Abstract: High-efficiency inverter circuits, particularly half-bridge devices, are especially suitable for energizing gas discharge lamps. The inverters preferably employ a series-connected combination of an inductor and a capacitor to be energized upon periodic transistor conduction. Transistor drive current is provided through the use of at least one saturable inductor to control the transistor inversion frequency to be equal to or higher than the natural resonant frequency of the inductor and capacitor combination. The inverters can develop high output voltages to supply external loads connected to the inductor-capacitor combination.

Abstract: A high efficiency, self-oscillating LC resonant multivibrator-inverter circuit employing a pair of switching transistor (Q1, Q2), two magnetically independent resonant inductors (L1, L2) and one common resonant capacitor (CR). Two secondary windings (NB2, NB1) of the resonant inductors provide feedback control for the switching transistors' bases, to provide intermittent feedback current to effect alternate and periodic conduction of the transistors. This results in the DC voltage rectified from the source S being converted to relatively high frequency AC voltage across output terminals (O1, O2). Such an arrangement enables construction of a cost effective, highly efficient, and highly reliable electronic ballast for fluorescent lamps.

Abstract: A circuit for driving an electric field luminous lamp includes a DC-DC converter for generating a constant DC electric power output. The DC electric power is inverted to an AC electric power to drive an electric field luminous lamp. This results in a constant consumption of an electric power, so that the decrease of a brightness is avoided, a life of the lamp becomes long, and a fluctuation of an input DC voltage does not affect a fluctuation of an electric power consumption.

Abstract: A circuit arrangement comprising a DC/AC converter for supplying power to a lamp upon receiving energy from a DC voltage source; the converter includes a branch A having at least one switching element and a control branch connected to the switching element; the control branch comprises a coil shunted by a capacitor; the circuit arrangement also includes a load branch with an inductor connected to a parallel arrangement of an inductance and capacitance.

Abstract: A circuit for dimmably driving fluorescent lamps (102, 104, 106) from a DC supply voltage includes: input nodes (174, 176) having input capacitors (184, 186) connected therebetween; a half-bridge transistor inverter (178, 180) connected between the input terminals; a series-resonant LC oscillator (196, 198) coupled in series between the half-bridge transistors and the input capacitors; an output transformer (212) having a primary winding (214) connected in series with the LC inductor (196) and in parallel with the LC capacitor (198) and a secondary winding (216) for connection to the lamp load; and first and second voltage clamp diodes (215A, 215B) connected between an intermediate point on the primary winding and the input nodes respectively.

Abstract: A circuit (100) for driving fluorescent lamps (102, 104, 106) and including: a half-bridge inverter (112) receiving a unidirectional voltage and producing an alternating voltage, and having control inputs (156, 166); a series-resonant oscillator (126) coupled to the inverter output (116) for producing an alternating signal; and a non-saturating feedback transformer (146) having a primary winding (148) coupled in series between the inverter and the oscillator and secondary winding (150, 152) coupled respectively to the control inputs of the inverter. Since the feedback transformer is non-saturating it provides to the inverter control inputs a linear feedback signal from the inverter. This results in safe, stable, predictable and well-defined circuit operation, in which the possibility of the inverter transistors being destroyed by cross-conduction is substantially removed, and the amount of input voltage "ripple" present in the signal applied to the lamps is reduced.

Abstract: A circuit (100) for driving a gas discharge lamp load (102, 104, 106) and including: an inverter (112) receiving a unidirectional voltage output and producing an alternating voltage, and having a control input (156, 166); a series-resonant oscillator (126) coupled to the inverter output (116) and having an inductance (128) and a capacitance (130) in series for producing an alternating current; an output transformer (134) coupling the lamp load to the oscillator in series with the inductance and in parallel with the capacitance; and a feedback transformer (146) having a primary winding (148) coupled in parallel with the output transformer and coupled in series with the capacitance and a secondary winding (150, 152) coupled to the control input of the inverter. Since the feedback transformer primary winding carries only capacitive current (I.sub.C), the frequency of the circuit is substantially independent of the load.

Abstract: The ballast is connected between the fluorescent lights and a source of power for the fluorescent lights. The source of power provides an input signal having a first waveform, usually a sine wave, at a first frequency. The ballast consists of a converter for coverting the first waveform to a second waveform at a second frequency different from the first frequency. A distribution arrangement distributes power to the fluorescent lights. The distribution system consists of a transformer, and capacitors are interposed between selected windings of the secondary of the transformer. In one embodiment, the sine wave is converted to a square wave by the converter and to a saw tooth waveform by the capacitors in the distribution arrangement so that the fluorescent lights are fed with the saw tooth waveform.

Abstract: An improved electronic ballast inverter for a gas discharge lamp includes an oscillator having at least two switching transistors for operating the gas discharge lamp at a high frequency during steady-state operation, a triggering circuit for initiating the operation of the oscillator, and an electrical circuit connected to the oscillator for gradually increasing the base current of at least one of the switching transistors immediately after start-up in order to delay the gas breakdown and thereby to produce preheating of the gas discharge lamp during startup.

Abstract: A fluorescent lamp control system operable from either an AC power supply of a first frequency or a power supply of a second frequency and which operates the lamp in a dimmed condition when the power supply is that of the second frequency.

Abstract: A self contained battery operated table lamp for use in restaurants, and the like. The lamp includes an electric light which is energized on an intermittent basis by a switching circuit to assure long battery life. A feed back loop is included in the switching circuit for establishing the duty cycle of the energizing power intermittingly applied to the lamp. A flicker signal generator is connected to the energizing circuit of the light to introduce a flicker into the output of the light. The flicker signal generator incorporates a plurality of independent oscillators, each operating at a slightly different frequency. The outputs of the various oscillators are summed in a summing network with each being given a slightly different weighting factor, and the resulting signal is injected into a feedback loop to modify the average voltage of the light. The lamp is caused to provide a pseudo-random candle simulating effect.

Abstract: A switchmode DC to AC converter, and particularly a master-slave half-bridge converter. The slave half-bridge power converter is controlled by a lower power self-oscillating half-bridge master converter. More particularly, the invention pertains to a high frequency ballast for gas discharge devices, especially, for high pressure sodium lamps, completed by a high voltage ignition apparatus.

Abstract: The invention circuit for a discharge lamp comprising a first switching circuit, a series resonant circuit, and a current transformer. The series resonant circuit energizes the discharge lamp by means of resonant output corresponding to the output from the first switching circuit. The current transformer incorporates the first, second, and the third windings. When the first winding inserted in the series resonant circuit is driven, the first winding outputs a predetermined amount of current to the second and third windings. The inverter circuit further comprises a second switching circuit, a pair of time constant circuits, and a control circuit. The second switching circuit controls ON-OFF operation of the first switching circuit in response to the output from the second winding.

Abstract: A lamp driver circuit includes a high voltage secondary winding connectable to a gas discharge lamp. The secondary is wound on a magnetic core together with a pair of primary windings. The primary windings are coupled to one another as well as to an R-C network and an amplifier stage, the latter of which comprises a plurality of fast-switching transistors connected in parallel with one another. The bases of each of the transistors are connected to the R-C network by way of an element such as an incandescent lamp filament whose resistance varies with the current through the element.

Abstract: A driver for a electroluminous lamp includes a bridge switching circuit comprising four MOSFETS, the lamp and a series connected inductance being connected as the load on the bridge circuit. The switching of the transistors of the bridge circuit is controlled by logic circuitry which generates a two-phase, non-overlapping gating control signal which causes the MOSFETS to be switched in pairs whereby current will flow in alternate directions through the lamp.

Abstract: A fluorescent lamp stabilizer circuit device of the type comprising two transistor switches is provided. The two transistor switches are alternatively switched on/off so as to control two charging circuits for providing an impulse voltage double that of power supply voltage for initiating operation of a fluorescent lamp to give off light. A resonance circuit is provided to generate a damped oscillation responsive to the impulse voltage to drop output voltage to the fluorescent lamp tube to a rated range immediately after the fluorescent lamp tube has turned on.

Abstract: A compact screw-in fluorescent lamp is mounted on an ordinary Edison-type screw-base. An inverter-type ballast is integrally included with the base, thereby making the fluorescent lamp capable of being screwed into an ordinary lamp socket and to be powered therefrom by ordinary power line voltage. The fluorescent lamp is folded and has a narrowed section of glass. The inverter-type ballast is powered via a voltage doubler and powers the fluorescent lamp via an tuned L-C circuit. Light output can be adjusted by way of an adjustment means functional to adjust the inverter frequency, thereby correspondingly to adjust the magnitude of the lamp current.

Abstract: A photoelectric switch having a light projector element (L) and a first oscillation circuit (2) for driving the light projector element by use of pulses includes a second oscillation circuit (4) and a coupling circuit (3) for coupling the second oscillation circuit with the first oscillation circuit. The second oscillation circuit sweeps an oscillation frequency of the first oscillation circuit at a predetermined period to vary the oscillation frequency of the first oscillation circuit in a periodical manner.

Abstract: A DC discharge lamp lighting device includes a main discharge means providing a main discharge-lamp current to a DC discharge lamp including a filament and at least one anode to form between them a discharge path. The main discharge means comprises means for switching an applied voltage between a main discharge starting voltage in synchronism with a luminance control signal and a main discharge maintaining voltage. Any contribution of a current limiting resistance element to power consumption in circuit operation upon lighting of the discharge lamp can be reduced, thereby reducing heat generation.

Abstract: A DC/AC converter for supplying two discharge lamps (12, 13). Two input terminals (4, 5) of the converter are interconnected by a series circuit comprising two switching elements (6, 7). A capacitor (8) connects one of the input terminals (4) to a common end (18) of two output circuits (17, 16, 15, 14; 23, 22, 21, 20), one of these output circuits (17, 16, 15,14) also is connected to a junction point (19) between the switching elements (6, 7). A second series circuit comprising two further switching elements (10, 11) is connected to the input terminals. The other output circuit is connected to a junction point (19.sup.a) between the two further switching elements. The converter thus can be readily used both for simultaneously supplying two lamps and for supplying only one lamp.

Abstract: A circuit is disclosed which is capable of positively shifting a gas discharge lamp from its off-state to its on-state without emitting light flashes and further positively maintains the gas discharge lamp in its on-state when first ignited. The circuit contains an oscillator device which generates and supplies an oscillator signal of a specific oscillator frequency from two output terminals of the oscillator device. It also contains a current limiting device an a parallel-resonance circuit comprising a capacitor and an inductor. The parallel resonance circuit has a frequency of resonance substantially identical to the oscillator frequency. The current limiting device and parallel-resonance circuit are connected in a series configuration across the output terminals of the oscillator device. Further, the gas discharge lamp is connected across or in parallel with the parallel-resonance circuit.

Abstract: The invention relates to an electronic converter for supplying a constant amplitude output voltage while taking from the main supply only a sinusoidal current in phase with the voltage. This device is constituted by an auto-oscillator comprising transistors 7a and 7b for which the duty cycle is automatically regulated, a first inductance 10 constituting an oscillator circuit to which the output energy is evacuated, and second inductance taking off part of the high frequency energy produced to reapply it, after rectification, in series with the mains voltage rectified by the bridge 13, so that the voltage between the common polarized terminals of the auto-oscillator becomes continuous and held at a potential at least equal to the peak mains voltage, which translates into a continuous output voltage envelope. This device is applicable to the production of electronic transformers, power supplies, electronic ballasts, etc., without necessarily requiring electrolytic smoothing capacitors.

Abstract: A lamp driver circuit is presented herein for driving a lamp circuit with an AC squarewave voltage at a relatively high frequency. The driver circuit includes a self-oscillating half-bridge circuit having a pair of input terminals connected across a DC voltage supply, which may be obtained from rectifying an AC voltage signal, and a pair of output terminals connected across a lamp circuit including a lamp, either a resistive lamp or a gaseous discharge lamp, to be energized. The circuit also includes a pair of capacitors connected together in series across the input terminals and having a junction therebetween connected to a first one of the output terminals. The bridge circuit also includes first and second switching transistors connected together in series across the input terminals.

Abstract: 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.

Abstract: A control system for lighting a bank of fluorescent lamps, includes input terminals (10, 11) for a mains voltage (e.g. 240 v) and output terminals (20, 21) to which the bank of lamps is connected. A transformer (T1) provides a reduced voltage (216 v) as compared to the mains supply voltage. The transformer (T2) provides a supplementary voltage (24 v). Upon start up of the circuit, a control circuit (CC) operates contact (A1) to energize the transformer (T2) so that terminals (20, 21) receive both the reduced voltage from (T1) and the supplementary voltage from (T2) (i.e. 240 v) which is sufficient to ignite the fluorescent lamps. The control circuit (CC), after a predetermined delay (e.g., 15 seconds), switches contact (A1) to disconnect the supplementary voltage from (T2). The lamps then continue to operate on the reduced voltage (216 v) thereby reducing the power consumed by the lamps.

Abstract: A DC/AC converter (8) having a half bridge circuit for igniting and feeding a gas and/or vapour discharge tube (1). A starting capacitor (94) of this converter is connected between a junction (A) between two branches--each comprising a semiconductor circuit element (60 and 61)--of the half bridge circuit on the one hand and a center tapping (E) of a voltage divider (90, 91) on the other hand. As a result, the converter (8) starts satisfactorily and hence the discharge tube (1) readily ignites, moreover undesired starting pulses during the operating condition are avoided.

Abstract: A DC/AC converter for igniting and supplying a gas discharge lamp (1). The converter has two input terminals (C, D) intended to be connected to a DC voltage source, said input terminals (C, D) being connected together by means of a series arrangement including a load circuit comprising at least an induction coil (10) and a parallel arrangement of the lamp and a capacitor (12), as well as a first semiconductor switching element (13). The load circuit is shunted by a circuit comprising a second semiconductor switching element (14). The semiconductor switching elements (13, 14) are rendered alternately conductive and non-conductive by means of control circuits (13a, 14a). A second capacitor (11) is arranged in series with the induction coil (10) and the lamp. The second capacitor is shunted by a third switching element (15) which is non-conductive during the pre-heat period of the lamp electrodes (2, 3) and is conductive at least during ignition of the lamp.

Abstract: An electric arrangement for igniting and supplying a gas discharge lamp (1). The arrangement is connected to an alternating voltage source and comprises a rectifier bridge (7) connected to a DC/DC converter provided with a rectifier element (11), a coil (10) and a high-frequency switched semiconductor switching element (12) coupled to a drive circuit. The DC/DC converter is connected to the input terminals (16, 17) of a high-frequency DC/AC converter incorporating the lamp and provided with semiconductor switching elements (21,24). A capacitor (15) is arranged between the input terminals of the DC/AC converter and a sensor (22) for measuring the converter current is arranged between one of the input terminals (17) and a semiconductor switching element (21) of the DC/AC converter. The lamp is connected in series with a frequency-dependent impedance 20.

Abstract: A circuit for cutting a "notch" in an alternating current supply waveform with the minimization of dissipated power comprising a pair of GTO's so poled to conduct current therethrough and also through a pair of power consuming diodes when the switches are "on" during alternate half cycles, the switches being turned "off" at the start of the "notches", and the current is resumed thereafter by a pair of oppositely poled SCR's which are turned "on" and which bypass power diodes so as to conserve power.

Abstract: An electronic supply system for fluorescent tubes with electrodes includes two MOS power transistors connected in series and, connected to a common point between those transistors, a series circuit including a primary winding of a transformer, of which two secondary windings control the transistors, a lighting unit or units and a capacitor 10. The capacitor is connected to a supply means output terminal opposite a secondary supply means output terminal where one of the transistors, which transistor is driven by a diac, is connected.

Abstract: A miniature, light weight, high voltage, high frequency, high power output unique ballast and a unique sealable neon lamp in a light weight, light reflective box containing the ballast for use as one of a plurality of ceiling lamps. The ballast includes a transformer with a tuned secondary due to distributed capacitance, as a result of spaced apart first and second halves of the secondary winding, particularly wound in three separate sections of a bobbin fitted on the center leg of the transformer E--E core and tightly coupled to a center tapped primary winding on the center leg of the other section of the E-core. The section of the core are separated by a high dielectric spacer which also gaps the core when the sections are placed together. An asymetrical starting circuit prevents burnout of the alternate conducting FET switching device by insuring that only a selected one FET always starts first, and the unique bobbin and secondary winding prevents breakdown in the secondary high voltage winding.

Abstract: Apparatus for reducing the effects of beat frequencies in systems having multiple oscillators wherein a wide band frequency modulator operates to alter the frequency supplied by one of the oscillators at a rate high enough that any beat frequencies occur at rates undetectable to the human eye.

Abstract: A DC-AC converter for igniting and supplying a gas discharge lamp (1). The converter has two input terminals (C, D) to be connected to a DC voltage source. The input terminals are interconnected by means of a series arrangement that includes a load circuit comprising at least the lamp (1) and an induction coil (5), and a first semiconductor switching element (6) including a freewheel diode. The load circuit is bridged by a circuit including a second semiconductor switching element (7) with a freewheel diode. The semiconductor switching elements (6, 7) are provided with control circuits for rendering said switching elements alternately conducting. The control circuit (9) of switching element (7) has a voltage measuring point which is connected via a rectifier element (10) to the control circuit (8) of the first switching element.

Abstract: Arc discharge lamps driven at frequencies in excess of 20 kHz may exhibit the phenomenon of `acoustic resonance` in which longitudinal and lateral acoustic waves are supported in the arc tube. This is a problem because the acoustic wave may give rise to an instability in the discharge arc, causing it to stretch or gyrate and invariably to extinguish. In some cases damage may be caused to the arc tube. A power supply suitable for an arc discharge lamp comprises a drive circuit arranged to supply voltage to the lamp and control means for causing a characteristic of the voltage to vary, with time, in accordance with a pseudo random sequence in order to reduce, or eliminate, acoustic resonance in the lamp.

Abstract: The present invention uses a variable frequency oscillator to drive a primary resonant converter output transformer circuit for exciting gas discharge tubes. The combination of the impedance of the resonant conversion circuit along with the impedance of the driven gas discharge tube taken in combination with the frequency of the variable oscillator will determine the output voltage of the circuit. By varying the frequency of the oscillator, the optimal output voltage and hence the optimal brightness of the gas discharge tube may be selected. At the optimal output voltage, the frequency of the switching supply may create an undesirable or desirable "bubble effect" in the gas discharge tube. An optional secondary frequency may be combined with the frequency of the variable frequency oscillator to create or eliminate the bubble effect according to the esthetic desires of the user.

Abstract: A discharge lamp driving circuit includes a chopper with a first switching circuit and an inverter with a second switching circuit. The chopper and inverter are connected to a dc voltage source and controlled to produce a composite lamp driving current composed of a high frequency alternating current interrupted by a dc current in order to keep the discharge lamp free from an acoustic resonance. The chopper and the inverter are arranged to have at least one common switching element in their first and second switching circuits.

Abstract: A ballast circuit and method of operating gas discharge lamps are disclosed. The ballast circuit generates a relatively low frequency regulated square-wave current which advantageously provides for operating the gas discharge lamps during their run mode. The square-wave current delivered to the electrodes of the gas discharge lamp reduces or substantially eliminates the cataphoresis effects typically created by D.C. and 60 Hz operation of the gas discharge lamp while also reducing or substantially eliminating the detrimental acoustics resonance effects typically created by operating the gas discharge lamps at relatively high frequency of excitations.

Abstract: An electronic ballast for high intensity discharge lamps is taught. A high speed electronic switch gates voltage across the lamp only for that period of time when the amount of resultant current flow will not adversely affect the lamp or the switch. At that point, the voltage is gated off for a period of time, after which the cycle repeats. This scheme eliminates the need for any inductive, resistive or capactive element, either saturable or conventional, in the post-ignition operation of the lamp, except perhaps for auxiliary functions. The elimination of such inductive elements results in a highly efficient, low cost electronic ballast having reduced electromagnetic and radio interference emissions.

Abstract: A system for driving a neon tube to form luminous bubbles and controlling the motion thereof in which a modulatable high AC voltage source is connected to control a pair of electronic switches in the primary circuit of a high voltage transformer which is connected to electrodes of said neon tube in such a way as to produce the luminous bubbles, which can be stationary or moved at varying speeds and direction by control of width and/or frequency of control pulses applied to the electronic switches. A memory stores predetermined patterns of the direction and speed of said luminous bubbles and microprocessor means for controlling said modulatable AC voltage in accordance with said predetermined pattern by said memory means to cause said luminous bubbles to move in said predetermined patterns of direction and speed. The memory may include a plurality of predetermined patterns stored, and selector for selecting one of said patterns and driving the neon tube therewith.

Abstract: Power is provided to a fluorescent lamp through a single integrated circuit (IC) chip. The IC chip contains control logic and power switches. The control logic operates the switches at a frequency which is optimum for the fluorescent lamp. The control logic includes circuits for thermal shut down, load status detection and voltage compensation.

Abstract: A discharge lamp operating circuit includes at least a discharge lamp, a condenser and four switches. The condenser is charged and discharged through the discharge lamp by the turn-on and turn-off of the switches so that an AC current is caused to flow through the discharge lamp to operate the discharge lamp. A time required for the complete charging and discharging of the condenser is selected to be longer than a time scheduled for the charging and discharging of the condenser in one period. A switching frequency f.sub.0 at the time of heating of the discharge lamp and a switching frequency f at the time of operating of the discharge lamp has a relation of 2.ltoreq.f/f.sub.0 .ltoreq.10.

Abstract: One or more power dimmers have a preshaped phase controlled input signal connected to their control input. The preshaped phase controlled input signal is generated from the output of a master dimmer having conventional phase control circuits operated from a manual or other control. A relay having contacts in the output circuit of the power dimmers is opened in response to the reduction of the phase controlled input signal to a value less than a given value. In an alternative embodiment, the power dimmers are replaced by an interface circuit which produces a variable frequency, pulse width modulated or other signal.

Abstract: To operate a fluorescent lamp having a lamp operating voltage of to about 0 V from a power supply having a nominal voltage level below lamp operating voltage, and without use of a voltage doubler circuit or a transformer to increase the power supply voltage, the power supply voltage is rectified, chopped, and then applied to the fluorescent lamp through a voltage increasing circuit which is formed as an LC resonance circuit. The inductive component can be formed by the current limiting choke, already present in a typical fluorescent lamp circuit, and the capacitative component by a small capacitor, for example of 6 nF value, connected to the choke to form a series resonance circuit.

Abstract: A starter assembly is provided for use with an inductively coupled plasma (ICP) tube to reliably initate a plasma at internal pressures above about 30 microns. A conductive probe is inserted within the inductor coil about the tube and insulated from the tube shield assembly. A capacitive circuit is arranged for momentarily connecting a high voltage radio-frequency generator to the probe while simultaneously energizing the coil. When the plasma is initiated the probe is disconnected from the generator and electrically connected to the shield assembly for operation.

Abstract: A circuit arrangement for A.C. operation of gas discharge lamps comprises a full-wave rectifier (1) connected to an alternating voltage source. The direct voltage is supplied to a combinatorial circuit part (3 to 8) in the form of a direct voltage converter, to which is connected a bridge circuit (9) which comprises four thyristors. The transverse branch of the bridge circuit includes the lamp (5). The full-wave rectifier (1) is followed by a smoothing capacitor (2) and an electronic switching element (14) is connected parallel to the bridge circuit (9). The switching element is switched to the conducting state in the vicinity of the zero passages of the input alternating voltage. As a result shortcircuits in the bridge circuit are avoided.

Abstract: According to the present invention, a portion of an applied commercial AC supply (60 Hz) is rectified, filtered and a controllable oscillator in a pulse width modulator chip serves as a signal generator which has both duty cycle and frequency control adjustments. An output signal is coupled via an impedance matching circuit to the input primary winding of a signal transformer having a pair of secondary windings which drive a pair of tandem connected electronic switches which, in turn, are connected across a second DC supply which has a high direct current voltage derived from the input AC line voltage (110-120 V AC 60 Hz).

Abstract: A converter of electric power at a first value of voltage and frequency produces a voltage at a second value and at a higher value of frequency by means of an inverter oscillator circuit having two serially connected transistors. An output power transformer is coupled to the transistors for receiving current excitation from alternate ones of the transistors during alternate half-cycles of the output voltage. Incoming voltage is converted by a diode bridge circuit to a DC voltage which drives the transistors. Serially connected capacitors bypass the bridge circuit to couple high frequency current from a primary winding of the transformer through the transistors. Additional windings of the transformer are coupled in the base-emitter circuit of each transistor for inducing states of saturation during conduction phases of each transistor so as to minimize power dissipation within each of the transistors.

Abstract: A circuit for operating a discharge lamp at a low frequency AC voltage while repetitively interrupting at a high frequency the voltage component to be applied to the lamp. The circuit includes at least one switching transistor for repetitively interrupting the voltage to be applied to the lamp at the high frequency, for example, 40 KHz so as to allow the use of a light and less bulky inductor as the current limiting conductor to be connected in series with the lamp. A bridge inverter is provided to have at least one pair of switching transistors for alternately reversing a DC voltage to apply the resulting AC voltage to the lamp at the low frequency, for example, 100 Hz low enough to stably operate the lamp without suffering from acoustic resonance. The high frequency component is bypassed through a bypass capacitor connected in parallel with the lamp.

Abstract: For the operation of warm start gas discharge lamps upon employment of an electronic ballast wherein the gas discharge lamp lies parallel to the effective capacitance of a series-resonant circuit and has its heater coils incorporated into this series-resonant circuit. An isolating switch is provided in series with the effective capacitance. This isolating switch interrupts the shunt to the lamp and, thus, the heater coil current as well, as soon as the lamp has ignited. It is assured in this way that the current flowing in the shunt to the lamp which otherwise represents a dissipated power is suppressed. Particular significance is accorded to this method when the effective capacitance of the series-resonant circuit is executed variably during the starting interval phase with the assistance of temperature-dependent resistors or is executed with time delayed electronic switches for the control of the lamp voltage.

Abstract: A circuit supplied with direct voltage serves for generation of voltages and/or currents of differing curve shape and differing frequency and/or differing polarity. A load L with ohmic, inductive, capacitive or complex resistance behavior is switched in series with a choke D. Furthermore, at least two controlled semiconductor switches T.sub.1 and T.sub.2 are provided, which are each, respectively in series, as far as the load L and the choke D are connected, but which, however, lie in current paths 1 and 2 which are connected at different potentials of the supply voltage. In operational use, the one switch T.sub.2 is held open while the other switch T.sub.1 is opened and closed in alternating sequence, and after termination of an adjustable and controllable time period, the switch T.sub.1, which has been hitherto operated in alternating sequence, is now kept open, while the switch T.sub.