One way to look at the circuit is that it functions as a charge "pump", pumping electric charge in one direction, up the stack of capacitors. The CW circuit, along with other similar capacitor circuits, is often called charge pump. For substantial loads, the charge on the capacitors is partially depleted, and the output voltage drops according to the output current divided by the capacitance. Characteristics[ edit ] In practice, the CW has a number of drawbacks. As the number of stages is increased, the voltages of the higher stages begin to "sag", primarily due to the electrical impedance of the capacitors in the lower stages. And, when supplying an output current, the voltage ripple rapidly increases as the number of stages is increased this can be corrected with an output filter, but it requires a stack of capacitors in order to withstand the high voltages involved.

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Any load in a practical circuit will lower these voltages. In both cases, VDC is produced. This is the input to a switching regulator producing lower voltages for powering, say, a personal computer. Half-Wave Voltage Doubler The half-wave voltage doubler in Figure below a is composed of two circuits: a clamper at b and peak detector half-wave rectifier in Figure prior, which is shown in modified form in Figure below c.

C2 has been added to a peak detector half-wave rectifier. Half-wave voltage doubler a is composed of b a clamper and c a half-wave rectifier. The right end is grounded by the conducting D2.

The left end is charged at the negative peak of the AC input. This is the operation of the clamper. During the positive half cycle, the half-wave rectifier comes into play at Figure c above. Diode D2 is out of the circuit since it is reverse biased. C2 is now in series with the voltage source.

Note the polarities of the generator and C2, series aiding. Thus, rectifier D1 sees a total of 10 V at the peak of the sinewave, 5 V from generator and 5 V from C2. D1 conducts waveform v 1 figure below , charging C1 to the peak of the sine wave riding on 5 V DC figure below v 2. Waveform v 2 is the output of the doubler, which stabilizes at 10 V 8.

Full-Wave Voltage Doubler The full-wave voltage doubler is composed of a pair of series stacked half-wave rectifiers. Figure below The corresponding netlist is in Figure below. The top rectifier charges C2 on the positive halfcycle. Each capacitor takes on a charge of 5 V 4. Note that the output v 5 Figure below reaches full value within one cycle of the input v 2 excursion.

Full-wave voltage doubler: v 2 input, v 3 voltage at mid point, v 5 voltage at output Deriving Full-wave Doublers from Half-wave Rectifiers Figure below illustrates the derivation of the full-wave doubler from a pair of opposite polarity half-wave rectifiers a. The negative rectifier of the pair is redrawn for clarity b. Both are combined at c sharing the same ground. At d the negative rectifier is re-wired to share one voltage source with the positive rectifier.

Full-wave doubler: a Pair of doublers, b redrawn, c sharing the ground, d share the same voltage source. Voltage Tripler A voltage tripler Figure below is built from a combination of a doubler and a half wave rectifier C3, D3. The half-wave rectifier produces 5 V 4. The doubler provides another 10 V 8. The netlist is in Figure below. Voltage tripler composed of doubler stacked atop a single stage rectifier. Note that V 3 in Figure below rises to 5 V 4.

Input v 4 is shifted upward by 5 V 4. And 5 V more at v 1 due to the clamper C2, D2. D1 charges C1 waveform v 2 to the peak value of v 1.

Voltage Quadrupler A voltage quadrupler is a stacked combination of two doublers shown in Figure below. Each doubler provides 10 V 8.

Voltage quadrupler, composed of two doublers stacked in series, with output at node 2. The waveforms of the quadrupler are shown in Figure below. Two DC outputs are available: v 3 , the doubler output, and v 2 the quadrupler output. Some of the intermediate voltages at clampers illustrate that the input sinewave not shown , which swings by 5 V, is successively clamped at higher levels: at v 5 , v 4 and v 1. Strictly v 4 is not a clamper output. It is simply the AC voltage source in series with the v 3 the doubler output.

Intermediate waveforms: Clampers: v 5 , v 4 , v 1. Furthermore, load resistors have been omitted. Loading reduces the voltages from those shown. If the circuits are to be driven by a kHz source at low voltage, as in the examples, the capacitors are usually 0.

If driven from line voltage, pay attention to the polarity and voltage ratings of the capacitors. Finally, any direct line driven power supply no transformer is dangerous to the experimenter and line operated test equipment. Commercial direct driven supplies are safe because the hazardous circuitry is in an enclosure to protect the user.

When breadboarding these circuits with electrolytic capacitors of any voltage, the capacitors will explode if the polarity is reversed. Such circuits should be powered up behind a safety shield. Cockcroft-Walton Multiplier A voltage multiplier of cascaded half-wave doublers of arbitrary length is known as a Cockcroft-Walton multiplier as shown in Figure below.

This multiplier is used when a high voltage at low current is required. The advantage over a conventional supply is that an expensive high voltage transformer is not required— at least not as high as the output. Cockcroft-Walton x8 voltage multiplier; output at v 8.

The pair of diodes and capacitors to the left of nodes 1 and 2 in Figure above constitute a half-wave doubler. Rotating the diodes by 45o counterclockwise, and the bottom capacitor by 90o makes it look like Figure prior a. Four of the doubler sections are cascaded to the right for a theoretical x8 multiplication factor. Node 1 has a clamper waveform not shown , a sinewave shifted up by 1x 5 V.

The other odd numbered nodes are sinewaves clamped to successively higher voltages. Node 2, the output of the first doubler, is a 2x DC voltage v 2 in Figure below. Output is v 8. Without diode drops, each doubler yields 2Vin or 10 V, considering two diode drops The bane of the Cockcroft-Walton multiplier is that each additional stage adds less than the previous stage.

Thus, a practical limit to the number of stages exist. It is possible to overcome this limitation with a modification to the basic circuit. It required 40 msec for the voltages to rise to a terminal value for this circuit. The Cockcroft-Walton multiplier serves as a more efficient high voltage source for photomultiplier tubes requiring up to V. The series string of multiplier taps replaces a heat generating resistive voltage divider of previous designs.

The most basic multiplier is a half-wave doubler. The full-wave double is a superior circuit as a doubler. A tripler is a half-wave doubler and a conventional rectifier stage peak detector.

A quadrupler is a pair of half-wave doublers A long string of half-wave doublers is known as a Cockcroft-Walton multiplier.


Voltage Multipliers (Doublers, Triplers, Quadruplers, and More)

Any load in a practical circuit will lower these voltages. In both cases, VDC is produced. This is the input to a switching regulator producing lower voltages for powering, say, a personal computer. Half-Wave Voltage Doubler The half-wave voltage doubler in Figure below a is composed of two circuits: a clamper at b and peak detector half-wave rectifier in Figure prior, which is shown in modified form in Figure below c.


Cockcroft–Walton generator

It is used in virtually every television set made to generate the kV second anode accelerating voltage from a transformer putting out kV pulses. It has the advantage of requiring relatively low cost components and being easy to insulate. It also inherently produces a series of stepped voltages which is useful in some forms of particle accelerators, and for biasing photomultipler tube dynodes. The CW multiplier has the disadvantage of having very poor voltage regulation, that is, the voltage drops rapidly as a function the output current. In some applications, this is an advantage. Furthermore, the ripple on the output, particularly at high loads, is quite high.

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