The Cockcroft-Walton (CW) generator , or multiplier , is an electrical circuit that produces a high DC voltage from a low-voltage AC or pulsing DC input. It was named after the British and Irish physicists John Douglas Cockcroft and Ernest Thomas Sinton Walton, who in 1932 used the design of this circuit to light their particle accelerators, performing the first artificial nuclear disintegration in history. They used this voltage multiplier cascade for most of their research, which in 1951 won them the Nobel Prize in Physics for "Transmutation of atomic nuclei by artificially accelerated atomic particles". This circuit was discovered in 1919, by Heinrich Greinacher, a Swiss physicist. For this reason, this doubler cascade is sometimes also referred to as the Greinacher multiplier . The Cockcroft-Walton circuit is still used in particle accelerators. They are also used in everyday electronic devices that require high voltage, such as X-ray machines, televisions, microwave ovens and copiers.
Video Cockcroft-Walton generator
Operasi
CW is a voltage multiplier that converts AC or pulsing DC power from low voltage level to higher DC voltage level. It consists of a network of multiplier voltages of capacitors and diodes to produce high voltages. Unlike transformers, this method eliminates the requirements for heavy core and most of the required insulation/potting. Only using capacitors and diodes, this voltage multiplier can increase the relatively low voltage to a very high value, while at the same time much lighter and cheaper than the transformer. The biggest advantage of such circuits is that the voltage at each stage of the cascade is equal to just twice the peak input voltage in the half wave rectifier. In full wave rectifier it is three times the input voltage. This has the advantage of requiring relatively low-cost components and easy to isolate. One can also tap the output of various stages, as in the multitapped transformer.
To understand the circuit operation, see the two-stage version diagram on the right. Assume this circuit is supported by alternating voltages V i with the peak value V p , and initially the capacitor is not charged. After the input voltage is turned on
- When the input voltage V i reaches its negative peak - V p , the current flows through the diode D1 to charge the capacitor C1 to the voltage V p .
- When v i reverses the polarity and reaches its positive peak V p , it adds the capacitor voltage to generate the 2 V p voltage on the right plate C1 . Since D1 is reverse biased, the current flows from C1 through the diode D2 , fills the capacitor C2 to the voltage of 2 V p .
- i reverses the polarity again, the current from C2 flows through the diode D3 , charging capacitor C3 also to voltage 2 V p .
- i reverses the polarity again, the current from C3 flows through the diode D4 , charging capacitor C4 also to voltage 2 V p .
With each change in the input polarity, the current flows up the "pile" of the capacitor through the diode, until they are all filled. All capacitors are charged to voltage 2 V p , except for C1 , which is charged to V p . The key to the voltage multiplication is that while the capacitors are charged in parallel, they are connected to the load in series. Since C2 and C4 are in a circuit between output and ground, the total output voltage (under no-load conditions) is V o = 4 V p .
Sirkuit ini dapat diperluas ke sejumlah tahapan. Tegangan output tanpa beban adalah dua kali tegangan input puncak dikalikan dengan jumlah tahapan N atau ekuivalen tegangan-ke-puncak ayunan tegangan masukan ( V pp ) kali jumlah tahapan
The number of stages is equal to the number of capacitors in series between the output and ground.
One way to look at a circuit is to function as a "pump" charge, pumping an electrical charge in one direction, up a stack of capacitors. The CW circuit, along with other similar capacitor circuits, is often called the charge pump. For substantial loads, the charge on the capacitor is partially depleted, and the output voltage falls according to the output current divided by the capacitance.
Maps Cockcroft-Walton generator
Characteristics
In practice, CW has a number of weaknesses. As the number of stages increases, the voltage from the higher stage begins to "sag", mainly due to the electrical impedance of the capacitor at the lower stage. And, when supplying the output current, the voltage ripple increases rapidly as the number of stages increases. For this reason, CW multipliers with a large number of stages are used only where relatively low output currents are required. This effect can be partially compensated by increasing the capacitance at the lower stage, by increasing the frequency of input power and by using AC power sources with square or triangular waveforms. By moving the CW from a high-frequency source, such as an inverter, or a combination of an inverter and an HV transformer, the physical size and overall weight of the CW power supply can be substantially reduced.
CW multipliers are typically used to develop higher voltages for relatively low current applications, such as bias voltages ranging from tens or hundreds of volts to millions of volts for high energy physics experiments or lightning security testing. CW multipliers are also found, with a higher number of stages, in laser systems, high voltage power supplies, X-ray systems, LCD backlighting, current tube amplifiers, ion pumps, electrostatic systems, air-ionries, particle accelerators, machine copies, instrumentation scientific, oscilloscopes, television sets and cathode ray tubes, electric shock guns, bug zappers and many other applications that use high-voltage DCs.
Picture gallery
See also
A similar circuit is a Marx generator, which has the same "stair" structure, but it consists of resistors, capacitors, and spark gaps. The Marx generator produces a short pulse, while the CW generator produces a constant DC.
Note
Further reading
- J. D. Cockcroft and E. T. S. Walton, Experiments with High Speed ​​Positive Ions. (I) Further Developments in Methods of Gaining High-Speed ​​Positive Ions, Proceedings of the Royal Society A, vol. 136, pp. 619-630, 1932.
- J. D. Cockcroft and E. T. S. Walton, Experiments with High Speed ​​Positive Ions. II. Disintegration Elements by High Speed ​​Protons, Proceedings of the Royal Society A, vol. 137, pp. 229-242, 1932.
External links
- Cockcroft-Walton Multiplier Tutorial - EEVBlog
- Cockcroft Walton
- Cockcroft Walton is used in particle accelerators
- US Department of Energy
Source of the article : Wikipedia
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