The Difference Between Switching Power Supply and Linear Power Supply

Switching power supply is a kind of power supply that uses modern power electronic technology to control the time ratio of switching on and off to provide the required stable output voltage for electrical appliances. Switching power supply is generally composed of pulse width modulation (PWM) controller and MOSFET. . A switching power supply is a system. At present, the switching power supply enclosure is widely used in almost all electronic equipment due to its small size, light weight and high efficiency, and it is an indispensable power supply method for the rapid development of today's electronic information industry.

The ordinary power supply usually refers to the linear power supply, and the linear power supply refers to the power supply in which the Zener tube works in a linear state. Switching power supplies are a relatively new type of power supply. It has the advantages of high efficiency, light weight, voltage rise and fall, and high output power. However, since the circuit works in the switching state, the noise is relatively large. Since the size of the transformer core is inversely proportional to the square of the operating frequency of the switching power supply, the higher the frequency, the smaller the core. In this way, the transformer can be greatly reduced, and the weight and volume of the power supply can be reduced. And because it directly controls DC, the power supply is much more efficient than a linear power supply.

Comparing the difference between switching power supply and linear power supply, in simple terms, the voltage regulation of linear power supply can be regarded as the resistance value, which is equivalent to changing the voltage by adjusting the sliding rheostat, while the switching power supply changes the voltage by adjusting the switching frequency. At the same time, compared with the linear power supply, the cost of the switching power supply increases with the increase of the output power, but the growth rate of the two is different.

1. The cost of linear power supply is higher than that of switching power supply at a certain output power point.

Therefore, with the development and innovation of power electronics technology, the technology of switching power supply has been continuously broken through and innovated. This cost issue has instead moved the technology of switching power supply to the low output power end, providing a wide range of development space for switching power supply.

2. The relationship between power electronic equipment and people's work and life is increasingly close, and electronic equipment is inseparable from a reliable power supply. After entering the 1980s, the computer fully realized the switching power supply. In the 1990s, the switching power supply entered various electronic and electrical appliances field.

3. In just ten years, switching power supply technology has quickly occupied the core position of power electronic equipment. Is this just because the switching power supply is small in size?

In fact, it can be known from the schematic diagram of the switching power supply that it does not use a bulky power frequency transformer, and at the same time, because the dissipated power on the adjustment tube is greatly reduced, the larger heat sink is omitted. This makes the switching power supply smaller and lighter in weight. However, the biggest advantage of switching power supply is - low power consumption and high efficiency. In the switching power supply circuit, under the excitation of the excitation signal, the transistor continuously repeats the switching state of 'on' and 'off', the conversion speed is extremely fast, and the frequency is only 50HZ, which greatly improves the power efficiency.

4. The switching power supply has a wide range of voltage regulation. The output voltage from the switching power supply is regulated by the duty cycle of the excitation signal, and the change of the input signal signal voltage can be compensated by frequency modulation or width modulation. In this way, when the power frequency grid voltage changes greatly, it can still ensure a relatively stable output voltage. Therefore, it is not without reason that switching power supply technology quickly becomes a part of power electronic equipment.

5. The operating frequency of the switching power supply is basically working at 50kHz at present, which is 1000 times that of the linear regulated power supply, which makes the filtering efficiency after rectification almost 1000 times higher; 500 times higher. Under the same ripple output voltage, when the switching power supply is used, the capacity of the filter capacitor is only 1/500~1/1000 of the filter capacitor in the linear regulated power supply.

The switching power supply is relative to the linear power supply. The input terminal rectifies the alternating current directly into direct current, and then under the action of the high-frequency oscillation circuit, the switch tube is used to control the on-off of the current to form a high-frequency pulse current. With the help of inductors (high-frequency transformers), stable low-voltage direct current can be output. The switch tube works in two states: the on-resistance is small; the cut-off resistance is high. A switching power supply usually consists of a pulse width modulation (PWM) control IC and a MOSFET. With the development and innovation of power electronic technology, current switching power supply has been widely used in almost all electronic equipment due to its advantages of small size, light weight and high efficiency.