| 摘要 |
PROBLEM TO BE SOLVED: To improve the sensor-less position detecting capability at low-speed revolution, by providing a switching sequence wherein a switching element in the open phase is turned on immediately after a chopper has seen turned off and is kept on for a short period, and the output capacitance of the switching element is quickly charged or discharged. SOLUTION: The chopper-off mode E is established immediately before the transition from the chopper-on mode A to the chopper-off mode B and is maintained for a short period. An upper switching element Tw 12 in phase W is turned on to charge an output capacitance Cz 17 with current Es, to short- circuit an output capacitance Cw 16, and to instantaneously discharge the electric charges. Charging/discharging current is supplied from a power supply, and the energization of a reflow blockade diode due to the charging/discharging current is thereby prevented. Similarly, a sequence is established, wherein the mode is changed in the order of the chopper-on mode C, the chopper-off mode F and the chopper-off mode D. This eliminates the influence of the output capacitance of a main circuit and facilitates position detection, even at low-speed operation. |
