The role of resistance in overcurrent protection circuit

Tell you about the role of resistance in overcurrent protection circuit

The role of resistance in overcurrent protection circuit:

1. Basic function:

The electronic engineer has learned the basic function of resistance, that is, used as voltage divider, shunt and load resistor in the circuit; Together with capacitors, it can form filters and delay circuits, and be used as sampling resistors in power supply circuits or control circuits. It can be used as bias resistors to determine the working points in semiconductor tube circuits. For these functions, there are many applications in circuits, and they are very important. I will not describe more. Here, we mainly introduce the role of zero resistance and special resistance in electronic circuit design and precautions in use

The role of 2 and 0 ohm resistance inovercurrent protection circuit:

I believe that there are many new electricians. When looking at some electronic products designed by predecessors, they often see a 0 ohm resistance on the circuit. Why should we design such a resistance? Why not draw a board directly and connect it directly? Why paint the snake to gild the lily? Through searching and sorting out the data, the key points are as follows:

1) Single-point grounding of analog ground and digital ground

As long as it is the ground, it will be connected together, and then enter the ground. If it is not connected together, it will be 'floating', there will be voltage difference, it is easy to accumulate charges, generate static electricity, and it is the reference zero potential of the ground. All voltages are obtained by reference to the ground, and the ground standard should be consistent, so all kinds of ground should be short-circuited together, People think that the earth can absorb all the electric charges and keep stable all the time, which is the reference point of the earth. Although some boards are not grounded, the power plant is grounded, and the power supply on the board still needs to return to the power plant and enter the ground. If the analog ground and digital ground are directly connected in a large area, it will cause mutual interference. There are four ways to solve this problem: 1. Connect with magnetic beads; 2. Connect with capacitor; 3. Connect with inductor; 4. Connect 0 ohm resistance The equivalent circuit of

magnetic beads is equivalent to a band stop limiter, which can only significantly suppress the noise at a certain frequency point. When using, it is necessary to estimate the noise frequency in advance so as to select the appropriate model. In the case of uncertain or unpredictable frequency, the magnetic beads do not match; Capacitors are isolated from each other, resulting in floating ground; Large inductance, many stray parameters, unstable; The 0 ohm resistance is equivalent to a very narrow current path, which can effectively limit the loop current and suppress noise. The resistance has attenuation effect in all frequency bands (0 ohm resistance also has impedance), which is stronger than magnetic beads

2) Current circuit used for jumpers

When dividing the electrical grounding layer, the return path of the signal is cut off. At this time, the signal circuit needs to be bypassed to form a large loop area. The influence of electric and magnetic fields becomes stronger and is easy to be interfered/interfered. The 0 ohm resistance on the partition can provide a shorter return path and reduce interference

3) Configure overcurrent protection circuit

Generally speaking, there should be no jumper and dial switch on the product. Sometimes the user will upset the setting, which is easy to cause misunderstanding. In order to reduce the maintenance cost, 0 ohm resistance should be used instead of jumper to weld on the board. The empty jumper is equivalent to the antenna at high frequency, and the patch resistance is effective

Well, I have explained the relevant knowledge points of overcurrent protection circuit to you today. Thank you for watching. Let's see you next time. The overcurrent protection circuit manufacturer wishes you a happy life