Patent ID: 7429846
Filing Date: 2008-09-30
Classification: H02P

Abstract:
1. A stepping motor control apparatus comprising: a controller for outputting a command pulse; a chopper-type constant current driver for outputting a drive current that corresponds to the command pulse input from the controller, wherein the chopper-type constant current driver includes a control part and an amplifier and, the control part outputs a chopper signal to the amplifier to keep the drive current constant; and a load detector for detecting the chopper signal, wherein the chopper signal is output when the drive current increases, a voltage of the drive current instantaneously drops at a time at which the chopper signal is output, and the chopper signal is indicative of a magnitude of a load of the stepping motor, the load detector comprises a waveform detector for detecting the chopper signal and for outputting an output waveform, which is a chopper waveform that corresponds to the chopper signal, the load detector detects the magnitude of the load based on the output waveform, the waveform detector includes a load resistor and a detector amplifier, and the load resistor is located in series between a power source and a coil of a stepping motor, a voltage drop occurs in the load resistor when the chopper signal is output, and through the voltage drop in the load resistor, the base voltage of the detector amplifier drops and a collector current of the detector amplifier flows as the output waveform, which is comb-shaped and synchronized with the chopper signal.