CHAPTER 2
COCKCROFT WALTON MUTIPLIER CIRCUIT
2.1 INTRODUCTION
A Cockcroft Walton Multiplier Circuit is an electric circuit used to convert low ac voltage to high dc voltage with the help of combination of capacitors and diodes. The characteristic of both the component build the voltage at desired high level. The British physicists Sir John Douglas Cockcroft and the Irish physicists Ernest Thomas Sinton Walton were designed the Cockcroft Walton circuit and used it for giving input to particle accelerator, performing the first artificial nuclear breakup in 1932[1]. They used this cascade voltage multiplier for many of their research particularly in high-energy physics and won them the Nobel Prize in Physics for "Transmutation of atomic nuclei…show more content… Cockcroft?Walton circuits are even used in particle accelerators nowadays. They also are used in electronic devices such as X-ray machines, photocopiers and television sets where high voltage is required. The most common type of voltage multiplier is the half-wave series multiplier, also called the Villard cascade.
2.2 CONVENTIONAL AC TO DC CIRCUIT
The conventional unregulated a.c. to d.c. converters started with half wave and full wave rectifier circuit and then extended to Villard circuit and Voltage doubler circuit.
2.2.1 Villard Circuit The Villard circuit shown in fig. 2.1 is constructed with a capacitor ?C? and a diode ?D?. The major advantage of the circuit is its simplicity, however the output voltage has high ripple. The capacitor is charged during the negative half cycles to the peak a.c. input voltage. The output is the summation of the input a.c. waveform ?v? and the d.c. voltage of the capacitor. The transformer ?T? in the diagram can be used to step up the input voltage. Consequently, the d.c value of the circuit is shifted above. The peak-to-peak ripple is the disadvantage of this circuit and cannot be smoothed unless the circuit is effectively turned into one of the more sophisticated forms. This circuit (with diode reversed) is used to supply the negative high voltage for the magnetron…show more content… 2.8.1 Cascaded boost converter
The cascaded boost converter shown in fig. 2.18 consists of inductors L1, L2?? Ln operates in the charging mode when switch S is turn ON. The energy stored in the inductor L1 is transferred to C1 through diode D1b and the energy stored in Ln is delivered to the load through diode Dna when switch is turned OFF. The voltage gain, number of elements, voltages across the capacitors, switches and diodes are shown in the table 2.3.
Figure 2.18 Cascaded boost converter
2.8.2 Diode- Capacitor multiplier circuit
The circuit shown in fig.2.19 is a diode-capacitor multiplier, formed from input inductor Li and switch S, the diode-capacitor multiplier, which contains a number of cells (each cell consists of two same capacitors C, C 'and two diodes D, D?) and an output inductor Lo. The analysis of the circuit is done by using the average through the period of the capacitor voltages and the inductor currents. The voltage gain, number of elements, voltages across the capacitors, switches and diodes are shown in the table