# Charge pump

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A charge pump is a kind of DC to DC converter that uses capacitors for energetic charge storage to raise or lower voltage. Charge-pump circuits are capable of high efficiencies, sometimes as high as 90–95%, while being electrically simple circuits.

A capacitor is a passive two-terminal electronic component that stores electrical energy in an electric field. The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The capacitor was originally known as a condenser or condensator. The original name is still widely used in many languages, but not commonly in English.

Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential between two points. The difference in electric potential between two points in a static electric field is defined as the work needed per unit of charge to move a test charge between the two points. In the International System of Units, the derived unit for voltage is named volt. In SI units, work per unit charge is expressed as joules per coulomb, where 1 volt = 1 joule per 1 coulomb. The official SI definition for volt uses power and current, where 1 volt = 1 watt per 1 ampere. This definition is equivalent to the more commonly used 'joules per coulomb'. Voltage or electric potential difference is denoted symbolically by V, but more often simply as V, for instance in the context of Ohm's or Kirchhoff's circuit laws.

The efficiency of an entity in electronics and electrical engineering is defined as useful power output divided by the total electrical power consumed, typically denoted by the Greek small letter eta.

## Description

Charge pumps use some form of switching device to control the connection of a supply voltage across a load through a capacitor. In a two stage cycle, in the first stage a capacitor is connected across the supply, charging it to that same voltage. In the second stage the circuit is reconfigured so that the capacitor is in series with the supply and the load. This doubles the voltage across the load - the sum of the original supply and the capacitor voltages. The pulsing nature of the higher voltage switched output is often smoothed by the use of an output capacitor.

An external or secondary circuit drives the switching, typically at tens of kilohertz up to several megahertz. The high frequency minimizes the amount of capacitance required, as less charge needs to be stored and dumped in a shorter cycle.

The hertz (symbol: Hz) is the derived unit of frequency in the International System of Units (SI) and is defined as one cycle per second. It is named for Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves. Hertz are commonly expressed in multiples: kilohertz (103 Hz, kHz), megahertz (106 Hz, MHz), gigahertz (109 Hz, GHz), terahertz (1012 Hz, THz), petahertz (1015 Hz, PHz), and exahertz (1018 Hz, EHz).

Charge pumps can double voltages, triple voltages, halve voltages, invert voltages, fractionally multiply or scale voltages (such as ×3/2, ×4/3, ×2/3, etc.) and generate arbitrary voltages by quickly alternating between modes, depending on the controller and circuit topology.

They are commonly used in low-power electronics (such as mobile phones) to raise and lower voltages for different parts of the circuitry - minimizing power consumption by controlling supply voltages carefully.

## Terminology for PLL

The term charge pump is also commonly used in phase-locked loop (PLL) circuits even though there is no pumping action involved unlike in the circuit discussed above. A PLL charge pump is merely a bipolar switched current source. This means that it can output positive and negative current pulses into the loop filter of the PLL. It cannot produce higher or lower voltages than its power and ground supply levels.

A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is related to the phase of an input signal. There are several different types; the simplest is an electronic circuit consisting of a variable frequency oscillator and a phase detector in a feedback loop. The oscillator generates a periodic signal, and the phase detector compares the phase of that signal with the phase of the input periodic signal, adjusting the oscillator to keep the phases matched.

## Applications

• A common application for charge-pump circuits is in RS-232 level shifters, where they are used to derive positive and negative voltages (often +10 V and −10 V) from a single 5 V or 3 V power supply rail.
• Charge pumps can also be used as LCD or white-LED drivers, generating high bias voltages from a single low-voltage supply, such as a battery.
• Charge pumps are extensively used in NMOS memories and microprocessors to generate a negative voltage "VBB" (about −3 V), which is connected to the substrate. This guarantees that all N+-to-substrate junctions are reversely biased by 3 V or more, decreasing junction capacitance and increasing circuit speed. [1]
• A charge pump providing a negative voltage spike has been used in NES-compatible games not licensed by Nintendo in order to stun the Nintendo Entertainment System lockout chip. [2]
• As of 2007, charge pumps are integrated into nearly all EEPROM and flash-memory integrated circuits. These devices require a high-voltage pulse to "clean out" any existing data in a particular memory cell before it can be written with a new value. Early EEPROM and flash-memory devices required two power supplies: +5 V (for reading) and +12 V (for erasing). As of 2007, commercially available flash memory and EEPROM memory requires only one external power supply – generally 1.8 V or 3.3 V. A higher voltage, used to erase cells, is generated internally by an on-chip charge pump.
• Charge pumps are used in H bridges in high-side drivers for gate-driving high-side n-channel power MOSFETs and IGBTs. When the centre of a half bridge goes low, the capacitor is charged through a diode, and this charge is used to later drive the gate of the high-side FET a few volts above the source voltage so as to switch it on. This strategy works well, provided the bridge is regularly switched and avoids the complexity of having to run a separate power supply and permits the more efficient n-channel devices to be used for both switches. This circuit (requiring the periodic switching of the high-side FET) may also be called a "bootstrap" circuit, and some would differentiate between that and a charge pump (which would not require that switching).

In telecommunications, RS-232, Recommended Standard 232 refers to a standard originally introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a DTE such as a computer terminal, and a DCE, such as a modem. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pinout of connectors. The current version of the standard is TIA-232-F Interface Between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. The RS-232 standard had been commonly used in computer serial ports.

In digital circuits, a logic level is one of a finite number of states that a digital signal can inhabit. Logic levels are usually represented by the voltage difference between the signal and ground, although other standards exist. The range of voltage levels that represents each state depends on the logic family being used.

In electrical engineering, spikes are fast, short duration electrical transients in voltage, current, or transferred energy in an electrical circuit.

The Cockcroft–Walton (CW) generator, or multiplier, is an electric circuit that generates 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 this circuit design to power their particle accelerator, 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". The 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. Cockcroft–Walton circuits are still used in particle accelerators. They also are used in everyday electronic devices that require high voltages, such as X-ray machines, television sets, microwave ovens and photocopiers.

A voltage multiplier is an electrical circuit that converts AC electrical power from a lower voltage to a higher DC voltage, typically using a network of capacitors and diodes.

A switched capacitor is an electronic circuit element implementing a filter. It works by moving charges into and out of capacitors when switches are opened and closed. Usually, non-overlapping signals are used to control the switches, so that not all switches are closed simultaneously. Filters implemented with these elements are termed "switched-capacitor filters", and depend only on the ratios between capacitances. This makes them much more suitable for use within integrated circuits, where accurately specified resistors and capacitors are not economical to construct.

## Related Research Articles

A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction.

A power inverter, or inverter, is an electronic device or circuitry that changes direct current (DC) to alternating current (AC).

A switched-mode power supply is an electronic power supply that incorporates a switching regulator to convert electrical power efficiently. Like other power supplies, an SMPS transfers power from a DC or AC source to DC loads, such as a personal computer, while converting voltage and current characteristics. Unlike a linear power supply, the pass transistor of a switching-mode supply continually switches between low-dissipation, full-on and full-off states, and spends very little time in the high dissipation transitions, which minimizes wasted energy. Ideally, a switched-mode power supply dissipates no power. Voltage regulation is achieved by varying the ratio of on-to-off time. In contrast, a linear power supply regulates the output voltage by continually dissipating power in the pass transistor. This higher power conversion efficiency is an important advantage of a switched-mode power supply. Switched-mode power supplies may also be substantially smaller and lighter than a linear supply due to the smaller transformer size and weight.

The Ćuk converter is a type of DC/DC converter that has an output voltage magnitude that is either greater than or less than the input voltage magnitude. It is essentially a boost converter followed by a buck converter with a capacitor to couple the energy.

A DC-to-DC converter is an electronic circuit or electromechanical device that converts a source of direct current (DC) from one voltage level to another. It is a type of electric power converter. Power levels range from very low to very high.

Power electronics is the application of solid-state electronics to the control and conversion of electric power.

A Marx generator is an electrical circuit first described by Erwin Otto Marx in 1924. Its purpose is to generate a high-voltage pulse from a low-voltage DC supply. Marx generators are used in high-energy physics experiments, as well as to simulate the effects of lightning on power-line gear and aviation equipment. A bank of 36 Marx generators is used by Sandia National Laboratories to generate X-rays in their Z Machine.

A voltage doubler is an electronic circuit which charges capacitors from the input voltage and switches these charges in such a way that, in the ideal case, exactly twice the voltage is produced at the output as at its input.

In electronics, a chopper circuit is used to refer to numerous types of electronic switching devices and circuits used in power control and signal applications. A chopper is a device that converts fixed DC input to a variable DC output voltage directly. Essentially, a chopper is an electronic switch that is used to interrupt one signal under the control of another.

A variable-frequency drive (VFD) or adjustable-frequency drive (AFD), variable-voltage/variable-frequency (VVVF) drive, variable speed drive, AC drive, micro drive or inverter drive is a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage.

A boost converter is a DC-to-DC power converter that steps up voltage from its input (supply) to its output (load). It is a class of switched-mode power supply (SMPS) containing at least two semiconductors and at least one energy storage element: a capacitor, inductor, or the two in combination. To reduce voltage ripple, filters made of capacitors are normally added to such a converter's output and input.

A buck converter is a DC-to-DC power converter which steps down voltage from its input (supply) to its output (load). It is a class of switched-mode power supply (SMPS) typically containing at least two semiconductors and at least one energy storage element, a capacitor, inductor, or the two in combination. To reduce voltage ripple, filters made of capacitors are normally added to such a converter's output and input.

The commutation cell is the basic structure in power electronics. It is composed of an electronic switch and a diode. It was traditionally referred to as a chopper, but since switching power supplies became a major form of power conversion, this new term has become more popular.

The single-ended primary-inductor converter (SEPIC) is a type of DC/DC converter that allows the electrical potential (voltage) at its output to be greater than, less than, or equal to that at its input. The output of the SEPIC is controlled by the duty cycle of the control transistor.

78xx is a family of self-contained fixed linear voltage regulator integrated circuits. The 78xx family is commonly used in electronic circuits requiring a regulated power supply due to their ease-of-use and low cost.

In electronics, a split-pi topology is a pattern of component interconnections used in a kind of power converter that can theoretically produce an arbitrary output voltage, either higher or lower than the input voltage. In practice the upper voltage output is limited to the voltage rating of components used. It is essentially a boost (step-up) converter followed by a buck (step-down) converter. The topology and use of MOSFETs make it inherently bi-directional which lends itself to applications requiring regenerative braking.

The Sparse Matrix Converter is an AC/AC converter which offers a reduced number of components, a low-complexity modulation scheme, and low realization effort . Invented in 2001 by Prof Johann W. Kolar , sparse matrix converters avoid the multi step commutation procedure of the conventional matrix converter, improving system reliability in industrial operations. Its principal application is in highly compact integrated AC drives.

A gate driver is a power amplifier that accepts a low-power input from a controller IC and produces a high-current drive input for the gate of a high-power transistor such as an IGBT or power MOSFET. Gate drivers can be provided either on-chip or as a discrete module. In essence, a gate driver consists of a level shifter in combination with an amplifier.

A Z-source inverter is a type of power inverter, a circuit that converts direct current to alternating current. It functions as a buck-boost inverter without making use of DC-DC converter bridge due to its unique circuit topology.

## References

1. Jenne, F. "Substrate Bias Circuit", US Patent 3794862A, Feb 26, 1974.
2. Kevin Horton. Colordreams Revision C. Last modified 2007-09-30. Accessed 2011-09-15.

Applying the equivalent resistor concept to calculating the power losses in the charge pumps

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Charge pumps where the voltages across the capacitors follow the binary number system

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Motorola, Inc. was an American multinational telecommunications company founded on September 25, 1928, based in Schaumburg, Illinois. After having lost \$4.3 billion from 2007 to 2009, the company was divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011. Motorola Solutions is generally considered to be the direct successor to Motorola, as the reorganization was structured with Motorola Mobility being spun off. Motorola Mobility was sold to Google in 2012, and acquired by Lenovo in 2014.