Rectifier-inverter circuit with low harmonic feedback, particularly for operation of fluorescent lamps

Claim 1

Rectifier - inverter circuit for operation of a load (LP) by supplying the load with electrical energy from an a-c power network, at an elevated frequency high with respect to the power network frequency, having a rectifier circuit (GL) coupled to the power network; a first capacitor (Cl) connected across the output terminals of rectifier; a push-pull oscillator circuit for providing said electrical energy at said elevated frequency, coupled to the output of the rectifier, said push-pull oscillator circuit including two transistors (T1, T2), a feedback circuit including a transformer having a first winding (RK1) in circuit with the load, and feedback winding means (RK2, RK3) in circuit with the transistors; an inductance (L1) connected between the output of the oscillator circuit and the load (LP); and an active harmonic filter circuit forming an elevated voltage maintenance, or step-up converter circuit coupled to the output of the rectifier circuit including a switching transistor (T3) having its switching path connected across the rectifier output; a choke (L2) in series with the switching path of said switching transistor, and a diode (D5) and a second capacitor (C2) circuit, coupled in circuit with the switching path of the transistor, and comprising, in accordance with the invention, means for controlling the switching of the switching transistor (T3) and for ensuring synchronous operation of the switching transistor and the oscillator circuit including circuit connection means (C7, R1) coupled to said oscillate circuit and to the control electrode of the switching transistor (T3) to control switching of the switching transistor from the same source of energy which provides the elevated frequency energy.