(1) if a node is found to be particularly sensitive to noise, the sensitivity of the node to serial mode interference can be reduced by using bypass capacitors. A small capacity capacitor is usually added between the node and the ground, or between the node and the input high voltage line, which can be used as a bypass. When selecting a bypass capacitor, ensure that it has a sufficiently low impedance in the buccal area that may cause problems. Its equivalent series resistor (ESR) and equivalent series inductor (ESL) increase its high frequency impedance, so ceramic capacitors with low ESR and ESL are particularly suitable for high frequency bypass capacitors.
(2) the location of fang road capacitors is also very important. In order to suppress high frequency interference, bypass capacitors can be directly parallel when wiring signal lines that need to be bypassed.
(3) no matter battery or power supply is used to power the LED driver, the power impedance cannot be zero. This means that the supply voltage will change as the controller absorbs rapidly changing current from the power supply. In order to reduce this transient change, input bypass capacitors are installed at the input end. Sometimes ceramic capacitors are used in parallel with electrolytic capacitors to limit the large current input into the power circuit and avoid interference to the low-noise circuit.
(4) some nodes are not allowed to adopt bypass measures, because this will change their frequency characteristics. For example, the resistor divider used for feedback is not allowed to connect bypass capacitors, otherwise it will cause phase distortion and destroy the stability of the feedback loop.
4. Heat dissipation
(1) from the perspective of heat dissipation, it is better to install the printed board along the vertical direction, and the distance between the board and the board is generally not less than 2cm. High-power components should be placed above the printed board as far as possible to reduce the influence of these heating elements on the temperature of other components.
(2) temperature-sensitive devices should be placed in a low-temperature area (such as near the bottom of the PCB), not installed directly above the heating device. The heat dissipation of the PCB mainly depends on air flow, and the design should be reasonably arranged according to the way of air flow
(3) radiator surface should be smooth, straight, no warping or rust, and fastened on the device. The device should be installed in the center of the radiator plate. If both are required to be insulated, mica liner and insulating sleeve shall be added. Polyester film can also be selected as insulation liner.
(4) the contact surface between the high-power components and the radiator should be coated with a layer of thermal conductivity silicone grease, so that the two can be closely fitted and the thermal resistance of the contact surface can be reduced to the minimum, which can not only improve the heat dissipation conditions, but also reduce the size of the radiator.
(5) radiator should be far away from high-frequency transformer, power switch tube, output rectifier tube and other heat sources.
(6) when using finished radiator, the maximum allowable heat resistance of radiator can be calculated according to RsA, and appropriate radiator can be selected.