When selecting a switching power supply, what factors should be considered?
Switching power supply selection for engineers is every programme power supply need to complete a process, it is a single selection on the outside, but in the final selection before the engineers need to think about a lot of factors, of course, we will be the first moment to think of the question of cost. Today's article would like to clarify is in the switching power supply selection process we in addition to the cost, in order to select the most appropriate power supply module need to pay attention to some of the connotative elements.
Switching power supply module selection, we need to pay attention to and think about many rules. For example, the nominal value of the fuse 1A, which refers to the 25 degrees when the guidelines, but assuming that the equipment is working at 50 degrees, the nominal value of the fuse can be lower than the 1A, the temperature of the programme margins should be selected a little larger. Similarly, the inductor of 1mH is not when all 1mH, it is 1kHz, assuming that you use it in 1MHz, plus industry and commerce to send the value of 1mH inductance can not be 1mH, due to 1M when the inductance of the inductor coil in the dispersion capacitance began to play a small impact, will offset some of the inductance of the role. Filter insertion loss IL = 25dB, is MHz Rs/RL = 50 ohms (source impedance and load impedance), while the practice, our filter applications, it is difficult to do the impedance to satisfy this central requirement, and thus 25dB of the insertion loss will be greatly reduced. Beads, capacitors, diodes, resistors ...... have similar rules. Here we talk about the switching power supply module selection in addition to the cost of the rules. Power module topology has a variety of structures, flyback, forward, push-pull, half-bridge, full-bridge a variety of, each due to its principle of difference, but also embodied in the superiority of certain characteristics of the policy.
Elucidation of several typical topological structure of the application rules. The first is the flyback power supply, its switching in a cycle, charging time without discharge, that is, because of this feature, its time care characteristics, ripple characteristics is very difficult to do extremely well, although the large storage capacitors can help deal with a little bit, but the principle of shortcomings is ultimately a hard injury, the intellectual shortcomings are able to compensate for the diligence, but make up to make up for the time to meet the critical problem of the time ultimately can not cross a certain hurdle. Leakage inductance is also large and so on, but its interests are circuit is simple, low cost, small size, without adding magnetic reset winding, and input voltage scheme is relatively wide. Because of this, it has its share of the total power supply mall more than 70% of the proportion.
