| 摘要 |
<p>A brushless motor drive circuit for soft switching, preventing transistors from saturating under any condition. The brushless motor drive circuit of the present invention has, for each phase, first transistors (Q7, Q8, and Q9) for driving output transistors (Q1, Q2, and Q3) connected to a DC power supply Vcc; second transistors (Q10, Q11, and Q12) constituting a current mirror circuit together with the first transistors (Q7, Q8, and Q9); reference voltage generating means (R1, R2, and R3) connected to the second transistors (Q10, Q11, and Q12) to generate a voltage proportional to the current flowing through the second transistors (Q10, Q11, and Q12); and current feedback means (Q13, Q14, and Q15) which are turned on with the voltage drop approximately equal to the voltage generated by the second transistors ((Q10, Q11, and Q12) to return part of the output current of the first transistors (Q7, Q8, and Q9) to the stage before the reference voltage generating means (R1, R2, and R3) in order to decrease the input current of the first transistors (Q7, Q8, and Q9) when the potential difference between the input and output terminals of the first transistors (Q7, Q8, and Q9) becomes approximately equal to the voltage generated by the reference voltage generating means (R1, R2, and R3).</p> |
