| 摘要 |
PURPOSE: To reduce the power loss when the phase current of a polyphase motor is switched by means of a switching transistor under control of a pulse width modulation signal. CONSTITUTION: When any one of switching transistors 25, 26, 25', 26', 25", 26" for a active coil among the coils 10, 11, 12 of a motor through which a current is flowing is turned on during a PWM mode chopping period, a nonrectified ground return path is provided for the flyback energy in the active driving coil. The nonrectified ground return path is provided by a switching transistor connected in parallel with flyback diodes 27, 28, 27', 28', 27", 28" operating in the mode of synchronous rectification. Consequently, another current path is provided for the coil current and the voltage drop across the diode is reduced while reducing power dissipation and heat in the chip. |
