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 dv/dt of $V_{\text {SW}}$ using additional $L_{\text {r}}$ and capacitors ( ${C} {_{1}}$ and ${C} {_{2}}$ ) to achieve zero-voltage switching (ZVS) and zero-current switching (ZCS). Simultaneously, the dv/dt of $V_{\text {SW}}$ is adjusted by the limiting pre-charge current $I_{L\text {r}}$ to lessen $V_{\text {SW}}$ ringing, thereby contributing to EMI suppression. Moreover, ERR recycles the ringing energy at $V_{\text {SW}}$ 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 $I_{\text {INJ}}$ through sense $V_{\text {IN}}$ information to eliminate the current ripple of ${I} {_{\text {Battery}}}$ 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 $V_{\text {Battery}}$ and $V_{\text {SW}}$ can be significantly reduced by 20 and 16 dB at $f_{\text {SW}}$ , respectively. By combining these three techniques, TESC reduces EMI by 33 dB at 2 MHz and 41 dB at 73 MHz.