What is the difference between a switching power supply and a transformer?

The difference between a switching power supply and a transformer A switching power supply is a power supply that uses modern power electronics technology to control the time ratio of the switch transistor on and off to maintain a stable output voltage. Switching power supplies can be divided into two categories: AC/DC and DC/DC; according to whether there is electrical isolation between the input and output, they can be divided into two categories: one is isolated and called an isolated DC/DC converter; the other is non-isolated and called a non-isolated DC/DC converter. The switching power supply has protection functions such as overcurrent, overheating, and short circuit, a wide voltage input range, and an isolation voltage between input and output. The isolation voltage between the isolated input and output is high. A transformer is a device that uses the principle of electromagnetic induction to transform voltage, current, and impedance. Transformers are mainly used in alternating circuit loops. What is a switching power supply

A switching power supply is a power supply that uses modern power electronics technology to control the time ratio of the switch tube on and off to maintain a stable output voltage. A switching power supply is generally composed of a pulse width modulation (PWM) control IC and a MOSFET.

Advantages and disadvantages of switching power supplies Advantages:

1. High efficiency and small size. Since the voltage control of the switching power supply is achieved by adjusting the opening time or frequency of the power semiconductor device in the saturation zone, there is no iron loss and copper loss, and the loss of components can be ignored. Compared with the transformer, the efficiency is higher; since it only has components and circuit boards, the volume will be small and the weight will be light.

2. Wide voltage input range. Generally, it can reach between 160V-270.

Disadvantages:

1) The switching power supply looks small, and the power is related to the core transformer and the control method. The electromagnetic interference is large and the ripple coefficient is large. Especially in the field of audio and video, it is very sensitive to electromagnetic interference. In audio, the tone is not pure and thick, and there may be a slight sound; in video, the image may have fine ripples and is not delicate.

2) Complex design and inconvenient maintenance and repair. The more complex the equipment, the greater the possibility of problems. Once the switching power supply has problems, it is generally impossible for non-professionals to repair it. Finding others to repair it is too expensive, so it is better to abandon it.

3. Small size is the advantage of the switching power supply, but poor design becomes its disadvantage. In order to pursue a smaller size, a large number of components are squeezed into a small shell, which has poor heat dissipation and the shell is deformed.

4. The components of the switching power supply are not very standardized in selection, which is a common problem of domestic switching power supplies. The relevant national quality inspection departments inspected the switching power supplies on the market and found that more than half of them were unqualified, including imported switching power supplies.

5. The biggest point is that the ability to resist lightning strikes is very low. In the monitoring system, the possibility of lightning strikes is also very high, mainly manifested in the series input from the power supply, and the possibility of direct lightning strikes is very small. Once the 220V voltage suddenly becomes high, the switching power supply is burned out in an instant. In a monitoring system some time ago, after a thunder, the monitoring main switch tripped. After closing the switch, most of the cameras still worked normally, and some monitors showed no video signal. After inspection, it was found that all the ones without video signals were switching power supplies (some places were inconvenient to install during construction, so switching power supplies were used). Finally, a power box was installed on the camera pole and a transformer power supply was replaced.

What is a transformer? A transformer is a device that uses the principle of electromagnetic induction to change the AC voltage. The main components are the primary coil, the secondary coil and the iron core (magnetic core). The main functions are: voltage conversion, current conversion, impedance conversion, isolation, voltage regulation (magnetic saturation transformer), etc. According to the purpose, it can be divided into: power transformers and special transformers (electric furnace transformers, rectifier transformers, power frequency test transformers, voltage regulators, mining transformers, audio transformers, medium frequency transformers, high frequency transformers, impact transformers, instrument transformers, electronic transformers, reactors, mutual inductors, etc.). Circuit symbols often use T as the beginning of the number. For example: T01, T201, etc.

Advantages and disadvantages of transformers

Advantages:

1. Linear looks bulky, and the power depends entirely on the transformer and the adjustment tube. Although the efficiency is low, it will not introduce additional interference, that is, the electromagnetic interference is small, and the ripple factor is very low and can be ignored. For monitoring, there is no better advantage than this. The quality of the image is very related to the power supply. Especially for small-amplitude analog signals (audio source and video source, etc.), the power supply requirements are very high, so some audiophile audio power supplies use transformers instead of switching power supplies.

2. High voltage regulation rate, simple design, very convenient maintenance, and technicians who know a little about electronics can repair it in case of failure. The maintenance cost is much less than that of switching power supplies.

3. Good lightning resistance. Since the structure of the transformer is two coils and an iron core, the voltage applied to both ends of the coil cannot change suddenly, so it has a strong inhibitory effect on instantaneous high voltage. Therefore, in a lightning accident, the power supply of the transformer survived, while the switching power supply burned without exception.

Disadvantages:

1. Low efficiency. Since the transformer is a "electric-magnetic-electric" conversion process, iron loss and copper loss are inevitable, and the efficiency is low.

2. Narrow input range. Generally, it is only between 200V and 240V. If it is less than this range, the output voltage is not enough. If it is greater than this range, the transformer may burn out. This voltage range is sufficient for most occasions, and there is no need to consider it too much. In addition, the transformer is larger and bulkier than the switching power supply.