₃ . and capacitor
_C3 to thyristor TH, transformer _T2 , diode
D ₃ are connected in sequence, further through diode D ₃ ,
Connected to capacitor _C2 for high voltage generation. Then, the dielectric breakdown voltage of the lamp 6 is charged to the capacitor _C2 .

During stable lighting, the lamp 6 is lit by the main circuit constituted by the inverter 10, rectifier _D1 , and smoothing circuit 4. Therefore, in order to design this main circuit most economically, stable lighting is carried out. The output voltage of the main circuit therein is set to the rated voltage of the lamp 6 or close to it. However, as it is, the transition from glow discharge to arc discharge seen at the beginning of lamp startup, that is, the ignitability of the lamp at startup, cannot be said to be good, and therefore the capacitor C ₁
A high voltage superimposition circuit 12 is connected to both ends of the high voltage superimposing circuit 12 . This high voltage superimposition circuit 12 is normally composed of a transformer, a rectifier, a resistor, and a superimposition capacitor (generally, it also serves as a smoothing capacitor), but in the example shown in FIG. It is configured by providing an output section 2B in T ₁ ,
One end thereof is connected to the positive side of the capacitor C ₁ forming the smoothing circuit 4 through a series circuit of a rectifier diode D ₂ and a resistor R ₁ , and the other end is connected to the negative side of the capacitor C ₁ . It is composed of
That is, in this example, the transformer _T1 is shared for the main circuit and the high voltage superimposition circuit, and the capacitor
_C1 is commonly used for the smoothing circuit and for high voltage superimposition.

On the other hand, the signal from the current detection element 3 is sent as a feedback signal to a pulse width control circuit 8 consisting of an error amplifier EA connected to a reference voltage source Vref and a pulse width converter PWM connected to an oscillator OSC. The switching pulse widths of the semiconductor switching elements TR ₁ and TR ₂ are increased or decreased through the drive circuit 9, and the current supplied to the lamp 6 is controlled to be constant.

The lamp 6 controls the operation of this lighting circuit with the above configuration.
Taking the case of using a 40V, 250W ultra-high pressure mercury lamp as an example, when the switch SW in the starter 5 is turned on, the capacitor _C3 is charged via the resistor _R2 and the diode _D4 . When the charging voltage of capacitor C ₃ reaches the breakdown voltage of thyristor TH, capacitor C ₃ is discharged, and this discharge voltage is boosted by transformer T ₂ and transferred to capacitor C ₂ via diode D ₃ . It will be charged. Then, when the charging voltage of capacitor C ₂ reaches the dielectric breakdown voltage of lamp 6, capacitor C ₂ is discharged,
The lamp 6 undergoes dielectric breakdown. This breakdown voltage is approximately 800V in this case. Following this dielectric breakdown, a large amount of charge is released from the capacitor _C1 , causing the lamp 6 to shift from glow discharge to arc discharge.

Then, after the voltage between the electrodes of the lamp 6 decreases,
A current is supplied from the 2A section of the transformer _T1 , and the lamp 6 goes to a stable state.

This timing chart is shown in FIG. Third
The figure is a timing chart showing the relationship between time and lamp current in the conventional method and in this invention. In FIG. 3, a solid curve A shows the change in the current of the lamp 6 in the conventional lighting device, and shows the change in the current of the lamp 6 in the conventional lighting device.
When the lamp 6 undergoes dielectric breakdown at to, approximately
A large current flows for 1 μsec, almost no lamp current flows for the next 1 μsec, and then the lamp current gradually flows from capacitor _C1 until a stable state is reached.

[Problem to be solved by the invention] In the conventional lamp lighting device as described above, _the capacitor _C2 in the starter discharges and dielectric breakdown occurs. is discharged to produce a peak current of approximately 20A. Then, the charge is discharged from the capacitor C ₁ charged by the superimposition circuit, and a current flows. However, this inheritance is not always carried out well, and after the charge from the capacitor C ₂ is discharged, the charge is discharged into the lamp. There may be a lack of flowing current, causing the device to turn off.

The reason for this is that the discharge distance between the electrodes becomes longer due to manufacturing variations in the main lamps. In such a case, even if the starter causes dielectric breakdown, the voltage across the lamp will not drop to a level that is sufficient to discharge the capacitor _C1 , and for a certain period of time, the lamp current will be almost negligible, as shown by curve A in Figure 3. It becomes a state where it does not flow. Therefore, after the charge is released from capacitor C ₂ in the starter, capacitor C ₁
No charge is released from the lamp, and the lamp will go out due to lack of current.

This idea was made to solve this problem. After the capacitor in the starter discharges and dielectric breakdown occurs between the lamp electrodes, the lamp current continues to flow and does not turn off, resulting in stable lighting. It is an object of the present invention to provide a discharge lamp lighting device that achieves the following conditions.

[Means for Solving the Problems] In order to achieve the above object, the starter in the discharge lamp lighting device of this invention includes a high voltage generation capacitor connected in parallel with the discharge lamp, and this capacitor and the discharge lamp. It is equipped with a chiyoke coil connected between electric lights.

[Function] With the above configuration, the initial current flowed by the energy of the starter is stored in the inductance by the inductance of the chiyoke coil and continues to flow _gradually . can be migrated.

[Embodiment] Fig. 1 is a circuit diagram showing a schematic configuration of the main parts of an embodiment of the discharge lamp lighting device of this invention _.
is a chiyoke coil connected in series with the lamp,
Other structures with the same reference numerals as in FIG. 2 and operations thereof are the same as in FIG. 2. Curve B indicated by a dotted line in FIG. 3 is a timing chart showing the relationship between time and lamp current in the device of FIG.

In the device shown in FIG. 1, when the switch SW is turned on to light the lamp 6, the capacitor _C3 is charged via the resistor _R2 and the diode _D2 .
Then, the charging voltage of capacitor _C3 is applied to the thyristor.
When the breakdown voltage of TH is reached, the capacitor C ₃ is discharged, and the discharge voltage is boosted by the transformer T ₂ and charged to the capacitor C ₂ via the diode D ₃ . Then, when the charging voltage of capacitor C ₂ reaches the breakdown voltage of lamp 6,
The capacitor C ₂ discharges and breaks down the insulation between the two electrodes of the lamp 6, but the lamp 6 has a chiyoke coil.
Since _L2 is connected, a large current flows instantaneously as shown by curve A in Fig. 3, and the current hardly stops flowing immediately after that, but the lamp current gradually flows and rises for the first time. Following this dielectric breakdown, a large amount of charge is released from the capacitor _C1 , causing the lamp 6 to transition from a glow discharge to an arc discharge. In this state, as shown by curve B in Fig. 3, there is a cascade of discharge from the capacitor C ₂ due to dielectric breakdown against the lamp 6, and a cascade of discharge from the capacitor C ₁ due to the open voltage. but,
Energy is temporarily stored by the inductance of the choke coil L ₂ (70 μH in this case) and gradually flows to the lamp 6 and rises, and the energy is transferred to the capacitors C ₂ and C _1.
A stable current value is reached by smoothly transitioning to a continuous discharge current.

Conventionally, due to variations in the manufacturing process of lamps, there was a relatively high probability that the lamp would go out due to the long discharge distance between the electrodes. By connecting the chiyoke coil _L2 in series with the lamp 6, the probability of the lamp not lighting due to extinguishing has become extremely low.

[Effects of the invention] As explained above, the starter in the discharge lamp lighting device of this invention consists of a high voltage generation capacitor connected in parallel with the discharge lamp, and a chiyoke coil connected between the capacitor and the discharge lamp. Since the initial current discharged by the energy of the starter is accumulated in the inductance by the inductance of the choke coil and continues to flow gradually, it is possible to smoothly transition to the main discharge current. .

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing a schematic configuration of the main parts of an embodiment of the discharge lamp lighting device of this invention, FIG. 2 is a circuit diagram of a conventional discharge lamp lighting device, and FIG. - This is a timing chart showing the relationship between lamp currents. In the figure, 1... AC power supply, 4... Smoothing circuit, 5...
...Starter, 6...Lamp, 9...Drive circuit,
10... Inverter, 11... Rectifier smoothing circuit, 1
2...High voltage superimposition circuit, _TR1 , _TR2 ...Semiconductor switching element, _C1 , _C2 , _C3 ...Capacitor,
L ₁ , L ₂ ... Chiyoke coil.

Claims (1)

[Scope of utility model registration request] a switching circuit having a semiconductor element; a rectifier circuit sequentially connected to the switching circuit;
In a discharge lamp lighting device including a smoothing circuit and a starter, the starter includes a high voltage generation capacitor connected in parallel with the discharge lamp, and a chiyoke coil connected between the capacitor and the discharge lamp. A discharge lamp lighting device characterized by being provided with.