Common types of switching power supplies in electronic control systems
With the increasing demand for control circuit safety in electronic control systems, the operating voltage of control circuits is becoming more and more inclined towards DC low voltage. As a result, there is an increasing number of electrical devices such as sensors and small and medium-sized DC relays that use DC power in the control circuit. As a result, there have been more switch mode power supplies of different brands in the electronic control system. Due to the involvement of the normal operation of the entire or most control circuits, it is necessary for us to have some knowledge of switching power supplies.
Firstly, let's understand the common types of switching power supplies in electronic control systems.
According to the different corresponding relationships between the same and different named terminals of 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 flyback switching power supplies; Good stability and reliability; The advantages of low price are more common in current electronic control systems (note: some integrated switch mode power supply modules used in electronic control systems also have a considerable number of flyback switch mode power supply circuits. The diagram shows two common types of flyback switch mode 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 practice, there are few products that exceed 1 kilovolt ampere. Interested peers can take a look at the surrounding environment switch mode power supply. If they find that the integrated circuit model used is UC3842/43/44/45, it is a typical form of flyback switch mode power supply (knowledge about this will be discussed in detail 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.
Next, let's take a look at the issues related to the input and output voltage of switch mode power supplies. Due to some switch power supply manufacturers' consideration of both the domestic market and the European, American, and Japanese markets, one switch power supply has two input voltage levels: AC110V and AC220V. This type of switch power supply often uses a selection 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 switch power supply matches the actual input voltage, otherwise it is very easy to cause damage and failure of the switch power supply!
