The reason for converting to high-frequency AC is that high-frequency AC is much more efficient in transformer circuits than 50Hz, so the switching transformer can be made very small and doesn't get very hot during operation, resulting in low cost. If the 50Hz frequency weren't converted to a higher frequency, there would be no point in using a switching power supply.
Working principle
1. AC power input is rectified and filtered into DC; 2. A high-frequency PWM (Pulse Width Modulation) signal controls the switching transistor to apply this DC power to the primary winding of the switching transformer; 3. A high-frequency voltage is induced in the secondary winding of the switching transformer, which is rectified and filtered to supply the load; 4. The output is fed back to the control circuit through a certain circuit to control the PWM duty cycle, thereby achieving stable output. AC power input generally passes through a choke coil or similar device to filter out interference from the power grid, as well as interference from the power supply to the grid. For the same power output, a higher switching frequency results in a smaller switching transformer, but places higher demands on the switching transistor. The secondary winding of the switching transformer can have multiple windings or multiple taps on a single winding to obtain the desired output. Generally, additional protection circuits should be added, such as no-load and short-circuit protection, otherwise the switching power supply may burn out. It is mainly used in industrial applications and some household appliances, such as televisions and computers.
DC switching power supply composition
The entire process of DC power supply input and output from the AC mains is as follows: 1. Input Filter: Its function is to filter out noise present in the power grid and also prevent noise generated by the unit from being fed back to the public grid. 2. Rectification and Filtering: The AC power from the mains is directly rectified into smoother DC power for the next stage of conversion. 3. Inverter: The rectified DC power is converted into high-frequency AC power. This is the core part of the high-frequency switching power supply. The higher the frequency, the smaller the ratio of size, weight and output power. 4. Output Rectification and Filtering: Provides a stable and reliable DC power supply according to the load requirements.
A switching DC power supply is a type of switching power supply that uses a circuit to control a switching transistor to conduct and cut off at high speed, converting direct current into high-frequency alternating current supplied to a transformer to generate one or more desired voltages. Today, we'll mainly discuss the working principle and structure of switching DC power supplies.
Working principle of switching DC power supply:
1. Alternating current (AC) is rectified and filtered to become direct current (DC);
2. By controlling the switching transistor with a high-frequency PWM (Pulse Width Modulation) signal, DC power is added to the primary winding of the switching transformer;
3. The high-frequency voltage induced on the secondary side of the switching transformer is rectified and filtered to power the load;
4. The output section is fed back to the control circuit through a certain circuit to control the PWM duty cycle in order to achieve stable output.
AC power input typically uses a choke coil or similar device to filter out interference from the power grid, as well as interference from the power supply to the grid. For the same power output, a higher switching frequency results in a smaller switching transformer, but also higher requirements for the switching transistors. The secondary winding of a switching transformer may have multiple windings or windings with multiple outputs required. Generally, some protection circuits should be added, such as no-load and short-circuit protection; otherwise, the switching DC power supply may burn out. Switching DC power supplies are mainly used in industrial applications and some household appliances, such as televisions and computers.
A DC switching power supply is essentially a power supply device that uses internal control circuitry to rectify, filter, cut, and invert the incoming power supply, ultimately providing a stable DC power supply to the load. Its working principle mainly includes the following steps:
Input power rectification and filtering: The operation of a DC switching power supply begins at the AC power input terminal. After processing by the rectifier and filter circuits, the AC signal is converted into a stable DC signal.
Control circuit: The circuit signal after power supply filtering is processed by a control circuit, which can accept the set potential signal and other auxiliary signals from the outside, and control the switching transistor to achieve the purpose of setting the output voltage, current, etc.
Switching control: The switching transistor is a shortcut for switching the power supply on and off. It is controlled by an internal drive circuit to achieve advanced PWM (Pulse Width Modulation) technology. The switched electrical signal passes through a filter circuit to obtain precise output voltage and current.
Output load handling: After the above three steps, the output terminal can provide a stable power supply to the load. Depending on the different requirements of the power load (common in industrial production settings, such as communication, lighting, and electrical testing instruments), overcurrent protection circuits, overvoltage protection circuits, short-circuit protection circuits, and current limiting circuits are often used to protect the safety of the load.
In summary, DC switching power supplies mainly manage and process DC power through various circuits such as rectification, filtering, and switching control. Their overall working principle is relatively simple, but they possess excellent characteristics such as high efficiency, stable output voltage, and strong load protection capabilities, and are commonly used in various practical applications and industrial electrical equipment.
