Patent ID: 7936140
Filing Date: 2011-05-03
Classification: H02P

Abstract:
1. A torque control circuit for an electrical motor of a hand tool, comprising: a motor driving circuit connected to said electrical motor, said motor driving circuit comprising a diode parallel-connected to said electrical motor and a semiconductor power element series-connected to said electrical motor; a gate of said semiconductor power element being connected to said control terminal of said motor driving circuit; and said semiconductor power element being series-connected to said current detection circuit; a current detection circuit series-connected to said motor driving circuit; a current limiting circuit having a first input terminal connected to a junction between said motor driving circuit and said current detection circuit, an output terminal of said current limiting circuit connected to a control terminal of said motor driving circuit, said current limiting circuit comprising a first operational amplification circuit and a second operational amplification circuit; said first operational amplification circuit comprises a first operational amplifier having a negative terminal connected to ground, and a positive terminal connected to said first input terminal of said current limiting circuit and to an output terminal of said first operational amplifier via parallel-connected resistor R a reference voltage generation circuit providing a reference voltage to a second input terminal of said current limiting circuit; a torque configuration circuit connected to said reference voltage generation circuit so that said reference voltage is produced in accordance with a desired torque level; and a control circuit having a plurality of input terminals connected to said reference voltage generation circuit, said current limiting circuit, and said torque configuration circuit, respectively, said control circuit having a plurality of output terminals connected to said control terminal of said motor driving circuit and said reference voltage generation circuit respectively, said control circuit providing a pulse-width-modulated signal to said control terminal of said motor driving circuit when turning said motor driving circuit off.