A transformer is a device that converts voltage, current, and impedance based on the principle of electromagnetic induction. The primary side of a transformer is used in AC circuits. A switching power supply is a power supply that uses modern power electronics technology to control the on and off times of switching transistors to maintain a stable output voltage. Switching power supplies can be divided into two categories: AC/DC and DC/DC. Based on the electrical isolation between input and output, they can be divided into two categories: one is isolated, called an isolated DC/DC converter; the other is not isolated, called a non-isolated DC/DC converter.
The disadvantages of transformers are:
1. Low efficiency. Since a transformer is an "electric-magnetic-electric" conversion process, iron loss and copper loss are unavoidable, resulting in low efficiency.
2. Narrow input range. Generally, it's only between 200V and 240V. Below this range, the output voltage is insufficient; above this range, the transformer may burn out. This voltage range is sufficient for most applications, so it doesn't need to be considered too much. Furthermore, transformers are larger and heavier than switching power supplies.
advantage:
1. Linear power supplies appear bulky, and their power consumption depends entirely on the transformer and regulating tube. While their efficiency is low, they do not introduce additional interference, meaning they have minimal electromagnetic interference and a negligible ripple coefficient. For surveillance, there is no better advantage than this, as image quality is highly dependent on the power supply. Especially for small-amplitude analog signals (audio and video sources, etc.), the power supply requirements are very high. Therefore, some high-end audio systems use transformers instead of switching power supplies.
2. It has a high voltage regulation rate, simple design, and is very convenient to repair and maintain. If a fault occurs, it can be repaired by a technician with basic electronics knowledge, and the repair cost is much lower than that of a switching power supply.
3. Excellent lightning protection. Because a transformer consists of two coils and an iron core, the voltage applied across the coils cannot change abruptly, thus providing strong suppression of instantaneous high voltage. Therefore, in a lightning strike, the transformer's power supply survived, while all switching power supplies were burned out.
Based on the above characteristics, we chose a linear power supply (transformer power supply) instead of a small, lightweight switching power supply. These two advantages are not decisive in a monitoring system; stability and maintainability are key. Imagine if a small power supply were constantly being sent to the construction site, potentially damaging cameras. The costs and labor involved would add up to a significant amount over time—a net loss that would only damage our reputation. Therefore, I advise everyone not to sacrifice the entire project for temporary convenience; I recommend using a stable and reliable power supply.
Transformers come in many types, and can be classified according to their uses as follows:
(1) Power transformers. They are mainly divided into step-up transformers, step-down transformers, distribution transformers, and plant service transformers. The capacity of these transformers ranges from tens of kilovolt-amperes to hundreds of thousands of kilovolt-amperes, and the voltage level ranges from hundreds of volts to hundreds of kilovolts. There are transformers for transmitting and receiving electrical energy over long distances, as well as transformers for supplying multiple electrical appliances over short distances.
(2) Special transformers. Based on the different requirements of departments such as transportation, chemical industry, metallurgy, machinery manufacturing, and automatic control systems, various special power supplies or other uses are provided, such as electric furnace transformers for metallurgy, electric welding transformers for electric welding, and rectifier transformers for chemical industry.
(3) Control transformers, which have a smaller capacity. They are used in automatic control systems such as power transformers, input transformers, output transformers, pulse transformers, voltage regulating transformers, etc.
(4) Instrument transformers. Such as voltage transformers and current transformers, used for measuring instruments and relay protection devices.
