| 摘要 |
PURPOSE:To increase the switching frequency of an inverter above the audible region without sacrifice of the inverter efficiency. CONSTITUTION:The difference between the output detection current (i) and he sine wave command current i* (=Isintheta) of an inverter 1 is inputted to an absolute value converting section 3. On the other hand, a variable hysteresis width DELTAi' variable with the phase theta of the command current i* is determined at an operating section 4. ¦i-i¦ from the converting section 3 is compared with the variable hysteresis width DELTAi' from the operating section 4 by means of a comparator 5. If ¦i-i*¦>=DELTAi', output of a flip-flop 6 is inverted thus inverting ON/OFF of the switches S1, S2. Consequently, the variable hysteresis width DELTAi' is sustained at a substantially constant level regardless of the switching frequency or the phase theta of inverter and the switching frequency is set above the audible region. Since the switching frequency is sustained constant, it can be set above the audible region without varying the average switching frequency. |
