Semiconductor switches are often paralleled to realize a power module with high current rating. They are driven preferably by a single driver that applies the same voltage/current to all switches' input terminals. Some of the switches will take more currents owing to mismatches among such parameters as on-resistances and threshold voltages, and suffer more losses, higher junction temperatures , and shorter lifespan. Equalization of performances is thus desirable, especially without using a large number of power supplies to generate multiple drive waveforms that compensate parameter mismatches.
The invention's objective is to generate, using a single on-state power supply, multiple drive waveforms that equalize the currents, losses, or temperatures among multiple paralleled switches with mismatched parameters. The heart oeach f "equalizer" is a capacitor carrying a voltage tailored to offset the power supply's voltage by the right amount so that each switch's input sees the voltage required for equalized performance. The offset voltage is controlled by modulating the amount of charge through the capacitor. The charge is provided by the switch's input current, obviating a separate current source. Modulation is achieved by shorting switch(es) realized by, e.g., commercial switch drivers. While several equalizer topologies could be conceived , those presented herein leverage readily available components and are scalable for an arbitrary number of paralleled switches.