PCB LED switching power supply design 2
Design input current source circuit and the output load circuit input filter design and output filter function according to circuit elements, all the components for the circuit layout, to comply with the following principles:
(1) The first thing to consider LED PCB size. PCB size is too large, the print line length, impedance increased, decreased noise immunity, the cost has also increased; too small then the heat is not good, and close to the line vulnerable to interference. The best shape of rectangular circuit board, an aspect ratio of 3:2 or 4:3, at the edge of circuit board components, from the edge of the circuit board is generally not less than 2mm.
(2) to consider when placing the device after welding, not too dense.
(3) to each function as the center core component of the circuit around it for layout. Components should be uniform, neat, compact arranged on the PCB to minimize and shorten the lead between the various components and connections, decoupling capacitors as close to the device's VCC.
(4) work in the high-frequency circuit, taking into account the distribution of parameters between components. General circuit components as possible to parallel. This not only beautiful, but easy to do LED pcb assembly and welding, easy-to-volume production.
(5) In accordance with the process of arranging circuit functional circuit elements, and make the pcb layout easy to signal flow, and to signal the direction consistent as possible.
(6) The first principle is to ensure that the layout routability routing, the mobile device when you pay attention to fly line connection, a connection between the devices together.
(7) reduce the loop area as possible to suppress interference radiation switching power supply.
Fourth, routing switching power supply contains high frequency signal, PCB printed on the line can play any role in the antenna, the length and width of the printed lines will affect the resistance and inductance, thus affecting the frequency response. Even if the signal produced by the DC line will be printed from the adjacent line coupling to the RF signal and cause the circuit (or even re-radiate interfering signals.) Therefore, all should be produced by alternating current lines are designed to be short and wide as possible, which means that all must be connected to the printing line and connect to other components of the power lines placed very close. The length of printed lines and its demonstrated capacity and impedance of the inductor is proportional to the width of the printed line with inductance and impedance is inversely proportional. Length of the printed line response reflects the wavelength, the longer the length, printed lines can send and receive the lower the frequency of electromagnetic waves, it can radiate more RF energy. According to the current size of the printed circuit board, the width of the power cord as rent, reducing loop resistance. Meanwhile, make the power line, ground the direction and current direction, which helps increase resistance to noise. Switching power supply ground is the bottom of the four current loop slip, as the circuit common reference point plays a very important role, it is an important method to control interference. Therefore, carefully consider the layout of the ground wire should be placed, will cause a variety of hybrid power supply ground unstable.