Cockcroft-Walton Circuit Research Articles

Design and Operation Verification of Integrated Battery Assembly Charger Using Cockcroft Walton Circuit

The new concept of charger for lithium ion battery assembly with several unit cells has been proposed and tested. The Cockcroft Walton (CW) circuit developed as a high voltage multiplier was applied for the battery charger of lithium ion battery assembly. The some capacitors in CW circuit were substituted with unit cells to design the charger circuit. This charger circuit worked well for the individual unit cell of integrated battery assembly. It is also considered that the wide application is feasible because of its simple circuit.

Development of Cockcroft-Walton Type High-Voltage DC Generator with RF Air-Core Transformer

A new Cockcroft–Walton (CW)-type high-voltage DC generator with RF air-core transformer used as a step-up transformer has been developed. The design concept of the air-core transformer is shown, which is operated on the resonance condition between the inductance of the secondary coil and the stray capacitance of CW circuit with the conical-type coil structure. Adapting the RF air-core transformer to CW circuit with DC-300 kV 100 mA, excellent performances have been demonstrated. In the new CW circuit, it results in downsizing of capacitors to operate at higher frequency than conventional ones, and reduction of the volume by approximately 40% has been shown in the typical DC generator with 1 MV 100 mA. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(1): 18–26, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20500

A CW CO 2 laser using a high-voltage Dc–dc converter with resonant inverter and Cockroft–Walton multiplier

I propose a high-voltage Dc–dc converter for a CW (continuous wave) CO 2 laser system using a current resonant half-bridge inverter and a Cockcroft–Walton circuit. This high-voltage power supply includes a two-stage voltage multiplier driven by a regulated half-bridge series resonant inverter. The inverter drives a step-up transformer and the secondary transformer is applied to the voltage multiplier. It is highly efficient because of the reduced amount of switching losses by virtue of the current resonant half-bridge inverter, and also due to the small size, low parasitic capacitance in the transformer stage owing to the low number of winding turns of the step-up secondary transformer combined with the Cockroft–Walton circuit. I obtained a maximum laser output power of 44 W, a maximum system efficiency of over 16%, and the stability of laser output power of about 4.6% in this laser system.

Demonstration of enhanced ‐edge angiography using a cerium target x‐ray generator

The cerium target x-ray generator is useful in order to perform enhanced K-edge angiography using a cone beam because K-series characteristic x rays from the cerium target are absorbed effectively by iodine-based contrast mediums. The x-ray generator consists of a main controller, a unit with a Cockcroft-Walton circuit and a fixed anode x-ray tube, and a personal computer. The tube is a glass-enclosed diode with a cerium target and a 0.5-mm-thick beryllium window. The maximum tube voltage and current were 65 kV and 0.4 mA, respectively, and the focal-spot sizes were 1.0 x 1.3 mm. Cerium Kalpha lines were left using a barium sulfate filter, and the x-ray intensity was 0.48 microC/kg at 1.0 m from the source with a tube voltage of 60 kV, a current of 0.40 mA, and an exposure time of 1.0 s. Angiography was performed with a computed radiography system using iodine-based microspheres. In coronary angiography of nonliving animals, we observed fine blood vessels of approximately 100 microm with high contrasts.

Improved Transient and Steady-State Performances of Series Resonant ZCS High-Frequency Inverter-Coupled Voltage Multiplier Converter with Dual Mode PFM Control Scheme

The A variety of switched-mode high voltage DC power supplies using voltage-fed type or current-fed type high-frequency transformer resonant inverters using MOS gate bipolar power transistors; IGBTs have been recently developed so far for a medical-use X-ray high power generator. In general, the high voltage high power X-ray generator using voltage-fed high frequency inverter with a high voltage transformer link has to meet some performances such as (i) short rising period in start transient of X-ray tube voltage (ii) no overshoot transient response in tube voltage, (iii) minimized voltage ripple in periodic steady-state under extremely wide load variations and filament heater current fluctuation conditions of the X-ray tube. This paper presents two lossless inductor snubber-assisted series resonant zero current soft switching high-frequency inverter using a diode-capacitor ladder type voltage multiplier called Cockcroft-Walton circuit, which is effectively implemented for a high DC voltage X-ray power generator. This DC high voltage generator which incorporates pulse frequency modulated series resonant inverter using IGBT power module packages is based on the operation principle of zero current soft switching commutation scheme under discontinuous resonant current and continuous resonant current transition modes. This series capacitor compensated for transformer resonant power converter with a high frequency transformer linked voltage boost multiplier can efficiently work a novel selectively-changed dual mode PFM control scheme in order to improve the start transient and steady-state response characteristics and can completely achieve stable zero current soft switching commutation tube filament current dependent for wide load parameter setting values with the aid of two lossless inductor snubbers. It is proved on the basis of simulation and experimental results in which a simple and low cost control implementation based on selectively-changed dual-mode PFM for high-voltage X-ray DC-DC power converter with a voltage multiplier strategy has some specified voltage pattern tracking voltage response performances under rapid rising time and no overshoot in start transient tube voltage as well as the minimized steady-state voltage ripple in tube voltage.

Transient analysis of Cockcroft-Walton cascade rectifier circuit after load short-circuit

Abstract On the basis of simulation results, analytical solutions of the transients in the main and branch discharging routes in a Cockcroft-Walton cascade rectifier circuit, in responce to a load short-circuit discharge, are derived. Using these analytical expressions, transient currents, energy dissipation in the circuit elements and the effects of circuit parameters on transients are investigated quantitatively for the first time. Results show that the diodes at the uppermost and lowest ends suffer stronger surges; inserting resistors and inductors into the circuit can weaken the undesirable effects of a surge on circuit elements.

Ripple due to asymmetry in symmetrical Cockcroft–Walton cascade rectifier circuit

We experimentally examine the ripple and its spectra in the dc output of a symmetrical Cockcroft–Walton (CW) cascade rectifier circuit. Results show that the ripple due to the load consists of even harmonics and the ripple due to the circuit asymmetry consists of odd harmonics. In the latter, the ripple caused by the asymmetry of circuit elements cannot be compensated for completely through the asymmetry of the input voltage because of nonlinearity of a CW circuit. Approximately, the residual ripple is inversely proportional to the load resistance.

Efficient compensation method for reducing ripple of Cockcroft–Walton generator in an ultrahigh-voltage electron microscope

To get ultrahigh stability of the dc high-voltage (HV) output, we propose a novel compensation method for reducing the periodic ripple included in the output of a Cockcroft–Walton (CW) generator circuit. A compensating signal is injected into the circuit via the ground end to compensate various ripple harmonics at the HV end. Considering the nonlinearity of a CW circuit, we first compose the signal with the linear superposition of harmonics minimizing individual ripple spectral components, and then reduce the deviation due to the nonlinearity through the fine adjustment on the synthesized signal. An experiment testing the method has been carried out in an ultrahigh-voltage electron microscope, compensating the ripple components from the fundamental to the ninth higher harmonics. Ripple has been decreased by above one order of magnitude, resulting in a percent ripple of less than 1×10−6.

A Numerical Analysis Approach to Cockcroft-Walton Circuit in Electron Microscope

A brief survey is given on the conventional methods of analyzing a Cockcroft-Walton (CW) circuit. It shows that these methods are not suitable for analyzing the surge and ripple performance. Thus this paper proposes a numerical approach to the CW circuits in electron microscopes (EM). In this approach, taking advantage of the cascade connection, we formulate the state equations of a CW circuit having arbitrary stages. The Gear's algorithm is used to solve the state equations numerically, overcoming the nonlinear stiff problem and obtaining accurate solutions effectively. As an example to confirm the effectiveness of the approach, we simulate the surge current and ripple voltage in the CW circuit for an ultra-High Voltage EM (ultra-HVEM) by using a supercomputer

Position Control of Electron Energy Loss Spectrum in Case of Accelerating-Voltage Fluctuation

In the parallel detection EELS, the fluctuation effect of the accelerating voltage is compensated both by the open loop and negative feedback controls. The fundamental frequency components of the AC power line and the excitation of Cockcroft-Walton circuit are canceled by applying the inverse-phase signal to the deflection coil, while the effect from the drift and the higher-order ripples is controlled by the negative feedback. The energy resolution is increased from 9.3 eV to 5.7 eV by the open loop control and can be improved up to 3.8 eV by the negative feedback. As the loop gain increases, the resolution increases at first, but then decreases. This decrease results from the shot noise of electron beam and the phase shift of the feedback loop. It is theoretically shown that the optimum condition to the loop gain and the bandwidth exists for the feedback control.

コッククロフト・ウォルトン回路の入力波形に対する動作

コッククロフト・ウォルトン回路の入力波形に対する動作

New Type High Voltage Generator

A high voltage generator has been developed with an extremely small ripple component by incorporating resistors in series in the filament transformer of the center-tapped Cockcroft Walton circuit. The rating of the prototype is 500 kV, and incorporates the following features, (See Fig. 1)1.The generator itself is perfectly symmetrical with respect to the output circuit.2.Stray capacitance (Cs) between the primary and secondary windings of the filament transformer can be reduced to negligible proportions.

A Newly Designed 650kv Electron Microscope

We have recently completed a newly designed 650KV electron microscope. An external view of this advanced instrument is shown in Figure 1. A symmetrical Cockcroft-Walton circuit has been adopted as the high voltage generator. The cathode is heated by high frequency power; a battery is not employed. The high voltage stability is better than 1 x 10-5/min.The sectional diagram of the column shown in Figure 2 is 420mm in diameter and 2750mm in height. The illuminating system consists of a double condenser lens and a magnetic alignment device. Dual deflector assemblies for dark and bright field images, selectable by push button, are built beneath the condenser lens. Two selectable stigmator power supplies are also provided for dark and bright field image operation.

The Cockcroft-Walton Voltage Multiplying Circuit

The conventional Cockcroft-Walton voltage multiplying circuit is studied considering it as a transmission line. It is shown that, even when no direct current is drawn from the high voltage electrode, there is an important loss in output voltage caused by circulating currents in the stray capacitances. This loss of voltage is independent of the supply frequency. Formulas are developed for the voltage efficiency resulting from a given choice of capacitor size and number of stages. Two modifications of the Cockcroft-Walton circuit which improve the voltage efficiency are suggested and analyzed. The first of these involves a loading coil at the high voltage end of the line. The second involves the addition of inductors in series with each of the capacitors of the circuit.