Various groundings should be considered in the actual wiring process of the switching power supply

“In switching power supply wiring, the basic principle is: according to the actual application, first distinguish the type of ground wire, and then choose different grounding methods; no matter what grounding method, the principle of “low impedance, low noise” must be followed. The following will introduce the characteristics and grounding methods of various “grounds” to be considered in the actual wiring process of the switching power supply.

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In switching power supply wiring, the basic principle is: according to the actual application, first distinguish the type of ground wire, and then choose different grounding methods; no matter what grounding method, the principle of “low impedance, low noise” must be followed. The following will introduce the characteristics and grounding methods of various “grounds” to be considered in the actual wiring process of the switching power supply.

Basic circuit topology loop

power ground

Due to the large current flowing through the power ground wire, if it is not handled properly, it will cause great interference, cannot carry heavy load, or even cannot work normally.

failure case

BUCK lines, due to the use of large areas of paving, cause too much interference and cannot carry heavy loads.

success case

1. 2KW BOOST line

Layout needs attention

●Different power ground wires need to be routed separately

● Try not to run parallel lines

● Minimize loop area

●The principle of “short, thick and straight” must be followed; because the di/dt of the power ground wire is large, the antenna effect of the wire that is too long is obvious; the wire that is too thin will produce a large voltage drop; bend too much or 90 degrees line will produce a reflection effect

drive ground

The ground wire of the driving source should be as close as possible to the driven device to form a minimum loop and reduce oscillation and EMI problems.

Ground point of Y capacitor

●About the concept of “source”

● “quietly” is the low end of the source

●The connection point of the Y capacitor should be “quiet”. Obviously, the best connection point of the Y capacitor in the above picture is the negative end of C1 and the secondary pin 7 of the transformer T1.

Radiator Ground

The heat sink is at the ground potential, and the active device is at the radio frequency potential, so the heat sink can be equivalent to a large common-mode decoupling capacitor when it works, connecting the RF current to the ground.

Application of Local Ground Plane

Local ground planes can capture the RF magnetic flux generated inside the device and oscillator, and are most common in high frequency circuits.

Summarize

●The actual wiring should be combined with the requirements of safety regulations and EMC

The key is to understand the role of “ground” in the power supply, and you need to weigh the pros and cons when wiring