Analyses of the power adapter circuit design grounding points _

Analyses of the power adapter circuit design grounding points in 2020-881 08 - 05 11:34:33 in power adapter design, circuit board technology is most often met in the ground, from the most common single analog circuit grounding, purely digital circuit loop grounding to a mixture of analog to digital circuit, exquisite design from these grounding way show the power adapter design development. If you design the 15 w power adapter and other requirements, such as through EMC testing, circuit board of the signal frequency is higher ( The rise time of a signal for 10 ns is even lower orders of magnitude) Grounding, then, to consider and to qualify for the factors. So, today to analysis shows that these factors under the ground. Grounding on the analysis of circuit board technology, the first thing to understand a reason, grounding technology is one of the factors in order to improve the circuit stability. In circuit design, through a variety of grounding technology to reduce the loop, is one of the method. Now simply reduce the loop effect technology. 一个。 Circuit are connected with optical coupling technique in the design of circuits, in order to fully protect level after circuit may be affected by the front circuit, optical coupling isolation technology is one of the commonly used method. In this design, can very good reduce send to accept the influence of the circuit in the circuit, it is caused by the introduction of decoupling, greatly reduced the influence of the loop on the circuit. B。 This method, using isolation transformer connection circuit adopts 1:1 transformer, so the isolation circuit of sending and receiving circuit. The receiving circuit of ground loop is greatly reduced. C。 Using common mode choke in circuit design, receiving circuit are connected to the transmission circuit through common mode choke coil, in this way, can reduce the circuit receiving circuit greatly, at the same time, also for EMC test of receiving circuit provides a good technical support. D。 The balancing circuit technology, this method often sent circuit for multipoint parallel power adapter, through various equivalent to parallel module circuit, the last of the various modules in parallel and duplicate point grounding. In balancing circuit, the current flow of each module does not affect each other, so as to improve the stability of the system. After introducing the methods for decreasing the ground loop, now to introduce the method to reduce the number of various grounding. , floating technology in the design of the 12 w power adapter, a common method is to float to the technology, the method of the circuit board signal and external public land is not connected, so as to ensure the good isolation circuit. Circuit with external systems have good isolation, not easily affected by external interference system on the, but the circuit is easy to accumulate static electricity generating electrostatic interference, is likely to produce dangerous voltage. Small at low speed, < 1 mhz) Equipment can be used in a workplace floating ground ( Or workplace single-point metal shell) , metal shell single point of the earth. Second, series single point grounding this grounding method is one of the companies and recommend methods, due to its simple, need not pay attention to so many in the circuit board design, so use more. However, this common impedance coupling circuit easily, make each circuit module influence each other. Three, and duplicate point grounding this approach, although out of the series of single point grounding impedance coupling problem, but in the course of actual use, can introduce grounding line is too much trouble, as to use what kind of need in the process of practical comprehensive evaluation. If the board area allows, using parallel mode, and if it kept simple connections between each circuit module, then adopt the series mode. Under normal circumstances, the download of the board of the power adapter module, analog circuit module, digital circuit and protection circuit module, this kind of circumstance, I adopt and duplicate point grounding method. Four, multipoint earthing multipoint base technology in the design of everyday use more, the module circuit design is used in more and more this grounding method can effectively reduce the high frequency interference problems, but also prone to ground loop design problem, it should fully consider the design of this, to improve the stability of the system design. Small high-speed ( > 10 mhz) Equipment should work with the metal casing to realize multipoint earthing, pick up location spacing should be less than 1/20 of the maximum working frequency, and the metal shell single point of the earth.