At present, the relationship between electronic equipment and people's work and life is becoming increasingly close, and electronic equipment cannot do without a reliable power supply.
Switching power supply is the abbreviation of switching regulated power supply, which generally refers to an AC (alternating current)-DC (direct current) converter with an input of AC voltage and an output of DC voltage. The power switch tube inside the switching power supply works in a high-frequency switching state, and the energy consumed by itself is very low.
The power efficiency can reach 75% to 90%, which is twice as high as that of ordinary linear regulated power supplies. Similar concepts are easily confused, such as switching power supplies and linear power supplies. Conceptually, there seems to be something in common, but in fact they are not the same. This article will introduce the difference between switching power supplies and linear power supplies.
First, let's understand what a linear power supply is and what a switching power supply is; from the literal meaning, it can be understood that: a power supply system made with a linear regulator is a linear power supply, and a power supply made with a switching regulator is a switching power supply. Next, we will introduce linear regulators and switching regulators.
Linear regulator
Linear regulator is what we often call LDO. Its transmission device works in the linear region. To put it bluntly, it is a resistor voltage divider. It can only be used for step-down conversion. The output current is almost equal to the input current. When the input-output voltage difference is large, the system conversion efficiency is low.
Advantages: pure output voltage, small ripple, low noise, and simple to use.
Disadvantages: can only achieve step-down output, and when the input-output voltage difference is large, the conversion efficiency is low.
Switching regulator
Switching regulator uses the power tube to continuously open and close, and cooperates with energy storage components (inductors, capacitors) to realize energy transmission and conversion, and realize voltage conversion.
According to the different connection methods of the devices in the system circuit, DC boost, step-down, negative pressure, step-up and step-down conversion can be realized. Under ideal conditions, inductors and capacitors will not have energy loss, so the system conversion efficiency is relatively high.
Advantages: high efficiency, small size, high power density, and can realize a variety of power conversion.
Disadvantages: Due to the electromagnetic transformation of the power tube switch and the energy storage device, the output voltage ripple and noise are relatively large, and electromagnetic interference is generated, and the system cost is relatively high.
The difference between switching power supply and linear power supply
Simply put, the voltage regulation of linear power supply can be regarded as adjusting 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 linear power supply, the cost of both switching power supply increases with the increase of 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, switching power supply technology has continued to break through and innovate.
This cost issue has made switching power supply technology move 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 becoming increasingly close, and electronic equipment cannot do without reliable power supply. After entering the 1980s, computers were fully realized as switching power supplies, and by the 1990s, switching power supplies have entered various electronic and electrical fields.
(3) In fact, from the schematic diagram of the switching power supply, we can understand that it does not use a bulky power frequency transformer. At the same time, because the power dissipation on the adjustment tube is greatly reduced, a large heat sink is omitted.
This makes the switching power supply smaller and lighter. However, the biggest advantage of the switching power supply is that it has low power consumption and high efficiency.
In the switching power supply circuit, the transistor is stimulated by the excitation signal and it 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 supply efficiency.
(4) The switching power supply has a wide voltage regulation range. The output voltage of the switching power supply is adjusted by the duty cycle of the excitation signal, and the change of the input 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.
(5) The operating frequency of the switching power supply is currently basically 50kHz, which is 1000 times that of the linear voltage regulated power supply, which makes the filtering efficiency after rectification almost 1000 times higher; even if half-wave rectification is used and capacitor filtering is added, the efficiency is also increased by 500 times.
Under the same ripple output voltage, when using a switching power supply, the capacity of the filter capacitor is only 1/500~1/1000 of the filter capacitor in the linear regulated power supply.
