Differential Effects of d, l-Sotalol and d-Sotalol on Isoproterenol-Increased Delayed Rectifier Outward Potassium Current in Guinea Pig Single Ventricular Myocytes

The aim of this study was to compare the effects of d, l-Sotalol and dSotalol on the delayed rectifier K+ outward current in the presence of isoproterenol at different concentrations. Time-dependent delayed rectifier K+ outward currents were measured in isolated guinea pig single myocytes using the whole-cell configuration of the patch-clamp technique. Currents were measured in response to 300 ms depolarizing pulses from a holding potential of -40 mV in three experimental protocols [control, isoproterenol (10^(9)mol/L - 10^(-6) mol/L ), and isoproterenol (10^(-9)mol/L - 10^(-6)mol/L ) plus either d, l-Sotalol (10^(-4) mol/L) or d-Sotalol (10^(-4) mol/L)]. IK tail currents were measured upon repolarization to -40 mV. It was found that Ik was significantly amplified in the presence. of isoproterenol (10^(-9) mol/L- 10^(-6) mol/L) plus d-Sotalol. At 10-8 mol/L isoproterenol, Ik was increased by 92. 7%±17. 1 % (P<0. 05) and 54. 3 %±13. 4 % after d-Sotalol addition (P<0. 05). In contrast, d, l-Sotalol completely conteracted the increase of iK by isoproterenol (<10^(-8) mol/L), and compared to control, Ic was decreased by 35. 6 % ±8. 1% at 10^(-8) mol/L isoproterenol plus d, l-Sotalol (P<0. 05). It is concluded that the β-adrenergic blocking property of d, l-Sotalol but not that of dSotalol maintains the delayed rectifier K+ outward current blockade in the presence of isoproterenol in guinea pig myocytes. This might contribute to a superior antiarrhythmic efficacy as compared to d-Sotalol.

Effects of sodium ferulate on the ultrarapid delayed rectifier K^+ current in human atrial myocytes

Objective：To study the effects of sodium ferulate on the ultrarapid delayed rectifier K^＋ current（IKur） in human atrial myocytes. Methods：Human atrial myocytes were isolated by enzyme dispersion method. IKur, in human atrial myocytes were recorded by using the whole cell patch clamp. The changes of IKur were compared in the absence and the presence of sodium ferulate. Results：There was no effect of 0.4 g/L sodium ferulate on I-V relation of IKur. However, 0.4 g/L sodium ferulate inhibited IKur to some degrees at each test pulse. The current densities of IKur at ＋60 mV decreased from 4.997 ± 0.35 PA/PF to 3.331 ± 0.26 PA/PF（n = 6, P 〈 0.05）. The inhibitory effect was concentration-dependent. IC50 was（0.41 ±0.03）g/L and the Hill coefficient was 0.95 ± 0.05. Conclusion：Sodium ferulate as a potassium channel blocker can inhibit IKur in human atrial myocytes effectively.

Distinct protein kinase C isozymes mediates inhibitory effects of different G-protein coupled receptors on cardiac rapidly activating delayed rectifier K ~ current

Aim Evidence has shown that stimulation of alA-adrenorecetors receptor （alA-AR） or angiotensin II type 1 receptor （AT1R） acutely down-regulates the rapid component of the delayed rectifier K ＋ current （IKr） via protein kinase C （PKC）. This study was designed to investigate which PKC isozymes mediate down-regulations of IKr by alA-AR and AT1R. Method The whole-cell patch-clamp technique was used to record IKr in native cardio- myocytes and in human embryonic kidney （HEK） 293 cells co-transfected with human ether-a-go-go related gene （hERG） encoding α-subunit of IKr and human alA-AR or AT1R gene. Result In isolated guinea-pig ventricular cardiomyocytes the inhibitory action of Ang II on IKr was little affected by Go6976 （selectively inhibiting PKCα, β and γ） and Go6983 （selectively inhibiting PKCα, β, γ , δ, and ζ）, but was significantly antagonized by an inter- nal dialysis with PKCe-selective inhibitory peptide εV1 -2. In contrast, the inhibitory action of alA-AR agonist A61603 on IKr was remarkably attenuated by Go6976 or Go6983, but not affected by peptide εV1 -2. Moreover, specific PKC-selective inhibitory peptide antagonized the effect of A61603. The results suggested that PKCe and PKCα isoform respectively mediated the inhibitory effect of AT1R and a1A-AR. In heterologous expression system, both PKCα and e-selective activator peptides down regulated hERG current with different manner. PKCα activator peptide shifted the activation curve of the channel to the right, but PKCe-selective activator peptide did not. Simi- larly, A61603 shifted the activation curve to the right, whereas Ang Ⅱ had no effect. In addition, both A61603 and PKCα activator peptide showed inhibitory action on bERG A PKC current （an bERG mutant in which 17 of the 18 ROSITE-predicted PKC acceptor serines/threonines were changed to alanine） with a similar potency to wild type bERG current. But, both Ang Ⅱ and PKCe-selective activator peptide exhibited no effects on bERG △ PKC cur- rent. The results indicated that PKCα and PKCe isoforms down-regulated bERG current through different mecha- nism. Conclusion PKCα and PKCe isoform respectively mediates the inhibition on IKr by stimulation of AT1R and alA-AR via different molecular mechanism.

Effects of Oxygen Concentration in Monocrystalline Silicon on Reverse Leakage Current of PIN Rectifier Diodes

The effects of initial oxygen concentration on the reverse leakage current of PIN rectifier diodes were studied.We fabricated the PIN rectifier diodes with different initial oxygen concentrations,and analyzed the electrical properties,anisotropic preferred etching by means of optical microscopy,Fourier transform infrared spectroscopy and transmission electron microscopy.It is pointed out that the reverse leakage current increases exponentially with the increasing initial oxygen concentration.Furtherly,we researched and analyzed the mechanism of the effects of initial oxygen concentration on the reverse leakage current of PIN rectifier diode.It is shown that the oxygen precipitations present in an "S" curve with increasing initial oxygen concentration after high temperature diffusion.The main reason is that the nucleation and growth of oxygen precipitation at high temperature induce bulk oxidation-induced defects (B-OSF),which are mainly dislocations,and a small amount of rod stacking faults.The density of B-OSF increases with the increasing initial oxygen concentration.The existence of B-OSF has great effects on the reverse leakage current of PIN rectifier diode.

A New Current Conveyor Full-Wave Rectifier for Low Frequency/Small Signal Medical Applications

This paper presents a new current conveyor (CCII+) full-wave rectifier for low frequency/small signal medical applications. The proposed rectifier is based on the current conveyor full-wave rectifier proposed previously, but the proposed rectifier is better in view of no need diodes to rectify, and no need bias sources to overcome the zero crossing error. It needs only two CCII+s, two resistors, and three simple current mirrors, which is easy for IC implementation and for building in many countries. The PSPICE simulation with the current conveyor CCII+ in the current feedback opamp AD844 IC and the 2N2222 bipolar current mirror shows the good low frequency/small signal rectification, the operation voltage of down to 6 .

Rectifier Configurations Based on Harmonic Injecting and Counteracting Principle

On the basis of detailed analysis of a novel harmonic counteracting method which can be used to effectively compensate the supply line harmonic currents of a passive single phase diode bridge rectifier, this paper presents two simpler single phase diode bridge rectifier configurations and their alternatives which can achieve low supply line current THD(total harmonic distortion) too. Moreover, this paper also proposes a few passive hamonic counteracting networks for multi single phase rectifiers which are connected in parallel.

Simulation of a kind of active harmonic reduction 18-pulse rectifier

To solve the input current harmonic pollution of the high power rectifier system,18-pulse rectifier based on a kind of active harmonic suppression technique at dc side is proposed in this paper.The pulse rectifier employs three-phase diode bridges,each of them followed by a boost converter.Unlike the conventional three-phase unity-power-factor diode rectifier,the ideal sinusoidal main currents of circuit topology are obtained by control its output current or input currents of three boost converters for approximately triangular modulation.The theoretical of modulation strategy and characteristics of input and output currents about the proposed rectifier are analyzed in detail.Simulation results by Matlab/Simulink demonstrate that the proposed rectifier draws nearly sinusoidal current and power quality index is improved.The correctness of the theoretical analysis is validated.

Junction barrier Schottky rectifier with an improved P-well region

A junction barrier Schottky （JBS） rectifier with an improved P-well on 4H-SiC is proposed to improve the VF-IR trade-off and the breakdown voltage. The reverse current density of the proposed JBS rectifier at 300 K and 800 V is about 3.3 × 10-s times that of the common JBS rectifier at no expense of the forward voltage drop. This is because the depletion layer thickness in the P-well region at the same reverse voltage is larger than in the P＋ grid, resulting in a lower spreading current and tunneling current. As a result, the breakdown voltage of the proposed JBS rectifier is over 1.6 kV, that is about 0.8 times more than that of the common JBS rectifier due to the uniform electric field. Although the series resistance of the proposed JBS rectifier is a little larger than that of the common JBS rectifier, the figure of merit （FOM） of the proposed JBS rectifier is about 2.9 times that of the common JBS rectifier. Based on simulating the values of susceptibility of the two JBS rectifiers to electrostatic discharge （ESD） in the human body model （HBM） circuits, the failure energy of the proposed JBS rectifier increases 17% compared with that of the common JBS rectifier.

Enhanced gated-diode-triggered silicon-controlled rectifier for robust electrostatic discharge (ESD) protection applications

A robust electron device called the enhanced gated-diode-triggered silicon-controlled rectifier (EGDTSCR) for electrostatic discharge (ESD) protection applications has been proposed and implemented in a 0.18-μm 5-V/24-V BCD process. The proposed EGDTSCR is constructed by adding two gated diodes into a conventional ESD device called the modified lateral silicon-controlled rectifier (MLSCR). With the shunting effect of the surface gated diode path, the proposed EGDTSCR, with a width of 50 μm, exhibits a higher failure current (i.e., 3.82 A) as well as a higher holding voltage (i.e., 10.21 V) than the MLSCR.

面向电流源型PWM整流器的双矢量模型预测直接功率控制

电流源型脉宽调制(Pulse width modulation,PWM)整流器因其网侧存在LC滤波器,系统的控制难度增加。传统直接功率控制策略下的整流器功率波形存在脉动,因模型预测控制具有卓越的动态特性以及直观的控制规律,采用模型预测直接功率控制(Model predictive direct power control,MPDPC)对传统控制策略进行改进。首先建立了三相PWM整流器的数学模型,给出了每个采样周期内的功率变化率,并推导出相邻采样周期之间的功率关系,然后给出基于单矢量的模型预测直接功率控制策略,提出了基于双矢量的模型预测直接功率控制策略,并优选出两个电流矢量,计算在一个采样周期内的作用时间,并对其进行修正。最后,在Matlab/Simulink仿真软件验证了所提控制策略的可行性和有效性。

不平衡电网下电流源型PWM整流器改进型无差拍控制

三相电流源型PWM整流器运行在电网电压不平衡情况下,引起直流侧及网侧电流存在大量低次谐波,势必对后级变换器供电稳定性、安全性等存在不利影响。针对该问题,首先建立整流器数学模型,推导出不平衡电网下直流侧电压和网侧电流表达式,揭示出系统直流侧和网侧电流产生低次谐波的机理。其次,根据瞬时功率理论设计内环电流参考指令,并利用无差拍控制实现网侧电流对参考电流的跟踪。然而传统无差拍控制存在延时问题,将影响网侧电流的跟随性能,造成电能质量下降。为解决该问题,提出了网侧电流内环改进型无差拍控制,利用两步预测法补偿系统延时。最后,基于Matlab/Simulink平台搭建仿真模型,验证所提控制策略的正确性与有效性。结果表明,所提方法能有效抑制直流侧和网侧电流低次谐波,实现网侧电流正弦化和直流侧电压稳定输出。

抑制采样白噪声干扰的PWM整流器无差拍控制

无差拍控制(DBC)是一种应用于整流器电流内环的预测控制,但该算法对系统参数敏感,当采样受到持续噪声干扰时波形畸变严重。为此,此处提出了一种基于DBC的白噪声抑制算法,实验结果表明,该算法在较大电感参数偏差下能保持稳定,在白噪声干扰下能够显著降低电流畸变率。

基于级联式整流电源的恒流均压控制方法

针对电磁探测的大功率电磁场激发需要,文中采用输入并联输出串联的级联式整流电源,提高输出电压等级,保证激发功率。为了满足电磁探测过程中输出电流的稳定性,提出了基于双闭环的恒流均压控制算法。分析了级联式直流电源恒流均压输出的原理,建立了电源的数学模型,设计了电压电流环的控制器,在MATLAB/Simulink中搭建仿真模型并通过控制器参数优化从而降低误差。级联式直流电源由于上下两部分可能存在器件参数不同的情况,这就导致在恒流控制下两级电源输出电压不同,在动态情况下的偏差会更大从而引起器件不均压而损坏,因此在考虑控制恒流输出的同时需要加入控制均压输出。通过对输出电流电压进行采样,经控制器转换为相应的脉冲触发所对应的开关器件从而实现恒流均压输出。仿真结果显示输出电流控制在2 A,电流变化在5%以下。

双闭环控制的三相电压型PWM整流器的研究

针对传统的不控整流电路中网侧电流谐波很大、晶闸管相控整流电路中深控时网侧功率因数低和闭环控制时动态响应慢等问题,设计出一种引入脉冲宽度调制技术的三相电压型整流器。在完成三相电压型整流器的电压外环电流内环的双闭环控制系统设计的基础上,对其进行了仿真实验。仿真结果表明,与不控或相控整流电路相比,该三相电压型PWM整流电路中,不仅输入电流的谐波大大减小,电能可双向流动,能够实现整流和逆变状态下的单位功率因数运行,还可较好地抑制负载突变时直流侧电压的波动,从而显著提高系统的抗扰能力,真正实现绿色环保和高效节能的高度结合。

基于自适应超螺旋滑模观测器的三相Vienna整流器无模型预测电流控制

三相Vienna整流器具有不需要考虑开关死区、可靠性高等优点,但参数易受外部扰动影响而导致控制性能下降。针对这些问题,该文提出一种基于自适应超螺旋滑模观测器的无模型预测电流控制策略(ASTSMO-MFPCC)。首先,通过分析三相Vienna整流器参数失配数学模型,构建不依赖系统物理参数的超局部模型。其次,设计超螺旋滑模观测器估计超局部模型中的动态部分,有效抑制系统扰动影响。同时,设计自适应增益,动态调整超螺旋滑模观测器参数,解决增益选择难题。最后,构建离散化预测模型和成本函数,实现无模型预测电流控制算法。仿真与实验结果表明,所提策略具有良好的鲁棒性和动稳态性能。

一种基于改进双二极管脉波倍增电路的串联型24脉波整流器

为了在不增加串联型12脉波整流器中移相变压器复杂度的前提下,有效地抑制整流器的输入电流谐波,该文提出一种基于改进双二极管脉波倍增电路(improved dual-diode pulse-doubling circuit,IDPC)的串联型24脉波整流器。提出的IDPC被安装在整流器的直流侧并由单相自耦变压器、平衡电抗器、2个电容器和2个辅助二极管组成。IDPC中的辅助二极管根据整流器中2个三相整流桥的输出电压和单相自耦变压器绕组电压之间的关系交替导通,使IDPC周期性工作在3种模态下,然后根据交直流侧电压和电流关系将整流器的脉波数从12增加到24,使得输入电流的THD减小为原来的二分之一,有效地抑制输入电流谐波。因IDPC中磁性器件的总容量仅为输出功率的2.35%,辅助二极管的电流应力仅为输出电流的6.8%,提出的方案具有电路结构简单、容量小,成本低和导通损耗小的优点。与类似结构相比,提出的整流器在中高压工业场合具有更好的应用前景。搭建了一台输出功率为1 kW的实验样机,实验结果验证了理论分析的有效性和正确性。

三相PWM整流器离散空间矢量无模型预测电流控制策略

针对PWM整流器模型预测控制对系数参数准确性高度依赖的问题,提出一种基于离散空间矢量的无模型预测电流控制(MFPCC)策略。该策略通过矢量合成,在每个控制周期应用两个基本矢量,提高了预测电流的准确性;通过峰谷采样,分别测量并存储上一控制周期两个基本矢量作用下的电流梯度;并建立电流梯度方程,从而根据应用矢量的电流梯度进一步更新剩余6个未应用矢量的电流梯度,结合当前时刻的电流采样值,实现未来时刻的电流预测,得到下一时刻最优的虚拟矢量。该方法不依赖于任何系统参数,且消除了传统MFPCC策略中电流梯度更新停滞现象,降低了输出电流谐波。最后,通过实验和仿真验证了所提方法的有效性和优越性。

基于钳位方式切换的Vienna整流器载波断续脉冲宽度调制策略

当Vienna整流器工作在直流电压不平衡条件下时,传统载波断续脉宽调制(carried-based discontinuous pulse-width modulation,CB-DPWM)会增加输入电流谐波和中点电压波动。为解决上述问题,提出一种基于钳位方式切换的CB-DPWM策略。为了减小输入电流谐波,根据变化的电压矢量对子区域和零序分量进行重新划分和计算。据此,建立统一的CB-DPWM调制波,分析可运行区域,得到直流电压不平衡度和可运行区域成反比的结论。结合中点电流分析不同钳位方式对中点电压大小的影响,并根据直流电压不平衡度的大小实时切换钳位方式,从而有效地减小中点电压波动。通过钳位区域判断和优化开关序列,减少切换钳位方式引入的开关动作,提高了Vienna整流器效率。最后,在Vienna整流器实验平台上验证所提策略的有效性。

一种低输入电流总谐波畸变率的三相Buck整流器不对称调制策略

传统空间矢量脉宽调制(SVPWM)三相Buck整流器没有考虑直流链电流纹波对输入电流的影响,且在扇区切换点处输入电流存在严重畸变,导致输入电流总谐波畸变率(THD)升高。该文分析直流链电流纹波对三相Buck整流器输入电流的影响,分析输入电流扇区切换点畸变产生的原因,提出一种新型不对称SVPWM策略,显著降低了三相Buck整流器的输入电流THD。最后,通过仿真和1 kW的实验样机验证了理论分析的正确性以及所提调制策略的有效性。

基于虚拟阻抗的三相Buck整流器输入不平衡控制策略

三相输入电压不平衡时,传统双环控制三相Buck整流器的输出电压存在二倍频脉动,输入电流发生明显畸变,严重影响整流器的性能和可靠性。为抑制输出电压脉动和输入电流畸变,该文通过建立三相Buck整流器在两相静止坐标系下的等效电路模型及功率传输数学模型,分析输出电压二倍频脉动及输入电流畸变产生的机理,在此基础上提出一种基于虚拟阻抗的输入不平衡控制策略,最后通过仿真和1 kW的实验样机验证了理论分析的正确性和所提控制策略的有效性。