Output resistance index of regulated power supply
Quality index of regulated power supply
The output voltage Uo of the voltage regulator circuit will be affected by three factors: the input voltage UI, the load current Io and the ambient temperature T, namely
Uo=f(UI,Io,T)
Therefore, the general expression of the variation of the output voltage of the regulated power supply can be recorded as Uo=f(UI, Io, T)
It can be seen that the four main indicators reflecting the quality of DC regulated power supply are Su, Ro, ST, and Ur. The following are respectively explained as follows:
(1) Input adjustment quotes and regulator coefficients
We call the ratio of the change in rectified and filtered input voltage to the change in output voltage caused by it as the input voltage regulation factor. In fact, the ratio of the relative variation of the output voltage to the input voltage is often used to characterize the voltage regulation performance of the power supply, which is called the voltage regulation coefficient. by definition can be written as or
(2) Output resistance
In the case of constant input voltage and temperature, the ratio of the output voltage change to the load current change is defined as the output resistance, denoted as
The negative sign in the formula means that ΔUo and ΔIo change in the opposite direction.
(3) Temperature coefficient
In the case of constant input voltage and load circuit, the output voltage change caused by unit temperature change is the temperature coefficient or temperature drift of the regulated power supply, which is recorded as
(4) Ripple voltage
In the case of rated operating current, the AC component value in the output voltage becomes the ripple voltage. The symbol of the effective value of the ripple voltage is Ur, and UIr can be regarded as the variation of the input voltage. Obviously, the voltage regulator circuit itself will suppress this variation. So Ur≈SuUIr
Sometimes the ripple rejection ratio is often used to describe the magnitude of the ripple voltage, which is written as 20lg(UIr/Ur)(dB). Obviously, the larger the ripple rejection ratio, the better.
For a high-performance voltage regulator circuit, the smaller the above-mentioned four indicators, the better.
