Patent ID: 7119504

Claim:
A circuit, for reducing electrical disturbances during the operation of a DC motor, comprising: a series transistor ( 62 ) arranged in a supply lead from a DC voltage source ( 12 ) to a DC motor; an auxiliary voltage source ( 52 ), associated with that series transistor, having a substantially constant auxiliary voltage, which source is configured to make the series transistor fully conductive when a supply voltage furnished by the DC voltage source, is substantially free of electrical interference; an analyzer circuit ( 32 , 34 , 36 ) for analyzing the supply voltage, which analyzer circuit is configured, upon occurrence of electrical interference in the supply voltage, to increase the resistance of the series transistor correspondingly, in order to reduce the influence of that electrical interference on the operation of the DC motor; wherein the analyzer circuit ( 32 , 34 , 36 ) comprises a diode ( 36 ) connected between the auxiliary voltage source ( 52 ) and a first conduction electrode of the series transistor ( 62 ), at which diode there occurs a diode voltage that, together with the auxiliary voltage, constitutes a control voltage for controlling the series transistor, the diode ( 36 ) being configured to vary the control voltage in such a way that fully conductive operation of the series transistor ( 62 ), in the ohmic range, occurs when the supply voltage furnished by the DC voltage source is substantially free of electrical interference.