Apparatus for reducing motor driving noise and method for generating motor driving noise reducing signal
AssigneesRenesas Technology Corp., Mitsubishi Electric Engineering Company Limited
InventorsSatoshi Narumi, Hiroyuki Tamagawa, Masaharu Hoashi
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Abstract
There is disclosed an apparatus for reducing motor driving noise, comprising: a selecting circuit for selecting and outputting a current increasing or reducing signal based on a commutation control signal; and a signal synthesizing circuit for synthesizing the current increasing or reducing signal selected by the selecting circuit with a current application control signal supplied to the power supply side switching element of at least a pair of switching elements.
Claims4
An apparatus for reducing motor driving noise, comprising:
- a plurality of switching circuits each including at least a pair of switching elements connected in series between a power supply and a ground;
- a motor, one end of each of its phase windings is connected to a switching element serial connection point of each of said switching circuits;
- a noise reducing circuit for generating a current increasing signal and a current reducing signal;
- a selecting circuit for selecting and outputting the current increasing signal and/or the current reducing signal based on a commutation control signal for changing a polarity at every prescribed electrical angle;
- a signal synthesizing circuit for synthesizing either the current increasing signal or the current reducing signal selected by said selecting circuit with a current application control signal supplied to a power supply side switching element of said pair of switching elements;
- a PWM waveform signal generator for outputting a PWM waveform signal based on a current control value;
- and
- a PWM synthesizer for synthesizing the PWM waveform signal with a current application direction deciding signal supplied to a ground side switching element of said pair of switching elements.
A method for generating a motor driving noise reducing signal, comprising the steps of:
- obtaining a current amplification factor by dividing a current changing width decided according to a motor revolution speed by a current control value:
- adding 1 to a duty control value every time a count value of a reference clock reaches the current amplification factor;
- determining whether the count value of the reference clock has reached a maximum value of the current amplification factor, until the count value of the reference clock reaches the duty control value;
- generating a current reducing signal by setting the count value and the current reduction rate to 0, if the maximum value has been reached;
- determining whether the count value of the reference clock has reached the maximum value of the current amplification factor, until the count value of the reference clock reaches a value obtained by adding to the duty control value the value which is obtained by subtracting the current control value from the upper limit of the current control value;
- generating a current increasing signal by setting the count value and the current amplification factor to 0, if the maximum value has been reached;
- and
- adding the current increasing signal and the current reducing signal to a current application control signal supplied to a power supply side switching element of switching elements connected in series between a power supply and a ground.
Dependencies are inferred from the claim text.