PCB News - Precautions for PCB design and manufacturing power supply

Precautions for PCB design and manufacturing power supply
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After having the design guidance reference, it seems that the layout engineer is left to look at the drawing design? Haha, when your veneer design becomes as shown in Figure 2 (in many cases, our veneer space is limited, and the information is not available from time to time): Structure limitation veneer space is insufficient, then how should we weigh our design? ? In the usual design of switching power supply, there are still some design experience to follow (special and unconventional switching power supply design, must be designed according to the datasheet).

Step 1: Determine the position of the switching power supply module on the PCB. The switch is a strong source of EMI radiation. It should be placed far away from sensitive components such as clocks and interfaces, and then as close as possible to our electrical terminals, while considering heat dissipation and assembly Factors such as sex.

Step 2: Determine the difference between the main power supply channel and the ground (power ground, signal ground, and other signal grounds) in the principle block diagram as shown in Figure 3: Main current channel (red); ground difference (rose red and cyan); Feedback channel (blue) Step 3: Determine the core components of each part in the schematic diagram: input filter, switch tube, control circuit, and output filter components.

1. Switch tube: The layout is compact, the layout considers the high current channel, and the input and output grounds can be directly connected.

2. Input filtering: Close to the switch tube to ensure that the large current can be filtered before entering the switch tube.

3. Output filtering: Close to the switch tube to ensure that the large current is filtered before entering the board plane.

4. Input and output circuit: MOS tube loop, freewheeling tube loop should be as small as possible.

5. Control circuit:

(1) The comparison circuit of the control circuit is placed close to the control chip;

(2) For the sampling circuit of the control circuit, the sampling resistor is placed in the middle of the output filter and comparison circuit. During layout, ensure that the sampling circuit is as close as possible to the chip pins and close to the comparison circuit;

1 Reduce the interference intensity of the interference source, or cut off the propagation path of the interference source

2 Circuit isolation is mainly to shield high-frequency parts and isolate analog and digital circuits

3 Use isolation devices to isolate noise interference

4 Harmony ground (divided into different types and designed separately, such as DC ground, AC ground, digital ground, analog ground, signal ground, power ground, etc.)

5 Install EMI filter

6 PCB layout should be reasonable
No minimum requirements

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