The switching circuit of the Nmos tube is generally placed on the D pole, but if the S pole puts a small sampling resistor (such as 0.02R) to sample the current of the circuit, is there any problem?
Georgia Posted on July 1, 2020
Yes, the R2 voltage is not too large. According to the schematic diagram, R2=10m ohm, V=0.1V at 10A, the voltage is too small for the microcontroller.
Justice Posted on July 1, 2020
Absolutely, but pay attention to two points:
1. The voltage on the sampling resistor cannot be too large, and the sampled value needs to be connected to the amplifier to amplify the sampled value, which is convenient for related control;
2. PCB wiring needs attention, especially the GND at the sampling end.
Itzel Posted on July 1, 2020
When the high-level Q1 of the single-chip microcomputer is turned on, the voltage drop of the drain D of the NMOS tube is still relatively high due to the series sampling resistance of the source S. Q1 works in a linearly amplified state instead of a saturated state, and the gate will be amplified if there is interference.
If the sampling resistance is very small, it is not that the current cannot be measured, but it is not good.
