| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an excess current protection circuit which stops the continuation of large current discharge for a prescribed time or longer in a power tool having a lithium ion battery as a power source. <P>SOLUTION: In the power tool including a motor to which electric power is supplied from a battery cell group through a switching element and a trigger switch, a current detector detecting a current value flowing in a current path and a controller are provided and the controller performs pulse driving for intermittently on/off-controlling current values using a semiconductor switching element when the current detector detects that the current value flowing in the battery cell group is continuously a given value or larger (e.g., 20 A or larger) for a first time period (e.g., 30 sec from t2), and turns off the switching element to forcibly stop the rotation of the motor when the current value is continuously kept to exceed the given value for a second time period (e.g., 50 sec from t2). <P>COPYRIGHT: (C)2012,JPO&INPIT |
