Parameter calculation and Simulation of SEPIC circuit

2020-12-06 11:14:05

Sepic The calculation of circuit parameters is simple , It can be used matlab To complete , The code is as follows .

``````clear;clc;

Vin = 12; % Input voltage unit V
Vout = 6; % Unit of output voltage V
Fs = 5000000; % Unit of switching frequency Hz
Iout = 1; % Unit of output current A
DeltaIin = 0.2; % Input current ripple unit A
DeltaIout = 0.2; % Output current ripple unit A
DeltaVc = 0.01; % Output voltage ripple unit V

Ts = 1/Fs; % Switching period
duty = Vout / (Vout+Vin);
L1 = (Vin * duty * Ts) / DeltaIin;
L2 = (Vin * duty * Ts) / DeltaIout;
C1 = (Iout * duty * Ts) / DeltaVc;
C2 = (Iout * duty * Ts) / DeltaVc;

duty = duty * 100; % Company %
Ts = Ts * 10^6; % Company us
L1 = L1 * 10^6; % Company uH
L2 = L2 * 10^6; % Company uH
C1 = C1 * 10^6; % Company uF
C2 = C2 * 10^6; % Company uF

fprintf('duty  = %.1f%%\n',duty);
fprintf('Ts	  = %.1fus\n',Ts);
fprintf('L1	  = %.1fuH\n',L1);
fprintf('L2	  = %.1fuH\n',L2);
fprintf('C1	  = %.1fuF\n',C1);
fprintf('C2	  = %.1fuF\n',C2);
``````

One 、 In depressurization mode , The output voltage is 6V when , give the result as follows ：

Sepic The circuit topology is as follows （ Just consider the ideal situation ）.

The simulation results are shown in the figure below .

It can be seen that , In steady state ,B The channel is the output voltage 6.054V,A The channel is the current ripple of the inductor 18.086mV / 0.1R=180.86mA.

This simulation is open-loop control , So the output voltage will not be very accurate , And it will change with the load , therefore , You have to add a closed loop .

Two 、 In boost mode , give the result as follows ：

The circuit topology is as follows ：

The simulation results are shown in the figure below .

It can be seen that , In steady state ,B The channel is the output voltage 18.002V,A The channel is the current ripple of the inductor 16.206mV / 0.1R=162.06mA.

This simulation is open-loop control , So the output voltage will not be very accurate , And it will change with the load , therefore , You have to add a closed loop .

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