| 摘要 |
PROBLEM TO BE SOLVED: To provide a circuit and method for suppressing backlash during rotation by changing the period for turning on/off a switching element for intermittently driving a DC motor when a load is applied and is not applied in the speed control circuit of a DC motor that is used for a power tool. SOLUTION: The speed control circuit is composed of a series drive circuit where a DC motor and a switching element are connected in series between plus and minus DC power supplies, a triangular wave oscillation circuit for generating a triangular wave voltage in a sawtooth wave shape, a duty ratio setting circuit that is formed to generate a duty voltage according to the decree of the pull of stroke and to induce a voltage drop following the voltage drop of a DC power supply when a load is applied to a DC motor by the duty voltage, and a comparison means for turning on/off the switching element based on a comparison result by comparing the triangular voltage with the duty voltage. |
