How to repair a switching power supply using an oscilloscope, which methods
Generally speaking, the ground of parallel switching power supply has two, namely "hot ground" and "cold ground". Take the circuit shown in Figure 1 as an example, the "◇" in the figure represents the "hot ground", this ground is the ground of the primary side of the switching power supply, and the utility ground is connected to the "hot ground" connected to the base plate is called the "hot base plate"; the "upper" in the figure represents the "hot base plate"; the "upper" in the figure represents the "hot base plate". The "upper" in the figure indicates "cold ground", this ground is the ground of the secondary side of the switching power supply, and the load is connected to the bottom plate connected to the "cold ground" is called "cold ground". This ground is the ground of the secondary side of the switching power supply, which is connected to the load, and the base plate connected to the "cold ground" is called the "cold base plate".
The fundamental difference between "hot ground" and "cold ground" lies in the zero-potential reference point of the machine base plate and the utility grid with or without "direct electrical connection". There is a direct connection between the ground is "hot ground", the machine's "hot ground" to the earth there is a voltage of about 100 volts, if you accidentally touch the machine's "hot ground" and the "hot ground" with the If you accidentally touch the "hot ground" inside the machine and the components connected to the "hot ground", it is very likely to suffer from electric shock, or even life-threatening; on the contrary, the "cold ground" and the utility grid has no "direct electrical connection", touching the "cold ground" with your hand is not a good idea. On the contrary, the "cold ground" has no "direct electrical connection" with the utility grid, and touching the "cold ground" and the components connected to the "cold ground" by hand will generally not cause an electric shock.
For series switching power supply, there is only one "hot ground", that is to say, the primary and secondary sides of the series switching power supply are the same ground, all for the "hot ground". Because the LCD monitor through the cable signal directly connected to the computer host, therefore, the LCD monitor switching power supply can not be used in series switching power supply, otherwise, the computer host will be charged, which is not allowed.
Problems to be noted in use:
1, use the original power cord of the oscilloscope;
2, confirm the stability of the power grid. When there is a high-power electrical appliance accessed in the power grid, turn off the oscilloscope first, unplug the power cord, and use it after the power grid is stable;
3,When switching on the oscilloscope: Plug in the AC power cord first, and then press the power on button to switch on the oscilloscope;
When switching off: switch off the oscilloscope by pressing the switch-off key first, and then unplug the AC power cord;
4, pay attention to the use of the instrument environment, clean up the dust regularly.
