An EMI Reduction Charge Pump With a Hybrid Modulation Technique for Motor Drive Applications in 0.18 um BCD Process

Abstract

Reducing the impact of electromagnetic interference (EMI) on switching inverters is an essential part of improving the performance of motor drives. This paper proposed a charge pump circuit with a hybrid modulation method to reduce the EMI of motor drive chips. This innovative method uses a combination of coarse modulation and fine modulation. The periodic modulation technique is used as coarse modulation to alter the spread spectrum range, while the random modulation technique is used as fine modulation to slow down switching transitions by adjusting the delay of the oscillating signal edges. Additionally, a buffer circuit is proposed to restrict the charge and discharge current of the charge pump, thus reducing the EMI due to the rapid variation of the current peak. Theoretical analysis and MATLAB simulation have confirmed that the hybrid modulation method has a pronounced effect on reducing the EMI of the circuit. The proposed motor drive system has been designed and verified by a 0.18 $\mu {\mathrm{ m}}$ BCD process, and the test results show that the proposed circuit can reduce the EMI by up to 22.27 dB compared to the non-modulated circuit. The motor drive chip area is $0.173~mm^{2}$ , and the power consumption is 5.677 mW.

Keywords

• EMI reduction
• charge pump
• hybrid modulation
• output buffer circuit
• oscillator