A 48–5-V Buck Converter With Triple EMI Suppression Circuit for Achieving 41-dB Peak EMI Reduction and Meeting CISPR 25 Automotive Standards

This article presents a triple electromagnetic interference suppression circuit (TESC) designed to reduce electromagnetic interference (EMI) value to meet CISPR 25 standards. The energy resonant recycling (ERR) technique is employed to control <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv</i>/<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {SW}}$</tex-math> </inline-formula> using additional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$L_{\text {r}}$</tex-math> </inline-formula> and capacitors (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C} {_{1}}$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C} {_{2}}$</tex-math> </inline-formula>) to achieve zero-voltage switching (ZVS) and zero-current switching (ZCS). Simultaneously, the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dv</i>/<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dt</i> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {SW}}$</tex-math> </inline-formula> is adjusted by the limiting pre-charge current <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{L\text {r}}$</tex-math> </inline-formula> to lessen <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {SW}}$</tex-math> </inline-formula> ringing, thereby contributing to EMI suppression. Moreover, ERR recycles the ringing energy at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {SW}}$</tex-math> </inline-formula> back to the input switched-capacitor (SC) network during light-load condition. The line impedance stabilization network-based front-end cancellation (LFC) generates a current <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\text {INJ}}$</tex-math> </inline-formula> through sense <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {IN}}$</tex-math> </inline-formula> information to eliminate the current ripple of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} {_{\text {Battery}}}$</tex-math> </inline-formula> from 4.5 to 0.8 mA, thereby preventing interference with other circuits and reducing EMI. The true-random spread-spectrum modulation (TR-SSM) utilizes dual TR-SSM to effectively mitigate harmonic tone. After applying TR-SSM, the EMI amplitude of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {Battery}}$</tex-math> </inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\text {SW}}$</tex-math> </inline-formula> can be significantly reduced by 20 and 16 dB at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\text {SW}}$</tex-math> </inline-formula>, respectively. By combining these three techniques, TESC reduces EMI by 33 dB at 2 MHz and 41 dB at 73 MHz.