Errata High power universal piezoelectric transformer by nikeborome


									               Errata - High power universal piezoelectric transformer
Priya, S.;   Hyeoungwoo Kim;   Ural, S.;   Uchino, K.Ultrasonics, Ferroelectrics and Frequency Control, IEEE Transactions
on810-816April 2006学术搜索

      810                         ieee transactions on ultrasonics, ferroelectrics, and frequency control, vol. 53, no. 4, april 2006


                       High Power Universal Piezoelectric
                      Shashank Priya, Hyeoungwoo Kim, Seyit Ural, and Kenji Uchino, Member, IEEE

         Abstract—This study describes a multilayer piezoelectric            power, no isolation between input and output region, and
      voltage and power transformer that has one direction pol-              two direction poling. Another problem with a Rosen-type
      ing, operates in a wide-frequency range and delivers both              transformer is that it cannot be used for step-down ap-
      step-up and step-down voltages by inverting the electrical
      connections. In this design, the input and output electrodes           plications because the generator section is so long (low
      are on the same side of the disk and are isolated from each            capacitance) that there is limited current flow.
      other by a fixed isolation gap. The electrode pattern is a                 In step-down applications, there are three promising
      ring/dot structure such that it uses radial mode for both
      input and output part that are built-in on the same ce-
                                                                             designs: thickness mode transformer [3]–[5], radial mode
      ramic disk. A prototype transformer was fabricated of size             transformer [6], and contour extensional vibration mode [7]
      15 2:78 mm2 having mass of 3.8 gm. In the step-down con-               transformer. Thickness-mode transformers work in mega-
      figuration at the constant output power of 6 W, the trans-              hertz frequency range, thus the driving circuit associated
      former characteristics across a 100 Ω load were found to be            with these transformers is quite complicated. It also is diffi-
      efficiency = 92%, gain = 0.21 input voltage = 110 Vrms ,
      and temperature rise = 20 C from the room temperature.
                                                                             cult to achieve a clear resonance spectrum for the ceramic
      In the step-up configuration at the constant output power               working in thickness mode. The other two transformers
      of 5 W, the transformer characteristics across a 5 kΩ load             work in the kilohertz frequency range but have problems
      were found to be efficiency = 97%, gain = 9.5, input volt-               associated with the insulation layer. Normally, alumina ce-
      age = 16 Vrms , and temperature rise = 8 C from the room               ramic is used as the insulation layer, which means the in-
      temperature. A detailed equivalent circuit analysis of the
                                                                             put and the output parts have to be fabricated separately
      transformer was done, and the results were found to be in
      excellent agreement with the experimental results.                     then bonded together. This results in the mismatching of
                                                                             the vibration spectrum. In case, the unpoled piece of the
                                                                             same composition is used as the insulating layer the trans-
                             I. Introduction                                 former does not have true isolation. Furthermore, in order
           he piezoelectric transformer (PT) offers several ad-
                                                                             to use these designs in the step-up mode, a new set of de-
                                                                             sign parameters has to be calculated, and a new structure
      T    vantages compared to the electromagnetic ones, such
      as higher electromechanical power density, no electrome-
                                                                             should be fabricated.
                                                                                Recently Priya et al. [8], [9], and Uchino et al. [10] pro-
      chanical noise, higher efficiency at resonance, miniaturiza-             posed a new structure of the unipoled transformer with
      tion is possible, wide frequency range, nonflammable, and               quite high-power density. In this design, the electrode pat-
      simpler fabrication technique. Various applications such as            tern is a ring/dot-strip structure. Investigations were per-
      backlight inverters, power supplies for notebook comput-               formed on a disk of diameter 29.1 mm. The power density
      ers, alternating current-direct current (AC-DC) convert-               for the optimized single-layer transformer was found to
      ers, power supply for displays, image intensifiers, and air             be 40 W/cm3 , and that for the three-layer structure was
      cleaners have been proposed and implemented for PT’s.                  found to be 25 W/cm3 . This design was a significant im-
      Several transformer designs have been proposed to meet                 provement over the previous ring-dot structure reported
      the specifications in both step-up and step-down applica-               by Berlincourt [11]. The dot-strip structure made the con-
      tions [1]–[5]. In step-up applications, Rosen type [1] still           struction of the multilayer structure possible. However, it
      remains the preferred design for the manufacturers. How-               has limitations in terms of the voltage gain, which has a
      ever, this design has inherent disadvantages, such as low              very narrow range.
        This paper was originally published with an incomplete author list      Uehara et al. [12] also reported the ceramic transformer
      as S. Priya, “High power universal piezoelectric transformer,” IEEE    based on the ring/dot-strip structure that uses the multi-
      Transactions on Ultrasonics, Ferroelectrics and Frequency Control      layer assembly in the input and output part for tuning
      vol. 53, no. 1, pp. 23–29, Jan. 2006. Please cite this version.
        Manuscript received March 4, 2005; accepted June 30, 2005.           the gain. The internal electrode layers are positioned such
        S. Priya is with the Department of Materials Science and Engineer-   that the third radial extensional vibration mode clearly
      ing, University of Texas at Arlington, Arlington, TX 76019 (e-mail:    can be obtained. The advantage of this design is that gain
        H. Kim, S. Ural, and K. Uchino are with Materials Research Insti-    of the transformer can be tuned by changing the ratio of
      tute, Pennsylvania State University, University Park, PA 16802.        the number of layers in input and output section. However,

                                                           0885–3010/$20.00 c 2006 IEEE 学术搜索
      priya et al.: high power universal piezoelectric transformer                                                                      811

      it suffers from the disadvantage that the working frequency
      lies in the high-frequency range of over 500 kHz because
      the resonant frequency in the third radial extensional vi-
      bration mode is about 2.7 times as high as the resonant
      frequency of the fundamental radial extensional vibration
      mode. Furthermore, the efficiency of the transformer is
      critically dependent upon the position of the input and
      output electrode layers because of the high-stress region
      present in the insulating region (gap between the input
      and output part). The displacement in the third radial vi-
      bration mode maximizes at the center and side-end face of
      the ceramic, the presence of the notches in the electrodes
      on both the sections affects the performance. Another dis-
      advantage of this design is that the isolation field between
      the input and output segment is not high because the elec-
      trode strips from the dot region are embedded beneath the
      outer ring electrode region. In practical applications, iso-
      lation potential of 3 kV or higher is required.
          In order to remedy these problems, a piezoelectric trans-
      former should be designed such that it uses higher coupling
      vibration modes for better energy conversion, one direc-
      tion poling (henceforth referred as “unipoled”) for easier
      electrical connections and isolation between the input and
      output parts for good insulation. The transformer design
      should be such that the power generated can be controlled
      by some physical parameter. Furthermore, the transformer
      design should be such that the same structure can be used
      for both step-up and step-down application.
          This study investigates a novel piezoelectric transformer

      that satisfies these conditions and provides a solution to
      the problems of previous designs. The structure uses a sim-
      pler ring-dot pattern eliminating the strip section that al-
      lows a complete isolation between the input and the out-

      put segment. The outer ring section is multilayered, and
      the central ring region is single layered, thus the electri-
      cal connections can be made very easily on the side faces
                                                                      Fig. 1. Schematics of the proposed high-power, universal piezoelec-
                                                                      tric transformer. (a) Electrode pattern of the internal layers showing
                                                                      the ring-dot pattern. (b) Electrical connections for the transformer
      in the ring region and top-bottom in the dot region. This       working in the step-down mode. (c) Electrical connections for the
                                                                      transformer working in the step-up mode. The ring part is multilay-
      transformer operates in the fundamental radial extensional      ered and in the fabricated prototype consisted of five layers. The dot
      mode so the presence of the notch on the side face in the       part is single layer.
      ring region does not have any effect on the performance.
      The gain and matching impedance of the transformer in
      this design is simply controlled by the number of the layers    tion, < 2 s) and then a constant high power in the satura-
      in the ring region. The fabrication process of this design      tion regime. The magnitude of the power level is dependent
      also is simplified because of no internal electrode layers in    upon the size of the lamps, such as a 5 W transformer is
      the inner dot region, thus eliminating the need of multiple     required for xenon headlights in toys.
      masks for electrode printing.
          The focus in this study was on developing a low pro-
      file, cost-effective transformer structure having dimensions                     II. Experimental Procedure
      about a half inch in diameter and 1/10 inch thickness
      targeting two different applications, cell phone charger            Fig. 1 shows the schematics of the electrode pattern and
      and headlights in automobile toys and robotics. The cell        electrical connections of the proposed transformer. The
      phone charger requires a small size, lightweight trans-         electrode pattern is a ring-dot separated by an isolation
      former with a gain of 0.15–0.25, power of 3–4 W and             gap. The ring part is a multilayered structure and the dot
      matching impedance of about 50 Ω. Such transformer also         part is a single layer. The transformers were fabricated us-
      could be used for the slim AC/DC adapters. For xenon            ing multilayer, co-fired process at Dong-Il Technology Ltd.,
      bulb (white light) a high-power, high-gain transformer is       Gyonggi-Do, Korea, using high-power PZT ceramics [13]–
      required because large voltage of the order of ∼kilovolt is     [15]. The process starts with a preparation of green sheet
      required for the arcing to take place (open circuit condi-      of PZT material. Calcined material is mixed in a ball mill 学术搜索
      812                      ieee transactions on ultrasonics, ferroelectrics, and frequency control, vol. 53, no. 4, april 2006

      for 36 hours with binder solution consisting of polyvinyl
      butyral (PVB), dibutyl phthalate (DBP), fish oil, methyl
      ethyl ketone (MEK), and toluene. Mixed slurry then is de-
      foamed under vacuum and cast into tapes of 90–100 µm
      in thickness on poly(ethylene terephthalate) (PET) film
      using a doctor blade casting machine. Green tapes then
      are cut into sheets with aligning holes, alternating pat-
      terns of electrode layers are printed using Ag/Pd paste.
      After drying the electrode paste, printed electrode sheets
      are stacked in registry with aligning holes and hot pressed
      under vacuum at 85◦ C. Hot-laminated green bars then are
      punched into separate green disk elements. Green disks
      then are fired at 260◦ C for binder burnout and sintered
      in the temperature range of 1100–1200◦C. Sintered pieces
      are poled in silicone oil bath at 130◦ C under the DC field
      of 3 kV/mm.
         Table I shows the dimensions of the fabricated trans-
      formers. Transformer characterization was done using the        Fig. 2. Picture of the fabricated prototype transformer using the
                                                                      multilayer, cofired process. All the transformers used in this study
      conventional equipments and home-built software. All the        were fabricated at Dong Il Technology, Korea.
      measurements were done under constant current condi-
      tions using the procedure described in detail elsewhere [8].
      Piezoelectric admittance circle was determined using HP
      4194 (Agilent, Palo Alto, CA) impedance analyzer under
      the short circuit conditions. Fig. 1(b) shows the electri-
      cal connection for the transformer in the step-down mode.
      Fig. 1(c) shows the electrical connection in the step-up
      mode, which is obtained by reversing the connections of
      Fig. 1(b). In the step-down mode, applying the electrical
      excitation to the center dot (input), the radial extensional

      vibration is generated and propagated to the external ring
      (output). At the output, the mechanical vibrations again
      are converted into electrical voltage through a direct piezo-
      electric effect. Because this transformer design uses a ra-

      dial mode for both input and output, which are built-in
      on the same ceramic disk, it has a much higher bandwidth
      as compared to other designs (because k33 > kp > k31 ).
      The multilayer section is equivalent to connecting multiple
      units in parallel. Basically, by connecting n units in par-
      allel, the motional resistance and inductance of the trans-
      former are reduced by 1/n times and the capacitance is
      increased by n times. The matching load is reduced by n
      times; and because of the lower impedance, the operating        Fig. 3. Equivalent circuit of the piezoelectric transformer determined
                                                                      using the admittance circle. (a) General representation of the piezo-
      frequency range also is reduced. The output power of the        electric transformer. (b) Measured equivalent circuit parameters of
      transformer is increased roughly by a factor of n, although     the step-down transformer. (c) Measured equivalent circuit parame-
      at a higher n the power density is reduced. In this way, a      ters of the step-up transformer.
      compact, high-power transformer is obtained. Fig. 2 shows
      the picture of the fabricated piezoelectric transformer.
                                                                      admittance values (Y (ω) = G(ω) + jB(ω), where G is the
                                                                      conductance and B is the susceptance) obtained by short
                III. Equivalent Circuit Analysis                      circuiting one of the terminals [16]–[18]. The admittance of
                                                                      the input terminal obtained by short circuiting the output
         A piezoelectric transformer operating near resonance         terminal is given as:
      point can be represented by the equivalent circuit shown
      in Fig. 3(a). In this circuit Rm , Lm , Cm are the motional
                                                                                   i1 (ω)
      resistance, inductance, and capacitance; ω is the angular         Y (ω) =           = jωC1
                                                                                   υ1 (ω)
      frequency; n is the transformation ratio; and C1 and C2
      are the input and output damped capacitance. The lumped                             jωCm 1 − ω 2 Lm Cm + ω 2 Rm Cm  2
                                                                                        +                   2            2 . (1)
      equivalent circuit components can be determined from the                              (1 − ω 2 Lm Cm ) + (ωRm Cm ) 学术搜索
      priya et al.: high power universal piezoelectric transformer                                                                   813

                                                                    TABLE I
                                                   Dimensions of the Fabricated Transformers.

                          Total size    Number of      One output layer       Insulation     Output diameter         Isolation
                           (mm2 )      output layers   thickness (mm)      layer thickness       (center)           gap (mm)
                          15 × 2.78            5             0.5                0.12                6                       1.5

        At the series resonance frequency:                                 where fr and fa are the resonance and antiresonance fre-
                                                                           quencies, Zr is the magnitude of impedance at the reso-
                          ω = ωr = 1       Lm Cm ,                   (2)   nance frequency, and C is the low-frequency capacitance
                                                                           measured at 1 kHz. A high magnitude of kef f and Qm was
      and (1) becomes:                                                     obtained for both input and output sections.
                                                                              At the resonance frequency, ωr , there is an optimal load
                       Y (ωr ) = jωr C1 + 1/Rm .                     (3)
                                                                           that provides the maximum efficiency. The efficiency of the
         Similarly, when the input terminal is short-circuited,            transformer, η, in terms of the equivalent circuit parame-
      the admittance converted to the output terminal is                   ters and output load (RL ) is given as:
      given as:                                                                        Output power                 1
                                                                               η=                   =                               .
                  i2 (ω)                                                                Input power         n2 Rm                 2 (10)
        Y (ω) =          = jωC2                                                                          1+       1 + (ωr C2 RL )
                  υ2 (ω)                                                                                     RL
             jωCm 1 − ω 2 Lm Cm /n2 + ω 2 n2 Rm Cm /n2                       The condition for the maximum efficiency is obtained
        +                              2               2           . (4)   by equating dη/dRL = 0 and is given as:
                    (1 − ω 2 Lm Cm ) + (ωRm Cm )
        At resonance, (3) becomes:                                                                  RL,opt =             .          (11)
                                                                                                                   ωr C2
                      Y (ωr ) = jωr C2 + 1/n2 Rm .                   (5)
                                                                           Substituting (11) in (10), the maximum efficiency at the
        The frequencies at ±45◦ from the origin, located at                optimum load then is found to be:

      (G, B) = (0, 0) on an admittance circle are related to the
      motional capacitance and inductance as:                                                  ηmax =
                                                                                                        2n m
                                                                                                          2R + R
                                                                                                                         .          (12)

                             1 (ω−45◦ − ω+45◦ )
                     Cm =       ·                   ,                (6)       The optimum load (RL,opt ) for the two types of trans-
                                    ω−45◦ · ω+45◦
                          = Rm ·
                                  (ω−45◦ − ω+45◦ )
                                                   .                 (7)
                                                                           formers was determined by using (11) and the parameters
                                                                           listed in Table II. It was found to be 87.85 Ω for the step-
                                                                           down transformer and 4.74 kΩ for the step-up transformer.
                                                                           The resonance frequency corresponding to a given load RL
         Using (1) to (7) all the equivalent circuit parameters
                                                                           is given by (13) [16]:
      can be determined if the complex admittance is measured
      from the admittance circle.                                                               1
         The complex admittance was measured using the HP                       ωr =                        ,
                                                                                               Cm · Cseries
      4194A impedance analyzer, and the equivalent circuit con-                           Lm ·
                                                                                               Cm + Cseries
      stants were determined from this data. Figs. 3(b) and (c)
      show the equivalent circuit parameters for the transformer           where:
      in step-down mode [Fig. 1(b)] and step-up mode [Fig. 1(c)],                                                                   (13)
      respectively. Table II shows the magnitude of the piezo-                               1 + (ωr · C2 · RL )
      electric coefficients computed using the equivalent circuit            Cseries = n2 C2                     2        .
                                                                                               (ωr · C2 · RL )
      parameters. The effective coupling factor (kef f ) and me-
      chanical quality factor (Qm ) were determined using the                 Using the above expressions, the maximum efficiency
      expressions [6], [8], [9]:                                           was determined to be 0.968 for the step-down transformer
                                                                           and 0.978 for the step-up transformer. The voltage gain
                                   fa − fr
                                    2    2
                                                                           of the transformer (G) can be derived by transferring the
                      kef f =          2
                                           ,                         (8)
                                      fa                                   output side of the equivalent circuit to the input side and
                                                                           analyzing the circuit equations as seen in (14) (see next
      and:                                                                 page) [18].
                                                                              Using the above expression, the gain for the step-down
                                   1         f2                            transformer is found to be 0.254 at the load of 100 Ω and
                       Qm =              · 2 a 2,                    (9)
                                2πfr Zr C fa − fr                          8.293 for the step-up transformer at the load of 5 kΩ. 学术搜索
      814                     ieee transactions on ultrasonics, ferroelectrics, and frequency control, vol. 53, no. 4, april 2006

                                                             TABLE II
                                Piezoelectric Properties Calculated from the Admittance Spectrum.

                                 Connection     fr (kHz)   fa (kHz)   Zr (Ω)    C (nF)     kef f     Qm
                                 Output short    147.1      155.45     51.74     0.2283    0.323   876.14
                                 Input short     147        152.3       1.764   12.316     0.261   728.70

                            υ2                                           1
                       G=      =                                                                                       .            (14)
                            υ1          1     C2               Rm
                                                                                        Lm                  1
                                   n      2
                                            +    − ω 2 Lm C2 +              + ω Rm C2 +             −
                                        n     Cm               RL                       RL              ωCm RL

      These numbers indicate that this design can work in both
      ways and provide efficient performance. The magnitude of
      the optimum load is close to that desired in the practi-
      cal applications and can be adjusted easily by changing
      the number of layers in the ring section. To exemplify in
      step-down transformer applications, a cell phone adapter
      has an output impedance of 6.5 Ω (Motorola Dyna-Tac,
      Chicago, IL), a laptop adapter has an output impedance
      of 10 Ω (Dell Inspiron 4000, Rand Rock, TX). In a typi-
      cal step-up application, a cold cathode fluorescence lamp
      (CCFL) may have the output impedance of a few kilohms
      to a few ten’s of kilohms in running condition, depending
      upon the power requirements and ignition characteristics.

                   IV. Results and Discussion

         Unipoled transformers are characterized by having the

      input and output electrodes on the same side of the disk,
      as shown in Fig. 1. The transformer characteristics for
      the unipoled structure are directly related to the ratio of
      the input/output area, which essentially means the capac-
      itance ratio of the input and output section. Figs. 4(a)
      and (b) show the experimental results for the transformer
      in the step-down configuration across an output load of
      100 Ω. It can be seen from this figure that, for a con-
      stant output power of 6 W, the efficiency is maximum at a
      frequency of 152 kHz having magnitude of 0.92. The mag-
      nitude of the efficiency is close to that determined from
      the equivalent circuit analysis. At this frequency, the gain    Fig. 4. Transformer characteristics in the step-down mode at con-
                                                                      stant power. (a) Gain and input voltage as a function of frequency.
      of the transformer is 0.21 and input voltage is 110 Vrms ,
                                                                      (b) Efficiency and temperature rise as a function of frequency.
      which roughly corresponds to the normal voltage supply in
      the household. The temperature rise under this operating
      condition is 20◦ C from the room temperature. This data
      clearly indicates that this design is very promising for the    load of 5 kΩ. It can be seen from this figure that, for a
      adapter applications. There will be a dramatic reduction        constant output power of 5 W, the gain is maximum at
      in the size and weight of the overall unit because the total    a frequency of 151 kHz having magnitude of 9.5. At this
      size of the transformer is 15 × 2.78 mm2 and the mass is        frequency, the efficiency of the transformer is 0.97 and the
      3.8 gm. It should be noted in this figure that, for step-        input voltage is 16 Vrms . The temperature rise under this
      down transformers, the efficiency is maximum beyond the           operating condition is 8◦ C from the room temperature, in-
      resonance frequency.                                            dicating the high thermal stability of the transformer. This
         Figs. 5(a) and (b) show the experimental results for the     data clearly indicates that this design is very promising for
      transformer in the step-up configuration across an output        the CCFL backlight inverter applications. The gain and 学术搜索
      priya et al.: high power universal piezoelectric transformer                                                                             815

                                                                              done using a point contact-low force spring assembly that
                                                                              avoids such problems. There is no sharp temperature rise
                                                                              at 149 kHz because the decrement in magnitude of the ef-
                                                                              ficiency is very small, and the decrement is not related to
                                                                              the piezoelectric losses.
                                                                                 The transformer design presented in this paper can pro-
                                                                              vide high-power density by tuning the ratio of the number
                                                                              of output to input layers. In general the lower this ra-
                                                                              tio, the higher is the voltage gain and the power density.
                                                                              The results of this study conclusively indicate that a high-
                                                                              efficiency, high-power transformer can be designed using
                                                                              the multilayer unipoled structure.

                                                                                                     V. Conclusions
                                                                                 This paper studies a novel high-power, unipoled piezo-
                                                                              electric transformer design that can be used for step-down
                                                                              or step-up application. The transformer operates with high
                                                                              efficiency in both configurations. The transformer charac-
                                                                              teristics can be controlled easily by changing the ratio of
                                                                              the input/output area and the number of layers. Experi-
                                                                              mental data is in excellent agreement with the equivalent
                                                                              circuit analysis and clearly indicates that this design is
                                                                              very promising for several applications.


                                                                                 The author is sincerely thankful to Dr. Young Min Kim

      Fig. 5. Transformer characteristics in the step-up mode at constant
      power. (a) Gain and input voltage as a function of frequency. (b) Ef-
      ficiency and temperature rise as a function of frequency.
                                                                              from Dong Il Technologies for providing the transformers
                                                                              used in this study and Mr. Hyeoung Woo Kim, Pennsyl-
                                                                              vania State University, for his help in conducting the mea-

      matching impedance of the transformer can be adjusted
      easily by changing the ratio of the input to output area                                          References
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      816                          ieee transactions on ultrasonics, ferroelectrics, and frequency control, vol. 53, no. 4, april 2006

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      [11] D. A. Berlincourt, “Piezoelectric transformer,” U.S. Patent         vices, energy harvesting, ceramic processing, ceramic composites,
           3764848, 1973.                                                      physics of electronic materials, high-power devices, and microelec-
      [12] K. Uehara, T. Inoue, A. Iwamoto, O. Ohnishi, and Y. Sasaki,         tromechanical devices. He has authored 45 publications in interna-
           “Piezoelectric ceramic transformer,” U.S. Patent 5,278,471,         tional journals and 5 patents. He is a member of the American Ce-
           Jan. 11, 1994.                                                      ramic Society; Materials Research Society; Metals, Materials and
      [13] Y. Ponomarev and Y. M. Kim, “Low temperature firable                 Metallurgical Transactions Society; American Society of Metals and
           PZT compositions and piezoelectric ceramic devices using the        Metallurgical Society of India. He is recipient of the TMS Shri Ram
           same,” U.S. Patent 6,878,307 B2, Apr. 12, 2005.                     Arora International Award of the year 2002, Vidya Bharti, IIM gold
      [14] Y. M. Kim, “Soft piezoelectric ceramic composition and piezo-       medal for the year 1999–2000, and K. K. Mallik Gold Medal for the
           electric device using the same,” U.S. Patent 6,808,649 B1,          year 1999–2000.
           Oct. 26, 2004.
      [15] H. Danov, Y. M. Kim, M. H. Choi, B. H. Lee, and S. K. Hoon,
           “Piezo ceramic transformer and circuit using the same,” U.S.
           Patent 6,278,226 B1, Aug. 21, 2001.                                                         Kenji Uchino (M’89), one of the pioneers
      [16] W. Huang, “Design of a radial mode piezoelectric transformer                                in piezoelectric actuators, is Director of Inter-
           for a charge pump electronic ballast with high power factor and                             national Center for Actuators and Transduc-
           zero voltage switching,” M.S. thesis, Blacksburg, VA: Virginia                              ers and Professor of Electrical Engineering at
           Tech., Apr. 2003.                                                                           Penn State University. He has also been Se-
      [17] P. J. M. Smidt and J. L. Duarte, “Powering neon lamp through                                nior Vice President of Micromechatronics Inc.
           piezoelectric transformers,” in Power Electron. Specialists Conf.                           since 2004. After being awarded his Ph.D. de-
           Record, Jun. 1996, pp. 310–315.                                                             gree from the Tokyo Institute of Technology,
      [18] H.-S. Jeong, B.-C. Choi, J.-H. Yoo, I.-H. Im, and C.-Y. Park,                               Tokyo, Japan, he became Research Associate
           “Parallel driving of piezoelectric transformers,” Jpn. J. Appl.                             in the physical electronics department at that
           Phys., pt. 1, vol. 38, pp. 5166–5169, 1999.                                                 university. Then, he joined Sophia University,
                                                                                                       Tokyo, Japan as an Associate Professor in
                                                                               physics in 1985. He then moved to Penn State in 1991. He was also
                                                                               involved with Space Shuttle Utilizing Committee in NASDA, Tokyo,
                                                                               Japan during 1986–1988, and was the Vice President of NF Elec-
                                                                               tronic Instruments, State College, USA, during 1992–1994. He is the
                           Shashank Priya received his B.Sc. degree            Chair of the Smart Actuator/Sensor Study Committee sponsored by
                           in physics from Allahabad University, Alla-         the Japanese Ministry of International Trading and Industries. He is
                           habad, India, B.S. and M.S. degrees in met-         also the associate editor for the Journal of Advanced Performance
                           allurgy from Indian Institute of Science, Ban-      Materials, the Journal of Intelligent Materials Systems and Struc-
                           galore, India, and Ph.D. degree in materials        tures, and the Japanese Journal of Applied Physics. His research
                           engineering from Pennsylvania State Univer-         interests are in the development of solid state actuators for precision
                           sity, University Park, PA, in 1996, 1998, 2000,     positioners, ultrasonic motors, etc. He has authored 500 papers, 54

                           and 2003, respectively. He is currently assis-
                           tant professor in the Department of Materials
                           Science and Engineering, University of Texas
                                                                               books, and 20 patents in the ceramic actuator area. He has been a
                                                                               Fellow of the American Ceramic Society since 1997 and a member of
                                                                               IEEE for 18 years. He is a recipient of the ASME Adaptive Struc-
                           at Arlington (UTA). Prior to joining UTA,           tures Prize (2005), Outstanding Research Award from Penn State
                           he was a senior transducer design engineer at       Engineering Society (1996), Best Movie Memorial Award at Japan

      American Piezo Ceramics International (APCI), Mackeyville, PA.
      Prior to joining APCI, he worked as group leader of the piezoelec-
                                                                               Scientific Movie Festival (1989), and the Best Paper Award from
                                                                               Japanese Society of Oil/Air Pressure Control (1987). 学术搜索

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