What is the purpose of paralleling the negative terminals of two switching power supplies? Does it eliminate power supply interference?
1. I disassembled a desktop computer power supply, outward output of a large number of plug wires, there are two, three, four, there is a large row, when the box cover is opened, there are Fan cooling, there is a large cluster of wires piled together, I power measurement, found that this pile of wires is a common negative line, I measured 12V, 5V, 3V and so on. The same output voltage, the negative pole are shared, because a rectifier circuit, in the low voltage end of the transformer to be divided into various ways or convert different voltages, from a negative Pole, of course, can only share the negative pole, so that the largest and most conspicuous copper foil on the board will have a large enough current for each positive branch cycle.
2. I am repairing the audio amplifier board, that is, the signal line, microphone cable, speaker cable, circuit board from the power input positive and negative poles are shared after the negative pole, because an electrical device's input power supply is the same as the negative pole. A power equipment input power on a positive and negative two wires, it is to enter the groups to complete the work cycle back to the negative pole, so the negative pole in a whole device on the So this negative terminal in a whole device is a common negative terminal.
3. I made two speakers, each with its own power supply, you can use the mobile phone's dual-channel (a negative and left and right channel signals) connected to the two stereo, then the signal line The ground line becomes a common ground, the connected signal line is shielded, the outer shielded mesh line connected to the negative pole, which also plays a long-distance signal transport without interference or distortion The benefits of the beginning of the no-load noise, I did not notice the random staggering, is not shared ground and shielded wire is not qualified to cause.
Shared ground can save material, save line, the circuit is clear, especially the two audio a common power supply or two power supply shared (such as two small transformer output is not the same) A different voltage, you can rectify the negative combined output, although different voltages for an overall power equipment, but the shared ground can be respective from the negative circuit. I often do this, is very normal!
