JP3305352B2 - Discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device for lighting a discharge lamp such as a high pressure discharge lamp (including a low pressure discharge lamp) using, for example, a high frequency inverter.

[0002]

2. Description of the Related Art High-pressure discharge lamps such as metal halide lamps have good luminous efficiency and can be miniaturized. Therefore, besides general lighting equipment, in-vehicle lamps such as headlights and liquid crystal projectors. It is increasingly used as a light source for television receivers. For these uses, instantaneous lighting is required.

FIG. 5 is a circuit diagram of a discharge lamp lighting device for lighting a high-pressure discharge lamp of this type at a high frequency using a full-bridge type inverter. This discharge lamp lighting device,
As shown in FIG. 5, the DC power supply E includes switch elements S ₁₁ and S ₁₁ .
₂₁ series circuits, and switch elements S ₁₂ ,
A series circuit of the S _22, the switch elements S _11, S _21,
Flywheel diodes D ₁₁ and D ₁₁ are connected to S ₁₂ and S ₂₂ respectively.
_21, D _12, is inversely connected in parallel D _22.

A secondary winding of the pulse transformer PT is connected between a connection point of the switch elements S ₁₁ and S _{21 and} a connection point of the switch elements S ₁₂ and S ₂₂ via an inductor L ₁ which is a current limiting element. The series circuit of the discharge lamp DL is connected.
The series circuit of the secondary winding and the discharge lamp DL of the pulse transformer PT, the bypass capacitor C ₁ is connected in parallel for high pressure pulse.

Further, the primary winding of the pulse transformer PT is the starting energy storage capacitor C ₂ is connected via the switch S _3. The starting energy storage capacitor C ₂ is connected to a booster circuit SA via a diode D _3.
And is charged to a high voltage state. Switch element S
_11, S _21, operation of the S _12, S ₂₂ and the switch element S ₃ and the step-up circuit SA control circuit CR controls.

[0006] Such a discharge lamp lighting device includes a booster circuit S
The starting circuit ST comprising circuit elements from A to the pulse transformer PT, and generates a high pulse voltage, across the discharge lamp DL to the high-pressure pulse voltage of several kV to several tens kV through a bypass capacitor C ₁ for a high-pressure pulse the application and by starting the discharge lamp DL, by supplying lighting power through the current limiting element including the inductor L ₁ from the lighting circuit TN consisting full-bridge inverter, it becomes the discharge lamp DL so as to sustaining ing.

[0007] Specifically, the discharge lamp DL at the time of starting the discharge lamp DL at both ends voltage V _LA is no-load secondary voltage V of
₂ is applied. At this time, the starting energy storage capacitor C from the booster circuit SA through the diode D _3
2 is charged. Then, when it is charged to a voltage value that is the starting energy storage capacitor C _2, to turn on the switching element S _3. Thereby, the starting energy storage capacitor C ₂ accumulates charge, switch element S
Through _{3 to the} primary winding of the pulse transformer PT,
High pulse voltage is induced in the secondary winding, and this voltage is applied to the discharge lamp DL through the bypass capacitor C ₁ for a high-pressure pulse. As a result, the discharge lamp DL causes dielectric breakdown, shifts to arc discharge, and starts.

When the discharge lamp DL starts, the lighting circuit T
By the power supplied from the N via the inductor L _1, to maintain the lighting. Here, the starting of the discharge lamp DL
Switch elements S ₁₁ , S before and after and after stable lighting
_21, S _12, the operation of S ₂₂ will be described. This discharge lamp point
The lamp unit is configured to operate as a step-down chopper,
Before and after starting the lamp DL (operation under no load)
The following operation is performed. Switch elements S ₁₂ and S ₂₁ are high frequency
Switching operation (for example, 100 kHz)
From the voltage of the source E (for example, 450 V),
The voltage drop to the voltage applied to the valve (for example, 380V)
Perform chopper-type operation. And the high pressure pulse bypass
Immediately before starting the capacitor C1, a no-load secondary voltage (for example,
380 V). During the above, switch
The elements S ₁₁ and S ₂₂ are both in the off state. afterwards,
When stable lighting is achieved, the voltage applied to the discharge lamp DL
Switch elements S ₁₁ , S ₂₂ and the switch
The high-frequency switching operation of the switching elements S ₁₂ and S ₂₁ and the
State alternately at a low frequency.

[0009]

In the above-described starting process, an arc discharge current of about several hundred mA to several A flows through the discharge lamp DL after starting.
Depending on the state, the arc discharge may extinguish. The reason is that the high-voltage pulse bypass capacitor C ₁
Voltage across V _C1 of is considered to decrease abruptly immediately after the start of the discharge lamp DL. The details below
explain. First, the high-voltage pulse bypass capacitor C ₁
The reason why the voltage V _C1 between both ends suddenly drops immediately after starting is as follows.
As described below. High pressure pulse to discharge lamp DL
Immediately after is applied, the discharge lamp DL shifts to arc discharge
However, at this time, the equivalent impedance of the discharge lamp DL is
The power drops sharply from several hundred MΩ to several Ω. That
Because, charged in the bypass capacitor C ₁ for a high-pressure pulse
The no-load secondary voltage (for example, about 380 V)
Out to the discharge lamp DL via the secondary winding of the
You. Therefore, the bypass capacitor C ₁ for a high-pressure pulse
The voltage V _C1 between both ends sharply drops immediately after starting. Next,
The voltage V _C1 across the high-voltage pulse bypass capacitor C ₁ is
The reason why the arc discharge disappears after a sharp decrease is as follows.
As described below. The characteristics of the discharge lamp DL
Therefore, during the period of several hundred μsec immediately after starting, the lamp current decreases.
In particular, arc discharge tends to be very unstable
There is. During this time, make sure that a sufficient amount of lamp current flows.
There is a need to. In particular, this tendency is that the discharge lamp DL
It becomes a remarkable phenomenon at restart. Therefore, immediately after starting
The voltage V _C1 across the bypass capacitor C ₁ for pressure pulse is sudden
If it drops sharply, the above stable arc discharge is obtained.
Because it is not possible to obtain sufficient lamp current
It becomes. In addition, a safety period of several hundred μsec
Supply sufficient lamp current to obtain a constant arc discharge
From the choke coil
There is L _1, to produce a time delay, supply is difficult.

FIG. 6 is a time chart showing the state before and after the start of the discharge lamp DL indicating this, and FIG.
A voltage V _C1 across the high-voltage pulse bypass capacitor C ₁ at the time of a successful start is shown, and (b) shows a current I _LA flowing through the discharge lamp at the time of a failed start (solid line) . In FIG. 6, when the discharge lamp DL starts at time t ₁ , an oscillating current flows as the current I _LA as shown in FIG. 6B, and at this time, the voltage across the high-voltage pulse bypass capacitor C ₁ is applied. V _C1 drops sharply, indicating a failure to start and the current I _{LA to} go to zero. Note that the broken line in FIG. 3B indicates a state in which the starting is successful. Here, FIG.
The change over time in the time chart will be described in detail.
First, before starting, the high-voltage pulse bypass capacitor C ₁
End voltage V _C1 is positive for directly no-load secondary voltage V
₂ does not change for the following reasons. Explained first
As described above, the switching elements S ₁₁ , S ₁₂ , S ₂₁ , and S ₂₂ fall.
A circuit configuration for performing pressure chopper type operation
Immediately before the start of the DL, charge to the specified no-load secondary voltage
After that, it is almost constant until the pulse voltage is applied
This is because it is controlled so that Next, after starting
To, the current I _LA vibrates, the switch element S ₃ is turned on
After the pulse is generated, the starting energy storage capacitor
Capacitor C ₂ , capacitor C ₃ for suppressing voltage drop , pulse transformer
Resonance current flows through the circuit formed by the primary winding of the
As a matter of course, the resonance current also flows to the secondary side of the pulse transformer PT.
Because it is Next, after a successful start,
Of the discharge lamp DL,
The _{reason that} the polarity of the voltage V _C1 and the polarity of the current I _LA does not change is as follows.
For the reason. In FIG. 6, the time axis is (a)
Is a unit of several hundred msec, and in FIG.
Is a unit of And especially metal halide lamps
In such cases, immediately after the start of the pulse, a few meters after the start of the discharge
It is for DC lighting during sec.
Because they do.

On the other hand, there is a discharge lamp lighting device disclosed in Japanese Patent Application Laid-Open No. H2-215093 as a device for preventing the extinguishing of arc discharge as described above and for stably instantaneously lighting a high-pressure discharge lamp. This discharge lamp lighting device detects a dielectric breakdown of a high-pressure discharge lamp, receives it, and turns on a switch element to supplement arc discharge.

This discharge lamp lighting device has a problem in that the circuit configuration is complicated, resulting in an increase in cost.
Accordingly, an object of the present invention is to provide an inexpensive discharge lamp lighting device which can stably perform instantaneous lighting of a discharge lamp and has a relatively simple circuit configuration.

[0013]

A discharge lamp lighting device according to the present invention controls a lighting circuit for lighting a discharge lamp, a starting circuit for applying a high starting voltage to the discharge lamp, and a lighting circuit and a starting circuit. A lighting control circuit. In the starting circuit, a secondary winding of a pulse transformer is inserted in series with the discharge lamp at the output end of the lighting circuit, and a high-voltage pulse bypass capacitor is connected in parallel to the series circuit of the discharge lamp and the secondary winding of the pulse transformer. ing.

A voltage drop suppressing capacitor is connected in series with the primary winding of the pulse transformer, and a connection point between the primary winding of the pulse transformer and the voltage drop suppressing capacitor is connected to the discharge lamp and the pulse transformer. It is connected to one end of the series circuit of the next winding. A starting energy storage capacitor is connected in parallel with the series circuit of the primary winding of the pulse transformer and the capacitor for suppressing voltage drop, and the primary winding of the pulse transformer and the capacitor for suppressing voltage drop are connected from the starting energy storage capacitor. And a booster circuit that charges a starting energy storage capacitor.

In addition, the charge accumulated in the capacitor for suppressing voltage drop is forward with respect to the discharge direction of the charge accumulated in the capacitor for suppressing voltage drop, and the series circuit of the secondary winding of the discharge lamp and the pulse transformer and the bypass capacitor for high voltage pulse are used. And a diode that forms a closed circuit that discharges to the parallel circuit of

[0016]

According to the structure of the present invention, the switching element is turned on to discharge the electric charge of the starting energy storage capacitor through the primary winding of the pulse transformer and to release the charge of the capacitor.
When the high voltage pulse voltage is generated in the next winding to start the discharge lamp, a part of the electric charge of the starting energy storage capacitor is stored in the voltage drop suppressing capacitor.

The electric charge accumulated in the capacitor for suppressing voltage drop is discharged to a parallel circuit of a series circuit of a secondary winding of a discharge lamp and a pulse transformer and a bypass capacitor for a high voltage pulse through a closed circuit including a diode. Will be done. As a result, it is possible to prevent the voltage of the high-voltage pulse bypass capacitor from rapidly dropping when the discharge lamp is started, to prevent the discharge lamp from extinguishing due to the low voltage of the high-voltage pulse bypass capacitor, and to reduce the discharge lamp voltage. It can be turned on stably instantaneously.

In addition, a voltage drop suppressing capacitor and a diode are provided as a configuration for this purpose. A parallel circuit of a series circuit of a secondary winding of a discharge lamp and a pulse transformer and a high-voltage pulse bypass capacitor, and a voltage drop suppressing capacitor are provided. It is only necessary to connect the circuits so as to form a closed circuit, so that the configuration is simple and can be realized at low cost.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. [First Embodiment] A first embodiment of the present invention will be described with reference to FIGS. This discharge lamp lighting device,
As shown in FIG. 1, the starting energy storage capacitor C
The _second voltage drop suppression capacitor C ₃ in the wiring path to the primary winding of the pulse transformer PT from the negative electrode terminal is inserted and connected, connection between the primary winding and the voltage drop suppression capacitor C ₃ of the pulse transformer PT The point is connected to one end of a series circuit of the secondary winding of the discharge lamp DL and the pulse transformer PT, in this example, the discharge lamp DL side. The other end of the secondary winding of the series circuit of the discharge lamp DL and the pulse transformer PT, to connect the anode side of the diode D ₄ of the secondary winding of the pulse transformer PT in this example, the cathode of the diode D ₄ connected to a connection point of the starting energy storage capacitor C ₂ and the voltage drop suppression capacitor C _3, 2 windings of the series circuit and the high pressure of the stored charge of the voltage drop suppression capacitor C ₃ discharge lamp DL and the pulse transformer PT and so as to emit through the parallel circuit and the diode D ₄ the pulse for bypass capacitor C _1.

The circuit configuration other than the above is the same as that of the conventional example shown in FIG. In the discharge lamp lighting device, a high-voltage pulse in the secondary winding of the emitted pulse transformer PT charge of starting the energy storage capacitor C ₂ to turn on the switching element S ₃ through the primary winding of the pulse transformer PT when starting the discharge lamp DL is generated, part of the charge of starting the energy storage capacitor C ₂ is accumulated in the voltage drop suppression capacitor C _3. Voltage of the voltage drop suppression capacitor C ₃ at this time is V _C3, this voltage V _C3 is higher than the voltage V _C1 of the high voltage pulse bypass capacitor C ₁ state.

The capacitor C for suppressing voltage drop
_ThreeCharge accumulated in the diode D _FourThrough a closed circuit containing
And the secondary winding of the discharge lamp DL and the pulse transformer PT
Line series circuit and bypass capacitor C for high voltage pulse₁When
Are released to the parallel circuit. As a result,
When starting the discharge lamp DL, the bypass capacitor for high pressure pulse
Sensor C₁Voltage can be prevented from dropping rapidly.
And high-voltage pulse bypass capacitor C₁Voltage
To prevent the discharge lamp DL from going out due to a decrease in
The lamp DL can be stably turned on instantaneously.

The operation other than the above relating to lighting of the discharge lamp DL is the same as that of the conventional example. 2, the discharge lamp DL is a time chart showing the states before and after starting of the discharge lamp DL indicating that instantaneous lighting stable, (a) shows the voltage across V _C1 bypass high voltage pulse capacitor C ₁ , (B) shows the current I _LA flowing through the discharge lamp.

[0023] In Figure 2, at time t _1, the discharge lamp DL
When but starting, as shown in FIG. (B), the vibration current flows as the current I _LA, reduction of the voltage across V _C1 of the high voltage pulse bypass capacitor C ₁ is compared to FIGS. 6 (a) at this time Significantly less, indicating a successful start. Further, the current I _LA is as shown in FIG. 3B, the arc discharge does not drop, the arc discharge is stabilized, and more complete instantaneous lighting becomes possible. Here, FIG.
The details of the change over time in the time chart are shown in FIG.
This is the same as described above.

Further, as a configuration for this, a voltage drop suppressing capacitor C ₃ and a diode D ₄ are provided, and a series circuit of a secondary winding of a discharge lamp DL and a pulse transformer PT and a high-voltage pulse bypass capacitor C ₁ are connected in parallel. it is only to circuits connected to form a closed circuit between the circuit and the voltage drop suppression capacitor C _3, the configuration is simple, inexpensive to implement.

Second Embodiment A second embodiment of the present invention will be described with reference to FIG. The discharge lamp lighting device, as shown in FIG. 3, and a resistor R for current detection in emission path of accumulated charge of the voltage drop suppression capacitor C _3, based on the voltage developed across the resistor R , Discharge lamp DL
Detecting the starting, the discharge lamp DL start upon detection of, or to stop charging of the booster circuit starting energy storage capacitor C ₂ by stopping the operation of the SA, or stops the on-off operation of the switching element S ₃ It is allowed to stop the discharge of the accumulated charge starting energy storage capacitor C _2.

In this embodiment, since the resistor R for detecting the start of the discharge lamp DL is provided, the start can be detected promptly. As a result, the operation mode of the lighting circuit TN is switched in response to the start. Becomes possible. The configuration and operation and effect other than those described above are the same as those of the first embodiment. [Third Embodiment] A third embodiment of the present invention will be described with reference to FIG.

This discharge lamp lighting device is a half bridge type
As the lighting circuit TN.
In this discharge lamp lighting device, the switch element of FIG.
Child S ₁₁, S_{twenty one}And flywheel diode D₁₁, D_{twenty one}
Instead of the capacitor C_Four, C_FiveUsing a series circuit of
Capacitor C_Four, C_FiveConnection point and switch element S₁₂, S _{twenty two}
L between the connection point of₁, Pulse transformer PT
And the series circuit of the discharge lamp DL
The DC cut capacitor C is connected in series with these circuits.
₀Is inserted. Voltage drop suppression capacitor C_ThreeAccumulation of
Diode D to create product charge release path_FourIs the anode
Is connected to the negative electrode of the DC power supply E in this example.
1 may be connected to the same location.

Since the specific operation of the circuit of FIG. 4 is well known, the description is omitted, but the current flowing through the discharge lamp DL in a steady state is substantially a sine wave. And the switch element S
₃ that the high-voltage pulse voltage is generated in the on is when the high voltage pulse bypass capacitor C ₁ of the voltage V _C1 becomes the direction of the arrow. Moreover, the effect of the accumulated charge of the voltage drop suppression capacitor C ₃ is discharged is the same as the previous embodiment.

The diode D ₄ may be connected to any position as long as the voltage drop suppressing capacitor C ₃ and the high-voltage pulse bypass capacitor C ₂ form a closed circuit.

[0030]

According to the discharge lamp lighting device of the present invention, the switch element is turned on to discharge the electric charge of the starting energy storage capacitor through the primary winding of the pulse transformer, and the high voltage pulse is applied to the secondary winding of the pulse transformer. When the discharge lamp is started by generating a voltage, a part of the charge of the starting energy storage capacitor is stored in the capacitor for suppressing voltage drop, and the capacitor is stored in the capacitor for suppressing voltage drop to store the charge and includes a diode. Through the discharge lamp and the parallel circuit of the secondary winding of the pulse transformer and the parallel circuit of the high-voltage pulse bypass capacitor, so that the voltage of the high-voltage pulse bypass capacitor drops rapidly when the discharge lamp is started. Discharge lamp extinguishes due to a drop in the voltage of the high-voltage pulse bypass capacitor. Preventing the discharge lamp can be stably instantaneous lighting.

Further, as a configuration for this purpose, a voltage drop suppressing capacitor and a diode are provided, and a voltage drop suppressing capacitor, a discharge lamp and a pulse transformer are used.
It is only necessary to make a circuit connection so that a closed circuit is formed by the series circuit of the next winding and the high-voltage pulse bypass capacitor, so that the configuration is simple and can be realized at low cost.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a discharge lamp lighting device according to a first embodiment of the present invention.

FIG. 2 is a time chart illustrating an operation of the discharge lamp lighting device of FIG. 1;

FIG. 3 is a circuit diagram showing a configuration of a discharge lamp lighting device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a discharge lamp lighting device according to a third embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a conventional example of a discharge lamp lighting device.

6 is a time chart showing the operation of the discharge lamp lighting device of FIG.

[Explanation of symbols]

E DC power supply TN lighting circuit ST starter circuit SA booster circuit D ₃ diode D ₄ diodes C ₁ high voltage pulse bypass capacitor C ₂ starting energy accumulating capacitor C ₃ capacitor voltage reduction inhibiting S ₃ switch devices PT pulse transformer DL discharge lamp CR Control circuit

Claims (1)

(57) [Claims] 1. A lighting circuit for lighting a discharge lamp, a starting circuit for applying a high voltage for starting to the discharge lamp,
A lighting control circuit that controls the lighting circuit and a starting circuit, wherein the starting circuit includes a pulse transformer having a secondary winding inserted in series with the discharge lamp at an output end of the lighting circuit;
A high-voltage pulse bypass capacitor connected in parallel to a series circuit of the discharge lamp and the secondary winding of the pulse transformer; and a connection point connected in series with the primary winding of the pulse transformer and connecting the connection point to the discharge lamp and the pulse transformer. A capacitor for voltage drop suppression connected to one end of a series circuit of the secondary winding of the above, a starting energy storage capacitor connected in parallel to the series circuit of the primary winding of the pulse transformer and the capacitor for voltage drop suppression, A switch element for controlling the release of electric charge from the energy storage capacitor to the series circuit of the primary winding of the pulse transformer and the voltage drop suppressing capacitor; a booster circuit charging the starting energy storing capacitor; The direction becomes forward with respect to the direction in which the accumulated charge of the capacitor is released. The discharge lamp lighting device and a diode forming a capacitor closed circuit to release accumulated charges for a parallel circuit with the discharge lamp and a secondary winding in series circuit with said bypass capacitor for high pressure pulses of the pulse transformer.