Working Principle of High-Power Switching Power Supplies
1. AC power input is rectified and filtered into DC;
2. A high-frequency PWM (Pulse Width Modulation) signal controls the switching transistor, applying 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 section is fed back to the control circuit through a specific circuit to control the PWM duty cycle, achieving stable output;
5. 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 power grid;
6. For the same power output, a higher switching frequency results in a smaller switching transformer, but places higher demands on the switching transistor;
7. The secondary winding of the switching transformer can have multiple windings or a single winding with multiple taps to obtain the desired output;
8. Protection circuits, such as no-load and short-circuit protection, should generally be added to prevent the switching power supply from burning out.
Basic Components of a High-Power Switching Power Supply
A high-power power supply generally consists of four main parts: the main power circuit, the PWM control circuit, the microcontroller control circuit, and the auxiliary power supply.
Main Power Circuit
Inrush Current Limiting: Limits the inrush current on the input side at the moment of power-on.
Input Filter: Filters out noise from the power grid and prevents noise generated by the unit from feeding back to the grid.
Rectification and Filtering: Rectifies the AC power from the power grid directly into smoother DC power.
Inverter: Converts the rectified DC power into high-frequency AC power; this is the core of the high-frequency switching power supply.
Output Rectification and Filtering: Provides a stable and reliable DC power supply according to the load requirements.
PWM Control Circuit
On one hand, it samples the output and compares it with the set value, then controls the inverter to change its pulse width or pulse frequency to stabilize the output. On the other hand, based on data provided by the test circuit and identified by the protection circuit, it provides the control circuit with various protection measures for the power supply.
Microcontroller Control Circuit
The microcontroller uses an ADC to sample the output voltage and current, and controls the changes in output voltage and current through a DAC output. It also monitors the entire power supply's operating status and is responsible for continuous communication with the computer.
Auxiliary Power Supply: Enables software (remote) startup of the power supply, providing power to protection circuits, control circuits (PWM chips, etc.), and microcontrollers.
Applications of High-Power Switching Power Supplies
High-power switching power supplies are widely used in industrial, communication, medical, and military fields, providing stable and reliable power to various devices and systems. They primarily convert DC power into high-frequency AC power by controlling the switching transistors to achieve high-speed switching, which is then supplied to a transformer for voltage transformation, thereby generating one or more required voltages.
The advantages of switching power supplies, such as small size, light weight, high efficiency, and strong anti-interference capabilities, make them widely used in various electronic devices. Specifically, high-power switching power supplies play an important role in industrial automation control, military equipment, electric vehicle motor testing, DC electronics, and electrical product testing. Furthermore, high-power DC power supplies are widely used in national defense, scientific research, universities, laboratories, industrial and mining enterprises, electrolysis, electroplating, and charging equipment for DC power supply.
In conclusion, high-power switching power supplies have a wide range of applications, and their stability and reliability are crucial for the normal operation of various devices and systems.
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