 DEPARTMENT OF ELECTRICAL POWER ENGINEERING COLLEGE OF ENGINEERING POWER ELECTRONICS Topics Covered - DC To DC Converters - Introduction TOPICS COVERED: DC TO DC CONVERTER Buck (Step Down) Converter Boost (Step Up) Converter Designing DC-DC Converters PULSE WIDTH MODULATED INVERTERS Single Phase Inverter Bipolar Switching (Single Phase) Unipolar Switching (Single Phase) Three Phase Inverter DC TO DC CONVERTER Introduction Convert the voltage level of a direct current (DC) source to a different dc voltage level. Very useful for electronic devices with components that run on various levels of voltage requirement, such as cellular phones, portable cassette radios, etc. In this course, we are going to learn about buck and boost converters. Linear Regulator: Transistor is operated in linear (active) mode. Output voltage is the product of the current and resistance. The transistor can be modelled by an equivalent variable resistor as shown in figure. can only produce output at lower voltages from the input. Inefficient when the voltage drop is large and the current is high as heat dissipated is equal to the product of the output current and the voltage drop Switching Converter: When switch is opened, no current flow in it. When switch is closed, no voltage drop across it. Power loss is zero for ideal switch. convert one DC voltage level to another by storing the input energy temporarily and then releasing that energy to the output at a different voltage. The storage is in magnetic field storage components (inductors) and electric field storage components (capacitors).  In general, DC-DC converters have the following properties when operating in the steady state: 1. The inductor current is perioodic (repeating). i L (t + T ) = i L (t) 2. The average inductor voltage is zero. V L = = 0 3. The average capacitor current is zero. Ic = 4. The power supplied by the source is the same as the power delivered to load. P in = P out The figure below shows the current in different states: Before going further, there are several important parameters with the symbol to be known: Click to go to NEXT page Go To TOP Page 