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Basic principles of chargers

Basic principles of chargers
Charger is a kind of power supply which USES modern power electronics technology to control the switching time ratio of on and off to stabilize the output voltage or current. The power adjustment tube in the charger works in the switching state, which has the prominent advantages of low power consumption, high efficiency and small power supply volume. It has been widely applied in the electronic circuits of communication equipment, numerical control device, instrument, video audio, household appliances and so on. The charger is praised as the high efficiency energy saving power supply, represents the development direction of the stabilized voltage power supply, has become the mainstream product of the stabilized voltage power supply. The charger with control integrated circuit has stable output, high reliability and remote control, which is the development trend of current power supply.
The working principle of charger can be explained by. The input dc unstable voltage U is added to the input end by switching s. S is the switch adjusting tube controlled by switch pulse. By periodically switching s on and off, the input dc voltage U can be changed into a rectangular pulse voltage. By smoothing the pulse voltage through the filter circuit, the stable dc output voltage is obtained. By controlling the duty cycle of the pulse voltage, the output voltage U can also be controlled.
(1) if the switching cycle is constant, the pulse and space ratio D can be changed only by changing the on-time t of switch S, so as to adjust the output voltage. This keeps constant and only changes. To achieve duty cycle regulation, called pulse width modulation (PWM) mode. Because the PWM mode switch frequency is fixed, the output filter circuit is easy to set juice, easy to achieve optimization, so the PWM mode charger used more.
(2) if keep 2. With no change in the switching frequency / =1/T, the pulse duty cycle can be adjusted to achieve the output dc voltage U. The way to stabilize voltage is called pulse frequency modulation (PFM) mode. Because the switching frequency is not fixed, the design of PFM output filter circuit is not easy to optimize.
(3) change both ton and T, so as to realize the regulation of pulse duty cycle voltage stabilization mode, called pulse frequency modulation and width modulation mode.
In a variety of chargers, the above three pulse duty ratio adjustment methods are applied.
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