Power tool with step-up converter

1. A power tool, comprising an electrical motor unit that is connectable to a battery unit, wherein:

a step-up converter is connectable between said battery unit and said electrical motor unit, which is arranged for converting, when enabled, a battery voltage U battery that is provided to said step-up converter by said battery unit to a higher step-up voltage U step-up , U step-up >U battery , said step-up voltage U step-up being provided to said electrical motor unit as an output voltage U output , U output =U step-up ;

a bypass circuit is arranged in parallel with said step-up converter and connects, when enabled, said battery unit to said electrical motor unit and provides said battery voltage U battery to said electrical motor unit as said output voltage U output , U output =U battery ;

at least one control unit is provided for controlling said step-up converter and said bypass circuit such that said output voltage U output is switchable between said battery voltage U battery and said step-up voltage U step-up ;

said control unit is configured to control said step-up converter and said bypass circuit to alter said output voltage U output that is provided to said electrical motor unit to achieve a higher rotational speed of said electrical motor unit and a lower torque provided by said power tool during a first phase of a screw tightening process, followed by a lower rotational speed of said electrical motor unit and a higher torque provided by said power tool during a second phase of the screw tightening process; and

said control by the control unit is performed based on at least one of a plurality of different tool related parameters, said parameters comprising (i) said output voltage U output , (ii) an output current I output being provided to said electrical motor unit, (iii) said rotational speed ω motor of said electrical motor unit multiplied with said torque T being provided by said tool, ω motor *T, and (iv) an output power P output being provided to said electrical motor unit.

2. The power tool according to claim 1 , wherein said step-up converter is a synchronous step-up converter including at least one step-up transistor, at least one inductor, and at least one step-up switch.

3. The power tool according to claim 2 , wherein said step-up converter includes a step-up control circuitry configured to control said at least one step-up transistor and said at least one step-up switch connecting said step-up converter to said electrical motor unit when enabled.

4. The power tool according to claim 3 , wherein said step-up control circuitry includes a voltage regulation circuitry configured to control said higher voltage U step-up towards a target voltage U target and having an output of said step-up converter as an input.

5. The power tool according to claim 1 , wherein said bypass circuit includes a bypass switch controlled by said at least one control unit.

6. The power tool according to claim 3 , wherein said bypass circuit includes a bypass switch controlled by said at least one control unit; and

wherein one or more of said at least one step-up switch, said step-up transistor, and said bypass switch are implemented as any one in the group of:

an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor); and

an P-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

7. The power tool according to claim 1 , wherein said at least one control unit is configured to provide said bypass circuit with a bypass enabling/disabling signal S bypass_on/off , said bypass circuit being configured to enable or disable the connection of said battery unit to said electrical motor unit based on said bypass enabling/disabling signal S bypass_on/off .

8. The power tool according to claim 1 , wherein said at least one control unit is configured to provide said step-up converter with a step-up enabling/disabling signal S step-up_on/off , said step-up converter being configured to enable or disable the voltage conversion of said step-up converter based on said step-up enabling/disabling signal S step-up_on/off .

9. The power tool according to claim 7 , wherein said at least one control unit is configured to provide said step-up converter with a step-up enabling/disabling signal S step-up_on/off , said step-up converter being configured to enable or disable the voltage conversion of said step-up converter based on said step-up enabling/disabling signal S step-up_on/off ; and

wherein said at least one control unit is configured to base said step-up enabling/disabling signal S step-up_on/off and/or said bypass enabling/disabling signal S bypass_on/off on a relation between the at least one of said parameters (U output , I output , ω motor *T, P output ) and at least one threshold value (U threshold , I threshold , ωT threshold , P threshold ) relating to the at least one of said parameters.

10. The power tool according to claim 7 , wherein said at least one control unit is configured to provide said step-up converter with a step-up enabling/disabling signal S step-up_on/off , said step-up converter being configured to enable or disable the voltage conversion of said step-up converter based on said step-up enabling/disabling signal S step-up_on/off ; and

wherein said at least one control unit is configured to base said step-up enabling/disabling signal S step-up_on/off and/or said bypass enabling/disabling signal S bypass_on/off on a relation between said output voltage U output and a voltage threshold U threshold .

11. The power tool according to claim 10 , wherein said at least one control unit is configured to generate a step-up enabling signal S step-up_on and a bypass disabling signal S bypass_off when said output voltage U output is equal to or higher than said voltage threshold U threshold (U output ≥U threshold ).

12. The power tool according to claim 7 , wherein said at least one control unit is configured to provide said step-up converter with a step-up enabling/disabling signal S step-up_on/off , said step-up converter being configured to enable or disable the voltage conversion of said step-up converter based on said step-up enabling/disabling signal S step-up_on/off ; and

wherein said at least one control unit is configured to base said step-up enabling/disabling signal S step-up_on/off and/or said bypass enabling/disabling signal S bypass_on/off on a relation between said output current I output being provided to said electrical motor unit and a current threshold I threshold .

13. The power tool according to claim 12 , wherein said at least one control unit is configured to generate a step-up disabling signal S step-up_off and a bypass enabling signal S bypass_on when said output current I output is equal to or higher than said current threshold I threshold (I output ≥I threshold ).

14. The power tool according to claim 7 , wherein said at least one control unit is configured to provide said step-up converter with a step-up enabling/disabling signal S step-up_on/off , said step-up converter being configured to enable or disable the voltage conversion of said step-up converter based on said step-up enabling/disabling signal S step-up_on/off ; and

wherein said at least one control unit is configured to base said step-up enabling/disabling signal S step-up_on/off and/or said bypass enabling/disabling signal S bypass_on/off on a relation between said rotational speed ω motor of said electrical motor unit multiplied with said torque T being provided by said tool, ω motor *T, and a speed and torque threshold ωT threshold .

15. The power tool according to claim 14 , wherein said at least one control unit is configured to generate a step-up enabling signal S step-up_on and a bypass disabling signal S bypass_off when said rotational speed ω motor multiplied with said torque T, ω motor *T, is lower than said speed and torque threshold ωT threshold (ω motor *T<ωT threshold ).

16. The power tool according to claim 7 , wherein said at least one control unit is configured to provide said step-up converter with a step-up enabling/disabling signal S step-up_on/off , said step-up converter being configured to enable or disable the voltage conversion of said step-up converter based on said step-up enabling/disabling signal S step-up_on/off ; and

wherein said at least one control unit is configured to base said step-up enabling/disabling signal S step-up_on/off and/or said bypass enabling/disabling signal S bypass_on/off on a relation between said output power P output being provided to said electrical motor unit and a power threshold P threshold .

17. The power tool according to claim 16 , wherein said at least one control unit is configured to generate a step-up enabling signal S step-up_on and a bypass disabling signal S bypass_off when said output power P output is lower than said power threshold P threshold (P output <P threshold ).

18. The power tool according to claim 7 , wherein said at least one control unit is configured to provide said step-up converter with a step-up enabling/disabling signal S step-up_on/off , said step-up converter being configured to enable or disable the voltage conversion of said step-up converter based on said step-up enabling/disabling signal S step-up_on/off ; and

wherein said bypass enabling/disabling signal S bypass_on/off and said step-up enabling/disabling signal S step-up_on/off are complementary signals.

19. The power tool according to claim 1 , wherein said step-up converter includes two step-up transistor circuits being operated in mutually opposite phases.

20. The power tool according to claim 1 , wherein said step-up converter and said bypass circuit are arranged integrated within a body of said power tool, said step-up converter and said bypass circuit being connected to said electrical motor unit and being connectable to said battery unit.

21. The power tool according to claim 1 , wherein said step-up converter and said bypass circuit are arranged integrated with and connected to said battery unit, and are connectable to said electrical motor unit.

22. The power tool according to claim 1 , wherein said step-up converter and said bypass circuit are arranged separately between said battery unit and said electrical motor unit, said step-up converter and said bypass circuit being connectable to said battery unit and to said electrical motor unit.

23. The power tool according to claim 1 , wherein said battery unit includes at least one super capacitor.

24. The power tool according to claim 1 , wherein said power tool includes a brake chopper arranged for consuming energy provided by said electrical motor unit when said rotational speed of said electrical motor unit is reduced.

25. A method for providing an electrical motor unit of a power tool with an output voltage U output , the method comprising:

converting, when a step-up converter that is connectable between a battery unit and said electrical motor unit is enabled, a battery voltage U battery that is provided to said step-up converter by said battery unit to a higher step-up voltage U step-up , U step-up >U battery , and providing said step-up voltage U step-up to said electrical motor unit as said output voltage U output , U output =U step-up ;

connecting, when a bypass circuit that is arranged in parallel with said step-up converter is enabled, said battery unit to said electrical motor unit, and providing said battery voltage U battery to said electrical motor unit as said output voltage U output , U output =U battery ; and

controlling, by use of at least one control unit, said step-up converter and said bypass circuit such that said output voltage U output is switchable between said battery voltage U battery and said step-up voltage U step-up , to alter said output voltage U output that is provided to said electrical motor unit to achieve a higher rotational speed of said electrical motor unit and a lower torque provided by said power tool during a first phase of a screw tightening process, followed by a lower rotational speed of said electrical motor unit and a higher torque provided by said power tool during a second phase of the screw tightening process;

wherein the controlling of said step-up converter and said bypass circuit is performed based on at least one of a plurality of different tool related parameters, said parameters comprising (i) said output voltage U output , (ii) an output current I output being provided to said electrical motor unit, (iii) said rotational speed ω motor of said electrical motor unit multiplied with said torque T being provided by said tool, ω motor *T, and (iv) an output power P output being provided to said electrical motor unit.

26. The method according to claim 25 , wherein said at least one control unit disables said step-up converter and enables said bypass circuit when the at least one of said parameters (U output , I output , ω motor *T, P output ) reaches above or below a certain threshold (U threshold , I threshold , ωT threshold , P threshold ) relating to the at least one of said parameters.

27. The method according to claim 25 , wherein said at least one control unit disables said step-up converter and enables said bypass circuit when said output voltage U output is lower than a voltage threshold U threshold (U output <U threshold ).

28. The method according to claim 25 , wherein said at least one control unit disables said step-up converter and enables said bypass circuit when said output current I output is higher than or equal to a current threshold I threshold (I output ≥I threshold ).

29. The method according to claim 25 , wherein said at least one control unit enables said step-up converter and disables said bypass circuit when said rotational speed ω motor of said electrical motor unit multiplied with said torque T that is provided by said power tool, ω motor *T, is lower than a speed and torque threshold ωT threshold (ω motor *T<ωT threshold ).

30. The method according to claim 25 , wherein said at least one control unit enables said step-up converter and disables said bypass circuit when said output power P output that is provided to said electrical motor unit is lower than a power threshold P threshold (P output <P threshold ).

31. The method according to claim 25 , wherein said screw tightening process includes:

enabling said step-up converter and disabling said bypass circuit during said first phase of said screw tightening process, thereby providing said step-up voltage U step-up to said electrical motor unit as said output voltage U output , U output =U step-up , whereby said rotational speed ω motor of said electrical motor unit is increased as a result of the higher step-up voltage U step-up ; and

enabling said bypass circuit and disabling said step-up converter during said second phase of said screw tightening process, thereby providing said battery voltage U battery to said electrical motor unit as said output voltage U output , U output =U battery , whereby said rotational speed ω motor of said electrical motor unit is decreased as a result of the lower battery voltage U battery .

32. A non-transitory computer readable medium storing a computer program that is executable by a computer of a power tool to perform the method according to claim 25 .