Method for operating a flyback converter for charging a dc link capacitor

A method (100) for operating a flyback converter (250) for charging a DC link capacitor (210), wherein the flyback converter (250) is connectable to a low-voltage network (295) on the input side and to a high-voltage network (205) on the output side, wherein the high-voltage network (205) comprises the DC link capacitor (210), wherein the flyback converter (250) comprises a series circuit consisting of a first circuit breaker (252) and a primary winding (254) of a transformer (260) between the input terminals (244_p, 244_n) on the input side, and comprises a series connection of a secondary winding (256) of the transformer (260) and a first diode (258) connected in the blocking direction between the output terminals (242_p, 242_n) on the output side, wherein a first capacitor (262) is connected between the output terminals (242_p, 242_n ) on the output side, the method comprising:

• determining (120) a voltage (Ux) characterizing the voltage at the DC link capacitor (210),
• specifying (140) a target charging current level (I_L) for charging the DC link capacitor (210) and specifying a corresponding duty cycle (Tx) for actuating the first circuit breaker (252) for as long as the determined voltage (Ux) falls below a first voltage level (U1), and
• specifying (150) a target charging voltage level (U_L) for charging the DC link capacitor (210) and specifying a corresponding duty cycle (Tx) for actuating the first circuit breaker (252) for as long as the determined voltage (Ux) corresponds to the first voltage level (U1) or the determined voltage (Ux) exceeds the first voltage level (U1) and the determined voltage (Ux) falls below a second voltage level (U2),
• wherein the first voltage level (U1) is less than the second voltage level (U2).