GB1440629A - Control circuits for the continuous adjustment of the speed of a direct current motor - Google Patents

Abstract

1440629 Automatic control of speed ROBERT BOSCH GmbH 15 June 1973 [19 June 1972] 28520/73 Addition to 1371854 Heading G3R [Also in Division H2] The control circuit for the stepless adjustment of the speed of a D.C. motor disclosed in Fig. 2 of Specification 1371854 is modified as shown in Fig. 3, wherein the motor 11 is supplied through a main transistor 13 and storage inductance 12, the transistor 13 being controlled by a transistor 18 of complementary conductivity type receiving a signal representative of a desired speed from a potentiometer 21, the two transistors being interconnected by a feedback resistor 19, the emitter of transistor 18 being connected to one armature terminal of the motor through resistor 22 and capacitor 27 and to the other armature terminal through at least one diode 23, and members 13, 18 and 19 forming a trigger stage which is switched on and off as a function of the voltage at one end of the inductance 12 connected to the other armature terminal. Compared with Fig. 2 of Specification 1371854 (which is again described in Fig. 2, (not shown), of the present Specification), energy fed to the motor during the off-periods of transistor 13 is supplied only by the inductance 12, the capacitor 27 being substantially smaller than the capacitor (17) of Fig. 2 (not shown) and serving to smooth the signal fed to the emitter of transistor 18, whose emitter resistor 22 has a high resistance compared to that of the motor 11, which operates with a higher power input. The capacitor idle current is also reduced. When the motor is used to drive a blower or windscreen wipers of a vehicle, as envisaged in the Parent Specification 1371854 the potentiometer 21 may be respectively replaced by a variable gain amplifier or a resistor variable in stages.