Below is a PLECS demo model of a 300 W switched-mode power supply with power factor correction. The simulation combines the electrical power circuit, the control system with a standard IC and the thermal behavior of the semiconductors.
The power supply is based on a diode rectifier and a power factor correction circuit in boost topology. After having passed the input EMI filter in CLC configuration, the single-phase line voltage is rectified by a standard diode bridge. To improve the efficiency, the boost converter is realized with a CoolMOSTM power switch and a Silicon Carbide (SiC) Schottky diode.
The controller IC (ICE1PCS01 from Infineon) is modeled with functional blocks. It operates in continuous conduction mode (CCM) with average current control. The control is cascaded and consists of the inner current loop and the outer voltage loop. The inner current loop controls the sinusoidal profile for the average input current while the outer voltage loop controls the output bus voltage. The model of the control IC supports soft start for low output voltage. However, other protection features such as overvoltage and peak current protection are not implemented.
A special component model is used to simulate the thermal behavior of the MOSFET. Within the MOSFET model, the heat sink represents the thermal capacitance of the chip. It collects all switching loss energy and conduction loss power from the dies of the MOSFET and the reverse diode. It also propagates its temperature back to the chip in order to receive the correct loss readings. The losses are propagated via a thermal RC chain which models the case of the component. The Ambient Temperature component at the end connects the component with an outside heat sink modeling the dissipator that the component is mounted on. In the SiC boost diode model, the thermal impedance of the device has been entered directly in the thermal description.
The simulation shows a start-up of the power supply under constant load. The Scope with the electrical quantities shows the sinusoidal mains current and the ramp-up of the output voltage. A 120 Hz ripple in the output voltage can be observed. The second Scope shows the junction temperatures of the MOSFET and the boost diode. The temperature of the external heat sink is rising very slowly in the timeframe of the simulation.
It is not practical to determine the stationary temperature levels of the dissipator and the semiconductors by running a simulation until the thermal transients have settled. Due to the large thermal time constants such a simulation would take several hours. A Steady-State Analysis is included to view the final operating conditions and temperatures.
This model is available in the PLECS Demo Model library provided in both versions of PLECS.