Grounding of LED drive power
(1) in electronic equipment, grounding is an effective way to control interference. The combination of grounding and shielding can often get twice the result with half the effort and solve most interference problems. The ground wire in the power system can be roughly divided into primary ground, secondary ground, analog ground (also known as signal ground), power ground, shielded ground (enclosure) and system ground.
(2) single-point grounding or multi-point grounding should be correctly selected. Multi-point grounding method is allowed for analog ground, and single-point grounding method (also known as kelvin connection method) should be used for power ground.
(3) if the ground wire is very thin, the grounding potential will change with the current, making the signal unstable and the anti-noise performance worse. Therefore, the grounding wire should be as thick as possible, and the line width can be selected according to the margin of 3 times working current. In general, the width of power grounding wire should be larger than 3mm
2. Methods to reduce noise interference
(1) there are three main ways to generate noise interference: firstly, switching noise. Due to distributed resistance and distributed inductance in the ground circuit, switching noise is generated on the ground wire when the grounding return current of the power circuit passes through the ground circuit of the controller (IC). Second, the noise of the ground circuit will not only reduce the output accuracy of voltage stabilization (or current stabilization), but also easily interfere with other sensitive circuits on the same board. Third, the switching noise at the positive end of the power supply or battery can be coupled to other components (including the controller chip) powered by the same power supply, so that the reference voltage fluctuates. If the voltage at both ends of the input bypass capacitor is found to be unstable, a level of RC filter can be added in front of the power pin of the controller to help stabilize its supply voltage. In addition, the larger the area of the circuit through which the ac current passes, the stronger the magnetic field generated, and the possibility of forming in disturbance is greatly increased. By placing the input bypass capacitor near the power circuit, the area enclosed by the input current loop can be reduced and interference can be avoided.
(2) the typical circuit structure of the booster converter is shown in figure 9-42. Point A in the figure is the node formed by energy storage inductor (L), output rectifier (VD) and power switch (MOSFET). When MOSFET is conducting, the potential UA at point A is close to the ground potential. When MOSFET was turned off,UA rose to one potential of diode forward pressure drop higher than Uo. PCB wiring shall minimize the distributed capacitance of the node. Since the voltage drop at both ends of the distributed capacitor cannot be changed, it can affect the transient characteristics of the voltage at the node.

The midpoint of the sampling resistance voltage divider (R1 and R2) at the output end and the input end of the internal comparator at the feedback end of the controller (FB) are both impedance. The two sampling resistors at the output end should be close to the feedback end. Make sure that the sampling resistance divider's midpoint to the FB terminal lead of the controller is the shortest. The voltage reference terminal URF inside the controller must be grounded through the bypass capacitor CRF installed next to it so that the noise of the voltage reference does not directly affect the output voltage.
(3) since inductance current cannot be changed suddenly, when inductance current changes rapidly, inductance voltage (UL) will produce high amplitude peak voltage and ringing, which will not only form electromagnetic interference. And easy to damage the components in the circuit. RC absorption circuit or clamp circuit should be added if necessary.