JP2003324945A - Piezoelectric dc-dc converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric DC-DC converter having a high efficiency and high reliability. <P>SOLUTION: The piezoelectric DC-DC converter comprises a DC power source, a half-bridge type inverter having first and second switching elements connected with the power source and receiving a DC from the power source to convert the DC into an AC, a step-down circuit for transforming the AC output of the inverter by a laminated press-bonded piezoelectric transformer using a series resonance with an inductance for the series resonance, a circuit for converting the AC output of the step-down circuit into a DC to supply the DC to a load, and a control circuit for controlling the first and second switching elements in response to the voltage to be applied to the load. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric DC-DC
Regarding the converter.

[0002]

2. Description of the Related Art An example of a half-bridge type PWM converter as a conventional DC-DC converter is shown in FIG.

This DC-DC converter comprises a DC voltage source 1, a capacitance 15 for dividing the output voltage into two equal parts, a first switch 2a connected to the positive electrode of the DC power source 1 and its negative electrode. A second switch 2b connected in series to the first and second switches 2a and 2b, respectively, and first and second diodes 3a and 3b connected in anti-parallel, respectively, An inverter 4 that receives direct current from the direct current power source 1 and converts it into alternating current, and an inductance 5 connected in series at the output side of this inverter 4.
And the capacitance 6, the transformer 7 connected to the inductance 5 and the capacitance 6, and the transformer 7.
Rectifier 8 for converting the output of the rectifier into a direct current, a load 9 connected to the output side of the rectifier 8, and first and second switches according to a setting signal of a voltage applied to the load 9 and a current flowing through the load. 2a and 2b, and means for controlling the on / off timing.

In FIG. 4, the first switch 2a and the first diode 3a, the second switch and the second diode 3b, and the first arm 10a, respectively.
And a second arm 10b. Further, the rectifier has four diodes 11a, 11b, 11c,
The input voltage is full-wave rectified at 11d. The capacitance 12 of the high voltage cable for applying the output voltage of the rectifier 8 to the load 9 smoothes the output voltage from the rectifier 8.

In contrast to the above circuit, for example, Japanese Patent Laid-Open No. Hei 7 (1998)
There is a technique disclosed in JP-A-123718 or JP-A-7-87740. In each of these techniques, there is a problem in that efficiency is reduced and noise is generated due to switching loss due to a surge voltage at the moment when the first switch 2a and the second switch 2b are turned on or off. Is solved by devising.

For example, in the technique disclosed in Japanese Patent Application Laid-Open No. 7-123718, soft switching is enabled by connecting an inductance L1 in series with the primary winding of the transformer 7.

Further, for example, in the technique disclosed in Japanese Patent Laid-Open No. 7-87740, lossless snubbers are connected to both ends of the switches 2a and 2b, and an auxiliary circuit is provided between the connection point of the switches 2a and 2b and the midpoint of the capacitance 15. High efficiency is possible by connecting the inductance of.

[0008]

However, in these circuit configurations, high efficiency is realized by devising the circuit.
Since a winding transformer is used as the secondary-secondary transformer, if the magnet wire has scratches or if excessive tensile stress is applied, a rare short circuit will occur between the windings, resulting in less reliability. There was one side that could not be raised. Further, in many cases, in order to ensure insulation between the primary and secondary sides of the transformer, an insulator is interposed between them and the transformer bobbin has a divided structure, so that the primary-
There was a case where the coupling between the second order became poor and the efficiency was lowered.

The present invention has been made in order to solve such a problem, and its technical problem is to use a piezoelectric DC circuit of high efficiency and high reliability by using a circuit configuration that makes use of the characteristics of a piezoelectric transformer. -To provide a DC converter.

[0010]

The present invention is a series resonance type DC-DC converter of a half bridge dip, wherein a transformer is a laminated crimp type piezoelectric transformer, and input voltage fluctuations, load fluctuations, and aging of the piezoelectric transformer. With respect to changes, pulse width control is performed so that a specific voltage can be stably supplied.

More specifically, the piezoelectric DC-DC converter of the present invention is a DC power supply and a first DC power supply connected to this DC power supply.
And a half-bridge type inverter, which comprises a second switching element and receives direct current from the direct current power source and converts it into alternating current, and a laminated crimp type piezoelectric transformer using series resonance with a series resonance inductance A step-down circuit for transforming an AC output, a circuit for converting the AC output of the step-down circuit to a DC and supplying it to a load, and a control circuit for controlling the first and second switching elements according to a voltage applied to the load With.

The laminated pressure bonding type piezoelectric transformer is
The output side is a laminated type, the input side and the output side are arranged vertically, and a sandwich structure in which an insulator having no piezoelectricity is interposed therebetween strengthens the insulation between the input side and the output side.

Further, the control circuit performs switching frequency control and pulse width control (PWM),
It operates so that a constant voltage is output with high efficiency and stability against variations in input voltage, variations in load, or changes with time of the piezoelectric transformer.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention. DC power supply 101 and FET switches 102 and 10
3 and other peripheral elements form a half bridge circuit.

A rectangular wave is generated by the FET switches 102 and 103, and the primary winding 105 of the series resonance inductance 104 and the equivalent input capacitor 1 of the piezoelectric transformer 107 are generated.
A sine wave (first order) is generated by causing series resonance at 08. The sine wave in the piezoelectric transformer 107 is N:
The voltage is stepped down to 1 and the sine wave (second order) is output.

Further, 109 and 113 are equivalent resistances, and 11
0 and 114 are equivalent coils, 111 and 115 are equivalent capacitors, and 112 is an equivalent output capacitor.

The sine wave (secondary) output is the diodes 116 and 117, the choke coils 118 and 11.
9, further rectified and smoothed by the capacitor 120, and supplied as a DC voltage to the load resistor 121.

Further, since the primary winding 105 and the auxiliary winding 106 are electromagnetically coupled, the primary winding 10 generated at the time of resonance
Part of the magnetic energy of No. 5 can be extracted via the auxiliary winding 106. This energy is supplied as an auxiliary power source for the pulse generator 125, the pulse width control circuit 126, and the driver (or pulse transformer) 129.

On the other hand, the output voltage of the DC-DC converter is compared with the reference voltage 123 by the error amplifier 122.
A feedback signal corresponding to the output voltage is input from the error amplifier 122 to the pulse width control circuit 126 via the optical coupling element 124. The pulse width control circuit 126 controls the ON-OFF time of the FET switches 102 and 103 according to the feedback signal amount, and the pulse generator 125 outputs an appropriate gate signal, so that the output voltage can be kept constant. It will be possible.

Next, the laminated pressure bonding type piezoelectric transformer according to the present embodiment will be described with reference to the drawings.

FIG. 2 is a structural diagram of the piezoelectric transformer of this embodiment. 2 (a) is an exploded perspective view showing the laminated structure, and FIG. 2 (b) is a perspective view showing its appearance.
(C) is the AA sectional view.

FIGS. 2A and 2C show a laminated structure in which an input portion, an insulating portion, and an output portion are vertically arranged. Further, in FIG. 2A, 21 is a piezoelectric ceramic plate, and 22 is an internal electrode printed thereon. In addition, the reason why the internal electrode pattern has a round shape and a quadrangular shape is to avoid concentration of stress at the boundary between the portion having the internal electrode and the portion having no internal electrode when the same shape is used.

In order to avoid such stress concentration, the diameter of the round shape may be different, or the length of the side of the quadrangle may be different. However, the same shape can be used depending on the manufacturing conditions. The insulating portion is shown in FIG. 2C as a uniform insulating layer having no piezoelectric property.
Illustration is omitted in (a).

In FIG. 2B, 23 is one of the external electrodes on the input side, and 24 is one of the external electrodes on the output side.

Further, as shown in FIG. 2C, the output part is formed by closely stacking internal electrodes in order to increase the capacitance, perform impedance matching, and improve efficiency.

A method of manufacturing this piezoelectric transformer will be described.
A piezoelectric ceramic green sheet was formed to a thickness of 60 μm by the green sheet method, and internal electrodes were formed by screen printing to form internal electrode patterns. By these, the input part, the output part, and the insulator having no piezoelectricity are integrally laminated and pressure-bonded, and then the binder is removed and the temperature is 1100 ° C.
It was produced as an integral sintered body by sintering for 2 hours.

As materials for the intermediate insulating layer, lead zirconate based antiferroelectric materials and lead titanate based materials having a small dielectric constant were studied and prototyped. After that, an external electrode was baked on each terminal extraction portion and polarized in a 180 ° C. silicon oil at an electric field strength of 1.5 kV / mm for both the input portion and the output portion to produce a piezoelectric transformer.

The half bridge type series resonance type DC-DC converter by the above circuit using this piezoelectric transformer has an efficiency of 88 to 90% at a switching frequency of 100 kHz, an input voltage of DC350V ± 10% and an output voltage of DC17V ± 3%. Was obtained.

In the present embodiment, a circuit structure that makes use of the high efficiency of the piezoelectric transformer is used, and a layer of an insulator having no piezoelectricity is provided between the input section and the output section, so that the input / output As a result of improving the insulation property of, a highly efficient and highly reliable piezoelectric DC-DC converter was obtained.

By the way, the structure of the piezoelectric transformer is roughly divided into two according to the arrangement of the external electrodes, and the vertical arrangement of the present embodiment in which the input portion, the insulating portion, and the output portion are vertically arranged according to the sectional structure. In addition to the type, there is a lateral arrangement type in which the input section, the insulating section, and the output section are arranged on the left and right, that is, in parallel to the substrate. FIG. 3 shows the structure of a horizontally arranged piezoelectric transformer.

FIG. 3 (a) is an exploded perspective view of the laminated structure, FIG. 3 (b) is a perspective view showing its appearance, and FIG. 3 (c).
Is a sectional view taken along line BB.

In FIG. 3A, 31 is a piezoelectric ceramic plate, and 32 is an internal electrode. Further, in FIG. 3B, reference numerals 33 and 34 denote external electrodes on the output side.

In the case of this horizontally arranged piezoelectric transformer,
Two external electrodes on the input side or the output side can be formed on one side surface. Therefore, in the vertical arrangement type in which the input portion, the insulating portion, and the output portion are vertically arranged as described in the above-mentioned embodiment, compared to the case where the external electrodes are formed by using the four side surfaces, it is possible to mount the substrate on the substrate. It is advantageous. Further, it is possible to use a piezoelectric vibration mode different from that of the vertically arranged type.

[0035]

As described above, according to the present invention, it is possible to provide a highly efficient and highly reliable piezoelectric DC-DC converter.

[Brief description of drawings]

FIG. 1 is a piezoelectric DC-D according to an embodiment of the present invention.
The circuit diagram of a C converter.

FIG. 2 is a structural diagram of a vertically arranged piezoelectric transformer according to an embodiment of the present invention. 2A is a perspective view showing the laminated structure, FIG. 2B is an external perspective view, and FIG. 2C is AA.
Sectional view.

FIG. 3 is a structural diagram of a horizontally arranged piezoelectric transformer. Figure 3
3A is a perspective view showing the laminated structure, FIG. 3B is an external perspective view, and FIG. 3C is a sectional view taken along line BB.

FIG. 4 is a circuit diagram of a conventional DC-DC converter.

[Explanation of symbols]

21, 31 Piezoelectric ceramic plate 22, 32 internal electrodes 23 Input side external electrode 24, 33, 34 Output external electrodes 101 DC power supply 102, 103 FET switch 104 Inductance for series resonance 105 Primary winding for resonance 106 auxiliary winding for power supply 107 Piezoelectric transformer 108 Equivalent input capacitor 109,113 Equivalent resistance 110,114 equivalent coil 111,115 equivalent capacitors 112 Equivalent output capacitor 116, 117 diode 118,119 choke coil 120 capacitors 121 Load resistance 122 Error amplifier 123 Reference voltage 124 Optical coupling element 125 pulse generator 126 pulse width control (PWM) circuit 127 Time constant resistance 128 time constant capacitor 129 Driver (or pulse transformer)

Claims (3)

[Claims] 1. A half-bridge type inverter comprising a direct current power source and first and second switching elements connected to the direct current power source, which receives direct current from the direct current power source and converts it into alternating current, and for series resonance A step-down circuit that transforms the AC output of the inverter by a laminated pressure bonding type piezoelectric transformer that uses series resonance with an inductance, and a circuit that converts the AC output of the step-down circuit to DC and supplies the load.
A piezoelectric DC-DC converter, comprising: a control circuit that controls the first and second switching elements according to a voltage applied to the load. 2. The laminated pressure-bonding type piezoelectric transformer has a sandwich structure in which an output side is a laminated type and an input side and an output side are vertically arranged, and an insulator having no piezoelectricity is interposed therebetween. The piezoelectric DC-D according to claim 1.
C converter. 3. The piezoelectric DC-DC converter according to claim 1, wherein the control circuit is a circuit that performs switching frequency control and pulse width control (PWM).