6th Power Analysis & Design Symposium 2017

Chaotic spread spectrum modulation in digitally controlled power supplies is very common and widely accepted as the most efficient technique to reduce electromagnetic interference and emissions. 

However, this permanently active, unpredictable behavior of this modulation technique might impact other control methods where accurate predictions are vital. This presentation introduces a control system which utilizes sub-cycle model predictive control to achieve true diode emulated sync rectifier control. This is done without analog circuit support within a chaotically modulated PWM scheme in a multiphase architecture. Both techniques, spread spectrum modulation and diode emulation of synchronous rectifiers, are introduced and then incorporated into the multi-loop real-time control concept preventing disruptions between the three control domains.

In this technical presentation the operation of the highly popular Continuous Conduction Mode Boost PFC is discussed. Starting from first principles the operation and design of the voltage loop, the current loop and the voltage feed forward filter are detailed. All design equations are presented along with a real life numerical design example. The session concludes with a live demonstration of a fully functioning PFC design.

All attendees will receive a complimentary license for Biricha Digital’s Analog and Digital Power Factor Loop Design Software (www.biricha.com/pld)

Increased computation capabilities and improved ADC and DPWM IPs make microcontroller based digital PWM controllers a viable solution for many applications. Nevertheless in high current-slew-rate applications increased controller performance is required to provide tight regulation of the output voltage. Thus, dedicated digital PWM controllers, where analog and digital HW is optimized to execute specific control tasks, are the preferred choice. 

In this presentation the architectural differences between a microcontroller based solution and a high performance digital PWM controller is explained. Further on a digital control method to achieve fast transient performance without sacrificing quiet and noise insensitive steady state operation will be presented.

Isolated channel oscilloscopes offer a safe and an economic way to measure floating voltages in switched mode power supplies. In the presence of fast common mode signal transitions the common mode rejection ratio becomes the critical parameter of the measurement system. In this case differential probes tend to be the best performing measurement concept. This presentation shows the performance differences between isolated input oscilloscopes and differential probes and gives hints on how to get the best out of your measurement.

On catalog and internet pages MLCC and Polymer capacitors are described under standard test conditions in accordance to EIA-198-2. This means, typically at room temperature, 1 kHz frequency, 1 Vrms sinusoidal voltage and no DC-bias.

However, in real-life applications capacitors are operated at higher frequencies, with DC voltage applied and in a wide temperature range from subzero °C to over 100 °C. In this presentation a simulation tool is introduced that allows to predict the capacitor's behavior under various operating conditions. The simulation covers certain rarely documented cases such as ripple current, pulse capability, reliability, lifetime and anti-resonance effects.

Input filters for DC/DC converters are often required to meet today's EMC requirements. Generally input filters are designed to have low loss which can result in high-Q circuits that are subject to oscillation. This can have a negative impact on the stability of DC/DC converters. Further on, the input impedance of a DC/DC converter is the critical parameter for a proper filter design. This presentation focuses on the theory of the filter stability and how to avoid problems. Different input impedance measurement methods as well as their advantages and disadvantages are presented and compared based on real-life measurement results.