This report is the basis for a Bachelor of Science thesis in engineering done at Volvo Powertrain in Gothenburg. The problem consisted of investigating a circuit with a PWM-controlled MOSFET driving a DC-motor. The problem was to investigate what caused the circuit to break the transistor. Finally an improvement of the circuit is designed making the MOSFET withstand the stressful conditions exposed to. An overall description of the problems with switching an inductive load using a MOSFET as switch is done. Some methods to protect the MOSFET from failure are also discussed. Finally a discussion is held to suggest what broke the MOSFET, and an improved design is proposed.

<p>This report is the basis for a Bachelor of Science thesis in engineering done at Volvo Powertrain in Gothenburg. The problem consisted of investigating a circuit with a PWM-controlled MOSFET driving a DC-motor. </p><p>The problem was to investigate what caused the circuit to break the transistor. Finally an improvement of the circuit is designed making the MOSFET withstand the stressful conditions exposed to. </p><p>An overall description of the problems with switching an inductive load using a MOSFET as switch is done. Some methods to protect the MOSFET from failure are also discussed. Finally a discussion is held to suggest what broke the MOSFET, and an improved design is proposed.</p>

This master`s thesis deals with design and realization of two-quadrant switching current source for inductive loads. Output current adjustable range is 0 – 1A. Selected topology enables change of current direction. Current supply is made with TDA8920 integrated circuit. Thesis also contains basic information about switching supplies and coils.