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 inter ference suppression circuit (TESC) designed to reduce electro magnetic interference (EMI) value to meet CISPR 25 standards. The energy resonant recycling (ERR) technique is employed to control dv/dt of V_SW using additional L_r and capacitors (C₁ and C₂) to achieve zero-voltage switching (ZVS) and zero current switching (ZCS). Simultaneously, the dv/dt of V_SW is adjusted by the limiting pre-charge current I_Lr to lessen V_SW ringing, thereby contributing to EMI suppression. Moreover, ERR recycles the ringing energy at VSW back to the input switched-capacitor (SC) network during light-load condition. The line impedance stabilization network-based front-end cancella tion (LFC) generates a current I_INJ through sense VIN information to eliminate the current ripple of I_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_Battery and V_SW can be significantly reduced by 20 and 16 dB at f_SW, respectively. By combining these three techniques, TESC reduces EMI by 33 dB at 2 MHz and 41 dB at 73 MHz.