Patent ID: 8439126

Claim:
A hand-held power tool comprising: a motor; a pulse width modulator for producing a pulse width modulated signal for operating the motor; a device for modulating a carrier frequency of the pulse width modulated signal with a noise signal or a pseudorandom signal, thereby reducing EMC interference emitted by the power tool; and a clock-pulse generator for producing a clock-pulse signal, the pulse width modulated signal being derived from the clock-pulse signal; wherein a counter register is provided for counting the elapsed clock cycles of the clock signal, a fold-back value register and an overflow value register are provided, and the pulse width modulator emits a first signal level if the value of the counter register is less than a fold-back value, emits a second signal level if the value of the counter register is equal to or greater than the fold-back value, sets the counter to a starting value if the value of the counter is equal to an overflow value, sets the fold-back value and overflow value to random new values if the value of the counter is equal to a previous overflow value, with the ratio of the new fold-back value to the new overflow value being essentially equal to the ratio of a previous fold-back value to the previous overflow value.