ES8506963A3 - Line operated fluorescent lamp inverter ballast - Google Patents

Abstract

Operating from normal 50Hz or 60Hz mains the resonant oscillator employs a two transistor, resonance maintenance circuit (15,16) connected to a series resonant circuit. The entire oscillator circuit includes a resonant current monitor for actuating switches in the oscillator circuit. Since it is the current flowing in the resonant circuit that commands the transistor switch, it is axiomatic that the command be in synchronism with that current. The circuitry ensures that the transistors switch at the instant when the resonant current passes through zero. The transformer (13) is a current transformer used to sense current in the resonant loop and to synchronize the switching of the transistors. - When power is applied to the input terminals (66,68) of the full wave rectifier (27) the output voltage is filtered by a capacitor (21). This resultant D.C. voltage is applied to the network which includes the transistors (11,12) causing the transistor (11) to turn on. This in turn causes the capacitor (22) to start charging through the primary windings (14,18). The primary winding (18) of the high leakage reactance transformer (17) is magnetically coupled to the secondary windings (19,20,21) of which the winding (20) is used to drive the fluorescent lamp (55) which is an ionizable gas type lamp. (1) GBAB- GB2113491 B A circuit for driving a load comprising: a resonant circuit, comprising the primary winding of a first transformer, the primary winding of a second transformer and a condenser connected in series, for carrying a resonant circuit current; an inverter, comprising first and second electronic valves, each valve having actuating means; and means on said circuit for connecting said first transformer primary winding to a load, wherein; the second transformer is a current transformer; the primary winding of the second transformer has negligible impedance; said first electronic valve is connected to a power supply and to said resonant circuit; said second electronic valve is connected in series with said resonant circuit to form a loop; a first secondary winding on said second transformer is connected directly to said actuating means on said first electronic valve for actuating said first electronic valve to charge said condenser to a first polarity; a second secondary winding on said second transformer is connected directly to said actuating means on said second electronic valve for actuating said second electronic valve when current flow through said first electronic valve passes through zero to allow current to flow in said loop to charge said condenser to a second polarity; and said first and second electronic valves are not actuated at the same time. - GB2113491 B A circuit for driving a load comprising: a resonant circuit, comprising the primary winding of a first transformer, the primary winding of a second transformer and a condenser connected in series, for carrying a resonant circuit current; an inverter, comprising first and second electronic valves, each valve having actuating means; and means on said circuit for connecting said first transformer primary winding to a load, wherein; the second transformer is a current transformer; the primary winding of the second transformer has negligible impedance; said first electronic valve is connected to a power supply and to said resonant circuit; said second electronic valve is connected in series with said resonant circuit to form a loop; a first secondary winding on said second transformer is connected directly to said actuating means on said first electronic valve for actuating said first electronic valve to charge said condenser to a first polarity; a second secondary winding on said second transformer is connected directly to said actuating means on said second electronic valve for actuating said second electronic valve when current flow through said first electronic valve passes through zero to allow current to flow in said loop to charge said condenser to a second polarity; and said first and second electronic valves are not actuated at the same time. USAB- US4459516 A The fluroescent lights include a source of electrical energy, a resonant circuit and a switch for connecting the source of electricity to the resonant circuit. Circuitry is also provided for connecting the resonant circuit to a load. A resonant circuit monitor controls the switch in synchronism with the resonant current so that the switch switches the resonant current when the resonant current passes through zero. - The resonant current monitor is a current transformer having a primary winding connected in series with the resonant circuit. Two secondary windings are connected to the bases of the two switching transistors in a two transistor inverter circuit at a polarity that will switch one of the transistors on and the other off at the time current passes through zero.