Ming Sun – Silicon achitect, design lead, researcher.

Block diagram

The Boost converter power stage block diagram is shown in Fig. 1.

Fig. 1Boost converter block diagram^[1]

Equations

In order to create the model in Matlab, we have to derive equations first. For a Boost converter inductor, we have the following:

`L*{di_L}/{dt}=D*V_{text(in)}-D^'*(V_{text(in)}-V_{out})`

(1)

Where,

`D^' = 1-D`

(2)

Eq. 1 can be simplified as:

`L*{di_L}/{dt}=V_{text(in)}-D^'*V_{out} = V_{text(in)} - V_{SW}`

(3)

Where,

`V_{SW} = -D^'*V_{out}`

(4)

Eq. 4 can be rewritten as:

`{di_L}/{dt}=(V_{text(in)} - V_{SW})/L`

(5)

For the output capacitor, we have the following:

`C*(dV_{out})/dt = D^'*i_L - V_{out}/R`

(6)

Eq. 6 can be rewritten as:

`(dV_{out})/dt = 1/C*(D^'*i_L - V_{out}/R)`

(7)

Simulink modeling

The overall process to model the open loop Boost converter is similar as the open loop Buck converter modeling as described in Ref. [2].

First, let us import to integrator into the simulink cavans as shown in Fig. 2.

Fig. 2Import integrator and mark the signal

To mimic the switching behavior on the VSW net, we will use a switch. Fig. 2 shows the connections. Basically, when duty cycle D is greater than 0.1, VSW is connected to ground and while D is less than 0.1, VSW is connected to Vout. This is exactly the switching behavior for a Boost converter.

Fig. 3Use switch and pulse generator to mimic the VSW waveform

The setting of the pulse generator is as shown in Fig. 4.

Fig. 4pulse generator properties

Since the overall process to build this Boost converter open loop model is similar of the process for the Buck converter, please refer to Ref. [2] if you are not familiar with the process. The completed open loop Boost converter model in Simulink is as shown in Fig. 5.