| 摘要 |
PURPOSE:To prevent a short-circuit of a bridge arm even for an instantaneous duration by interlocking a PWM signal and a rotating direction signal and also by giving an adequate on-delay time. CONSTITUTION:When PWM, CW and CCW signals rise, on-delay is made by a time constant determined by R and C. When a signal fall, an electric charge in C is discharged by a diode D. Therefore, an on-delay time is created when the turning directions CW and CCW are switched and the ON of switching elements B and F at low side are shifted, and OFF state occurs during this time period. PWM signal is converted into signals (a) and (e) for opening/closing the switching elements A and E of high side. It is converted into signal (e) if the turning direction is CW and signal (a) if it is CCW. Therefore, at the time of switching of turning direction, signal (a) and (e) are switched, on-delay occurs and a pause begins. Also, at the AND gates, the signals (a), (b), (e) and (f) will never become H at the same time and interlocked to prevent short-circuit of the arm independently from H and L of PWM signal and turning direction signal. |
