A Frequency Synchronization Method for a Self-Oscillating PWM Signal Generator

作者：Li Weibo^*; Niimi Yoshitaka; Orino Yuichiro; Hirata Shinnosuke; Kurosawa Minoru Kuribayashi

来源：IEEE Transactions on Circuits and Systems II-Express Briefs, 2014, 61(4): 244-248.

DOI：10.1109/TCSII.2014.2304892

• Delta-sigma (Delta Sigma) modulation
• fixed switching frequency
• frequency synchronization
• pulsewidth modulation (PWM)
• self-oscillation

This brief proposes a frequency synchronization method for a full-digital self-oscillating pulsewidth modulation (PWM) signal generator. The self-oscillating PWM signal generator (PSG) generates a variable switching frequency, which results in poor drive performance for a three-phase power inverter or converter. The proposed frequency synchronization method utilizes an additional carrier signal, such as a triangular wave, to fix the switching frequency of a self-oscillating PSG. The switching frequency is synchronized by the triangular wave. As a test case, a switching frequency of 312.5 kHz is used for a performance evaluation of the proposed PSG with a sampling frequency of 12.5 MHz. A first-order noise-shaped output has been obtained. A high-precision PWM signal with low distortion and high resolution of the effective duty cycle has been achieved within the bandwidth. The proposed synchronized self-oscillating PSG is implemented in a three-phase brushless dc motor driver system to confirm the three-phase synchronization performance. Undesirable ripple current from asynchronous operation was not observed. The switching frequencies were synchronized among the three phases.

• 出版日期2014-4