JP2002260888A - Lighting device of discharge lamp and illumination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp device and an illumination device in which preheating power of the filament can be reduced and the preheating is performed appropriately even during illumination adjustment of the discharge lamp. SOLUTION: A saturable current transformer T1 is connected in series between a resonance capacitor C3 that generates a starting voltage of a discharge lamp 1 by resonance with a ballast L1 and a ground, and preheating current is supplied to the filament 2 of the discharge lamp 1 from the secondary coil of this saturable current transformer T1 through a filament preheating circuit. The preheating adjustment circuit 7 makes short-circuiting of the switch element 6 connected in parallel to the primary side of the saturable current transformer T1 or cut-off or lowering of preheating by impedance conversion during lighting of the discharge lamp 1.

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 and a lighting device for lighting a discharge lamp by converting a DC power supply into a high-frequency AC power supply.

[0002]

2. Description of the Related Art Generally, a discharge lamp lighting device rectifies a commercial frequency AC power supply by a rectifier to obtain a DC power supply once, converts the AC power supply into a high frequency AC power supply by an inverter circuit, and lights the discharge lamp at a high frequency. I have. In this case, the filament of the discharge lamp is preheated so that the discharge can be smoothly performed at the start of the discharge.

FIG. 5 is an explanatory diagram of a conventional preheating circuit in the case of constant current preheating in which the filament 2 of the discharge lamp 1 is preheated with a constant current. When the preheating capacitor C1 is connected in parallel with the discharge lamp 1 and the discharge lamp 1 is turned off, the filament current If flows through the preheating capacitor C1 due to the voltage VL applied to the discharge lamp 1 to preheat the filament. I have. The filament current If in this case is If = ω · C
It is represented by 1 · VL.

FIG. 6 is an explanatory diagram of a conventional preheating circuit in the case of constant voltage preheating in which the filament 2 of the discharge lamp 1 is preheated at a constant voltage. Transformer T for preheating in parallel with inverter circuit 3
1 and the filament 2 of the discharge lamp 1 is connected to the secondary winding of the preheating transformer T1. A DC cut capacitor C2 and a switch S are connected to the preheating transformer T1, and when the discharge lamp 1 is turned on and preheating is no longer necessary, the switch S is turned off to prevent preheating.

A starting voltage for lighting the discharge lamp 1 is generated by resonance between the ballast L1 and the resonance capacitor C3. C4 is a DC cut capacitor.

[0006]

However, in the case of the constant current preheating shown in FIG. 5, the filament preheating current If
Is the voltage V applied to the preheating capacitor C1 and the discharge lamp 1.
Therefore, there is no degree of freedom in preheating design, and it is difficult to save energy of preheating power.

On the other hand, in the case of constant voltage preheating shown in FIG.
Since the filament preheating power can be cut when the discharge lamp 1 is turned on, energy can be saved. However, when the preheating transformer T1 is saturated, an excessive current flows through the inverter circuit 3 and the inverter circuit 1 may be damaged. Therefore, it is necessary to use a transformer having a large shape (core size, winding, etc.) so that the preheating transformer T1 is not saturated.
Also, the switch S must have a large withstand voltage.

An object of the present invention is to provide a discharge lamp lighting device and an illuminating device which can reduce the filament preheating power and can appropriately perform preheating even when dimming the discharge lamp.

[0009]

According to a first aspect of the present invention, there is provided a discharge lamp lighting device for converting an output of a DC power supply into a high frequency power and lighting the discharge lamp at a high frequency; A resonance capacitor for generating a starting voltage of the discharge lamp by resonance with a ballast input; a saturable current transformer connected in series between the resonance capacitor and ground; a secondary winding of the saturable current transformer A preheating circuit for supplying a preheating current to a filament of the discharge lamp; a switch element connected in parallel to a primary side of the saturable current transformer; and a short circuit or a short circuit for the switch element when the discharge lamp is turned on. A preheating adjustment circuit that performs preheating cut or preheating reduction by impedance conversion.

In the present invention and the following inventions, definitions and technical meanings of terms are as follows unless otherwise specified.

The inverter circuit converts the output of the DC power supply into a high-frequency AC power supply by turning on and off a switching element. The DC power supply also includes a DC power supply obtained by rectifying the AC power supply.

The resonance capacitor inputs high-frequency power from an inverter circuit via a ballast and generates a starting voltage of the discharge lamp by resonance with the ballast.

The saturable current transformer saturates when the applied voltage exceeds a predetermined value, and flows a constant current after the saturation. The primary winding of the saturable current transformer is connected in series between the resonance capacitor and the ground, and the secondary winding is connected to a filament preheating circuit that supplies a preheating current to the filament of the discharge lamp. The saturable current transformer is designed to saturate after proper preheating is performed according to the filament characteristics of the lamp.

When the lamp is removed from the inverter circuit at the time of lamp replacement or the like, the saturable transformer is immediately saturated when all the filaments are removed from the inverter circuit so that the filament current does not flow. It is preferable to design in such a manner.

The switch element has a switching function and an amplifying function, and is, for example, a field effect transistor FET. Depending on the magnitude of the gate voltage, the switch element is on when the impedance is substantially zero, and is off when the impedance is large (for example, infinite). In the intermediate state, the current flowing through the switch element is adjusted by the amplification function.

The switching function and the amplifying function of the switch element are performed by a preheating adjustment circuit. The preheating adjustment circuit adjusts the current so that current flows through the saturable current reactor by turning off the switch element before starting the discharge lamp.When the discharge lamp is turned on, the switch element is short-circuited or short-circuited based on the voltage applied to the discharge lamp. Preheating cut or preheating reduction is performed by impedance conversion.

According to the present invention, since the saturation characteristic of the saturable current transformer is used, an appropriate filament preheating current can be obtained, and the withstand voltage of the switching element can be reduced.

A discharge lamp lighting device according to a second aspect of the present invention is the discharge lamp lighting device according to the first aspect, further comprising a step-up transformer having a primary side connected to a series circuit of the resonance capacitor and the saturable current transformer. The discharge lamp is connected to a secondary side of the discharge lamp.

According to the present invention, a boosting transformer for boosting the voltage applied to the discharge lamp is provided in the first aspect of the present invention. In this case, a series circuit of a resonance capacitor and a saturable current transformer is provided. Is provided on the primary side of the step-up transformer. According to the present invention, since the resonance capacitor is provided on the primary side, the filament circuit is simplified.

According to a third aspect of the present invention, in the discharge lamp lighting device according to the first or second aspect of the present invention, the preheating adjustment circuit may be configured such that the dimming degree of the discharge lamp becomes deeper based on a load voltage of the discharge lamp. The present invention is characterized in that a current flowing through the switch element is controlled so that a preheat amount increases.

According to the present invention, the current flowing through the switch element is controlled so that the amount of preheating increases as the dimming degree of the discharge lamp increases. If the dimming degree is increased when the discharge lamp is turned on, the frequency and voltage of the load voltage of the discharge lamp increase. The preheating adjustment circuit detects that the degree of dimming has increased based on the load voltage of the discharge lamp, and controls the current flowing through the switch element so that the amount of preheating increases.

According to the present invention, an appropriate preheating current can be supplied to the filament when preheating is required, so that energy can be saved.

According to a fourth aspect of the present invention, there is provided a lighting device comprising: the discharge lamp lighting device according to any one of the first to third aspects; and a fixture main body to which the discharge lamp lighting device is mounted. I do.

According to the present invention, when the filament needs to be preheated, an appropriate preheating current can be supplied, so that the energy saving of the entire lighting device can be achieved.

[0025]

Embodiments of the present invention will be described below. FIG. 1 is a circuit configuration diagram of a discharge lamp lighting device according to an embodiment of the present invention. The AC power supply 4 is rectified by the rectifier 5 to be DC, and this DC power is input to the inverter circuit 3. The inverter circuit 3 converts the output of the DC power supply into high-frequency power, and the high-frequency power obtained here is input to the step-up transformer T1 via the ballast L1, boosted, and the high-frequency power is supplied to the discharge lamp 1 via the DC cut capacitor C4. Light.

On the primary side of the step-up transformer T1, a series circuit of a resonance capacitor C3 and a saturable current transformer CT is connected in parallel with the primary winding of the step-up transformer T1. Also, on the primary side of the saturable current transformer CT,
The switching element 6 is connected in parallel via a DC cut capacitor C5. On the other hand, the saturable current transformer C
In the secondary winding of T, a filament preheating circuit for supplying a preheating current to the filament 2 is formed.

The preheating adjusting circuit 7 performs preheating cut or preheating reduction by short-circuiting or impedance conversion of the switch element 6 when the discharge lamp 1 is turned on.

FIG. 2 is a voltage-current characteristic diagram of the drain current Id and the source-drain voltage Vsd using the gate voltage Vg of the field effect transistor as the switch element 6 as a parameter. Now, it is assumed that the voltage-current characteristics change in the characteristic curves S1 to Sn depending on the magnitude of the gate voltage Vg. Then, in the case of the characteristic curve S1, the switching element 6
Is on, and when the characteristic curve is Sn, the switch element 6 is off. In the intermediate state, the drain current Id increases / decreases with a small change in the gate voltage Vg, and the current flowing through the switch element 6 is adjusted by a so-called amplification function. The preheating adjustment circuit 7 adjusts the gate voltage of the switch element based on the voltage applied to the discharge lamp 1 and performs on / off control or amplification control of the switch element 6.

Before the discharge lamp 1 is started, the voltage (no-load open voltage) applied to the discharge lamp 1 is maintained at a low voltage by the inverter circuit 3 so that the discharge lamp 1 is not turned on. In this case, the frequency of the no-load open-circuit voltage is higher than the frequency at the time of lighting. When the discharge lamp 1 is started, a high voltage necessary for starting the discharge lamp 1 is generated due to resonance between the ballast L1 and the resonance capacitor C3. It is lower than the frequency of the open circuit voltage.

FIG. 3 is a characteristic diagram of the preheating current If flowing through the filament 2 of the discharge lamp 1 when the preheating current is not adjusted by the preheating adjusting circuit 7.

Before the discharge lamp 1 is started, the voltage V0 applied to the saturable current transformer CT is lower and higher in frequency than the voltage at the time of lighting. Then, due to the saturable characteristic of the saturable current transformer CT, a current corresponding to the area of the hatched portion in the drawing flows as the preheating current If. Therefore, the discharge lamp 1
Before the start, the preheating current If flows more due to the higher frequency, and the filament 2 can be appropriately preheated.

Next, during the operation of the discharge lamp 1, the frequency of the voltage V0 becomes lower than before the start. Therefore, during the lighting of the discharge lamp, the preheating current is reduced by the lower frequency as shown in the figure.

On the other hand, when the voltage V0 decreases during lighting and the voltage V0 falls below a predetermined value, the saturable current transformer CT
Is no longer saturated. In the figure, the saturable current transformer C
This shows the characteristics when T does not saturate.

When the lighting of the discharge lamp 1 is confirmed by the load voltage of the discharge lamp 1, the preheating adjusting circuit 7 turns on the switch element 6 to reduce the voltage V0 applied to the saturable current transformer CT to zero. As a result, the preheating current flowing to the secondary side of the saturable current transformer CT becomes zero, and the preheating current is cut off during lighting that does not require preheating. Therefore, energy can be saved.

When the degree of dimming is increased, the filament needs to be preheated even during lighting. Therefore, the dimming is increased by the load voltage of the discharge lamp 1 and the preheating is required. When it is confirmed that the current is equal to, the current shunted to the switch element 6 is controlled so as to supply a preheating current required for preheating. Thereby, the saturable current transformer C
The voltage V0 applied to T is adjusted, and the preheating current flowing to the secondary side of the saturable current transformer CT is adjusted.

According to the embodiment of the present invention, the filament circuit can be simplified and the filament can be preheated properly.

The discharge lamp lighting device configured as described above is mounted on the fixture body 8 to form a lighting device as shown in FIG. That is, the discharge lamp lighting device is housed inside the fixture body 8, and the discharge lamp 1 is mounted outside the fixture body 8 to form a lighting device. According to this lighting device, the preheating current can be appropriately supplied when the filament needs to be preheated, so that the energy saving of the entire lighting device can be achieved.

[0038]

As described above, according to the first aspect of the present invention, since the saturation characteristic of the saturable current transformer is used, an appropriate filament preheating current can be obtained, and the withstand voltage of the switching element is low. I'm done. According to the second aspect of the present invention, in addition to the effect of the first aspect, since the resonance capacitor is provided on the primary side, the filament circuit is simplified.
According to the invention of claim 3, in addition to the effect of the invention of claim 1 or 2, an appropriate preheating current can be supplied to the filament when preheating is required, so that energy can be saved. According to the fourth aspect of the present invention, it is possible to provide a lighting device that can save energy.

[Brief description of the drawings]

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

FIG. 2 is a voltage-current characteristic diagram of a drain current Id and a source-drain voltage Vsd using a gate voltage Vg of a field-effect transistor as a switching element according to the embodiment of the present invention as a parameter.

FIG. 3 is a characteristic diagram of a preheating current If flowing through a filament of a discharge lamp when a preheating current is not adjusted by a preheating adjustment circuit according to the embodiment of the present invention.

FIG. 4 is a perspective view of a lighting device according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram of a conventional preheating circuit in the case of constant current preheating in which a filament of a discharge lamp is preheated with a constant current.

FIG. 6 is an explanatory diagram of a conventional preheating circuit in the case of constant voltage preheating in which a filament of a discharge lamp is preheated at a constant voltage.

[Explanation of symbols]

1: discharge lamp, 2: filament, 3: inverter circuit,
4: AC power supply, 5: Rectifier, 6: Switch element, 7: Preheating adjustment circuit

Claims (4)

[Claims] 1. An inverter circuit for converting an output of a DC power supply into high-frequency power and lighting a discharge lamp at high frequency; and a resonance for receiving high-frequency power from the inverter circuit and generating a starting voltage of the discharge lamp by resonance with a ballast. A capacitor; a saturable current transformer connected in series between the resonance capacitor and ground; and a filament preheater connected to a secondary winding of the saturable current transformer and supplying a preheating current to a filament of the discharge lamp. A switching element connected in parallel to the primary side of the saturable current transformer; and a preheating adjustment circuit that cuts or reduces preheating by short-circuiting or impedance conversion of the switching element when the discharge lamp is turned on. A lighting device for a discharge lamp, comprising: 2. A step-up transformer having a primary side connected to a series circuit of the resonance capacitor and the saturable current transformer, and the discharge lamp is connected to a secondary side of the step-up transformer. 2. The discharge lamp lighting device according to 1. 3. The preheating adjustment circuit controls a current flowing through the switch element based on a load voltage of the discharge lamp so that a preheating amount increases as a degree of dimming of the discharge lamp increases. The discharge lamp lighting device according to claim 1. 4. A lighting device, comprising: the discharge lamp lighting device according to claim 1; and a fixture main body to which the discharge lamp lighting device is mounted.