High-Frequency Switching Power Supply Principle
Main circuit
The entire process of input and output from the AC power grid, including:
1. Input filter: Its function is to filter out the clutter present in the power grid, while also hindering the feedback of the clutter generated by the machine to the public power grid.
2. Rectification and filtering: Directly rectifying the AC power grid into smoother DC power for the next level of transformation.
3. Inversion: Transforming rectified direct current into high-frequency alternating current, which is the core part of high-frequency. The higher the frequency, the smaller the ratio of volume, weight to output power.
4. Output rectification and filtering: Provide stable and reliable DC power supply according to load requirements.
control circuit
On the one hand, samples are taken from the output end, compared with the set standards, and then the inverter is controlled to change its frequency or pulse width to achieve stable output. On the other hand, based on the data provided by the test circuit and identified by the protection circuit, control circuits are provided to provide various protection measures for the entire machine.
Detection circuit
In addition to providing various operating parameters in the protection circuit, it also provides various display instrument data.
Auxiliary power supply
Provide different required power supplies for all single circuits. The principle of switch control voltage stabilization is that switch K repeatedly turns on and off at certain time intervals. When switch K is turned on, input power E is provided to the load RL through switch K and filtering circuit. During the entire switch on period, power E provides energy to the load; When switch K is turned off, the input power supply E interrupts the supply of energy. It can be seen that the input power supply provides energy to the load intermittently. In order for the load to receive continuous energy supply, the switch regulated power supply must have a set of energy storage devices. When the switch is turned on, a portion of the energy is stored, and when the switch is turned off, it is released to the load. The circuit composed of inductor L, capacitor C2, and diode D in the figure has this function. Inductance L is used to store energy. When the switch is disconnected, the energy stored in inductance L is released to the load through diode D, allowing the load to obtain continuous and stable energy. Because diode D causes the load current to be continuous, it is called a freewheeling diode. The average voltage EAB between AB can be represented by the following formula: EAB=TON/T * E. In the formula, TON is the time when the switch is turned on each time, and T is the working cycle of the switch on/off (i.e. the sum of the switch on time TON and off time TOFF). As can be seen from the formula, changing the ratio of switch on time and working cycle also changes the average voltage between AB. Therefore, automatically adjusting the ratio of TON and T with changes in load and input power voltage can maintain the output voltage V0 unchanged. Changing the on time TON and the duty cycle ratio, also known as changing the pulse duty cycle, is a method called Time Ratio Control (TRC).
