| 摘要 |
A power output stage (1a) exhibits a bridge circuit having four electronic switches formed by FETs (T1 to T4) which are connected to drive electronics (3). The bridge null arm contains an inductance (2) which can be the winding of a DC motor or of a stepping motor. In this full bridge circuit, the direction of the current can be reversed by the inductance (2). This is a chopped control arrangement. When a current flows for example through the FET (T3), the inductance (2) and the FET (T2), the FET (T1) is used as freewheeling FET, this FET being turned on by the drive electronics in each case during the freewheeling phase. Compared with a freewheeling diode, which is normally located at this point, this is of considerable advantage in that a short-time short circuit otherwise occurring due to the blocking delay of the diode is avoided. In addition, much less power is dissipated by the FET turned on in each case during the freewheeling phase than by a diode. Finally, the elimination of a protective circuit with diodes otherwise required is also advantageous. The total power dissipation occurring can be reduced to one half or less. <IMAGE> |
