A charge pump is a kind of DC to DC converter that uses capacitors as energy storage elements to create either a higher or lower voltage power source. Charge pump circuits are capable of high efficiencies, sometimes as high as 90–95% while being electrically simple circuits.
Charge pumps use some form of switching device(s) to control the connection of voltages to the capacitor. For instance, a two-stage cycle can be used to generate a higher pulsed voltage from a lower-voltage supply. In the first stage of the cycle, a capacitor is connected across the supply, charging it to that same voltage. In the second stage of the cycle, the circuit is reconfigured so that the capacitor is in series with the supply to the load. Ignoring leakage effects, this effectively provides double the supply voltage to the load (the sum of the original supply and the capacitor). The pulsing nature of the higher voltage output is typically 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 capacitor used as the charge pump is typically known as the "flying capacitor".
Another way to explain the operation of a charge pump is to consider it as the combination of a DC to AC converter (the switches) followed by a voltage multiplier.
The voltage is load-dependent; higher loads result in lower average voltages.
Charge pumps can double voltages, triple voltages, halve voltages, invert voltages, fractionally multiply or scale voltages such as x3/2, x4/3, x2/3, etc. and generate arbitrary voltages, depending on the controller and circuit topology.
The term 'charge pump' is also used in phase-locked loop (PLL) circuits. This is a completely different application. In a PLL the phase difference between the reference signal (often from a crystal oscillator) and the output signal is translated into two signals – UP and DN. The two signals control switches to steer current into or out of a capacitor, causing the voltage across the capacitor to increase or decrease. In each cycle, the time during which the switch is turned on is proportional to the phase difference, hence the charge delivered is dependent on the phase difference also. The voltage on the capacitor is used to tune a voltage-controlled oscillator (VCO), generating the desired output signal frequency. The use of a charge pump naturally adds a pole at the origin in the loop transfer function of the PLL, since the charge-pump current is driven into a capacitor to generate a voltage (V=I/(sC)). The additional pole at the origin is desirable because when considering the closed-loop transfer function of the PLL, this pole at the origin integrates the error signal and causes the system to track the input with one more order. The charge pump in a PLL design is constructed in integrated-circuit (IC) technology, consisting of pull-up, pull-down transistors and on-chip capacitors. A resistor is also added to stabilize the closed-loop PLL.
Other articles related to "charge, pump, charge pump, charge pumps":
... Converters also charge the house batteries ... the RV Enough house-battery power to supply basic camping needs (low voltage lights, water pump, control portion of refrigerator, etc.) A means of recharging the house battery(s), such as solar panels or generators ... Generators also charge the house batteries ...
... A bang-bang charge pump phase detector supplies current pulses with fixed total charge, either positive or negative, to the capacitor acting as an integrator ... A phase detector for a bang-bang charge pump must always have a dead band where the phases of inputs are close enough that the detector fires either both or neither of the ... A proportional phase detector employs a charge pump that supplies charge amounts in proportion to the phase error detected ...
... Another basic concept is the charge pump, a version of which is shown schematically in figure 6 ... The charge pump capacitor, CP, is first charged to the input voltage ... It may take several cycles before the charge pump succeeds in fully charging CO but after steady state has been reached it is only necessary for CP to pump a ...
... 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 ... 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 ...
Famous quotes containing the words pump and/or charge:
“Vivacity, leadership, must be had, and we are not allowed to be nice in choosing. We must fetch the pump with dirty water, if clean cannot be had.”
—Ralph Waldo Emerson (18031882)
“Yet I would bear my shortcomings
With meet tranquility,
But for the charge that blessed things
Id liefer not have be.
O, doth a bird deprived of wings
Go earth-bound wilfully!”
—Thomas Hardy (18401928)