The switching power supply is intermittently controlled, but the output has an inductance freewheeling capacitor filter (inductance and capacitor form a low-pass filter) to make the waveform rule a continuous DC voltage waveform. Refer to the power electronics chopper and step-down DCDC circuit, inductance, and capacitor nonlinear components Will make the voltage change slowly from 0 to the maximum value, without sudden change, so the LM2596 fixed voltage 5V, the instantaneous value of the 3.3V output terminal 0 point can not be equal to 12V
The output voltage is calculated according to the volt-second balance principle of the inductance during steady-state operation
Low-pass filter principle
Lm2596VIN and output terminal also have series resistance
Actually test LM2596-5.0v output, the voltage waveform of the inductor
The inductance is close to the LM2596 end (thick)
The inductance is close to the LM2596 end (fine)
Between the two terminals of the inductor itself
Inductor and capacitor parallel terminal
LM2596 fixed frequency 150KHZ, period=6.66US