Spread-spectrum frequency modulation is a technique commonly adopted in dc/dc converters with pulse width modulation (PWM) control to reduce electromagnetic interference induced by switching. It typically requires a dedicated circuit. This article introduces a novel technique to implement spread-spectrum modulation in a dc/dc converter with time-based control, requiring only an additional transconductor. Modulating the bias current of the voltage-controlled oscillators used in the controller via a common-mode signal, the switching frequency of the converter is modulated without affecting the duty cycle. A theoretical analysis providing the link between modulation factor and design parameters is shown, and the circuit implementation in a time-based buck converter for general-purpose applications in a bipolar-CMOS-DMOS (BCD) process with 180 nm CMOS is described, together with a comparison between the simulated and the measured spectrum. The measured EMI reduction is 11.2 dB. The area occupation of the SSFM circuit is 0.032 mm2.
Spread-Spectrum Frequency Modulation in a DC/DC Converter With Time-Based Control
Leoncini, Mauro;Melillo, Paolo;Levantino, Salvatore;Ghioni, Massimo
2023-01-01
Abstract
Spread-spectrum frequency modulation is a technique commonly adopted in dc/dc converters with pulse width modulation (PWM) control to reduce electromagnetic interference induced by switching. It typically requires a dedicated circuit. This article introduces a novel technique to implement spread-spectrum modulation in a dc/dc converter with time-based control, requiring only an additional transconductor. Modulating the bias current of the voltage-controlled oscillators used in the controller via a common-mode signal, the switching frequency of the converter is modulated without affecting the duty cycle. A theoretical analysis providing the link between modulation factor and design parameters is shown, and the circuit implementation in a time-based buck converter for general-purpose applications in a bipolar-CMOS-DMOS (BCD) process with 180 nm CMOS is described, together with a comparison between the simulated and the measured spectrum. The measured EMI reduction is 11.2 dB. The area occupation of the SSFM circuit is 0.032 mm2.File | Dimensione | Formato | |
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Spread-Spectrum_Frequency_Modulation_in_a_DC_DC_Converter_With_Time-Based_Control.pdf
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