Basic principles of switching stabilized power adapter


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Basic principles of switching stabilized power adapter

Switching regulator is composed of full-wave rectifier, switching tube, excitation signal, continuation diode, energy storage inductor and filter capacitor. There are many kinds of switch stabilized power supply adapters. The switching transistor Q is connected in series between the input voltage E true and the output voltage E signal. When the base of a transistor is fed a switch pulse signal, the transistor is periodically switched on, alternating between saturation conduction and cut-off. Assuming that Q is an ideal switch, the voltage drop between the emitter poles of the set is approximately zero when saturated conduction occurs, and the input voltage E true longitude Q is added to the output end. On the other hand, during the transistor cutoff, the output is zero. After periodic switching, the transistor gets the pulse voltage at the output end, and the dry average dc voltage can be obtained through the filter circuit t-so the output voltage Eo is l two E: sheep. Where Tc is switching on time and T is switching l pulse cycle. Thus, the series switch voltage regulator circuit can control the output dc voltage value by changing the duty cycle of the switch pulse, namely the switching on time Tc.
Switch regulator power adapter high efficiency, wide voltage range, the output voltage is relatively stable, because the switch tube work in the switching state, power consumption is small, so the power adapter can work efficiency of 80% ~ 90%. However, the efficiency of the normal linear adjustable stabilized voltage power adapter is only about 50 %

Power adapter internal power switch tube in the high frequency switch state, itself is very low consumption of energy, power adapter efficiency can reach 75% 90%, higher than that of ordinary linear regulated power supply adapter nearly doubled by the input ac voltage or load current changes caused by the change of output voltage, also can through sampling circuit in its variation with the reference circuit, by comparing the error voltage amplifier amplification, to control the switch pulse width, in order to achieve the purpose of the stability of the dc output. The function of the pulse width modulation circuit is to modulate the width of the switch pulse.
The above is the most simple switch voltage regulator circuit, and the application is more than a pulse transformer coupling switch voltage regulator adapter. The switch tube Q is connected with the pulse transformer at the input end. Q is periodically switched on and off under the control of the switch pulse, so the pulse voltage is obtained at the collector. By pulse transformer coupling, in the secondary stage
Tian obtained the corresponding pulse voltage, and then rectified and filtered to obtain the required dc voltage Eo. In this process, there is a process of converting the dc voltage obtained by rectifying and filtering into the pulse voltage, which is called inverter. The working process of contravariant is described in detail in the next section.
The switch voltage stabilizing power adapter coupled with pulse transformer is designed to boost or reduce voltage by changing the turns ratio of the primary stage of the pulse transformer. At the same time, multiple groups of secondary windings can be used to obtain multiple dc output voltages of different values.

| release time：2019.09.16 Source：

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Basic principles of switching stabilized power adapter