Principle of switching power supply and Design of Circuit Parameters for Switching Power Supply of forward-facing Transformer (15th)

1-6-3. Calculation of circuit parameters of the switch power supply of the forward-facing Transformer
The circuit parameter calculation of the switching power supply of the excited transformer mainly calculates the energy storage filter inductance, the energy storage filter capacitor, and the parameters of the switching power supply transformer.
Calculation of energy storage filter inductance and energy storage filter capacitance parameters of the switch power supply of the excited Transformer
In Figure 1-17, the calculation of the energy storage filter inductance and the energy storage filter capacitance parameters is basically the same as that of the parameter calculation method of the energy storage filter inductance and the energy storage filter capacitance in the tandem power supply in Figure 1-2. Therefore, we can directly reference (1-14) and (1-18), that is:
 
 

In the formula, Io is the current (average current) flowing through the load. When d = 0.5, its size is exactly equal to 1/2 of the maximum current flowing through the energy storage inductance l ilm; T is the working cycle of the switching power supply, t is equal to 2 times the switching time ton; Delta up-P is the ripple voltage of the output voltage, ripple Voltage Delta up-P is generally used to take the peak-peak value, so the ripple voltage is equal to the voltage increment when the capacitor is charged or discharged, that is, Delta up-P = 2 △uc.
Similarly, the calculation results of the (1-90) and (1-91) types only show the median value for calculating the filtering inductance L of the switching power supply of the positive transformer and the filtering capacitor C, or the average value. In extreme cases, you can multiply the average value by a factor greater than 1.
For more information about the working principle and parameter calculation of the average voltage output filter circuit, see "voltage filter output circuit of the tandem Switching Power Supply" in "1-2. tandem Switching Power Supply.