With the continuous development of China's electronic power technology, the power switches used in homes or other places have achieved a major breakthrough in physical development. At present, switching power supply is widely used in all electronic and electrical equipment, and it is the most indispensable power supply method in the current electronic information industry.
For people who love power physics, it is still very good to understand the working principle of switching power supply. In linear power supply, the power transistor is working, and the linear power supply causes the PWM switching power supply to be closed or disconnected. When the two states are disconnected, and the voltage of the power transistor is relatively small, a large current is generated. When the switching power supply is turned off, the voltage is large and the current is special. Small, and the controller that controls the working principle of the switching power supply is to be able to maintain stability and bring safety to people's living environment.
Switching power supply working principle and working conditions
In addition to the working principle of the switching power supply described above, while the working principle of the switching power supply is running, the switching power supply is also a certain working condition, such as the switch, when working, it is not a linear state, but under the work of electronic appliances. In the case of DC, the switching power supply is DC when it is working, not AC; the high frequency of the last switching power supply is high frequency, not close to the low frequency state of the working state. In the working principle of the switching power supply, these working conditions are certain.
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Switching power supply working principle and main features
The birth of each product has its main characteristics, even the switching power supply is the same. So in addition to the above different switching power supply operating principles, what are the main characteristics of the switching power supply? First of all, from the appearance, the weight is lighter and smaller, because the power frequency transformer is not used, so the weight and volume of the switching power supply is only 20% to 30% of the linear power supply; Important characteristics, from the working principle of the switching power supply, the efficiency is higher, the energy consumption is smaller, and the power transistor used is in a closed or disconnected state, and the conversion efficiency is very high, generally about 60% to 70%. , while the linear power state is around 30% to 40%.
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Switching power supply working principle and working mode
Speaking of switching power supply, understanding the working principle of switching power supply, people can understand the working mode of switching power supply, and in addition to understanding the working mode of switching power supply, it is the biggest understanding of switching power supply. There are three types of pulse width, frequency and fixed mode, pulse width and frequency variable mode, another pulse width, frequency fixed variable mode, two variable modes, the former is based on DC/DC voltage. The latter is based on a DC/AC inverter power supply. More commonly used in switching regulated power supplies.
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In the field of switching power supply technology, people develop related power electronic devices and develop switching frequency conversion technology. The two promote each other to promote the switching power supply to a lighter, smaller, thinner, lower noise and high reliability. The direction of anti-interference is developing. These advantages are especially obvious in household appliances, which has given birth to a lot of ideas for hands-on transformation into switching power supplies. The first task is to start by understanding the switching power supply circuit diagram.
The main circuit of the switching power supply is composed of an input electromagnetic interference filter (EMI), a rectification and filtering circuit, a power conversion circuit, a PWM controller circuit, and an output rectification and filtering circuit. The auxiliary circuit has an input over-voltage protection circuit, an output over-voltage protection circuit, an output over-current protection circuit, and an output short-circuit protection circuit.
First, the main circuit
The entire process from AC grid input and DC output, including:
1. Input filter: Its function is to filter the clutter existing in the power grid, and also hinder the clutter generated by the machine from being fed back to the public power grid.
2. Rectification and filtering: The AC power supply of the power grid is directly rectified into a smoother DC power for the next level of transformation.
3. Inverter: The rectified DC power is changed into high frequency AC power, which is the core part of the high frequency switching power supply. The higher the frequency, the smaller the ratio of volume, weight and output power.
4. Output rectification and filtering: Provide stable and reliable DC power supply according to load requirements.
Second, the control circuit
On the one hand, sampling from the output, comparing with the set standard, then controlling the inverter, changing its frequency or pulse width to achieve output stability, on the other hand, according to the data provided by the test circuit, identified by the protection circuit, provided The control circuit performs various protection measures on the whole machine.
Third, the detection circuit
In addition to providing various parameters in the protection circuit, various display instrument data are also provided.
Fourth, auxiliary power supply
Provides different power requirements for all single circuits.
Switch control voltage regulation principle
The switch K is repeatedly turned on and off at a certain time interval. When the switch K is turned on, the input power source E is supplied to the load RL through the switch K and the filter circuit, and the power source E supplies energy to the load during the entire switch-on period; When the switch K is turned off, the input power source E interrupts the supply of energy. It can be seen that the input power supply provides energy to the load intermittently. In order to provide continuous energy supply to the load, the switching power supply must have a set of energy storage devices to store a part of the energy when the switch is turned on. Released to the load when disconnected.
Switching power supply circuit diagrams have different circuit design methods based on different uses. Even if the same use can be used for diversified placement, the working principle and the most important circuit components of the switching power supply will not change. Point, then analyze the specific switching power supply circuit diagram is much simpler.
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