Patent ID: 8612098

Claim:
A drive arrangement for driving a seat belt pre-tensioner having an electric motor, the arrangement comprising: a power supply circuit which is configured to receive power from a power supply providing a positive voltage supply input, the power supply circuit incorporating: a first pair of switches (S 1 and S 2 ) having a first switch (S 1 ) and a second switch (S 2 ), the first pair of switches connected with a first output provided therebetween and with the first switch (S 1 ) connected with the positive voltage supply input and the second switch (S 2 ) connected with the negative voltage supply input. a second pair of switches (S 3 and S 4 ) having a third switch (S 3 ) and a fourth switch (S 4 ), the second pair of switches connected with a second output provided therebetween with the third switch (S 3 ) connected with the positive voltage supply input and the fourth switch (S 4 ) connected with the negative voltage supply input, the first and second outputs being configured to be connected to the motor in a seat belt pre-tensioner; a control unit connected to the first, second, third, and fourth switches (S 1 , S 2 , S 3 , and S 4 ) to control the first, second, third, and fourth switches to output a voltage across the first and second outputs; and a voltage boost circuit which, upon activation by the control unit, increases the voltage across the switches (S 1 -S 4 ), which increases the voltage across the outputs ( 7 , 8 ) to increase the speed of rotation of a motor ( 9 ) connected to the outputs ( 7 , 8 ); wherein the drive arrangement is configured to drive the motor in at least two phases of operation, with the control unit only activating the voltage boost circuit in one of the at least two phases of operation.