Hans-Peter Kreuter

Digital Slew Rate and S-Shape Control for Smart Power Switches to Reduce EMI Generation

Smart power switches are power switches with integrated control and protection functions for the switching of middle- and high-current loads. In particular in automotive applications, smart power switches have to be operated without additional stabilization networks, EMI filters, and heat sinks to keep the weight, required space and costs of the circuit boards as low as possible. Therefore, the generated electromagnetic emissions must be reduced by another measure without significantly increasing the switching losses. This can be achieved by the active control of the first and/or second derivative of the output voltage. This paper presents a digital slew rate control and its extension to an S-shape control strategy, which in addition to the slew rate, also controls the second derivative of the output voltage. Both strategies are based on feedforward gate current profiles, which are iteratively adapted by an iterative learning control strategy to compensate for load variations and temperature dependences. A rapid prototyping test bench is presented, and the performance and robustness of the control strategies are demonstrated by a series of measurement results. An EMC compliance test according to the CSIPR 25 standard shows that the generation of conducted electromagnetic emissions can be reduced in a power efficient way by the proposed approach.

Slew rate control strategies for smart power ICs based on iterative learning control

Smart Power ICs are Power Switches with integrated control and protection functions for the switching of middle and high current loads in industrial and automotive applications. Due to customer specifications and electromagnetic compatibility requirements it is often desired to limit the current and voltage slew rate at the output terminal of the Smart Power IC by minimizing the switching losses at the same time. In order to reduce the development effort and costs, a reusable control strategy is strived for. Therefore, a power optimal digital slew rate control strategy is developed which allows for a systematic limitation of the current and/or voltage slew rates. The strategy is based on the optimization of a gate current profile using Iterative Learning Control. A rapid prototyping test bench is developed for the verification of the control strategy. The performance and robustness is demonstrated by means of measurement results.

System level modeling of smart power switches using SystemC-AMS for digital protection concept verification

This paper presents a method for the compact modeling, simulation and experimental verification of digital protection functions of smart power switches consisting of a digital controller and a power MOSFET with analog driving circuitry. We focus on short circuit events in an automotive environment where high power dissipation and thermal stress severely affect device reliability. For accurate temperature calculation, a non-linear thermal network including coupling between power transistor channels is used. A digital strategy for over current limitation, short circuit detection and over-temperature shutdown is modeled using SystemC-AMS and verified experimentally using a hardware-in-the-loop system.

Power optimal gate current profiles for the slew rate control of Smart Power ICs

Abstract Smart Power ICs are Power Switches with integrated control and protection functions. In order to meet the electromagnetic compatibility requirements, the output terminal slew rate has to be limited during the switching operation. In this context, special feedforward gate current profiles are widely used to control the switching slew rate. These profiles are typically determined on the basis of a linearized mathematical model of the Smart Power IC. However, due to the nonlinear characteristics of the IC, these profiles may lead to a reduced switching speed and thus to higher switching losses. In this work, an optimal control problem is considered which systematically accounts for the nonlinearities of the Power Switch, the switching losses and the limitation of the slew rate. In particular, a tailored mathematical model of the Smart Power IC is developed and parametrized. Based on this, the optimal control problem is formulated, numerically solved and the results are presented.

Modellierung eines Smart High-Side Power ICs

Zusammenfassung Dieser Beitrag behandelt die mathematische Modellierung eines Smart High-Side Power ICs. Smart Power ICs sind Leistungsschalter mit integrierten Regelungs- und Schutzfunktionen. Ausgehend von der vollständigen Schaltung des ICs wird eine für die Systemanalyse und den Reglerentwurf geeignete Ersatzschaltung abgeleitet und mathematisch modelliert. Damit ist es möglich, das Großsignalverhalten des Smart Power ICs mit Hilfe eines Differentialgleichungssystems fünfter Ordnung zu beschreiben. Anhand von Simulationsergebnissen wird das mathematische Modell mit der vollständigen Schaltung verglichen.