In any switching power supply design, the physical design of the PCB board is crucial. A poorly designed PCB board can result in excessive electromagnetic interference, leading to unstable power supply operation. The following key points should be considered at each step of the design process:
1. Design process from schematic diagram to PCB board: Establish component parameters – input schematic netlist – set design parameters – manually layout components – manually route traces – verify design – review – output CAM file.
2. In parameter setting, the spacing between adjacent traces must meet electrical safety requirements. For ease of operation and production, wider spacing is preferable. The spacing should be sufficient for withstand voltage requirements. When wiring density is low, signal line spacing can be increased. Trace spacing should be set to 8mil. The distance from the edge of a pad’s inner hole to the edge of the PCB should be greater than 1mm to prevent pad defects during processing. For thin traces connected to pads, use a water drop shape design for connections to prevent peeling and disconnection.
Component layout practice has shown that the reliability of electronic equipment can be negatively affected if printed circuit boards are not designed properly, even if the circuit schematic design is correct. For instance, when two thin parallel lines on the printed board are very close, it can lead to signal waveform delay and create reflection noise at the end of the transmission line, degrading performance. Therefore, it is crucial to use the correct method when designing printed circuit boards. Each switching power supply consists of four current loops:
1) AC circuit of the power switch
2) Output rectifier AC circuit
3) Input signal source current loop
4) Output load current loop
The input loop charges the input capacitor through an approximate DC current, while the filter capacitor primarily serves as broadband energy storage. Similarly, the output filter capacitor is used to store high-frequency energy from the output rectifier and removes DC energy from the output load circuit. Thus, the terminals of the input and output filter capacitors are crucial, and the input and output current loops should only be connected to the power supply from these terminals. If the connection between the input/output loop and the power switch/rectifier loop cannot be made directly, AC energy may be radiated into the environment by the input or output filter capacitors.
The AC loop of the power switch and the AC loop of the rectifier contain high-amplitude trapezoidal currents with high harmonic content and peak amplitudes up to 5 times the amplitude of the continuous input/output DC current. These currents are prone to electromagnetic interference, so these AC loops must be laid out before routing other traces in the power supply. The three main components of each loop – filter capacitors, power switches or rectifiers, and inductors or transformers – should be in phase with each other and placed adjacent to each other to minimize current path length. The layout of a switching power supply follows a similar flow to its electrical design:
a. Place the transformer
b. Design the power switch current loop
c. Design the output rectifier current loop
d. Connect control circuit to AC power circuit
e. Design the input current source loop and input filter
f. Design the output load loop and output filter
When laying out all components, certain principles should be followed:
1) Consider PCB board size to prevent long printed lines, high impedance, decreased anti-noise ability, and increased costs
2) Avoid overly dense device placement for easier soldering
3) Design around functional circuit elements, evenly and compactly arrange components with minimal lead length
4) Consider distribution parameters for high-frequency circuits and arrange components in parallel when possible
5) Layout positions based on circuit flow and keep signal directions consistent
6) Ensure efficient routing rate, connect devices with a relationship closely, avoid loop areas to suppress radiation interference
In a switching power supply, any printed wire can act as an antenna due to high-frequency signals. The length and width of the wire affect its impedance and inductance, impacting frequency response. Traces carrying AC current should be short and wide, with components placed close together. Grounding is crucial as the common reference point, aiding in interference control. Proper selection of single-point grounding and thickening of ground wires are essential to maintain stability and anti-noise performance. Input and output grounds should be interconnected in local switching power supplies to ensure a common reference ground.
After wiring design, checks should be made to ensure adherence to designer rules and production process requirements. Outputting light drawing files involves layer outputs, silk screen layers, solder mask layers, drilling layers, and generating drill files (NC Drill). Attention to detailed settings and layer selections is crucial to accurately output the necessary files.
1. Design process from schematic diagram to PCB board: Establish component parameters – input schematic netlist – set design parameters – manually layout components – manually route traces – verify design – review – output CAM file.
2. In parameter setting, the spacing between adjacent traces must meet electrical safety requirements. For ease of operation and production, wider spacing is preferable. The spacing should be sufficient for withstand voltage requirements. When wiring density is low, signal line spacing can be increased. Trace spacing should be set to 8mil. The distance from the edge of a pad’s inner hole to the edge of the PCB should be greater than 1mm to prevent pad defects during processing. For thin traces connected to pads, use a water drop shape design for connections to prevent peeling and disconnection.
Component layout practice has shown that the reliability of electronic equipment can be negatively affected if printed circuit boards are not designed properly, even if the circuit schematic design is correct. For instance, when two thin parallel lines on the printed board are very close, it can lead to signal waveform delay and create reflection noise at the end of the transmission line, degrading performance. Therefore, it is crucial to use the correct method when designing printed circuit boards. Each switching power supply consists of four current loops:
1) AC circuit of the power switch
2) Output rectifier AC circuit
3) Input signal source current loop
4) Output load current loop
The input loop charges the input capacitor through an approximate DC current, while the filter capacitor primarily serves as broadband energy storage. Similarly, the output filter capacitor is used to store high-frequency energy from the output rectifier and removes DC energy from the output load circuit. Thus, the terminals of the input and output filter capacitors are crucial, and the input and output current loops should only be connected to the power supply from these terminals. If the connection between the input/output loop and the power switch/rectifier loop cannot be made directly, AC energy may be radiated into the environment by the input or output filter capacitors.
The AC loop of the power switch and the AC loop of the rectifier contain high-amplitude trapezoidal currents with high harmonic content and peak amplitudes up to 5 times the amplitude of the continuous input/output DC current. These currents are prone to electromagnetic interference, so these AC loops must be laid out before routing other traces in the power supply. The three main components of each loop – filter capacitors, power switches or rectifiers, and inductors or transformers – should be in phase with each other and placed adjacent to each other to minimize current path length. The layout of a switching power supply follows a similar flow to its electrical design:
a. Place the transformer
b. Design the power switch current loop
c. Design the output rectifier current loop
d. Connect control circuit to AC power circuit
e. Design the input current source loop and input filter
f. Design the output load loop and output filter
When laying out all components, certain principles should be followed:
1) Consider PCB board size to prevent long printed lines, high impedance, decreased anti-noise ability, and increased costs
2) Avoid overly dense device placement for easier soldering
3) Design around functional circuit elements, evenly and compactly arrange components with minimal lead length
4) Consider distribution parameters for high-frequency circuits and arrange components in parallel when possible
5) Layout positions based on circuit flow and keep signal directions consistent
6) Ensure efficient routing rate, connect devices with a relationship closely, avoid loop areas to suppress radiation interference
In a switching power supply, any printed wire can act as an antenna due to high-frequency signals. The length and width of the wire affect its impedance and inductance, impacting frequency response. Traces carrying AC current should be short and wide, with components placed close together. Grounding is crucial as the common reference point, aiding in interference control. Proper selection of single-point grounding and thickening of ground wires are essential to maintain stability and anti-noise performance. Input and output grounds should be interconnected in local switching power supplies to ensure a common reference ground.
After wiring design, checks should be made to ensure adherence to designer rules and production process requirements. Outputting light drawing files involves layer outputs, silk screen layers, solder mask layers, drilling layers, and generating drill files (NC Drill). Attention to detailed settings and layer selections is crucial to accurately output the necessary files.
