| 摘要 |
PURPOSE: To reduce power consumption and to design a hearing aid with higher performance for a hard limiter which is provided between the output drive transistor of a D-class amplifier and a pulse width modulator. CONSTITUTION: This limiter 31 achieves operation by controlling the duty cycle of the output of the pulse width modulator, directly corresponding to the size of a voltage appearing at both terminals of a load output transducer 16. Pulse modulated(PWM) signals are compared with the output of a pair of one-shot circuits (single pulse generators). In the case that the positive pulse or negative pulse of the PWM signals is shorter than a one-shot pulse, the PWM pulse is replaced with the one-shot pulse. Thus, the maximum value and minimum value of the duty cycle of the PWM signals are set and thus, the positive and negative values of a corresponding output voltage are limited. |
