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M.H.F. Lim

Bio: M.H.F. Lim is an academic researcher from University of Virginia. The author has contributed to research in topics: Inductor & Boost converter. The author has an hindex of 3, co-authored 3 publications receiving 61 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, a low profile power inductor suitable for planar integration is designed and fabricated based on low temperature co-fired ceramics technology for microprocessor power delivery applications.
Abstract: A novel low profile power inductor suitable for planar integration is designed and fabricated based on low temperature co-fired ceramics technology for microprocessor power delivery applications. The inductor was designed to operate at a switching frequency of 4 to 5MHz, carrying a nominal dc current of 20A with a ripple current of 8 to 10A in a 5-V to 1-V dc-dc converter. The design and fabrication procedure is discussed in this paper, followed by small signal measurement and magnetic characterization results. The inductor was implemented in a prototype converter and the large signal measurement results are presented and its performance evaluated

35 citations

Proceedings ArticleDOI
M.H.F. Lim1, J. Dong1, J.D. van Wyk1, T.C. Lee1, K.D.T. Ngo1 
17 Jun 2007
TL;DR: In this paper, the presence of a metal shield reduces trace inductance and improves circuit performance, and a minimum shield thickness is required to minimize losses associated with ringing, and traces should be placed close to the shield to minimize inductance.
Abstract: The presence of a magnetic substrate below the circuitry created additional parasitic inductances, which resulted in low-frequency oscillations. From simulation, the presence of a metal shield reduces trace inductances and improves circuit performance. There is a minimum shield thickness required to minimize losses associated with ringing. High shield conductivity is necessary to lower the trace inductance and minimize power loss. Traces should be placed close to the shield to minimize inductance.

17 citations

Proceedings ArticleDOI
19 Mar 2006
TL;DR: In this article, a low profile power inductor suitable for planar integration is designed and fabricated based on low temperature co-fired ceramics (LTCC) technology for microprocessor power delivery applications.
Abstract: A novel low profile power inductor suitable for planar integration is designed and fabricated based on low temperature co-fired ceramics (LTCC) technology for microprocessor power delivery applications. The inductor was designed to operate at a switching frequency of 4 to 5 MHz, carrying a nominal DC current of 20 A with a ripple current of 8 to 10 A in a 5 V to 1 V DC-DC converter. The design and fabrication procedure is discussed in this paper, followed by small signal measurement and magnetic characterization results. The inductor is being implemented in a prototype converter and the measurement results are presented and its performance evaluated.

10 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, a review of the available technologies for inductor hybrid integration is given in accordance with low voltage and high current requirements, low-temperature co-fired ceramics (LTCC) technology is identified to be a suitable candidate for power electronics passives integration.
Abstract: A review of some of the available technologies for inductor hybrid integration is given in this paper. In accordance with low voltage and high current requirements, low-temperature co-fired ceramics (LTCC) technology is identified to be a suitable candidate for power electronics passives integration. This paper will discuss the various limitations of the current LTCC processing technique and introduce a fabrication technique which will open a new field for chip inductors for hybrid power electronics integration. The design of an LTCC inductor will also be presented. This inductor exhibits an inherent current dependent inductance, leading to high efficiency at low loads as an important systems advantage in portable electronics.

85 citations

Dissertation
16 Apr 2012
TL;DR: In this paper, the authors explore and propose methods to improve the power de-noise and performance of point of load modules ranging from 10 to 600W by using a three level converter, which can reduce the voltage stress across the devices by a factor of two compared to the traditional buck.
Abstract: The increased power consumption and power density d emands of modern technologies combined with the focus on global energy savings ha ve increased the demands on DC/DC power supplies. DC/DC converters are ubiquitous in every day life, found in products ranging from small handheld electronics requiring a few watts to warehouse sized server farms demanding over 50 megawatts. To improve efficiency and power d nsity while reducing complexity and cost the modular building block approach is gaining popularity. These modular building blocks replace individually designed specialty power suppl ies, providing instead an optimized complete solution. To meet the demands for lower loss and h igher power density, higher efficiency and higher frequency must be targeted in future designs . The objective of this dissertation is to explore and propose methods to improve the power de nsity and performance of point of load modules ranging from 10 to 600W. For non-isolated, low current point of load applica tions targeting outputs ranging from one to ten ampere, the use of a three level convert er is proposed to improve efficiency and power density. The three level converter can reduce the voltage stress across the devices by a factor of two compared to the traditional buck; reducing swit ching losses, and allowing for the use of improved low voltage lateral and lateral trench dev ic s. The three level can also significantly reduce the size of the inductor, facilitating 3D co nverter integration with a low profile magnetic by doubling the effective switching frequency and r e ucing the volt-second across the inductor.

73 citations

Proceedings ArticleDOI
01 Sep 2011
TL;DR: In this paper, the inductance and core loss of LTCC ferrite tape materials are measured under different pre-magnetization conditions to estimate inductance of the inductor in high frequency integrated converters.
Abstract: Low temperature co-fired ceramic (LTCC) ferrite materials are promising candidates for magnetic substrate of high frequency converters. The inductors can be fabricated into the magnetic substrate so the power density of the converter can be dramatically increased. There are three types of LTCC ferrite tape materials from ESL Electro Science®: 40010, 40011 and 40012. To utilize these materials for suitable applications, their permeability and core loss characteristics under different pre-magnetization conditions should be measured in order to estimate the inductance and core loss of the inductor in high frequency integrated converters. The measurement uses a new high frequency measurement setup, which can provide permeability and core loss density information under DC pre-magnetization condition. Finally, three LTCC ferrite materials' characteristics are compared and discussed.

47 citations

Journal ArticleDOI
Wenli Zhang1, Yipeng Su1, Mingkai Mu1, David Gilham1, Qiang Li1, Fred C. Lee1 
TL;DR: In this article, a planar inductor made by mixed laminates of low-temperature sintered Ni-Cu-Zn ferrite tapes and metal-flake composite materials is used for high-density integration of point-of-load (POL) modules.
Abstract: Planar inductors made by mixed laminates of low-temperature sintered Ni-Cu-Zn ferrite tapes and metal-flake composite materials are used for high-density integration of point-of-load (POL) modules Incremental permeability and core loss density were characterized on toroidal samples under high dc bias to demonstrate that both materials are suitable for application in high-frequency high-current POL converters In order to realize a high power density POL module, a multilayer ferrite inductor laminated with alternating layers of ESL 40010 and ESL 40012 in a 1:1 ratio has been fabricated and integrated with the active layer Meanwhile, standard printed circuit board (PCB) processing has been adopted for the POL integration with a PCB-embedded inductor using NEC-TOKIN's metal-flake composite materials These developed 3-D integration approaches can be used to reduce the footprint and increase the power density for POL converters It has been demonstrated that the power efficiency of both POL modules with integrated planar inductors can achieve above 87% at an operating frequency of 2 MHz and an output current of 15 A Additionally, no obvious efficiency degradation was observed on the integrated POL modules after a certain number of thermal cycling from -40 °C to +150 °C

47 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a hybrid integrated buck converter with a conductive shield layer to reduce trace inductance and improve circuit performance in the 20 A range, where a minimum shield thickness is required to minimize losses associated with ringing.
Abstract: Miniaturization of hybrid integrated buck converters is impeded by the difference in growth laws in current rating for silicon and for inductors as current rating increases. In the 20 A range, this leads to the attractive feasibility of planarizing the output inductor as the largest component by utilizing low-temperature cofired ceramic technology in the form of the (magnetic) substrate to carry the rest of the converter circuit. The presence of a magnetic substrate below the circuitry creates additional parasitic inductances, which results in low-frequency oscillations. From simulation, the presence of a conductive shield reduces trace inductances and improves circuit performance. There is a minimum shield thickness required to minimize losses associated with ringing. High-shield conductivity is necessary to lower the trace inductance and minimize power loss. Traces should be placed close to the shield to minimize inductance. Experimental results on converters with ceramic-based shield layers and organics-based shield layers bear out the theoretical expectations and establish the practical viability of the proposed hybrid integration technology.

43 citations