Introduction to several circuits of high-frequency switching power supply
Main circuit
The entire process from AC power grid input to DC output, including: 1. Input filter: Its function is to filter out the clutter existing 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 rectify the AC power grid into smoother DC power for the next stage of conversion. 3. Inverter: Convert rectified DC power into high-frequency AC power, which is the core part of high frequency. 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.
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 testing circuit, various protection measures are provided by the control circuit for the whole machine after identification by the protection circuit.
Detection circuit
In addition to providing various parameters that are currently running in the protection circuit, it also provides various display instrument data.
Auxiliary power supply
Provide different power supply requirements for all individual circuits. The principle of switch controlled voltage regulation is that switch K is repeatedly turned on and off at certain time intervals. When switch K is turned on, input power E is provided to 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 disconnected, 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 for the load to receive continuous energy supply, the switch stabilized power supply must have an energy storage device that stores a portion of the energy when the switch is turned on and releases it to the load when the switch is turned off. In the diagram, the circuit composed of inductor L, capacitor C2, and diode D has this function. Inductance L is used to store energy. When the switch is turned off, the energy stored in inductance L is released to the load through diode D, allowing the load to receive continuous and stable energy. Because diode D keeps the load current continuous, it is called a freewheeling diode. The average voltage EAB between AB can be expressed as follows: EAB=TON/T * E, where TON is the time the switch is turned on each time, and T is the duty cycle of the switch (i.e. the sum of the switch on time TON and off time TOFF). As can be seen from the equation, changing the ratio of switch on-time to duty cycle also changes the average voltage between AB, therefore, automatically adjusting the ratio of TON and T with changes in load and input power supply voltage can maintain the output voltage V0 unchanged. Changing the on-time TON and duty cycle ratio, that is, changing the pulse duty cycle, is a method called "Time Ratio Control" (TRC).
