It's so easy to understand the PID control principle

Figure 16: Integral operation circuit - discharge

As shown in Figure 17, the input and output waveforms of the integral operation circuit are shown. Combined with the previous analysis results, Uo reflects the accumulation process of Ui, thus achieving the effect of delayed stabilization.

Figure 17: Integral operation circuit waveform

Figure 18 shows the integral operation simulation circuit. In order to prevent the operational amplifier from saturation, a resistor R3 needs to be connected in parallel across the capacitor C2 in actual use. The circuit after the parallel resistor is no longer an ideal integral operation circuit, but as long as the input signal period is greater than 2 times the RC constant, it can be approximated as an integral operation circuit.

Figure 18: Integral operation simulation circuit

Figure 19 shows the waveform of the integral operation simulation circuit, where IN- is the waveform of the op amp input terminal.

Figure 19: Integral operation simulation circuit waveform

Key points:

① Differential and integral operation circuits use the characteristic that the voltage of a capacitor cannot change suddenly when it is charged and discharged to achieve the purpose of adjusting the output, which is meaningful for changing input signals;

② Differential D control has the characteristics of advanced prediction, and integral I control has the characteristics of delayed stability. In terms of PID adjustment speed, differential D control> proportional P control> integral I control;