JP2002119061A - Drive unit for cold-cathode tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a small-sized, low voltage-operated, and high-efficiency drive unit for discharge tube and a laminated, integral-type piezoelectric transformer that attains both a high boosting ratio and high efficiency therefor. SOLUTION: The integrally sintered piezoelectric transformer is so designed that, when the number of laminations in the piezoelectric transformer is not less than six and the alternating-current input voltage is not more than 14 V, the efficiency of the transformer is not less than 90% in a range in which the tube current passed through a cold-cathode tube is not less than 3 mA. The drive unit for cold-cathode tube uses the piezoelectric transformer and is so designed that, when the direct-current input voltage is not more than 14 V, the inverter efficiency is not less than 80% in a range in which the tube current passed through a cold-cathode tube is not less than 5 mA.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a cold cathode tube used in, for example, a liquid crystal display and a laminated integrated piezoelectric transformer used in the driving device.

[0002]

2. Description of the Related Art Generally, in a liquid crystal display, a backlight system in which a discharge tube such as a cold-cathode tube is disposed on the back and side surfaces of a liquid crystal display is mainly used because the liquid crystal itself does not emit light.

[0003] In order to drive this discharge tube, an AC high voltage of several hundred volts or more is required, depending on the length and diameter of the discharge tube itself. A high-frequency inverter using an electromagnetic transformer shown in FIG. 14 is generally used as a drive device for a discharge tube that generates an AC high voltage. Electromagnetic transformer 70
High output voltage V ₄ generated in the secondary winding 75 of the is applied to the discharge tube 60 such as a cold-cathode tube via the ballast capacitor 81 for limiting the tube current I _O, it emits light discharge tube 60. Since this electromagnetic transformer requires a large number of thin windings to be wound, there is a limit to miniaturization and cost reduction of the driving device.

As another method, a driving device for a discharge tube using a piezoelectric transformer is disclosed in Japanese Patent Publication No. 55-26600.
JP-A-52-113578, JP-A-5-1144
No. 92 publication. Piezoelectric transformers are much simpler than electromagnetic transformers, so they are smaller and thinner.
Cost reduction is possible. The principle and characteristics of this piezoelectric transformer are disclosed in “Electronic Ceramics”, July 1971, “Characteristics and Applications of Piezoelectric Transformers” published by Gakusensha.

FIG. 11 shows a Rosen-type piezoelectric transformer published by CA Rosen of the United States in 1956. FIG.
The principle of the Rosen-type piezoelectric transformer will be described with reference to FIG. 2. Reference numeral 2 denotes a plate-shaped piezoelectric ceramic element made of, for example, lead zirconate titanate (PZT). For example, a pair of input electrodes 4 and 5 provided by baking silver is formed, and an output electrode 6 is formed on the right end face in the same manner. Then, the left half driving section of the ceramic element 2 is polarized in advance in the thickness direction, and the right half power generation section is longitudinally polarized in advance.

In the piezoelectric transformer thus formed, when an AC voltage having substantially the same frequency as the natural resonance frequency in the longitudinal direction of the ceramic element 2 is applied between the input electrodes 4 and 5 from the AC voltage source 8, this ceramic element 2 generates a strong mechanical vibration in the longitudinal direction, whereby electric charges are generated by the piezoelectric effect in the right half of the power generation unit, and an output voltage V _O is generated between the output electrode 6 and one of the input electrodes, for example, the input electrode 5. .

FIG. 12 shows the load resistance characteristics of the output voltage of the Rosen-type piezoelectric transformer, and FIG. 13 shows the load resistance characteristics of the efficiency. Here, the AC input voltage V _i is 10 [V], the drive mode is full-wavelength mode, the piezoelectric material HCEPC-28 dimension of the ceramic element in (Hitachi Metals, Ltd.) is the length 28 [mm], a width 7.5 [ mm] and a thickness of 1.0 [mm]. As can be seen from these characteristics, the Rosen-type piezoelectric transformer has an output voltage 7 in a relatively high load resistance region, for example, 3 [MΩ].
00 [V] and a step-up ratio of 70 times can be obtained, but the efficiency is as low as 40% or less. In a region near a load resistance of 100 [kΩ], high efficiency of 90% or more can be obtained, but the output voltage is 85 [V] and the boost ratio is 8.5 times.

A piezoelectric transformer for a high voltage power supply of a television receiver, which has been actively studied in the 1970's, uses the former relatively high resistance load region. However,
Since it is used in an inefficient area, it cannot surpass the electromagnetic transformer due to problems such as heat generation of the element, and has not yet reached practical use. On the other hand, FIG. 1 shows an example of using the latter piezoelectric transformer using a region where relatively high resistance and high efficiency can be obtained.
It is shown in FIG. FIG. 15 is a circuit diagram of a discharge tube driving device using the Rosen-type piezoelectric transformer described above. The tube diameter is 3.0 [m].
m] and a relatively small cold-cathode tube having a tube length of 80 [mm]. The tube voltage V _O at the time of light emission is 260 [V], and the inverter efficiency is 7 when the tube current I _O is 2 [mA].
It is as high as 5.0%. This is because the operating resistance of the discharge tube 60 at the time of light emission is 130 [kΩ] (= 260 [V] ｍ2 [mA]), which corresponds to the relatively low resistance region described above, and the piezoelectric transformer 1
0 but is because operating at high efficiency, since the step-up ratio of the piezoelectric transformer 10 is an area that is reduced, the DC input voltage V ₂ is high as 25 [V]. Even when a relatively small tube current of 2 [mA] flows through such a small cold-cathode tube,
Since a high DC input voltage of 5 [V] is required, a battery-operated portable information terminal or personal computer (hereinafter, referred to as a personal computer) cannot be used due to an increase in the size of a battery unit.

[0009]

In a portable information terminal device or a personal computer using a liquid crystal display, low voltage operation and high efficiency are required in order to cope with downsizing of a power supply battery portion and use for a long time. However, such a device for driving a discharge tube requires a high step-up ratio and high efficiency that generate a high output voltage at a low input voltage, but a conventional Rosen-type piezoelectric transformer and a discharge tube driving device using the same are required. Could not balance these two points.

[0010] The present invention focuses on the above problems,
It was created to solve this effectively. SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer piezoelectric transformer that simultaneously realizes a high step-up ratio and high efficiency, and a drive device for a discharge tube using the same.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a multilayer integrated piezoelectric transformer and an inverter for converting a DC input voltage to an AC input voltage and supplying the AC input voltage to the multilayer integrated piezoelectric transformer. A driving device for a cold cathode tube including a portion, wherein the laminated integrated piezoelectric transformer is a piezoelectric transformer having a first region polarized in a longitudinal direction and a second region polarized in a thickness direction, The first region and the second region are formed by laminating piezoelectric sheets and integrally sintering. In the second region polarized in the thickness direction, an internal electrode is formed on the surface of the piezoelectric sheet. Thereby, the piezoelectric body and the internal electrode are alternately laminated, the internal electrode is connected to every other layer with the external electrode provided on the side surface in the longitudinal direction, the number of laminated layers is 6 or more, and the laminated integrated piezoelectric transformer is Before 14V or less In the AC input voltage, a tube current flowing through the cold cathode tube trans efficiency at 3mA or more areas 90%
A driving device for a cold cathode tube, wherein the inverter efficiency is 80% or more in a region where the tube current flowing through the cold cathode tube is 5 mA or more at the DC input voltage of 14 V or less. Further, in the above-described cold cathode tube driving device, the resonance frequency of the multilayer integrated piezoelectric transformer and the parallel capacitance including the input capacitance thereof is made substantially equal to the natural resonance frequency of the multilayer integrated piezoelectric transformer. Is more preferred.

(Operation) Since the present invention is constructed as described above, an input voltage is applied to each of the laminated thin layers to the driving portion of the laminated piezoelectric transformer, so that the laminated type has a larger size than the conventional single plate type. The boost ratio is multiplied by approximately the number of layers. Therefore,
As described above, a high voltage can be obtained with a relatively low load resistance from the output of the multilayer piezoelectric transformer, and a discharge tube such as a cold cathode tube can be driven with high efficiency.

In particular, the resonance frequency of the inductance of the inductor and the parasitic capacitance of the switch means or the parallel capacitance including the input capacitance of the multilayer piezoelectric transformer is made substantially equal to the natural resonance frequency of the multilayer piezoelectric transformer itself. In such a case, higher efficiency and a boost ratio can be obtained.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a laminated integrated piezoelectric transformer (hereinafter, referred to as a laminated piezoelectric transformer) according to the present invention. The manufacturing method of this multilayer piezoelectric transformer is as follows.
PZT ceramics (HCEPC-
28) A green sheet is prepared by a doctor blade method, and platinum internal electrodes (input internal electrodes) 57 and 58 are printed on a part of the green sheet by a screen printing method, and the sheets are laminated and pressed. And sinter. afterwards,
After cutting and polishing, the input external electrode 5
1 and 52 and an output electrode 55 are provided, an internal electrode 57 is connected to the external electrode 51, and an internal electrode 58 is connected to the external electrode 52. At this time, an insulating layer 59 is provided between the internal electrodes 57, the external electrodes 52, and the internal electrodes 58 to prevent the external electrodes 51 from contacting each other. The polarization process in the thickness direction of the drive unit and the longitudinal direction of the power generation unit is performed to complete the process. When the laminated piezoelectric transformer is excited in a commonly used full-wavelength mode, a quarter of the total length has the smallest vibration displacement.
When the external electrodes 51 and 52 are provided at this position as shown in the drawing,
Even if the external electrodes 51 and 52 are fixed by the external terminals, the characteristics of the multilayer piezoelectric transformer are not impaired. FIG. 2 shows the tube current characteristics of the input voltage when the cold cathode fluorescent lamp is loaded, and FIG. 3 shows the tube current characteristics of the efficiency, with the number of laminations of the laminated piezoelectric transformer thus manufactured as a parameter. The cold cathode tube has a tube diameter of 3.0 [mm],
A tube with a length of 210 [mm] was used. The external dimensions of the laminated piezoelectric transformer are 30 [mm] in length and 6.5 [m] in width.
m] and a thickness of 1.2 [mm], and the resonance frequency varies with the tube current, but is about 111 [kHz] in the full wavelength mode.

The cold-cathode tube used is of the type installed on the long side of the liquid crystal display of a notebook personal computer. From the characteristics shown in FIG. 2, the tube current required for the liquid crystal display is 5 to 7 [mA]. In order to obtain
An AC input voltage of 3 to 90 [V] or more is required. If a laminated piezoelectric transformer having six or more layers is used, tube power required for a liquid crystal display of a notebook computer can be obtained with an AC input voltage of 14 [V] or less. From the characteristics of FIG. 3, the transformer efficiency is 90 in the region where the tube current is 3 mA or more.
[%] Or more, which is an efficiency comparable to that of a conventional electromagnetic transformer.

Another embodiment of the laminated piezoelectric transformer according to the present invention is shown in FIGS. FIG. 16 is a perspective view, FIG.
Is a cross-sectional view in the width direction. By slightly shifting the opposing internal electrodes 57 and 58 in the width direction, the internal electrodes and the external electrodes are connected without using the insulating layer 59. FIG. 18 shows still another embodiment of the multilayer piezoelectric transformer according to the present invention. In this embodiment, the internal electrodes 57 and 58 are slightly opposed in the longitudinal direction to connect the internal electrodes and the external electrodes without using the insulating layer 59. However, the vibration displacement is the largest at all wavelengths. External electrodes 51, 5 are provided on the end face and half of the total length.
2 will be provided. In this case, the external electrode and the external terminal are not directly connected, but are connected via a lead wire having sufficient strength.

In a portable information device such as a notebook personal computer, a DC voltage is used as an input power supply. The multilayer piezoelectric transformer of the present invention is provided with an inverter for converting DC to AC, and is used as a device for driving a discharge tube. Used for portable information devices. FIG. 4 is a circuit configuration diagram of the discharge tube driving device according to the present invention, and the operation of this circuit will be described below. When the DC voltage V ₂ is input, the positive voltage (V ₂ ) is applied to the input electrodes 51 and 52 of the multilayer piezoelectric transformer 50 via the inductor 30, but immediately the starting current is increased via the resistor R _1. flow, (hereinafter referred to as MOSFET) transistor 22 and the MOS field effect transistor 21 is turned on, the input voltage V ₃ of the multilayer piezoelectric transformer is zero. That is, during this time the pulse shaped voltage is applied to the input of the laminated piezoelectric transformer, the voltage of the cathode is generated in the output electrode 55 from its operating principle, to turn on the transistor 24 through a feedback resistor R _2. When the transistor 24 is turned on, the transistor 22 is turned off and the transistor 23 is turned on.
The OSFET 21 is turned off instantaneously, and the positive electrode voltage is applied again to the input electrode 51 of the multilayer piezoelectric transformer. Then, the output voltage of the laminated piezoelectric transformer is inverted, and turns off the transistor 24 through a feedback resistor R ₂ becomes a negative electrode,
Since the transistor 22 is turned on and the transistor 23 is turned off, the MOSFET 21 is turned on instantaneously. Thereafter, the same operation is repeated, and a boosted high-frequency voltage is generated between the output electrode 55 and the common electrode 52 of the multilayer piezoelectric transformer and supplied to the electrodes 61 and 62 to cause the discharge tube 60 to emit light.

The inversion operation for turning on and off the MOSFET 21 is a self-excited oscillation operation performed by a voltage generated at the output of the multilayer piezoelectric transformer 50. In this self-excited oscillation, the detection unit of the feedback signal has the maximum mechanical displacement. Also,
In order to obtain the maximum output, the mechanical displacement of the right end face where the output electrode is located needs to be maximum. Accordingly, there are a method of directly obtaining the feedback signal from the output of the multilayer piezoelectric transformer as shown in FIG. 4 and a method of detecting the feedback signal by providing an electrode or an antenna near the output electrode as in another embodiment described later.

The example shown in FIG.
The FET 21 and the multilayer piezoelectric transformer 50 constitute a class E amplifier circuit. The Class E amplifier circuit was introduced in 1975 by N. O. Proposed by Sokal et al., Published by Nikkan Kogyo Shimbun, Inc.
It is described on pages 53 to 155. Output capacitance C _OS of the inductance L ₁ and MOSFET21 inductor 30, the resonance due to the input capacitance C ₀₁ of the multilayer piezoelectric transformer 50, half-wave as the input voltage V ₃ Figure 8 of the laminated piezoelectric transformer 50 Since it is sinusoidal, MO
The switching loss of the SFET 21 is reduced. This is a characteristic of the class E amplifier circuit. Further, when the frequency of this resonance is made substantially equal to the natural resonance frequency f _O of the multilayer piezoelectric transformer 50 as in the following equation, harmful harmonic components are small,
Since the fundamental wave component is large, particularly good efficiency and boost ratio can be obtained.

[0020]

(Equation 1)

The output capacitance C of the MOSFET 21
_OS, when the laminated piezoelectric transformer 50 in the input capacitance C ₀₁ In can not substantially match the resonant frequency, there is a method of connecting a capacitor C ₁ in parallel. It is also equivalent to connect a capacitor in parallel with the inductor 30.
In the present embodiment, the circuit configuration of FIG.
FIG. 9 shows the tube current characteristics of the input voltage and FIG. 10 shows the tube current characteristics of the efficiency in the case of using the laminated piezoelectric transformer having two layers and 12 layers. The used cold cathode tube has a tube diameter of 3.0 [mm] as described above,
The tube length is 210 [mm]. From the characteristics of FIG. 9, the tube current 5 to 7 [mA] required for the liquid crystal display is
The sixth layer can be obtained with a DC input voltage of 14 [V] or less, and the 12th layer can be obtained with a DC input voltage of 8 [V] or less. If the number of layers is increased, the DC input voltage can be further reduced.
~ 7 [mA] can be obtained. From the characteristics of FIG.
In the region where the required tube current is 5 [mA] or more, an inverter efficiency of 80% or more is obtained, which is a high efficiency comparable to an inverter using an electromagnetic transformer.

The polarization direction of the multilayer piezoelectric transformer of this embodiment is in the direction indicated by the mark → in the figure, and is excited in the full wavelength mode. When the maximum output is obtained under this condition, the phase of the input / output voltage of the multilayer piezoelectric transformer is advanced by about 90 degrees. Therefore, in the present embodiment, the above-mentioned input / output phase is obtained by adjusting the resistance values of the feedback resistor R ₂ and the starting resistor R ₁ . Since a high-frequency high voltage is generated at the output of the multi-layer piezoelectric transformer 50, an induced voltage is generated in components and wirings arranged in the vicinity thereof, and an oscillation operation deviating from the above-mentioned input / output phase is performed to improve efficiency and boost ratio. May be worse. FIG. 8 shows the voltage waveform of the present embodiment. As described above, the output voltage V _O is advanced by about 90 degrees with respect to the input voltage V ₃ of the multilayer piezoelectric transformer. Obtained.

In the above-described example, when the phase of the output voltage V _O is advanced by about 90 degrees with respect to the input voltage V ₃ of the multilayer piezoelectric transformer, good efficiency and step-up ratio are obtained. When the polarization direction of the driving unit is reversed or when the vibration mode is changed to the half-wavelength mode, it is preferable that the phase of the output voltage V _O is delayed by about 90 degrees with respect to the input voltage V ₃ of the multilayer piezoelectric transformer. Efficiency and boost ratio were obtained.

FIG. 5 is a circuit diagram of a discharge tube driving device according to the present invention in which a feedback signal is detected by a feedback electrode 53 provided near an output electrode. The maximum output can be obtained from the output electrode as in the example of FIG.

FIG. 6 is a circuit diagram of a discharge tube driving device according to the present invention, in which a feedback signal is detected by an antenna 54 arranged near an output electrode. Also in this case, the maximum output can be obtained from the output electrode as in the example of FIG.

FIG. 7 shows an embodiment of the present invention having a dimming function for adjusting the light emission amount of the discharge tube. The configuration is obtained by adding a tube current detection unit 200 and a pre-stage voltage control unit 100 to the embodiment of FIG. A tube current detector 200 is provided for detecting a current flowing through the discharge tube 60. The level of the detection signal 210 can be changed by detecting the tube current with the variable resistor R5 and changing the resistance value. Front voltage control unit on the basis of the detection signal that controls the supply voltage V ₂ to the inverter unit. Specifically, when the resistance value of the variable resistor R5 is reduced, the pre-stage voltage control unit operates so as to increase the tube current in order to keep the detection signal constant, and the supply voltage V
Increase ₂ Front voltage controller are well known in the art buck, boost, using a chopper control or dropper control such as inverting controls the supply voltage V _2. There is also a method dimmer for controlling the tube current in duty control for intermittently supplying voltage V _2.

Hereinafter, another embodiment of the present invention will be described with reference to the drawings. FIG. 19 is a circuit configuration diagram of a discharge tube driving device according to the present invention. When the DC voltage V ₂ is applied, a boosted high-frequency voltage is generated between the output electrode 55 of the piezoelectric transformer and the common electrode 52 and supplied to the electrodes 61 and 62 to cause the discharge tube 60 to emit light. The inversion operation of turning on and off the MOSFET 21 is a self-excited oscillation operation performed by a voltage generated at the output of the piezoelectric transformer. The feedback signal may be obtained directly from the output of the piezoelectric transformer as shown in FIG. 19, or may be detected by providing an electrode or antenna near the output electrode. This DC voltage V ₂ is applied to the electromagnetic transformer 13
0 primary winding 131 (the number of turns is n ₁ ) and secondary winding 132
Since the voltage is boosted to a turn ratio (n ₁ + n ₂ ) / n ₁ times (turns is n ₂ ) and applied to the piezoelectric transformer, the cold cathode tube is driven even with a 3 [V] input used in portable information terminal equipment. can do.

As described above, the present invention can be implemented in various modes. It is obvious that the present invention can be implemented in cases other than those shown here, depending on the polarization direction and vibration mode of the multilayer piezoelectric transformer, and the configuration of the switch means and the drive / oscillation means.

[0029]

According to the present invention, since the driving portion of the laminated piezoelectric transformer is laminated, a discharge tube such as a cold cathode tube can be driven with high efficiency even at a low input voltage used in a portable electronic device. be able to. In particular, the resonance frequency of the parasitic capacitance of the inductor and the switching means provided in series with the multilayer piezoelectric transformer or the parallel capacitance including the input capacitance of the multilayer piezoelectric transformer is substantially equal to the natural resonance frequency of the multilayer piezoelectric transformer itself. If they are made to match, higher efficiency and a boost ratio can be obtained. Further, since the multilayer piezoelectric transformer has a large output impedance, the ballast capacitor for limiting the tube current used in the electromagnetic transformer method is not required. Furthermore, since the laminated piezoelectric transformer has an extremely simple structure and a small size as compared with a conventional electromagnetic transformer, the driving device for the discharge tube can be reduced in size and thickness.

[Brief description of the drawings]

FIG. 1 is a perspective view of a multilayer piezoelectric transformer according to the present invention.

FIG. 2 shows tube current characteristics of an input voltage of the multilayer piezoelectric transformer according to the present invention.

FIG. 3 shows tube current characteristics of the efficiency of the multilayer piezoelectric transformer according to the present invention.

FIG. 4 is a circuit diagram of a discharge tube driving device using the multilayer piezoelectric transformer according to the present invention.

FIG. 5 is a circuit diagram of a discharge tube driving device according to the present invention in which a feedback signal is detected by a feedback electrode provided near an output electrode.

FIG. 6 is a circuit diagram of a discharge tube driving device according to the present invention in which a feedback signal is detected by an antenna arranged near an output electrode.

FIG. 7 is a diagram showing a circuit configuration of an embodiment of the present invention having a dimming function for adjusting a light emission amount of a discharge tube.

FIG. 8 is a diagram showing waveforms of an input voltage and an output voltage of a laminated piezoelectric transformer in the discharge tube driving device according to the present invention.

FIG. 9 shows tube current characteristics of an input voltage of the discharge tube driving device according to the present invention.

FIG. 10 shows tube current characteristics of the efficiency of the discharge tube driving device according to the present invention.

FIG. 11 is an explanatory diagram showing the operating principle of a Rosen-type piezoelectric transformer.

FIG. 12 shows a load resistance characteristic of an output voltage of a Rosen-type piezoelectric transformer.

FIG. 13 shows a load resistance characteristic of the efficiency of the Rosen-type piezoelectric transformer.

FIG. 14 is a circuit diagram of a conventional discharge tube driving device using an electromagnetic transformer.

FIG. 15 is a circuit diagram of a conventional discharge tube driving device using a piezoelectric transformer.

FIG. 16 is a perspective view of a laminated piezoelectric transformer according to another embodiment of the present invention.

FIG. 17 is a cross-sectional view in the width direction of a multilayer piezoelectric transformer according to another embodiment of the present invention.

FIG. 18 is a perspective view of a laminated piezoelectric transformer according to still another embodiment of the present invention.

FIG. 19 is a circuit diagram of a driving device for a discharge tube using the multilayer piezoelectric transformer according to the present invention.

[Explanation of symbols]

21: MOS field effect transistor, 22: transistor, 23: transistor, 24: transistor, 3
0: inductor, 50: laminated piezoelectric transformer, 51: input electrode, 52: input electrode (common electrode), 53: feedback electrode, 54: antenna, 55: output electrode, 57: internal electrode, 58: internal electrode, 59 : Insulating layer, 60: discharge tube, 1
30: Electromagnetic transformer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K072 AA01 AA19 AC02 AC11 AC20 BA03 BC05 BC07 CA16 DD04 DE03 DE04 DE05 DE07 GA01 GA03 GB03 GB17 GC01 GC07 HA05 5H007 AA00 BB03 CA02 CB07 CB09 CB22 DA05 DA06 DB01 DC02 DC05 5H730 AA AS BB61 DD04 EE59 ZZ19

Claims (2)

[Claims] 1. A cold-cathode tube driving device comprising: a multilayer integrated piezoelectric transformer; and an inverter unit that converts a DC input voltage into an AC input voltage and supplies the AC input voltage to the multilayer integrated piezoelectric transformer. The body type piezoelectric transformer is a piezoelectric transformer having a first region polarized in the longitudinal direction and a second region polarized in the thickness direction, and the first region and the second region are formed by laminating a piezoelectric sheet. Piezoelectric bodies and internal electrodes are alternately laminated by forming internal electrodes on the surface of the piezoelectric sheet in the second region, which is formed by integral sintering and polarized in the thickness direction, and the internal electrodes are An external electrode provided on the longitudinal side surface is connected to every other layer, and the number of layers is 6 or more. The laminated integrated type piezoelectric transformer has a tube current flowing through the cold-cathode tube at the AC input voltage of 14 V or less. Is 3mA or more A cold cathode having a transformer efficiency of 90% or more in a region and an inverter efficiency of 80% or more in a region where the tube current flowing through the cold cathode tube is 5 mA or more at the DC input voltage of 14 V or less. Tube drive. 2. A resonance frequency of a parallel integrated capacitance including an input capacitance of the multilayer integrated piezoelectric transformer substantially coincides with a natural resonance frequency of the multilayer integrated piezoelectric transformer. 2. The driving device for a cold cathode tube according to claim 1.