Voltage multiplier

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Image:Voltage Multiplier diagram.PNG A voltage multiplier is an electrical circuit that converts AC electrical power from a lower voltage to a higher DC voltage by means of capacitors and diodes combined into a network.

Voltage multipliers can be used to generate bias voltages of a few volts or tens of volts or millions of volts for purposes such as high-energy physics experiments and lightning safety testing.

The most common type of voltage multiplier is the half-wave series multiplier, also called the Villard cascade. Such a circuit is shown opposite.

Assuming that the peak voltage of the AC source is +U_s we can describe the (simplified) working of the cascade as follows: Image:Voltage amplifier explain.png

negative peak (−U_s): The C₁ capacitor is charged through diode D₁ to 0V (potential difference between left and right plate of the capacitor is U_s)
positive peak (+U_s): the potential of C₁ adds with that of the source, thus charging C₂ to 2U_s through D₂
negative peak: potential of C₁ drops to 0V thus allowing C₃ to be charged through D₃ to 2U_s.
positive peak: potential of C₁ rises to 2U_s (analogously to step 2), also charging C₄ to 2U_s. The output voltage (the sum of voltages under C₂ and C₄) raises till 4U_s.

In reality more cycles are required for C₄ to reach the full voltage. Adding more segments analogous to C₁-D₁-D₂-C₂, we can increase output voltage by 2U_s.

A common type of voltage multiplier used in high-energy physics is the Cockcroft-Walton generator (which was designed by John Douglas Cockcroft and Ernest Thomas Sinton Walton for a particle accelerator, for use in research that won them the Nobel Prize in Physics in 1951).

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