• Nuclear Engineering and Technology
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• v.50 no.7
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• pp.1006-1016
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• 2018

Since the early forties, researchers from around the world have been studying the phenomenon of deadtime in radiation detectors. Many have attempted to develop models to represent this phenomenon. Two highly idealized models; paralyzable and non-paralyzable are commonly used by most individuals involved in radiation measurements. Most put little thought about the operating conditions and applicability of these ideal models for their experimental conditions. So far, there is no general agreement on the applicability of any given model for a specific detector under specific operating conditions, let alone a universal model for all detectors and all operating conditions. Further the related problem of pile-up is often confused with the deadtime phenomenon. Much work, is needed to devise a generalized and practical solution to these related problems. Many methods have been developed to measure and compensate for the detector deadtime count loss, and many researchers have addressed deadtime and pulse pile-up. The goal of this article is to summarize the state of science of deadtime; measurement and compensation techniques as proposed by some of the most significant work on these topics and to review the deadtime correction models applicable to present day radiation detection systems.

• Nuclear Engineering and Technology
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• v.51 no.4
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• pp.1081-1090
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• 2019

Detailed pulse shape analysis of a Geiger-$M{\ddot{u}}ller$ counter is performed to understand the pulse shape dependence on operating voltage. New data is presented to demonstrate that not all pulses generated in a GM counter are identical. In fact, there is a strong correlation between the operating voltage and the pulse shape. Similar to detector deadtime, pulse shapes fall in three distinct regions. For low voltage region, where deadtime was reported to reduce with increasing voltage, pulse generated in this region was observed to have a fixed pulse width with a variable tail. The pulse width and fall time of the tail was observed to be a function of applied voltage; exponentially reducing with increasing voltage with an exponent of negative 6E-04 and 2E-03 respectively. The second region showed a pulse without any significant tail. During this time the detector deadtime was earlier reported to be at its minimum. The highest voltage region demonstrated a different deadtime mechanism where the second pulse was reduced in width. During this time the deadtime seemed to be increasing with increasing voltage. This data allows us to gain some unique insight into the phenomenon of GM detector deadtime not reported thus far.

• Journal of Biomedical Engineering Research
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• v.17 no.4
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• pp.443-448
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• 1996

Sequential brain SPECT imaging has been used to assess the cerebral perfusion reserve(CPR) in cerebrovascular diseases(UD). We have realized parametric images of CPR using deadtime correction of gamma camera and normalized difference ratio. For the anatomical localization of CPR, the parametric images were registered to the contours of the cerebral regions using optimal threshold method, which showed to reflect the CPR more reliably and distinctively than the simple subtraction. We conclude that the quantitative estimation of CPR using normalized difference ratio image could be useflll for the diagnosis and prognostic assessment of CVD.

• Journal of Power Electronics
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• v.19 no.3
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• pp.727-743
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• 2019

This paper presents a pulse-width modulation strategy to eliminate the common mode voltage (CMV) with reduced CMV spikes in multilevel inverters since a high CMV magnitude and its fast variations dv/dt result in bearing failure of motors, overvoltage at motor terminals, and electromagnetic interference (EMI). The proposed method only utilizes the zero CMV states in a space vector diagram and it is implemented by a carrier-based pulse-width modulation (CBPWM) method. This method is generalized for odd number levels of inverters including neutral-point-clamped (NPC) and cascaded H-bridge inverters. Then it is extended to the over-modulation mode. The over-modulation mode is implemented by using the two-limit trajectory principle to maintain linear control and to avoid look-up tables. Even though the CMV is eliminated, CMV spikes that can cause EMI and bearing current problems still exist due to the deadtime effect. As a result, the deadtime effect is analyzed. By taking the deadtime effect into consideration, the proposed method is capable of reducing CMV spikes. Simulation and experimental results verify the effectiveness of the proposed strategy.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.221-222
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• 2011

본 논문은 인버터의 PWM구동 시 출력 전류에 발생하는 DC offset을 제거 하는 방법을 제안한다. 인버터의 PWM구동 시 소자 단락을 막기 위해 필수적으로 적용하는 deadtime과 각 스위치 소자의 voltage drop으로 인해 출력에 왜곡이 발생한다. 이상적인 스위치인 경우에는 이 두 가지의 왜곡을 feedforward로 보상하면 된다. 하지만 스위치 소자가 이상적이지 않기 때문에 각 스위치 소자의 voltage drop의 차이와 on & off time delay의 차이는 출력 전류에 DC offset을 발생시킨다. 따라서 deadtime과 스위치 voltage drop에 대한 보상과 함께 출력 전류의 DC offset을 feedback으로 하여 보상되지 못한 왜곡을 추가적으로 보상하여 결론적으로 출력 전류의 DC offset을 제거할 수 있게 하였다. 제안된 기법은 시뮬레이션을 통하여 그 타당성을 확인하였다.

• Proceedings of the KIEE Conference
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• 1999.11c
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• pp.515-517
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• 1999

This paper considers the design of the effective controllers for the plant with an integrator and a long deadtime. The structure of the new DTC(DeadTime Compensator) that has an additive filter is proposed. Our DTC shows the improved performance in set-point response and disturbance rejection. Especially the bad effect of the long deadtime in the disturbance rejection is fairly reduced by using the additive filter. Illustrative examples are provided to show the availability of the proposed controller.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.680_681
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• 2009

본 논문에서는 인버터 시스템에서 발생하는 소자 단락을 막기 위해 필수적인 시간 지연 요소인 데드타임 보상을 통하여 인버터시스템의 출력전류 파형 개선과 고조파 저감을 위한 방법을 제안하였다. 제안된 방법을 3KW 급 인버터에 적용하여 실험을 통하여 파형 개선과 고조파 함유율이 현저히 감소함을 확인하고 본 논문에서 제안한 데드타임 보상 방법의 유효성과 우수성을 확인하였다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.102-103
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• 2017

본 논문에서는 MMC 시스템에서 데드타임에 의한 전압 왜곡현상을 수식적으로 분석하여 발생하는 고조파 성분을 보상하는 새로운 데드타임 보상기법을 제안한다. 알고리즘은 시뮬레이션으로 그 타당성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.399-400
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• 2014

본 논문은 출력전류에 저역통과필터를 적용함으로써 최적으로 보상할 수 있는 데드타임 보상기법을 제안한다. 제안된 보상기법은 출력전류에 필터보상 알고리즘 적용으로 출력전류의 고조파성분을 저감할 수 있음을 시뮬레이션 해석을 통해 검증한다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.453-454
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• 2020

본 논문은 PWM에 의한 전압 고조파를 분석하여 LC 필터를 설계하는 방안을 제안한다. 전압형 인버터는 PWM 방식을 이용하여 출력전압을 합성하며, PWM에 의한 전압 고조파는 직류단 전압, Modulation index, Deadtime 등에 의해서 결정된다. 출력 전압 고조파와 PWM 전압고조파와의 관계를 풀어 LC 필터를 설계한다. 제안된 방법으로 설계된 LC 필터는 시뮬레이션을 통해 설계의 타당성을 확인하였다.