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Instrumentation, Particle Accelerators, and Particle and Radiation Detection
Published in Zeev B. Alfassi, Max Peisach, Elemental Analysis by Particle Accelerators, 2020
Voltage-doubling or voltage-multiplying circuits were adapted by Cockcroft and Walton to meet their needs, in particles acceleration. The voltage multiplier is in principle a circuit for charging capacitors in parallel and discharging them in series. The elementary voltage-doubling circuit is shown in Figure 14a. In this circuit, the two capacitors are charged on successive half-cycles and a doubled voltage appears across the capacitors in series. Since neither end of the output is at the potential of one end of the transformer secondary, this circuit has some disadvantages in making ground connections. For this reason, the circuit of Figure 14b is usually preferred. Here the voltage applied to the output capacitor includes the transformer output AC (alternating current) voltage plus the DC charge of the first capacitor. This circuit is appropriate for addition of further stages of multiplication (Figure 15). By adding units to a total of N capacitors and N rectifiers, one can obtain voltage multiplication by a factor of N. The circuit shown in Figure 15 to give a fourfold voltage multiplication was the one used by Cockcroft and Walton.
Design and test results of a 200 kV, 15 mA high voltage DC test generator
Published in B. Raneesh, Nandakumar Kalarikkal, Jemy James, Anju K. Nair, Plasma and Fusion Science, 2018
S. Amal, urmil M. Thaker, kumar saurabh, ujjwal k. Baruah
One of the cheapest and popular ways of generating high voltages at relatively low currents is the classic multistage diode/capacitor voltage multiplier, known as Cockroft-Walton multiplier. The output voltage is several times the input voltage and is used where the load has high input impedance and is constant or where the input voltage stability is not the major issue. For increasing and decreasing voltage conventional transformer can be used which can step up or down the AC voltage and current which can be rectified using diodes or thyristors or other semiconductor devices and further can be filtered using capacitors. But here the problem is the weight of transformer, as the voltage which is to be stepped up increases the insulation level of the transformer increases and hence it becomes bulky. Apart from this the rectification process is carried out using rectifier grade diodes which are slow and filtering is done using high value capacitors which are heavy in weight.
Energy Harvesting Issues in Wireless Sensor Networks
Published in Vidushi Sharma, Anuradha Pughat, Energy-Efficient Wireless Sensor Networks, 2017
Gourav Verma, Vidushi Sharma, Anuradha Pughat
The rectifiers in the voltage multiplier consume some power and this reduces the efficiency of the voltage multipliers. The power efficiency of an impedance transformation network is defined as the ratio of the power delivered to the multiplier (PL) to the power available at the input of the impedance transformation network (Pin): η=PLPin
Overview of High-Step-Up DC–DC Converters for Renewable Energy Sources
Published in IETE Technical Review, 2018
Subhransu Padhee, Umesh Chandra Pati, Kamalakanta Mahapatra
Voltage multiplier techniques use additional diodes and capacitors to step-up the output voltage. Cockcroft-Walton (CW) and Dickson voltage multiplier cell (VMC) use diode-capacitor-based voltage multiplier cell (DCVMC) [51]. Transformerless step-up converter using CW voltage multiplier cell proposed by [52] provides a higher voltage ratio rather than the conventional CW voltage multiplier cell. A comparative analysis of the performance of diode-assisted converter has been reported in [53]. In [54], a hybrid VMC-based DC–DC converter is proposed which employs bipolar VMC. The proposed topology decreases the power rating of the output filter capacitor. DCVMC used along with non-isolated DC–DC converter can provide a better switch utilization factor and the converter has low commutation losses as well as low EMI [55,56]. Though voltage multiplier cell based converter provides a larger voltage conversion ratio, the increase in the number of components is one of the major limitations in such topologies.
Multiple lift DC–DC boost converter using CLC cell
Published in Australian Journal of Electrical and Electronics Engineering, 2019
Yiyang Li, Swamidoss Sathiakumar, John Long Soon
The switched capacitor (SC) is a famous voltage boosting technique which is based on the charge pump circuit. SC topologies are popular because they are good at structural modularity and monolithic integration (Palumbo and Pappalardo 2010; Makowski and Maksimovic 1995). In the basic charge pump circuit, there are two switches in the circuit to control the on–off state of it. The first capacitor from the input side is charged by the input source when the first switch is on. Then the second capacitor is charged by the first one when the second switch is on and so on. All switches are operating as phased alternatively. This process will cause the energy ‘pump’ from one capacitor to another and after several periods, the output voltage will reach a higher level than the input voltage. The SC design has a high voltage gain theoretically but this design does not perform well in reality since switch and capacitor voltage stresses are too high and most switches are not ground-referenced, leading to unstable performance during operations and affecting the usage of this design. Moreover, high current transients in the circuit are also required to be reduced, which will cause power density degrading, leading a low efficiency. Voltage multiplier circuits consist of diodes and capacitors to obtain high voltage gain. These circuits are simple, low in cost and efficient. There are two major groups of voltage multiplier circuits, the voltage multiplier cell (VMC) and the voltage multiplier rectifier (VMR). VMC is imbedded between the input side and output side in the circuit. Some of VMC consist of diodes and capacitors only (Ismail et al. 2008; Axelrod, Berkovich, and Ioinovici 2008). Some of VMC have more components, for example, an auxiliary switch (Rivera et al. 2011). And, some others use inductors in circuits to obtain a high voltage gain (Fardoun and Ismail 2010). The main advantage of this design is that most of diodes and switches in this structure can operate under zero current switching condition, which will reduce the power loss significantly and largely increase the efficiency (Prudente, Pfitscher, and Gules 2005). The main drawback of it is the high voltage stress on diodes and capacitors. And with high order multiplications, the power loss in the circuit will increase as well, causing the significant decline of efficiency.