Switching Noise of Power Drivers in the 150 kHz to 10 MHz Range

Electronic control modules for engine control applications have an increasing number of power drivers. Most of them are switching in a PWM mode or synchronously with engine speed. Fast switching of load currents and voltages generates a noise in the lower AM band (150 kHz … 10 MHz) exceeding given limits for radiated emissions. The objective was to determine how the switching noise could be reduced by means of controlled current and/or voltage slopes. Finally ways were identified to implement appropriate voltage slope controls into a fully integrated quad low side driver ASIC.

The paper will show results from practical measurements in the time and frequency domain as well as theoretical data to describe the switching behavior before and after implementation of the improvements

A major result was that both current and voltage slope control are necessary to achieve best results. A special method of wave shaping was identified as the optimum.