Patent ID: 7847494
Filing Date: 2010-12-07
Classification: H02P

Abstract:
1. A drive unit comprising a DC motor having a rotor consisting of a plurality of coils connected to a commutator in connection with a set of brushes to establish a voltage across the coils, said DC motor, via a transmission, driving an adjustment means for adjusting an adjustable element in a structure in which the drive unit is incorporated, a power supply for driving said drive comprising a transformer having a primary side for connection to a mains voltage (alternating current) and a secondary side with rectification and smoothing for connection to the DC motor, a first control means to compensate for loss in the motor, thereby maintaining a speed thereof constant for a first period of time, a second control means that removes ripples in the voltage, thereby maintaining the speed of the motor constant for a second period of time, said second period of time being shorter in duration than said first period of time, and including an astable timer having a duty cycle which is controlled by output voltage and adjusted by input voltage, and wherein said first period of time is 30 msec. to 1 sec. and said second period of time is less than 10 msec.