Control devices can be destroyed or damaged by their supply voltage in the event of malfunction. The voltage supply according to the present invention comprises a means (12) having a primary part (121) and secondary part (122), the primary part (121) being connected to the voltage source (10) and being controllable by means of the voltage output (112) of the voltage converter (11), and the secondary part (122) comprising a first and a second mutually independent winding, a supply voltage for the control device being made available by means of the first winding, and the second winding being connected to the voltage input (111) of the voltage converter (11) so that a supply voltage, additional to the voltage source (10), for the voltage converter (11) is implemented by means of the second winding. The manner in which the object of the invention is achieved thus enables a delayed shutoff (in particular with automatically self-adjusting off delay times) of the control device upon actuation of the key switch, and reliable operation of the control device.