Patent ID: 6677723
Filing Date: 2004-01-13
Classification: B60K,H02P

Abstract:
A circuit for driving a stepping motor to control a needle position of a meter mounted in a vehicle by needle control signals, comprising:an excitation signal generating means for generating excitation signals having one electrical cycle being formed by a plurality of excitation steps supplied in drive coils to rotate a rotor with N-poles and S-poles, magnetized equally and alternately, of said stepping motor; and a first excitation signal supply controlling means for controlling said excitation signal generating means to supply said excitation signals to said drive coils, wherein the needle is connected with the rotor through a speed change gear and rotates correspondingly to the rotor rotation, so that said excitation signals correspond to a needle rotating angle greater than a maximum needle rotating angle toward a zero position to respond to the needle control signals generated at a timing when a vehicle battery turns ON, wherein said excitation signal generating means comprises: a filtering means for filtering the needle control signals to move the needle faster to the zero position; a SIN/COS table for generating SIN/COS data corresponding to the excitation signal of micro-steps based on filtering result by means of the filtering means; and an output circuit for outputting excitation signals supplied into the drive coil as a required voltage value to rotate the rotor based on SIN/COS data by the SIN/COS table, wherein said filtering means comprises: a first filter for filtering the needle control signals to add or subtract predetermined value corresponding to change values of the needle control signals; a second filter for smoothing data change value to weighted-average filtering results by the first filter every predetermined time period; and a third filter for weighted-averaging filtering results by the second filter every predetermined time period to prevent out-of-step of said stepping motor and sending the data to said SIN/COS table.