How to generate waveforms in MATLAB from pre-calculated converter values?

Hello everyone,

I am working on a buck converter and I have already calculated the key values analytically (such as inductor current ripple, maximum/minimum current, and capacitor voltage change per switching interval).

What I am trying to do now is generate the corresponding waveforms in MATLAB (for example, inductor current and capacitor voltage vs. time) using these calculated values.

I am not using Simulink, and I am completely new to MATLAB.

Specifically, I would like to understand:

1. How to convert my calculated values (e.g., current slopes, ripple magnitudes, switching times) into time-domain waveforms in MATLAB?

I am not looking for a full circuit simulation—just a way to plot waveforms based on known equations and switching intervals.

Any guidance, examples, or recommended approach would be greatly appreciated.

Thank you!

Answer 1

[Sabin]

If you only want to visualize the steady-state periodic waveforms of a buck converter, using only analytical calculations, you can do something similar to this:

% Parameters
Vin = 12; Vout = 5; L = 10e-6; C = 100e-6;
Iload = 2; fs = 100e3; Ts = 1/fs;
D = Vout / Vin; %  Duty Cycle

% Calculated values
delta_IL = (Vin - Vout) * D * Ts / L; % Inductor ripple
IL_avg = Iload;
IL_max = IL_avg + delta_IL/2;
IL_min = IL_avg - delta_IL/2;

delta_VC = delta_IL / (8 * fs * C); % Capacitor voltage ripple
VC_avg = Vout;
VC_max = VC_avg + delta_VC/2;
VC_min = VC_avg - delta_VC/2;

% Number of cycles
num_cycles = 2;

% Time vector for multiple cycles
N = 1000 * num_cycles; % 1000 points per cycle
t = linspace(0, num_cycles*Ts, N);

% Inductor current waveform for multiple cycles
IL = zeros(size(t));
for k = 1:N
    % Time within current cycle
    t_in_cycle = mod(t(k), Ts);
    if t_in_cycle < D*Ts
        % ON interval: current rises
        IL(k) = IL_min + (IL_max - IL_min)/(D*Ts) * t_in_cycle;
    else
        % OFF interval: current falls
        IL(k) = IL_max - (IL_max - IL_min)/((1-D)*Ts) * (t_in_cycle - D*Ts);
    end
end

% Capacitor voltage waveform (approximate, triangle)
VC = VC_min + (VC_max - VC_min) * (IL - IL_min) / (IL_max - IL_min);

% Plotting
figure;
subplot(2,1,1);
plot(t*1e6, IL, 'b', 'LineWidth', 2);
xlabel('Time (\mus)');
ylabel('Inductor Current (A)');
title('Inductor Current');
grid on;
ylim([IL_min-0.2, IL_max+0.2]);

subplot(2,1,2);
plot(t*1e6, VC, 'r', 'LineWidth', 2);
xlabel('Time (\mus)');
ylabel('Capacitor Voltage (V)');
title('Capacitor Voltage');
grid on;
ylim([VC_min-0.01, VC_max+0.01]);

[Arnob]

Hello Sabin,

Thank you so very much. It means a lot!