Common types of switching power supplies and DC voltage levels in electronic control systems
According to the different correspondence between the same and synonymous terminals of the same primary winding in the secondary winding of switching power supplies, switching power supplies can be roughly divided into two categories: flyback and self-excited. Due to the relatively fixed circuit structure of the flyback switching power supply; Stable and reliable; The advantages such as low price are commonly seen in current electronic control systems (add: some of the integrated switch power modules used in electronic control systems are also flyback switch power circuits. The diagram shows two common flyback switch power supplies).
However, due to the limitations of the working principle of flyback switching power supplies, their output capacity is mostly between tens of volts to hundreds of volts, and in reality, there are very few products that exceed 1 kilovolt ampere. Interested peers can take a look at the surrounding environment of switching power supplies. If you find that the integrated circuit model used is UC3842/43/44/45, it is a typical form of flyback switching power supply (knowledge about this will be discussed later).
By the way, the switching power supply circuits in various electronic industrial control devices such as frequency converters and servo controllers are mostly flyback type.
Secondly, let's take a look at matters related to the input and output voltages of switching power supplies. Due to some switch power supply manufacturers not only facing the domestic market, but also taking into account the European, American, and Japanese markets, one switch power supply has two input voltage levels: AC110V and AC220V. This type of switching power supply often uses a selector switch installed on the circuit board to complete voltage level selection (as shown in Figure 2). Therefore, before installation and use, we must check whether the input voltage level switch of the switching power supply matches the actual input voltage, otherwise it is very easy to cause damage to the switching power supply!
Next, let's take a look at the DC voltage levels commonly used in practical work. Based on the actual situation, we often come into contact with the following four DC voltage levels in our work:
1、 +5V: This voltage is usually supplied to the control board containing a microcontroller in the electronic control system, as well as some LED indicator lights;
2、 +12V: This voltage is widely used in industrial control systems, and its power supply range includes proximity switches, infrared sensors, solid-state relays, small electromagnetic relays, etc;
3、 +15V: This voltage is usually used by various detection instruments, but it is not very common in practice;
4、 +24V: This circuit has a voltage level of+12V, which is also very commonly used in electronic control systems. In addition to the various loads carried by+12V, the+24V power supply also serves as the power supply for various touch screens, text editors, touch industrial control integrated machines, and other devices.
