Microcontroller-Based Trapezoidal Slope Compensation Technique for Peak Current Mode Control at MHz Frequencies

Abstract

Slope compensation is necessary for the peak cur-rent mode control technique to ensure the stability of the power converter. Micro-controllers (μCs) existing in the market implement the slope compensation using built-in digital to analog converters (DACs). DACs exhibit finite transient times, which can be negligible when the μCs are used to control the power converters at switching frequencies in the order of a few hundreds of kHz. However, for high device switching frequency (HDSF) operation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\geq 1\, \rm{MHz}$</tex-math></inline-formula> ), the DAC transient time becomes significant and can make it difficult, if not impossible, to achieve the conventional ramp slope compensation. Hence, in this paper, a novel concept of ‘trapezoidal’ slope compensation is proposed by considering the transient time of the μC. A detailed analysis is performed to understand the effect of the transient period on the converter stability. The proposed technique is validated with an experimental prototype of 400 W at 1 MHz switching frequency and it is shown to ensure stability of the converter at all operating points within the specification.