Patent Treuhand Gesellschaft Fur Elektrische Gluhlampen Mbh

Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen Mbh

Patent-Treuhand-Gesellschaft F. Elektrische Gluehlampen Mbh

Walter Hirschmann

Klaus Fischer

Harald Schmitt

Hans-Jurgen Fahnrich

Ludwig Reiser

Peter Haeussinger

The invention relates to a circuit arrangement for operating a lamp (EL), particular a low-pressure discharge lamp, with a load circuit which has at least one inductor (L2) and at least one capacitor (C7, C8, C9), and with an invertor which may be configured as a half-bridge arrangement with two switching elements (T1, T2), and with a drive circuit (AS) for driving the switching elements (T1, T2). The invention provides that the drive circuit (AS) has at least one LC parallel tuned circuit (L3C3, L4C4). The circuit arrangement according to the invention can be produced without separate cost-intensive wound parts.

Circuit arrangement having LC parallel tuned drive circuitry

To operate a low-pressure discharge lamp, typically a fluorescent lamp, from a low voltage source of, for example, between 5 and 24 V, two diodes (D1, D2) polarized to provide for current passage towards the lamp are connected between the output of a blocking oscillator and the lamp (L). At least one diode (D2) provides for preheating the lamp electrode. The other diode (D1) prevents immediate starting of the lamp; it is integrated in the circuit between the secondary winding (N2) of the blocking oscillator transformer (TR) and one lamp electrode (E1). The first diode (D2) is connected between the primary winding (N1) and the other terminal of the secondary winding (N2), and also to the other lamp electrode (E2). An additional capacitor (C4) connected, effectively, across the lamp (L) improves the starting of the lamp. The circuit is readily adaptable for association with a recharging circuit (FIG. 3) for recharging a rechargeable battery to supply the lamp.

Circuit arrangement for operating a low-pressure discharge lamp,

To decrease the losses in the starting circuit for a compact fluorescent p, a positive temperature coefficient (PTC) resistor (KL) is connected in a resonance circuit of the lamp and also connected to the power supply of the lamp through a diode, polarized in blocking direction with respect to direct current, so that, before the lamp fires, a-c provided from an inverter (INV) can pre-heat the electrodes (E1, E2) of the lamp (LP), which will also cause current flow through the PTC resistor (KL); upon heating of the PTC resistor, this d-c current decreases and the voltage across the electrodes of the lamp will rise. When the lamp fires, it will drop below the supply voltage of the operating circuit for the lamp, thus causing the removal of the PTC resistor from the current carrying circuit, thereby eliminating energy loss through that resistor, and heating of the operating circuit assembly.

Method and circuit to operate a low-pressure discharge lamp,

To ensure synchronous operation of push-pull connected oscillator transistors (T1, T2), receiving rectified power via a rectifier (GL) from a power network (U), in which the circuit includes an elevated voltage maintenance or step-up converter circuit having a choke (L2), a switching transistor (T3) and a diode - capacitor circuit (D5, C2), the switching transistor (T3) is controlled from the same source of control voltage as the push-pull connected oscillator transistors (T1, T2), for example by coupling the base of the switching transistor (T3) to receive control energy from a feedback coil (RK3) of a feedback transformer (RK1, RK2, RK3) also supplying feedback energy to the push-pull oscillator transistors (T1, T2). The switching transistor (T3) can be controlled by a controllable resistor (R2) connected to its base, which may receive a control voltage through a control amplifier (FIG. 3: RV) representative of voltage levels in the circuit. A further transistor (T4) can be connected serially between the rectifier (GL) and the choke (L2) of the step-up converter circuit which improves approximation of sinusoidal wave form and voltage level maintenance of the circuit, the further transistor (T4) being likewise controlled from the same energy source as the switching transistor (T3).

Rectifier-inverter circuit with low harmonic feedback, particularly for

To permit dimming of a halogen incandescant lamp, or set of lamps connected to an electronic transformer circuit which receives operating voltage from a power network, rectifies the current supply and chops the rectified power to provide high-frequency alternating voltage for transformation to low voltage of the incandesent lamp, a non-current compensated choke having an inductance of at least 50 mH is connected in series between the rectifier output terminals and the rectifier system terminals, an oscillation start acceleration circuit including a CR circuit is connected in parallel with the starting circuit for the alternately operating transistors and a pair of symmetry resistors (R6,R7) are connected in parallel to symmetry defining capacitors (C6,C7), connected across the rectifier output terminals and a mid-point (M) of the oscillation transistors. The arrangement permits soft starting of the transistors, even if a serially connected phase controlled dimmer circuit suddenly connects line voltage at peak value across the rectifier, while providing for continuous energy release, even if the dimmer control is turned beyond the 90.degree. phase angle position and, for example, to 135.degree. phase angle.

Dimmable electronic transformer circuit

To suppress introduction of harmonics into the power supply network of a high-frequency operated fluorescent lamp, an input capacitor (C2) connected across a direct current supply (P1, P2) for a transistor push-pull high-frequency circuit--operating at between 25-50 kHz--has a pair of serially connected diodes (D4, D5) connected thereto. The junction point (M2) of the diodes is connected via a coupling capacity (C7) to a common junction (M1) of the push-pull connected transistors (T1, T2). The power line circuit has a line choke (L2, L2') connected, either in advance or behind a rectifier (G1) supplying direct current to the transistor push-pull circuit. The circuit effectively suppresses harmonics, particularly the third harmonic, without introducing additional losses in the circuit, especially if a further capacitor (C8) is connected in the resonance circuit of the fluorescent lamp and to the diode junction (M2) between the two diodes (D4, D5).

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Munich, Germany

Walter Hirschmann