Low-pressure discharge lamp, particularly fluorescent lamp high-frequency operating system with low inductance power network circuit

In combination with a fluorescent lamp (LP1, LP2),

• a low inductance power network circuit, adapted to be connected to a power line circuit (U) at power line voltage and frequency, including
• a power rectifier (2) having output terminals (P1, P2) which form positive (P1) and negative (P2) lamp circuit input terminals, respectively;
• an input capacitor (C2) connected across said lamp circuit input terminals (P1, P2);
• a push-pull transistor frequency generator (3) having two alternately conducting transistors (T1, T2) and having a common junction (M1);
• and an operating circuit for the transistors, including
• said lamp, an oscillator transformer (RK), including first (RK1), second (RK2) and third (RK3) windings, the second and third windings being, respectively, connected to the base of a respective transistor (T1, T2) and the first winding being connected between said common junction (M1) and a first electrode (E1, E3) of the lamp electrodes, and
• a series resonance circuit (4) having a series inductance (L1, L1') defining two terminals and having a first terminal connected to the common junction (M1) of the transistors (T1, T2) and a second terminal (M3, M3') connected through a series coupling capacitor (C5, C5') and through lamp filaments of the lamp electrodes (E1, E2, E3, E4) to a resonance capacitor (C6, C6') in the preheating circuit of the lamp (LP1, LP2),
• and comprising a harmonic filter including
• a first and a second diode (D8, D9), serially connected in forward current passing direction and defining a first diode junction (M2) between said first and second diodes;
• a first coupling capacitor (C7) coupling said first diode junction to said common junction (M1) between said transistors (T1, T2);
• a second coupling capacitor (C8, C8') coupling said first diode junction (M2) to said second terminal (M3, M3') of the series inductance (L1, L1');
• third and fourth diodes (D10, D11), serially connected in forward current passing direction and defining a second diode junction (M4) between said third and fourth diodes, said third and fourth diodes being connected in parallel to said first and second diodes (D8, D9);
• a third coupling capacitor (C9) coupling said second diode junction (M4) to the common junction (M1) between said transistors (T1, T2) of said push-pull transistor frequency generator (3);
• and
• wherein said first and second serially connected diodes, and said third and fourth serially connected diodes (D8, D9;
• D10, D11) are connected between one (P1) of said lamp circuit input terminals (P1, P2) and a second electrode (E2, E4) of the lamp electrodes.