.ModelicaDEVS.Examples.Electrical.FlybackConverter.FlybackConverterDymola

Information

Dymola Flyback Converter

This model shows the flyback converter with a voltage source connected to the primary winding of the converter and a load to its secondary winding.

The flyback converter can be used to transform a given input voltage to a different output voltage. It belongs to the group of DC-DC converters.
The operation of the flyback converter consists of two phases:

Phase 1: When the switch is closed, the diode is locked and current flows through the inductor on the left side of the transformer (primary winding), setting up a magnetic field. The consumer load (a resistor in our case) is driven by the energy stored in the capacitor.
Phase 2: When the switch is opened, the voltage source is separated from the circuit. The magnetic field of the inductance is responsible for creating a current that flows through the diode now, since it cannot flow via the voltage source anymore. The inductor serves as a source of energy, which means that it charges the capacitor and runs the load.

The two phases are repeated in high frequency (controlled by the boolean signal that is connected to the switch), thereby providing the load with an almost constant current.

The figure below shows the first two milliseconds of a simulation run of the flyback converter circuit. Additionally, it also shows a more detailed view (only 0.19 milliseconds) in order to illustrate the influence of the switch on the trajectory of the voltage/current at the load: when the switch (green) is closed, the resistor is driven by the capacitor, so the voltage (blue) and the current (red) at the resistor decreases slowly (phase 1) (note that given the fact that it is an IdealClosingSwitch, it is closed if the variable control equals 1). When the switch is open, it is the voltage source to power supply the resistor, so the resistor voltage/current increases (phase 2).

The converter circuit can be described by the following equations (consider the above figure for a definition of the variables): U₀ = constant
0 = if open₁ then i₀ else u_S
u_L = L * di_L/dt
i_C = C * du_R/dt>
u_R = R * i_R
0 = if open₂ then i_D else u_D
open₂ = u_D < 0 and i_D <= 0
u_T = -u_L
i_T = -i_D
i₀ = i_L+i_T
i_D = i_C+i_R
u₀ = u_S+i_L
0 = u_T+u_D+u_R

Note that these equations give an acausal description of the flyback converter, which is not what we will need to set up a flyback model in ModelicaDEVS or PowerDEVS. However, this issue is explained in more detail in the documentation section of the FlybackConverterDEVS example.

Output:

The two output variables, Inductor_i and Resistor_u, give the current through the inductor and the voltage across the load resistance.

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