- Power Electronic Converters Definition: Power electronic converters are devices that change power from one form to another and adjust voltage levels in power electronics.
- Signal Conditioning: Signal conditioning helps ensure cleaner input and output signals by reducing harmonic content, often using low-pass LC filters.
- Types of Converters: Converters in power electronics include DC to DC, AC to DC (rectifiers), DC to AC (inverters), and AC to AC converters, each serving different purposes.
- Switching Frequency: The frequency at which solid-state devices switch on and off affects the size, efficiency, and power density of the converters.
- Control Strategies: Control of converters involves using analog or digital methods, such as Pulse Width Modulation (PWM), to manage the switching of solid-state devices.
Power electronics focuses on converting power from one form to another and changing voltage levels using power electronic converters. The four families are DC to DC, AC to DC, DC to AC and AC to AC. Control and signal conditioning sit around those converters.
The conditioning of signals is the attempt to keep input and output waveforms free from harmonics. Absolutely clean signals are not obtained in practice. Harmonic content can be reduced; a common first step is a low-pass LC filter.
Power electronic converters mainly use solid-state switches like Power MOSFETs, Power BJTs, IGBTs and Thyristors, along with inductors and capacitors. Inductors and capacitors are preferred because an ideal L or C stores energy and has no average dissipation, unlike resistances. Real parts still have winding, core and ESR loss.
Resistances dissipate power, so converters are designed for high conversion efficiency. Extra loss in the converter also heats the rest of the plant. Related practice questions are in basic electronics questions.
In power electronics, solid-state devices act as switches, turning on and off rather than operating as linear amplifiers. The rate at which they switch is called the switching frequency. Inductors and capacitors can increase the weight and size of converters, reducing power density. Using a higher switching frequency can reduce passive size but also increases switching losses.
Switching losses can be smaller or larger than conduction losses, depending on voltage, current and frequency. Both heat the die. If the junction-to-ambient rise is too large, junction temperature can exceed the datasheet limit, often 150°C or 175°C class. Heat sinks and airflow are sized to keep that margin.
The main types of conversion are DC to DC, AC to DC, DC to AC and AC to AC. DC to DC converters step a DC voltage up or down. A line-frequency transformer cannot do that on DC, because DC would saturate the core. AC to DC is rectification, used to supply DC loads, such as DC motors, from an AC supply.
DC to AC conversion, or inversion, is used wherever a DC source must feed an AC load, including batteries to AC motors in electric vehicles. AC to AC conversion uses cycloconverters or matrix converters. Some industrial drives, such as cement and rolling mill machines, still use Cycloconverters. Certain cycloconverter and matrix topologies can change phase count; that is not true of every AC-AC stage.
Control of converters is the logic, analog or digital (microcontrollers, DSP processors or FPGA’s), that turns the switches on and off. Pulse Width Modulation (PWM) is a common scheme. Feedback loops add measurement and a regulator on top of that modulator.
