The impedance characteristic of the switching power supply module is that the power circuit composed of internal resistors, capacitors and inductors has the function of blocking ac current. The characteristic impedance of a resistor is itself. The resistance of a capacitor inductor to ac current is called reactance.

Capacitor is called capacitive resistance to ac current blocking in power supply circuit. The larger frequency of AC current is, the smaller the capacitive resistance is, and it has the effect of isolating direct contact. Inductor in the power circuit to ac current blocking is called inductive reactance, the higher the frequency of ac current, the more inductive reactance, it has the effect of direct separation of ac current, can develop filter.

The resistance in the power module is very large, and the work of the load voltage regulator circuit is very serious. All the changes of load current are caused by the output fluctuation of the control module. The harm of fluctuation to the detection is the same as that of monopulse and noise to the detection results.

When line voltage or load current changes, the output working voltage of dc power supply module will fluctuate. The level of the regulator tube is determined by the main parameters of the regulator circuit, the volume of the filter capacitance and the speed of the kinetic energy released. The stable size is the percentage or transformation value of the output working voltage under full load or full load.

Transient no response or repair time Usually at load transition 12%, the common output offset valley operating voltage millivolts calibrate the output offset, and the repair time is usually indicated by the output repair to the standard value of millivolts.

The size of the transient response and repair time of the power module indicates the size of the voltage regulator circuit's ability to recover the working voltage when the output load suddenly changes, which is usually calibrated with the offset value of the output when the load suddenly changes greatly or the time when the output is repaired back to the original value.

Impedance matching can adjust the output power of load and suppress the reflection surface of data signal. The video signal or transmission line and load more than fit between matching is called impedance matching.

When the optical wavelength and transmission line strength of the data signal are the same weight, the reflector data signal is easy to be mixed with the original data signal, while impedance matching can reasonably reduce and clear the reflector of the high frequency data signal.

In the high frequency industry, the data signal frequency is very harmful to the characteristic impedance value of Pcb wiring. When the edge time of analog signal is less than 1ns or the frequency of analog signal is over 400M, the characteristic impedance problem should be considered.

At present, there are two key ways of impedance matching: changing characteristic impedance force or adjusting transmission line. To change the characteristic impedance is to adjust the characteristic impedance of the load in series according to the capacitor, inductor and load, exceeding the matching of source and load impedance.