1 foreword
The portable communication product such as mobile phone, cordless telephone, interphone is to use batteries to serve as power source, use cell reasonably, dig its latent capacity adequately to be able to improve the use efficiency, life that prolongs batteries. The LCD color screen of the mobile phone needs the Bai Guang LED of tall brightness to illume, the 5V job voltage that Bai Guang LED needs to stabilize, if working voltage drops, the brightness of white smooth LED is reduced, colour with respect to smudginess, the indication effect of LCD color screen is not ideal. Bai Guang LED cannot direct by batteries power supply, because batteries is used at the beginning, voltage is degressive, the influence shows the result. Need to use a charge pump that rises profiling on circuit design so, stabilize step-down voltage in 5V inside a paragraph of longer time.
Principle of the classification of 2 charge pump, job reachs representative application circuit
2.1 charge pump is classified
Charge pump can divide for:
-- pump of step up of switch type regulator, if pursue,1(a) place is shown.
-- without adjust pump of capacitance type charge, if pursue,1(b) place is shown.
-- can adjust pump of capacitance type charge, if pursue,1(c) place is shown.

2.2 jobs process
The working process of pump of 3 kinds of charge all is: Above all energy of keep in storage, release energy with controlled means next, in order to obtain a needed output voltage. Pump of step up of switch type regulator uses inductor to come energy of keep in storage, and pump of capacitance type charge uses capacitor to come energy of keep in storage.
Pump of capacitance type charge is mixed through switch array oscillator, logistic circuit, compare controller to realize voltage promotion, use capacitor to come energy of keep in storage. Because work at more high frequency rate, can use capacitor of small-sized pottery and porcelain (1 μ F) , take up the space is the least, use cost is inferior. Charge pump can offer ± with exterior capacitor only the output voltage of 2 times. The resistor of equivalent series connection that its loss basically comes from capacitor (the RDS of ESR) and in-house switch transistor (ON) . Charge pump converter does not use inductor, its radiate EMI is accordingly negligible. The input carries noise to be able to use a small-sized capacitor filter is divided. Its output voltage is the nicety when the factory is produced beforehand of buy, can carry back end piece on linear regulator is adjusted, the switch that because this charge pump is when the design,can increase charge pump by need is progressional, so that provide enough mobile space for back end regulator. Charge pump very the design that applies to portable application product. The internal composition of pump of capacitance type charge is shown 2 times like the graph. It is actually fiducial, quite, changeover and the system that control circuit composition.
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