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A charge pump is a kind of
DC-to-DC converter 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 conversion, electric power converter. Power levels range from ...
that uses
capacitor In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...
s for energetic charge storage to raise or lower
voltage Voltage, also known as (electrical) potential difference, electric pressure, or electric tension, is the difference in electric potential between two points. In a Electrostatics, static electric field, it corresponds to the Work (electrical), ...
. Charge-pump circuits are capable of high efficiencies, sometimes as high as 90–95%, while being electrically simple circuits.


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 kilo
hertz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), often described as being equivalent to one event (or Cycle per second, cycle) per second. The hertz is an SI derived unit whose formal expression in ter ...
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. Charge pumps can double voltages, triple voltages, halve voltages, invert voltages, fractionally multiply or scale voltages (such as ×, ×, ×, 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 A phase-locked loop or phase lock loop (PLL) is a control system that generates an output signal whose phase is fixed relative to the phase of an input signal. Keeping the input and output phase in lockstep also implies keeping the input and ou ...
(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.


Applications

* A common application for charge-pump circuits is in
RS-232 In telecommunications, RS-232 or Recommended Standard 232 is a standard introduced in 1960 for serial communication transmission of data. It formally defines signals connecting between a ''DTE'' (''data terminal equipment'') such as a compu ...
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 A power supply unit (PSU) converts Mains electricity, mains AC to low-voltage regulated DC power for the internal components of a desktop computer. Modern personal computers universally use switched-mode power supply, switched-mode power supplies ...
. * Charge pumps can also be used as
LCD A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liquid crystals do not em ...
or white-
LED A light-emitting diode (LED) is a semiconductor device that emits light when current flows through it. Electrons in the semiconductor recombine with electron holes, releasing energy in the form of photons. The color of the light (corresp ...
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. * A charge pump providing a negative
voltage spike In electrical engineering, spikes are fast, short duration electrical transients in voltage (voltage spikes), current (current spikes), or transferred energy (energy spikes) in an electrical circuit. Fast, short duration electrical transients ...
has been used in NES-compatible games not licensed by Nintendo in order to stun the Nintendo Entertainment System lockout chip. * As of 2007, charge pumps are integrated into nearly all
EEPROM EEPROM or E2PROM (electrically erasable programmable read-only memory) is a type of non-volatile memory. It is used in computers, usually integrated in microcontrollers such as smart cards and remote keyless systems, or as a separate chip d ...
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). , 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 MOSFET A power MOSFET is a specific type of metal–oxide–semiconductor field-effect transistor (MOSFET) designed to handle significant power levels. Compared to the other power semiconductor devices, such as an insulated-gate bipolar transistor (IG ...
s and
IGBT An insulated-gate bipolar transistor (IGBT) is a three-terminal power semiconductor device primarily forming an electronic switch. It was developed to combine high efficiency with fast switching. It consists of four alternating layers (NPNP) that ...
s. 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). * High-voltage vertical deflection signal generation for
cathode-ray tube A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a ...
(CRT) monitors, done for example with the TDA1670A integrated circuit. To achieve maximum deviation, a CRT coil needs around 50 V. Using a charge pump voltage doubler from an existing 24 V supply eliminates the need for another supply voltage. * Higher-power fast charge solutions for mobile devices rely on a charge pump instead of a
buck converter file:Commutation cell in converters.svg, Comparison of non-isolated switching DC-to-DC converter topologies: buck, Boost converter, boost, Buck–boost converter, buck–boost, Ćuk converter, Ćuk. The input is left side, the output with load is ...
to reduce the voltage, as higher efficiency reduces heat generation. The Samsung A23, which takes an input current of 3  A, can charge its internal battery packs at 6 A thanks to a 2:1 current pump. Oppo's 240  W SUPERVOOC goes further and uses three charge pumps in parallel (98% claimed efficiency) to go from 24V/10A to 10V/24A, which is then taken by two parallel battery packs.


See also

*
Cockcroft–Walton generator The Cockcroft–Walton (CW) generator, or multiplier, is an electric circuit that generates a high DC voltage from a low-voltage AC. It was named after the British and Irish physicists John Douglas Cockcroft and Ernest Thomas Sinton Walton, ...
*
Voltage multiplier image:Voltage Multiplier diagram.PNG, 280px, Villard cascade voltage multiplier. A voltage multiplier is an electrical circuit that converts Alternating current, AC electrical power from a lower voltage to a higher Direct current, DC voltage, typ ...
*
Switched capacitor A switched capacitor (SC) is an electronic circuit that implements a function by moving charges into and out of capacitors when electronic switches are opened and closed. Usually, non-overlapping clock signals are used to control the switches ...
* Charge transfer switch *
Voltage doubler 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. The simplest of the ...


References

Applying the equivalent resistor concept to calculating the power losses in the charge pumps * * * * * * * * Charge pumps where the voltages across the capacitors follow the binary number system * * * * *


External links


Charge Pump, inductorless, Voltage Regulators

On-chip High-Voltage Generator Design


Applications, circuits and solutions using inductorless (charge pump) dc/dc converters.
DC/DC Conversion without Inductors
General description of charge pump operation; example applications using Maxim controllers. * tp://ftp.dei.polimi.it/outgoing/Massimo.Ghioni/Power%20Electronics%20/Power%20electronic%20devices/MOSFET/gate%20drive/charge%20pump/Charge%20pump%204.pdf Charge pump circuits overviewhttps://picture.iczhiku.com/resource/eetop/wYkRpwFlHrpHWnNB.pdf Tutorial by G. Palumbo and D. Pappalardo {{Electronic components Electric power conversion Voltage regulation es:Multiplicador de tensión