Board mount voltage multipliers are AC-to-DC conversion devices mounted to a printed circuit board (PCB) that produce a high potential DC voltage from a lower voltage AC source. They are used to produce high voltages where low current is required.
Voltage multipliers convert an AC waveform into a DC output that is either N times greater than the peak-to-peak voltage of the input waveform, or 2 x N times the peak of the input voltage. N represents the number of stages, a value usually between two and twelve. To increase the voltage, multipliers use series-aiding sources that are comparable to the connection of dry cells (batteries) in series. The input AC waveform can be sinusoidal (sine wave), rectangular (square wave), or in the form of another shape. Voltage multipliers are usually classified as doublers, triplers, quadruplers, pentuplers, etc. The classification depends on the ratio of the output voltage to the input voltage. For example, devices that increase the peak input voltage by a factor of two are called voltage doublers.
A stage in a voltage multiplier consists of sets of capacitors and diodes (typically two of each). The number of stages in a voltage multiplier describes the capabilities of the voltage multiplier. The higher the stage, the larger the output voltage range achievable. This video shows a twelve stage (homemade) voltage multiplier used to generate high voltage discharges:
Video Credit: Virgilius1979
Manufacturers will specify voltage multipliers based on a number of different specifications. These include:
- AC input voltage - the peak to peak input voltage, in amps (A).
- DC output voltage - the output DC voltage of the device, in volts (V).
- Input frequency - the supported inpt voltage frequency, in kilohertz (kHz).
- Output power - the maximum power output, in watts (W).
- Output current - the maximum DC output current range
- Operating temperature - the full-required range of ambient operating temperatures
Mounting options include surface mount technology (SMT) and through hole technology (THT).
- SMT is a mounting style that adds components to a printed circuit board (PCB) by soldering component leads or terminals to the top surface of the board. Typically, the PCB pad is coated with a paste-like formulation of solder and flux. With careful placement, SMT components on solder paste remain in position until elevated temperatures, usually from an infrared oven, melt the paste and solder the component leads to the PCB pads.
- THT, a conventional placement method, mounts components by inserting component leads through holes in the board and then soldering the leads in place on the opposite side of the board.
Voltage multipliers are commonly used as the anode for cathode-ray tubes (CRT) in radar scopes, oscilloscopes, and television picture tubes. They may also be used as primary power supplies in devices that rectify AC inputs to pulsating DC. Although the measured output voltage may be several times greater than the input voltage, connecting a load causes the value of the output voltage to decrease. Consequently, voltage multipliers are used mainly in specialized applications where the load remains constant and with high impedance, or when input voltage stability is not critical.