Practical capacitor charging losses

The video “Back to Basics #2: Practical Capacitor Charging Losses” by Sam Ben-Yaakov explores the topic of energy losses during the charging of capacitors, with a focus on practical applications and the underlying physics. The presentation builds on a previous discussion of current management in systems involving capacitors, such as inverters or converters, where high inrush currents can damage components. The use of a pre-charging circuit, which incorporates a resistor, is highlighted as a common solution to limit current during the initial connection. Saakov delves into the energy loss associated with this process, showing that regardless of resistance or the presence of an inductor, the energy loss converges to a fixed value, determined by the equation CΔV2/2C \Delta V^2 / 2CΔV2/2. This behavior reflects the fundamental principles of charge conservation and energy dissipation.

In the second part of the presentation, Saakov introduces a circuit modification using a diode and an inductor, which alters the energy loss dynamics. With the addition of the diode, the output voltage can exceed the input voltage due to the inductor’s quality factor, reducing energy losses compared to a purely resistive circuit. The explanation demonstrates that the energy loss depends on whether the capacitor voltage matches, exceeds, or falls below the input voltage, and how the inclusion of an inductor enables a near-lossless transfer of energy under ideal conditions. Saakov concludes by resolving the apparent paradox of energy loss variance, emphasizing how circuit design influences capacitor charging efficiency, with potential applications in resonant circuits and beyond. The presentation is both educational and practical, shedding light on the intricacies of capacitor charging mechanisms.

This video is a follow-up to the previous video Capacitor charging currents explained with LTspice

Resource: EPCI Blog