What is the difference between a linear power supply and a switching power supply?
What is the difference between a linear power supply and a switching power supply? Firstly they are both power supplies that provide a stable voltage or current to a load within the rated specifications. But the means by which they achieve their purpose are different. The scope of adaptation is not quite the same.
Linear power supply working principle is relatively simple, its working process can be equated to an adjustable resistor, step down the voltage higher than the required voltage part into heat consumption. It is like doing a table of ten people at a banquet if only one person on the menu, the linear power supply approach is to find nine people to help eat. Therefore, the larger the voltage drop, the lower the efficiency, the greater the waste.
So the linear power supply is not suitable for high-voltage differential circuits and can only step down the voltage can not be boosted. Because the transistors in this power supply work in the linear amplification area instead of switching state.
So the output is smooth and clean without harmonics, no interference with the load is more suitable for precision equipment.
The biggest advantage of the switching power supply is high efficiency, so it is more suitable for high-voltage and high-power occasions. If you use a banquet as an analogy, it will automatically adjust the amount of food according to the number of people on the menu. Adjust the amount of food, there are a few people to do a few people's meals, basically will not be wasted.
The reason why it is called switching power supply is because its internal power devices are working in the switching state, which is the key to its high efficiency. People usually often People usually often explore how to save electricity, some people answer the most dry: do not use the most provincial! This is originally a joke, but the switching power supply is in accordance with the principle of research and development. The switching power supply is developed according to this principle. It adopts two states of complete conduction and complete cut-off alternately, unlike linear power supply, there is a large resistor in a moment of non-stop consumption of "excess" power. energy.
The switching power supply has a very low internal resistance when it is on, and no energy consumption at all when it is off, so it has a very high efficiency. This type of circuit uses different times (i.e., duty cycle) to adjust the on-state and cut-off times. (i.e., duty cycle) to achieve different energy transfers. Since the frequency of on-off is several tens of thousands of times per second, the transformer inside the power supply can be made very small, thus achieving a small power supply. is very small, thus achieving the miniaturisation of the power supply volume, but also allows the switching power supply can be used to step down the voltage can also be used to boost the voltage. It is currently the most widely used power supply.
But the disadvantage of switching power supply is also obvious, is the power tube switching process generates a large number of harmonics. Due to the high frequency and complex spectrum, it is difficult to filter out. These disturbances Disturbance can be propagated with the wire can also be radiated into space, so the external interference is very serious, and now almost become a public nuisance. This is also the reason why electrical appliances now emphasise the electromagnetic compatibility performance This is also the reason why nowadays electrical appliances are emphasising on the electromagnetic compatibility performance.
