I am making a TL494-controlled boost converter from discrete components which has these specs:
- Max output power: 120 W
- Max output voltage: 100 V
- Max output current: 10 A
- Supported input voltage: 7-18 V
- Max input current: 12 A (Absolute max is 15 A, but not recommended)
- Switching frequency is 100 kHz
I will be using a high-current inductor so I don't have big inductance options unless I make the inductor myself. As far as I know inductance is important for current ripple; if I get a huge ripple it may overshoot the maximum current rating. Here is the circuit and simulation:
In the simulation the current ripple is 2 A which is acceptable. A closer look:
But when I calculate the ripple with the formula:
$$I_{ripple}=\frac{V_i\cdot D}{L\cdot f}=\\ \frac{12\cdot 0.87}{4.7\cdot10^{-6}\cdot 100000}=22\ \mathrm{A}$$
I don't know which one to trust.
Can you tell me if this is an acceptable design for a student project?
Is the way I do my calculations alright?
Does it matter when the converter operates at CCM or DCM?
Matlab:
clear; clc;
%% Parameters
f = 100000;
Vi = 12;
P = 120;
Vo_max = 100;
Iomax = 10;
%% Requested Scenario
Vo = 100;
Io = 1.2;
deltaV = 0.1;
%% variables of the scenario
R = Vo/Io;
D = 1-(Vi/Vo)
%% Results for CCM
%L = (D*(1-D)^2*R)/(2*f);
L = 4.7 * 10^-6;
Ii = Vo/Vi * Io % = IL
%Iripple = Vi*D/(L*f)
C = D/(R*(deltaV/Vo)*f)
%% Results for boundary conditions
D1 = (Vo_max/Vi)*(2*L*f/(R*D));
IL_max = Vi*D/(L*f)