JP2708813B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a discharge lamp lighting device for starting and lighting a high pressure discharge lamp.

[Prior Art] FIG. 7 shows a conventional discharge lamp lighting device. The discharge lamp lighting device an alternating current flows in the transistor Q ₁ to Q square wave to the high-pressure discharge lamp la inverter 4 of a full bridge configuration of _four, in which the high-pressure discharge lamp la lighted square wave. Note that this discharge lamp lighting device is a high pressure discharge lamp la.
A high voltage pulse of several tens of kV is applied by the high voltage pulse generation circuit 2 to the high voltage discharge lamp 2 so that the high pressure discharge lamp la can be restarted instantly even immediately after it is turned off. That is, in the high-voltage pulse generating circuit 2, an AC power source V and switch S ₁ is closed when starting a high-pressure discharge lamp la
_AC is supplied, and a voltage obtained by boosting the voltage of the _AC power supply VAC by a boost transformer T is applied to a discharge gap G to cause a discharge. The discharge current of the discharge gap G is applied to the primary winding L of the pulse transformer PT. by flowing to _31, to induce a high voltage pulse in the secondary winding L _32. The capacitor C ₀ is for supplying a current to the secondary winding of the step-up transformer T. High voltage pulse induced in the secondary winding L ₃₂ is applied to the high pressure discharge lamp la via the capacitor C _1. When the high pressure discharge lamp l is started, the switch S ₁ is opened, the application of the high voltage pulse to the high pressure discharge lamp la is stopped.

The transistors Q ₁ and Q ₂ that constitute the full-bridge inverter 4 operate at a high frequency (for example, several tens of kHz), the transistors Q ₃ and Q ₄ operate at a low frequency (for example, several hundred Hz), and the transistor Q ₃ transistor Q ₂ is turned on and off when on, also the transistor Q ₁ when the transistor Q ₄ is turned on
Is turned on and off, and a low-frequency rectangular wave lamp current Ila flows through the high-pressure discharge lamp la. Note that contains high frequency components in the current flowing through the choke coil L ₁ of the current limiting element.
Therefore, the high-frequency component is bypassed by the capacitor C _1, are to prevent contains many high-frequency components in the lamp current Ila. That is, if the lamp current Ila contains a large amount of high-frequency components, arc instability due to the acoustic resonance phenomenon occurs, and problems such as flickering and disappearance occur. For this reason, it is necessary to suppress the content of the high frequency component of the lamp current Ila to 20% or less. In this way, high frequency components are reduced,
In addition, a discharge lamp lighting device in which the high-pressure discharge lamp la operates stably is disclosed in Japanese Patent Application No. 60-164388.

[SUMMARY OF THE INVENTION Incidentally, in addition to the work in the secondary winding L ₃₂ of the pulse transformer PT for applying a high voltage pulse to the high pressure discharge lamp la at startup, when the lighting of the high pressure discharge lamp la (constant This secondary winding L
The impedance of the lamp current path of the high pressure discharge lamp la through _32, a high-frequency manner to high impedance by the inductance of the secondary winding L _32, are high-frequency components to have functions to easily bypass the capacitor C ₁ side. For this reason, the pulse transformer PT becomes very large. That is, while obtaining an appropriate inductance (several mH) depending on the number of turns,
Since it is necessary to ensure insulation against high-voltage pulses, the pulse transformer PT increases.

Therefore, as shown in FIG.
With winding L ₃₂ only for the generation of high voltage pulse, the impedance of the lamp current path in order to increase the high frequency, there is connected in series separate the coil L ₂ to the high pressure discharge lamp la. In this case, the same operation as in the case of FIG. 7 can be obtained. However, because of the high voltage to the coil L ₂ when the high-pressure discharge lamp la began weak discharge is applied, it is necessary to ensure sufficient insulation for high voltage pulse in the coil L _2.
For this reason, it is still insufficient for miniaturization. That is, when the pulse transformer PT and the coil L ₂ small, increases the high frequency component of the lamp current Ila is, the arc instability is the flickering occurs.

The present invention has been made in view of the above points, and an object of the present invention is to provide a discharge lamp lighting device that does not increase in size even if the high-frequency component of the lamp current is reduced.

Means for Solving the Problems In order to achieve the above object, the present invention provides a first method for applying a high-voltage pulse to a high-pressure discharge lamp in parallel with a series circuit of a high-pressure discharge lamp and a secondary winding of a pulse transformer. And the capacitor
A second capacitor for bypassing a high-frequency current generated by chopping so as not to flow to the high-pressure discharge lamp; and a coil for increasing the impedance of a current path of the high-pressure discharge lamp at high frequencies to bypass the high-frequency current to the second capacitor side. And a filter circuit composed of

[Operation] With the present invention having the above-described configuration, a high-voltage pulse at the time of micro-discharge is applied to the coil for increasing the impedance of the current path of the high-pressure discharge lamp at a high frequency by the first capacitor of the filter circuit. In order to prevent the coil from becoming large, the high frequency component is bypassed by this coil and the second capacitor so that the content of the high frequency component of the lamp current is reduced to stabilize the arc. It was made.

Embodiment 1 FIGS. 1 and 2 show an embodiment of the present invention. FIG. 1 is a diagram showing a basic configuration of a main part of the present invention, between the series circuit of the secondary winding L ₃₂ of the high pressure discharge lamp la and the pulse transformer PT, a choke coil L ₁ of the current limiting element And a filter circuit 1 composed of a coil and a capacitor. A voltage (a) obtained by chopping the DC voltage _VDC or a voltage (b) obtained by alternating the chopping voltage (a) at a low frequency is applied between the terminals c and d of the main circuit.

High voltage pulse induced in the secondary winding L ₃₂ of the pulse transformer PT in the circuit is applied to the high pressure discharge lamp la via the capacitor C _2. Here, the high-voltage pulse is, for example, several hundred kHz.
Because it is to several MHz, the capacitance of the capacitor C ₂ may be small. The coil L ₄ of the filter circuit 1 and a capacitor C ₁
Works to bypass the high frequency component in order to reduce the high frequency component of the lamp current Ila. A capacitor C ₂ to form such loop to apply a high voltage pulse to the high pressure discharge lamp la, when provided separately and a capacitor C ₁ for bypassing a high frequency component, high-voltage pulse is applied to the coil L ₄ by the capacitor C ₂ since that will not be, the coil L ₄ can be reduced in size. Note that the filter circuit 1 may be further configured in multiple stages.

Coil L ₄ and the capacitor C ₂ of the filter circuit 1, C ₁
Is set as follows. Assuming that the chopping frequency (the switching frequency of the transistors Q ₁ and Q _{2 in} the conventional example of FIG. 7) is f ₁ , the impedance Zc of the capacitor C ₁
Is And the impedance Z _R of the circuit in parallel with the capacitor C ₁ is Becomes However, it is ignored because the value of the capacitor C ₂ and the secondary winding L ₃₂ is small. Here, the ratio of the impedances Z _C and Z _R is given by Z _R = KZ _C in order to reduce the high frequency component of the lamp current Ila and to reduce the size of the capacitor C ₁ and the choke coil L ₁ . The value may be selected in the range of 3 to 30.

FIG. 2 is a circuit diagram of a main part in the case where the circuit of FIG. 1 is applied to the conventional circuit of FIG. 7, and terminals c and d of FIG.
The terminals are rewritten as terminals a and b in the figure, and there is no change in circuit. The operation of the circuit shown in FIG.
The description is omitted because it is the same as the figure. By configuring as in this embodiment, the high frequency component flowing through the choke coil L ₁ Bypass capacitor C _1, the arc by reducing high frequency components of the lamp current Ila can be advantageously stabilized. Further, high voltage pulse at the weak discharge of the high pressure discharge lamp la by the capacitor C ₂ of the filter circuit 1 is no longer applied to the coil L _4, this order can coils L ₄ small, it is possible to reduce the size of the discharge lamp lighting device Become. The above filter circuit 1
Accordingly, high frequency noise generated from the high voltage pulse generation circuit 2 can be reduced. For this reason, an adverse effect on the outside due to the noise wrapping around the power supply can also be prevented.

Embodiment 2 FIG. 3 shows another embodiment. In this embodiment, a DC power supply V _DC
The transistor Q _5, the diode D _5, first obtained by chopping step-down chopper circuit 3 consisting of the choke coil L ₁
A voltage having a waveform (a) in the figure is applied to the high-pressure discharge lamp la. That is, this discharge lamp lighting device is for lighting the high-pressure discharge lamp la with direct current. Note that the transistor Q ₅ is turned on and off at a high frequency. Filter circuit 1 is a pulse transformer
It is connected between the secondary winding L ₃₂ and a series circuit and the step-up chopper circuit 3 of the high-pressure discharge lamp la of PT. In this embodiment, effects similar to those of the first embodiment can be obtained.

Embodiment 3 FIG. 4 shows still another embodiment, in which an inverter 4 having a full-bridge configuration is connected to the output of the step-down chopper circuit 3 in FIG. This is more preferable for the high-pressure discharge lamp la than in the case of DC lighting as in the second embodiment. However, the inverter 4, the transistor Q ₆ to Q ₉ are intended all off at a low frequency, on and off the transistors Q _6, Q ₉ and Q ₇ Q ₈ as a pair. Similar effects can be obtained in the case of this embodiment.

[Example 4] Fig. 5 shall have at different connecting position of the coil L ₄ and a capacitor C ₁ which constitutes the filter circuit 1 of the third embodiment, the output of the step-down chopper circuit 3 and a capacitor C ₁ And a coil L ₄ is connected between the step-down chopper circuit 3 and the inverter 4. Thus coil L ₄ and the filter circuit 1 be different connection point between the capacitor C ₁
There is no change in the basic operation. Moreover, according to the structure as described above, it means that the DC voltage is applied to the capacitor C _1, it can be used an electrolytic capacitor as a capacitor C _1, a small even by increasing the capacitance advantage There is.

[Embodiment 5] Fig. 6 shows a case where the present invention is applied to a discharge lamp lighting device using an inverter having a half-bridge configuration, and a transistor.
With Q _10, Q ₁₁ are turned on and off together in a high frequency, transistor Q _10, Q ₁₁ are those so as to operate alternately every half cycle of the low frequency. That is, when the half-cycle, for example, the transistor Q ₁₀ that is off operations at high frequencies, the transistor Q ₁₁ is turned off, during the next half cycle the transistor Q ₁₁ is turned on and off at a high frequency, transistor Q ₁₀ is turned off and Become. The voltage waveform in this case is (b) in FIG. However, the voltage amplitude is DC power supply V
Half of _DC . In this case, since the number of switching elements is reduced, the size can be further reduced. The capacitors C ₃ and C ₄ divide the voltage of the DC power supply _VDC .

As described above, the present invention employs a first capacitor that is connected in parallel to a series circuit of a high-pressure discharge lamp and a secondary winding of a pulse transformer and applies a high-voltage pulse to the high-pressure discharge lamp, A second capacitor that bypasses the generated high-frequency current so as not to flow to the high-pressure discharge lamp, and a coil that increases the impedance of the current path of the high-pressure discharge lamp at high frequencies and bypasses the high-frequency current to the second capacitor side. With the filter circuit configured, it is possible to prevent a high-voltage pulse at the time of micro-discharge from being applied to a coil that increases the impedance of the current path of the high-pressure discharge lamp at a high frequency in the first capacitor of the filter circuit, Therefore, the coil does not become large and the high frequency component of the lamp current is bypassed by the coil and the second capacitor. Has an effect that the arc can be stabilized. Further, this filter circuit can prevent high-frequency noise generated due to a high-voltage pulse applied to the high-pressure discharge lamp at the time of starting from flowing to the power supply side, and thus has an advantage that an adverse effect on the outside can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a basic configuration of a main part of the present invention.
FIG. 3 is a circuit diagram of a main part of one embodiment of the present invention, FIG. 3 is a circuit diagram of another embodiment, FIGS. 4 to 6 are circuit diagrams of still another embodiment, and FIG. FIG. 8 is a circuit diagram of a main part of another conventional example. 1 is a filter circuit, V _DC is a DC voltage, la is a high-pressure discharge lamp, P
T is the pulse transformer, L ₃₂ secondary winding, C _1, C ₂ is a capacitor, L ₄ is a coil.

Claims (1)

(57) [Claims] A high-voltage pulse is applied to a high-pressure discharge lamp through a pulse transformer having a secondary winding connected in series with the high-pressure discharge lamp to start the high-pressure discharge lamp and to chop a DC power supply at a high frequency. In a discharge lamp lighting device for lighting a high pressure discharge lamp by applying a voltage to the high pressure discharge lamp, a high voltage pulse is applied to the high pressure discharge lamp in parallel with a series circuit of the high pressure discharge lamp and a secondary winding of a pulse transformer. A first capacitor, a second capacitor that bypasses a high-frequency current generated by chopping so as not to flow to the high-pressure discharge lamp, and a high-frequency impedance of a current path of the high-pressure discharge lamp that is high in frequency to increase the high-frequency current to a second high-pressure discharge lamp. A discharge lamp lighting device including a filter circuit including a coil bypassed to a capacitor side.