Small, Multi-Level PWM Power Converter with Low Losses

Most AC-DC power converter topologies use AC inductors for filtering harmonic currents, but their power rating and size can be quite limiting, largely due to high magnetic field densities and power losses in the magnetic core. For example, the 1-switch boost rectifier is often considered for low power applications and the 6-switch 2-level 3-phase pulse width modulated (PWM) inverter is the preferred industrial power inverter (DC-AC). The performance of both of these power converters are often limited by large inductor sizes, with large losses that cause many problems including decreased efficiency and excessive heating, especially for high speed drive applications.

Researchers at the University of Alberta have developed a new circuit topology that provides valuable improvements to rectifiers and inverters. The unique location and use of coupled inductors with interleaved PWM switching greatly reduces the losses and the heat produced by those losses. This is extremely important because any reduction in heat will further reduce losses and lengthen the lifespan of the device. This is achieved by increasing the frequency and number of PWM voltage levels available in the power converter. The complexity and size of connected external circuits are also reduced as a result.

• Lower losses due to reduced current ripple.
• Reduced circuit complexity (50% fewer semiconductors).
• Can be used in both rectifiers and inverters.
• Eliminates dead-time signal delays associated with switching.
• Does not require a split-capacitor DC-rail.
• Smaller inductor size results in smaller circuit (4 times smaller than standard topologies).