JPH05114492A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To provide a discharge lamp lighting device capable of being made thin, compact, lightweight and high efficient type, and ensuring high safety. CONSTITUTION:There are provided a high frequency circuit 36, a transformer 24 excited and driven with the circuit 36, and a discharge lamp lighting device fitted with a discharge lamp 38 to light upon receipt of high voltage from the transformer 24. In this case, a piezoelectric voltage conversion element is used for the transformer 24 and the primary side of the element is excited with the circuit 36. High voltage corresponding to a conversion ratio (n) [approximately equal to square root of (capacitance C1 across primary side terminals)/(capacitance C0 across secondary side terminals)] is thereby generated at the secondary side of the element for lighting the discharge lamp 38.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a discharge tube such as a fluorescent lamp.
The present invention relates to a highly safe transformer configuration that can achieve high efficiency.

[0002]

2. Description of the Related Art Recently, liquid crystal technology has rapidly advanced,
Liquid crystal displays for word processors, personal computers, etc. are required to be thinner, smaller, lighter, more efficient, and safer than ever.

Discharge tubes such as fluorescent lamps have been used in a wide variety of liquid crystal display backlights or other lighting. In this discharge tube lighting device, a high-frequency inverter transformer of electromagnetic conversion type is used in a high-frequency lighting circuit. Was using.

FIG. 5 is a circuit diagram of a conventional discharge tube lighting device. In the figure, 1 is an input terminal, 2 is an oscillator for exciting and driving the transformer 6, and 3 is a high frequency inverter transformer 6.
A transformer circuit including a protection element 7 and 4 is a discharge tube, and 5 is a ground.

The DC input voltage from the input terminal 1 operates the oscillator 2, which excites the transformer 6 to generate a high voltage on the secondary side and light the discharge tube 4. The protection element 7 operates due to the temperature rise of the transformer 6 at the time of abnormality,
It is an element that prevents smoke and ignition.

[0006]

By the way, when this high frequency inverter transformer is used, the size of the transformer 6 is inevitably increased in order to secure a predetermined withstand voltage, which makes the device thinner, smaller and lighter. There is a natural limit to conversion.

Further, there is a fear of smoking and ignition due to overvoltage and overcurrent of the high voltage output, which is insufficient in terms of safety. In order to prevent this from happening, it is necessary to provide a special protective element such as the protective element 7 in view of the circuit or structure, which further reduces the device thickness, size, and weight. It will be difficult and costly.

An object of the present invention is to solve the above-mentioned drawbacks of the prior art and to provide a discharge tube lighting device which is thin, compact, lightweight and highly efficient, and which is highly safe. It is in.

[0009]

To achieve the above object, the present invention provides a high frequency circuit such as an oscillator, a transformer excited and driven by the high frequency circuit, and a high voltage output from the transformer. The present invention is intended for a discharge tube lighting device provided with a discharge tube that lights according to a voltage.
Then, a piezoelectric voltage conversion element is used for the transformer, the primary side of the piezoelectric voltage conversion element is excited by the high frequency circuit, and the conversion ratio n [≈ (primary terminal capacitance C ₁ ) / (square root of electrostatic capacitance C ₀ between secondary terminals)] is generated, and the discharge tube is lit.

[0010]

[Function] A transformer using a piezoelectric voltage conversion element (hereinafter,
(Piezoelectric transformer) can be easily thinned, and there is no concern about smoking or ignition due to overvoltage, overcurrent, etc., which is extremely advantageous in terms of safety, and there is no need to provide a protective element as in the past The cost can be reduced.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.
1 is a circuit configuration diagram of a discharge tube lighting device according to an embodiment, and FIG. 2 is a perspective view of a piezoelectric transformer used in the discharge tube lighting device.

In FIG. 1, 35 is an input terminal, 36 is a drive circuit including an oscillator for exciting and driving the piezoelectric transformer 24, 37 is a circuit block including the piezoelectric transformer 24,
38 is a discharge tube, 39 is a feedback circuit, and 40 is a ground.

By the DC input voltage from the input terminal 35,
A high frequency is generated by the oscillator 36 and applied to the piezoelectric transformer 24 in the circuit block. With this piezoelectric transformer 24, a high voltage output is obtained on the secondary side with the characteristics described below, and the discharge tube 3
8 is turned on and a continuous discharge is made. After lighting, the discharge tube 38
However, the piezoelectric transformer 24 can also sustain discharge in accordance with this characteristic. In order to stabilize the operating frequency f at the time of this discharge continuation and realize a stable lighting continuity, a part of the output is detected from the side surface 41 of the piezoelectric transformer 24, and the feedback circuit 39 is passed through the oscillator 3
Return to 6.

The piezoelectric transformer 24 is made of a piezoelectric material such as barium titanate, lithium tantalate, lithium niobate, rosier salt, and a three-component system (PZT system) containing PbZrO ₃ -PbTiO ₃ and is shown in FIG. It has a cubic shape as shown, and has electrodes 25, 26 on the upper and lower surfaces thereof.
Are opposed to each other, and an electrode 27 is adhered to a side surface of the side away from the electrodes 25 and 26. The electrode 27 may be attached to the upper surface or the lower surface apart from the electrodes 25 and 26. When a high frequency voltage is applied to the terminals 28 and 29, high voltage outputs are obtained from the terminals 29 and 30.

In such a structure, the input voltage is V _i , the output voltage is V _o , and the electrodes 25 and 26 (terminals 28 and 2).
9), the electrostatic capacitance between the terminals (primary side terminal electrostatic capacity) is C _i , the electrostatic capacity between the electrodes 27, 26 (terminals 30, 29) (secondary side terminal electrostatic capacity) is C _o , When the conversion ratio between the input voltage and the output voltage is n, the relationship of the following Expression 1 is established.

[0016]

[Equation 1]

The present invention replaces the conventional high frequency inverter transformer with the piezoelectric transformer 2 having the above-described relationship.
4 is used in the discharge tube lighting device shown in FIG.
FIG. 3 is a characteristic diagram showing the relationship between the output voltage V _{0 with} respect to the load R _L of the piezoelectric transformer 24, the conversion efficiency η which is the input / output ratio, and the frequency f at which the piezoelectric transformer 24 is excited.
In the figure, the solid line is the characteristic curve of the output voltage V ₀ , the two-dot chain line is the characteristic curve of the conversion efficiency η, and the dotted line is the characteristic curve of the frequency f.
Point A shows the start of discharge, and point B shows the continuous discharge.

FIG. 4 is a characteristic diagram showing the relationship between the discharge current I _L of the discharge tube 38 and the load R _L and the voltage V _L applied to the load. The solid line in the figure is the characteristic curve of the voltage V _L , and the dotted line is the characteristic curve of the load R _L. Point A shows the start of discharge, and point B shows the continuous discharge.

When the discharge tube 38, which is a load, is connected to the output side of the piezoelectric transformer 24 and a voltage is applied, the output voltage V ₀ drops from the point A to the point B as shown in FIG. At this time, the voltage V _L and the load R _L drop from point A to point B, respectively, as shown in FIG.

The frequency f and the conversion efficiency η also change in the direction of the arrow as shown in FIG.

As shown in FIGS. 3 and 4, the characteristics of the piezoelectric transformer 24 and the discharge tube 38 substantially match each other, so that the present invention uses the piezoelectric transformer for the lighting device of the discharge tube. Is.

[0022]

EFFECTS OF THE INVENTION A transformer using a piezoelectric voltage conversion element can be easily thinned, and there is no fear of smoking or ignition due to overvoltage or overcurrent, which is extremely advantageous in terms of safety. There is no need to provide a protective element on the
The cost can be reduced.

Therefore, it is possible to provide a highly safe discharge tube lighting device which can be made thin, compact, lightweight and highly efficient.

[Brief description of drawings]

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

FIG. 2 is a perspective view of a piezoelectric transformer used in the discharge tube lighting device.

FIG. 3 is a characteristic diagram showing a relationship between an output voltage V _{0 with} respect to a load R _{L of the} piezoelectric transformer, a conversion efficiency η, and a frequency f for exciting the piezoelectric transformer.

FIG. 4 is a characteristic diagram showing a relationship between a discharge current I _{L of} a discharge tube and a load R _L and a voltage V _L applied to the load.

FIG. 5 is a circuit configuration diagram of a conventional discharge tube lighting device.

[Explanation of symbols]

 24 Piezoelectric Transformer 27-30 Terminal 35 Input Terminal 36 Drive Circuit Including Oscillator 37 Circuit Block 38 Discharge Tube 39 Feedback Circuit 40 Ground

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kenji Yasuhiko Kitano, Mizushiro-shi, Iwate Prefecture No. 1 Kitano, Hitachi Mizusawa Electronics Co., Ltd. Mizusawa Electronics

Claims (2)

[Claims] 1. A discharge tube lighting device comprising a high-frequency circuit, a transformer excited and driven by the high-frequency circuit, and a discharge tube lit by a high voltage output from the transformer, wherein the transformer comprises: A piezoelectric voltage conversion element is used for the piezoelectric voltage conversion element, the primary side of the piezoelectric voltage conversion element is excited by the high frequency circuit, and the conversion ratio n [≈ (capacitance between primary terminals C ₁ ) / (Square Root of Capacitance between Secondary Terminals C ₀ )]
A discharge tube lighting device, characterized in that a high voltage corresponding to is generated to light the discharge tube. 2. The feedback circuit according to claim 1, wherein a part of the output from the piezoelectric voltage conversion element is detected and fed back to the high frequency circuit to stabilize the frequency of the discharge tube during continuous discharge. A discharge tube lighting device characterized by the above.