Stationary position detection circuit and motor drive circuit

Abstract

A stationary position detection circuit and a motor drive circuit capable of more properly detecting the rotor position are disclosed. The stationary position detection circuit supplies an alternating current to each phase load of the motor. The time during which the current flows in a first direction and the time during which the current flows in a second direction opposite to the first direction are converted into electrical signals and amplified. In accordance with the value of the electrical signals, the position of the motor rotor in stationary mode is determined. The use of the alternating current, unlike the kickback voltage, makes it possible to improve the detection accuracy by amplifying the electrical signals with an increased number of alternations. An increased number of alternations can amplify the electrical signals without increasing the value of the alternating current, and therefore, unlike in the case of the kickback voltage, the alternating current of a large value is not required. As a result, the alternating current can be reduced to a small value and the vibration can be suppressed.

1 . A motor drive circuit comprising: 
 an output circuit for driving a motor;    an output control circuit for controlling said output circuit;    a resistor connected to said output circuit; and    a detection circuit coupled to said output circuit for detecting the amount of current in said resistor and supplying said output control circuit with a control signal.    
   
   
       2 . The motor drive circuit according to  claim 1 , wherein 
 said detection circuit includes:    a comparator for comparing a voltage at a connection node between said output circuit and said resistor with a predetermined voltage.    
   
   
       3 . The motor drive circuit according to  claim 2 , wherein 
 said motor is a three-phase DC brushless motor.    
   
   
       4 . The motor drive circuit according to  claim 2 , wherein 
 said motor is a Hall sensorless motor.