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        Low-dropout linear regulators in the switching power supply application

        Number of visits: Date:2016-04-22

        Power is a variety of electronic devices must be an integral part of the performance of electronic devices directly related to the merits of the technical indicators and whether security can * work. The most commonly used sub-linear DC power supply and switching power supply into two categories, the key components within the switching power supply switch state at high frequency, low energy consumption itself, switching power supply efficiency up to 80% to 90% than the average linear power supply to nearly double the power supply has become a mainstream product.


        Switching power supply structure

        Figure 1 plots the switching power supply schematic and block diagram of the equivalence principle, it is a full-wave rectifier, switch Vi, excitation signal, diode VD, inductor and filter capacitor, C,. In fact, the core of the switching power supply is a DC transformer. Here we have the DC converter and the inverter to make the following explanation. Inverter, which is the DC into AC device. Inverter is usually used widely in the level or composition of the backup battery power supply. DC converter, it is converted to AC to DC and then again converted into direct current AC devices. This device is widely used in switching power supply in the. DC converter can be converted into a DC supply voltage polarity, the value of the different variety of DC supply voltage.

         

         

        Switching power supply of the advantages and disadvantages

        Advantages of switching power supply

        Power consumption and high efficiency. In Figure 1, the switching power supply circuit, the transistor V Inspired by the excitation signal, which in turn alternately to work - and the cut-off cut-off - turn on and off, fast conversion speed, frequency, generally 50kHz or so, In some technologically advanced countries, can do a few hundred or nearly 1000kHz. This makes the switch transistor V is so low, the power efficiency can be greatly improved, and its efficiency can reach 80%.

        Small size and light weight. From the block diagram of switching power supply can be clearly seen here does not use heavy-frequency transformer. As the regulator power dissipation on V, after a significant reduction, but also eliminates the need for a larger heat sink. Because these two reasons, so switching power supply, small size, light weight.

        Voltage range. From the switching power supply output voltage from the excitation signal to adjust the duty cycle of the input signal voltage changes can be transferred through the FM or width to compensate. Thus, in the frequency grid voltage change is large, it is still able to ensure a more stable output voltage. The switching power supply regulator with a wide range, voltage regulation, very good. In addition, methods to change the duty cycle of the pulse-width modulation and frequency modulation type two. Switching power supply voltage range is not only the advantages, and the methods to achieve more regulation, the design may be based on practical applications, the flexibility to use various types of switching power supply.

        Filtering efficiency gains in the capacity of the filter capacitor and volume greatly reduced. Frequency switching power supply in the current work is basically 50kHz, is a linear regulated power supply of 1,000 times, which makes the filter after the rectifier efficiency is almost up to 1,000 times; even with half-wave rectifier plus capacitor filter efficiency also increased 500-fold. In the same output voltage ripple, the use of switching power supply, the filter capacitor is a linear regulated power supply filter capacitor in the 1 / 500 to 1 / 1000. Form of flexible circuit, a self-excited, and he excited, there is a wide-and FM-type transfer, a single-ended and double-end type, etc., can play all types of circuit designer's expertise, designed to meet different application where the switching power supply.

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