A converter unit has a main
printed circuit board (8) on which at least one
functional module (1, 5) is arranged. By means of the
functional module (1, 5), at least one alternating
voltage (L1, L2, L3, U, V, W) fed to the
functional module (1, 5) via a first power supply interface (2, 7) of the functional module (1, 5) can be converted into at least two direct-current piezoelectric potentials (U +, U-, U0) output via a second power supply interface (3, 6) of the functional module (1, 5). The main
printed circuit board (8) has conductor tracks (10, 11, 14, 15) via which the control signals (C11 to C46) can be fed to the control interfaces (12, 13, 16, 17). The main
printed circuit board (8) has conductor tracks (10, 11, 14, 15) extending from the
control unit (9) to the first and second control interfaces (12, 13, 16, 17) of the main printed circuit board (8), and the first and second control signals (C11 to C46) can be fed to the first and second control interfaces (12, 13, 16, 17) via the conductor tracks. The functional module (1, 5) is at least mechanically connected to the main printed circuit board (8) at least in the region of the first and second control interfaces (12, 13, 16, 17). However, the functional module is designed in such a way that it does not use the first
control signal (C11 to C16, C31 to C36) and / or the second
control signal (C21 to C26, C41 to C46).