Energy recycling from multigigahertz clocks using fully integrated switching converters

Large digital chips use a significant amount of energy to broadcast a low-skew, multigigahertz clock to millions of latches located throughout the chip. Every clock cycle, the large aggregate capacitance of the clock network is charged from the supply and then discharged to ground. Instead of wasting this stored energy, it is possible to recycle the energy by controlling its delivery to another part of the chip using an on-chip dc-dc converter. The clock driver and switching converter circuits share many compatible characteristics that allow them to be merged into a single design and fully integrated on-chip. Our buck converter prototype, manufactured in 90-nm CMOS, provides a proof-of-concept that clock network energy can be recycled to other parts of the chip, thus lowering overall energy consumption. It also confirms that monolithic multigigahertz switching converters utilizing zero-voltage switching can be implemented in deep-submicrometer CMOS. With multigigahertz operation, fully integrated inductors and capacitors use a small amount of chip area with low losses. Combining the clock driver with the power converter can share the large MOSFET drivers necessary as well as being energy and space efficient. We present an analysis of the losses which we confirm by experimentally comparing the merged circuit with a conventional clock driver. © 2012 IEEE.

IGBT converters conducted EMI analysis by controlled multiple-slope switching waveform approximation

IGBTs realise high-performance power converters. Unfortunately, with fast switching of the IGBT-free wheel diode chopper cell, such circuits are intrinsic sources of high-level EMI. Therefore, costly EMI filters or shielding are normally needed on the load and supply side. In order to design these EMI suppression components, designers need to predict the EMI level with reasonable accuracy for a given structure and operating mode. Simplifying the transient IGBT switching current and voltage into a multiple slope switching waveform approximation offers a feasible way to estimate conducted EMI with some accuracy. This method is dependent on the availability of high-fidelity measurements. Also, that multiple slope approximation needs careful and time-costly IGBT parameters optimisation process to approach the real switching waveform. In this paper, Active Voltage Control Gate Drive(AVC GD) is employed to shape IGBT switching into several defined slopes. As a result, Conducted EMI prediction by multiple slope switching approximation could be more accurate, less costly but more friendly for implementation. © 2013 IEEE.

Improved switching uniformity and low-voltage operation in TaO x-based RRAM using Ge reactive layer

Significant improvements in the spatial and temporal uniformities of device switching parameters are successfully demonstrated in Ge/TaOx bilayer-based resistive switching devices, as compared with non-Ge devices. In addition, the reported Ge/TaOx devices also show significant reductions in the operation voltages. Influence of the Ge layer on the resistive switching of TaOx-based resistive random access memory is investigated by X-ray spectroscopy and the theory of Gibbs free energy. Higher uniformity is attributed to the confinement of the filamentary switching process. The presence of a larger number of interface traps, which will create a beneficial electric field to facilitate the drift of oxygen vacancies, is believed to be responsible for the lower operation voltages in the Ge/TaO x devices. © 1980-2012 IEEE.

Narrow line high power picosecond pulse generation in a multicontact distributed feedback laser using modified Q switching

High power bandwidth-limited picosecond pulses with peak powers in excess of 200 mW have been generated using multi-contact distributed feedback laser diodes for the first time. The pulses have widths typically less than 10 ps, time-bandwidth products of as little as 0·24, and can be generated on demand at generator limited repetition rates of up to 140 MHz.

Reversible nanoscale switching of polytwin orientation in a ferroelectric thin film induced by a local electric field

The response to a local, tip-induced electric field of ferroelastic domains in thin polycrystalline lead zirconate titanate films with predominantly (110) orientation has been studied using Enhanced Piezoresponse Force Microscopy. Two types of reversible polytwin switching between well-defined orientations have been observed. When a-c domains are switched to other forms of a-c domains, the ferroelastic domain walls rotate in-plane by 109.5°, and when a-c domains are switched to c-c domains (or vice-versa), the walls rotate by 54.75°. © 2013 AIP Publishing LLC.

Modelling of free-space optoelectronic switching with MPLS for storage area networks (SANs)

Low-cost optical switches based on SLMs have conventionally been considered unsuitable for packet switching due to slow reconfiguration time. In this paper, we demonstrate that the constraint of SLM reconfiguration time in a hybrid three-stage electronic/optical switching node architecture can be compensated through the utilization of MPLS label switching mechanism to achieve the best performance for SAN applications. © 2012 SEE.

On-chip switching of a silicon nitride micro-ring resonator based on digital microfluidics platform.

We demonstrate the switching of a silicon nitride micro ring resonator (MRR) by using digital microfluidics (DMF). Our platform allows driving micro-droplets on-chip, providing control over the effective refractive index at the vicinity of the resonator and thus facilitating the manipulation of the transmission spectrum of the MRR. The device is fabricated using a process that is compatible with high-throughput silicon fabrication techniques with buried highly doped silicon electrodes. This platform can be extended towards controlling arrays of micro optical devices using minute amounts of liquid droplets. Such an integration of DMF and optical resonators on chip can be used in variety of applications, ranging from biosensing and kinetics to tunable filtering on chip.

Polarization switching induced decrease of bulk resistivity in ferroelectric Pb(Zr0.45Ti0.55)O3 thin films and a method to improve their fatigue endurance

Significant reduction of the bulk resistivity in a ferroelectric Pb(Zr 0.45Ti0.55)O3 thin film is observed before the remnant polarization started to decrease noticeably at the onset of its fatigue switching process. It is associated with the increase of charge carriers within the central bulk region of the film. The decrease of bulk resistivity would result in the increase of Joule heating effect, improving the temperature of the thin film, which is evaluated by the heat conduction analysis. The Joule heating effect in turn accelerates the polarization reduction, i.e. fatigue. Enhancing the heat dissipation of a ferroelectric capacitor is shown to be able to improve the device's fatigue endurance effectively. © 2013 Chinese Physical Society and IOP Publishing Ltd.

Comparative analysis of static and switching performance of 1.2 kV commercial SiC transistors for high power density applications

This paper presents a critical comparison of static and switching performance of commercially available 1.2 kV SiC BJTs, MOSFETs and JFETs with 1.2 kV Si IGBTs. The experiments conducted are mainly focussed on investigating the temperature dependence of device performance. As an emerging commercial device, special emphasis is placed on SiC BJTs. The experimental data indicate that the SiC BJTs have relatively smaller conduction, off-state and turn-off switching losses, in comparison to the other devices. Furthermore, SiC BJTs have demonstrated much higher static current gain values in comparison to their silicon counterparts, thereby minimising driver losses. Based on the results, the suitability of SiC devices for high power density applications has been discussed. © 2013 IEEE.

Understanding the cascode switching process

Cascode circuits are useful for driving normally-on wide-bandgap devices, but the switching process must be properly understood to optimise their design. Little detailed consideration has previously been given to this. This paper proposes an idealised mathematical description of the cascode switching process, which is used to show that the stray inductance between the two devices plays a critical role in switching. This idealised model is used to propose methods for optimising cascode performance in different applications. © 2013 IEEE.

Predictive optimisation of high-power IGBT switching under Active Voltage Control

Active Voltage Control (AVC) is an implementation of classic Proportional-Derivative (PD) control and multi-loop feedback control to force IGBT to follow a pre-set switching trajectory. The initial objective of AVC was mainly to synchronise the switching of IGBTs connected in series so as to realise voltage balancing between devices. For a single IGBT switching, the AVC reference needs further optimisation. Thus, a predictive manner of AVC reference generation is required to cope with the nonlinear IGBT switching parameters while performing low loss switching. In this paper, an improved AVC structure is adopted along with a revised reference which accommodates the IGBT nonlinearity during switching and is predictive based on current being switched. Experimental and simulation results show that close control of a single IGBT switching is realised. It is concluded that good performance can be obtained, but the proposed method needs careful stability analysis for parameter choice. © 2013 IEEE.

Fast low-cost FIR filter processed ECDM labels for optical label switching

A code-label recognition time of less than 500ps is demonstrated using low-cost FIRfilters. The electronically-processed label provides a control signal from an auto-correlated label. Error-free electronic code-label switching of an optical 10Gb/s signal is demonstrated. © 2010 Optical Society of America.

Chirp limitation on Mach-Zehnder interferometer ultrafast switching employing semiconductor optical amplifiers

We show for the first time that for a given switching pulse width, the maximum switching speed obtainable from a Mach-Zehnder interferometer employing semiconductor optical amplifiers is strongly dependent on the SOA chirp characteristics. © 2005 Optical Society of America.

Experimental demonstration of femtosecond switching of a fully packaged all-optical switch

We experimentally demonstrate femtosecond switching of a fully packaged hybrid-integrated Mach-Zehnder switch. A record switching window of 620fs at full-width-half-maximum is achieved. © 2004 Optical Society of America.

Chirp limitation on Mach-Zehnder interferometer ultrafast switching employing semiconductor optical amplifiers

We show for the first time that for a given switching pulse width, the maximum switching speed obtainable from a Mach-Zehnder interferometer employing semiconductor optical amplifiers is strongly dependent on the SOA chirp characteristics. © 2005 Optical Society of America.