Design of GaN Switching Power IC With Auto-Phase-Aligned EMI Adaptive Self-Cancellation and BER-Conscious Spread Spectrum Modulation

To address mounting electromagnetic interference (EMI) challenges in electric vehicle autonomous driving applications, this article develops an on-chip EMI adaptive self-cancellation (ASC) technique, which stays effective in varying operation conditions. It incorporates an auto-phase-aligned control mechanism to significantly enhance the effectiveness of the ASC technique. Meanwhile, to improve high-frequency EMI suppression, a spread-spectrum modulation (SSM) technique works harmoniously with the ASC to modulate the switching frequency f_SW, adaptive to operation conditions. The maximum spread range Δf_SW of the SSM is actively regulated to strictly limit the bit error rate (BER) in the communication system for safety and security. To validate the effectiveness of this article, a switching power converter IC prototype was implemented on a 180-nm BCD process, with a chip area of 1.3 mm². The converter is purposely designed using GaN power switches and operating at a nominal f_SW of 2.2 MHz, imposing more severe di/dt and dv/dt challenges than classic kilohertz-level silicon counterparts. Experimental results prove that the on-chip ASC technique achieves adaptive ripple self-cancellation in response to 150% input and 200% output dynamic voltage changes from the respective nominal levels. The ASC technique alone achieves a maximum EMI reduction of 9.5 dB. In collaboration with the BER-conscious SSM technique, a total EMI reduction of 16.5 dB is achieved at the nominal f_SW, satisfying stringent automotive CISPR 25 Class 5 standard.