| 摘要 |
In the case of a DC motor (10) which has no commutator and whose stator winding (25) is operated in a bridge circuit (40'), it is necessary to prevent all the transistors in the bridge circuit (40') being in the switched-on state simultaneously. A delay capacitor (87) and two driver stages (54, 88 and 94, 95) are provided for this purpose, which have a low internal impedance whenever the associated bridge transistor is switched off, so that this transistor is switched off quickly. In contrast, when this transistor is switched on, it has a high internal impedance so that only a relatively small switching-on current can flow which initially has to reverse the charge on the delay capacitor (87) before it can switch this transistor on. The bridge transistors are preferably Darlington transistors having a high current gain. - An adequate current pause is thus produced between one pair (for example 71, 72) of transistors in the bridge circuit (40') being switched off and the subsequent pair (for example 70, 73) of transistors being switched on. - The invention allows the use of a rotor position sensor (32) with "digital" output signals, that is to say signals which jump between only two values. <IMAGE> |
